With the release of Libntlm version 1.8 the release tarball can be reproduced on several distributions. We also publish a signed minimal source-only tarball, produced by git-archive which is the same format used by Savannah, Codeberg, GitLab, GitHub and others. Reproducibility of both tarballs are tested continuously for regressions on GitLab through a CI/CD pipeline. If that wasn t enough to excite you, the Debian packages of Libntlm are now built from the reproducible minimal source-only tarball. The resulting binaries are reproducible on several architectures. What does that even mean? Why should you care? How you can do the same for your project? What are the open issues? Read on, dear reader This article describes my practical experiments with reproducible release artifacts, following up on my earlier thoughts that lead to discussion on Fosstodon and a patch by Janneke Nieuwenhuizen to make Guix tarballs reproducible that inspired me to some practical work. Let s look at how a maintainer release some software, and how a user can reproduce the released artifacts from the source code. Libntlm provides a shared library written in C and uses GNU Make, GNU Autoconf, GNU Automake, GNU Libtool and gnulib for build management, but these ideas should apply to most project and build system. The following illustrate the steps a maintainer would take to prepare a release:

git clone https://gitlab.com/gsasl/libntlm.git
cd libntlm
git checkout v1.8
./bootstrap
./configure
make distcheck
gpg -b libntlm-1.8.tar.gz

The generated files libntlm-1.8.tar.gz and libntlm-1.8.tar.gz.sig are published, and users download and use them. This is how the GNU project have been doing releases since the late 1980 s. That is a testament to how successful this pattern has been! These tarballs contain source code and some generated files, typically shell scripts generated by autoconf, makefile templates generated by automake, documentation in formats like Info, HTML, or PDF. Rarely do they contain binary object code, but historically that happened. The XZUtils incident illustrate that tarballs with files that are not included in the git archive offer an opportunity to disguise malicious backdoors. I blogged earlier how to mitigate this risk by using signed minimal source-only tarballs. The risk of hiding malware is not the only motivation to publish signed minimal source-only tarballs. With pre-generated content in tarballs, there is a risk that GNU/Linux distributions such as Trisquel, Guix, Debian/Ubuntu or Fedora ship generated files coming from the tarball into the binary *.deb or *.rpm package file. Typically the person packaging the upstream project never realized that some installed artifacts was not re-built through a typical autoconf -fi && ./configure && make install sequence, and never wrote the code to rebuild everything. This can also happen if the build rules are written but are buggy, shipping the old artifact. When a security problem is found, this can lead to time-consuming situations, as it may be that patching the relevant source code and rebuilding the package is not sufficient: the vulnerable generated object from the tarball would be shipped into the binary package instead of a rebuilt artifact. For architecture-specific binaries this rarely happens, since object code is usually not included in tarballs although for 10+ years I shipped the binary Java JAR file in the GNU Libidn release tarball, until I stopped shipping it. For interpreted languages and especially for generated content such as HTML, PDF, shell scripts this happens more than you would like. Publishing minimal source-only tarballs enable easier auditing of a project s code, to avoid the need to read through all generated files looking for malicious content. I have taken care to generate the source-only minimal tarball using git-archive. This is the same format that GitLab, GitHub etc offer for the automated download links on git tags. The minimal source-only tarballs can thus serve as a way to audit GitLab and GitHub download material! Consider if/when hosting sites like GitLab or GitHub has a security incident that cause generated tarballs to include a backdoor that is not present in the git repository. If people rely on the tag download artifact without verifying the maintainer PGP signature using GnuPG, this can lead to similar backdoor scenarios that we had for XZUtils but originated with the hosting provider instead of the release manager. This is even more concerning, since this attack can be mounted for some selected IP address that you want to target and not on everyone, thereby making it harder to discover. With all that discussion and rationale out of the way, let s return to the release process. I have added another step here:

make srcdist
gpg -b libntlm-1.8-src.tar.gz

Now the release is ready. I publish these four files in the Libntlm s Savannah Download area, but they can be uploaded to a GitLab/GitHub release area as well. These are the SHA256 checksums I got after building the tarballs on my Trisquel 11 aramo laptop:

91de864224913b9493c7a6cec2890e6eded3610d34c3d983132823de348ec2ca  libntlm-1.8-src.tar.gz
ce6569a47a21173ba69c990965f73eb82d9a093eb871f935ab64ee13df47fda1  libntlm-1.8.tar.gz

So how can you reproduce my artifacts? Here is how to reproduce them in a Ubuntu 22.04 container:

podman run -it --rm ubuntu:22.04
apt-get update
apt-get install -y --no-install-recommends autoconf automake libtool make git ca-certificates
git clone https://gitlab.com/gsasl/libntlm.git
cd libntlm
git checkout v1.8
./bootstrap
./configure
make dist srcdist
sha256sum libntlm-*.tar.gz

You should see the exact same SHA256 checksum values. Hooray! This works because Trisquel 11 and Ubuntu 22.04 uses the same version of git, autoconf, automake, and libtool. These tools do not guarantee the same output content for all versions, similar to how GNU GCC does not generate the same binary output for all versions. So there is still some delicate version pairing needed. Ideally, the artifacts should be possible to reproduce from the release artifacts themselves, and not only directly from git. It is possible to reproduce the full tarball in a AlmaLinux 8 container replace almalinux:8 with rockylinux:8 if you prefer RockyLinux:

podman run -it --rm almalinux:8
dnf update -y
dnf install -y make wget gcc
wget https://download.savannah.nongnu.org/releases/libntlm/libntlm-1.8.tar.gz
tar xfa libntlm-1.8.tar.gz
cd libntlm-1.8
./configure
make dist
sha256sum libntlm-1.8.tar.gz

The source-only minimal tarball can be regenerated on Debian 11:

podman run -it --rm debian:11
apt-get update
apt-get install -y --no-install-recommends make git ca-certificates
git clone https://gitlab.com/gsasl/libntlm.git
cd libntlm
git checkout v1.8
make -f cfg.mk srcdist
sha256sum libntlm-1.8-src.tar.gz 

As the Magnus Opus or chef-d uvre, let s recreate the full tarball directly from the minimal source-only tarball on Trisquel 11 replace docker.io/kpengboy/trisquel:11.0 with ubuntu:22.04 if you prefer.

podman run -it --rm docker.io/kpengboy/trisquel:11.0
apt-get update
apt-get install -y --no-install-recommends autoconf automake libtool make wget git ca-certificates
wget https://download.savannah.nongnu.org/releases/libntlm/libntlm-1.8-src.tar.gz
tar xfa libntlm-1.8-src.tar.gz
cd libntlm-v1.8
./bootstrap
./configure
make dist
sha256sum libntlm-1.8.tar.gz

Yay! You should now have great confidence in that the release artifacts correspond to what s in version control and also to what the maintainer intended to release. Your remaining job is to audit the source code for vulnerabilities, including the source code of the dependencies used in the build. You no longer have to worry about auditing the release artifacts. I find it somewhat amusing that the build infrastructure for Libntlm is now in a significantly better place than the code itself. Libntlm is written in old C style with plenty of string manipulation and uses broken cryptographic algorithms such as MD4 and single-DES. Remember folks: solving supply chain security issues has no bearing on what kind of code you eventually run. A clean gun can still shoot you in the foot. Side note on naming: GitLab exports tarballs with pathnames libntlm-v1.8/ (i.e.., PROJECT-TAG/) and I ve adopted the same pathnames, which means my libntlm-1.8-src.tar.gz tarballs are bit-by-bit identical to GitLab s exports and you can verify this with tools like diffoscope. GitLab name the tarball libntlm-v1.8.tar.gz (i.e., PROJECT-TAG.ARCHIVE) which I find too similar to the libntlm-1.8.tar.gz that we also publish. GitHub uses the same git archive style, but unfortunately they have logic that removes the v in the pathname so you will get a tarball with pathname libntlm-1.8/ instead of libntlm-v1.8/ that GitLab and I use. The content of the tarball is bit-by-bit identical, but the pathname and archive differs. Codeberg (running Forgejo) uses another approach: the tarball is called libntlm-v1.8.tar.gz (after the tag) just like GitLab, but the pathname inside the archive is libntlm/, otherwise the produced archive is bit-by-bit identical including timestamps. Savannah s CGIT interface uses archive name libntlm-1.8.tar.gz with pathname libntlm-1.8/, but otherwise file content is identical. Savannah s GitWeb interface provides snapshot links that are named after the git commit (e.g., libntlm-a812c2ca.tar.gz with libntlm-a812c2ca/) and I cannot find any tag-based download links at all. Overall, we are so close to get SHA256 checksum to match, but fail on pathname within the archive. I ve chosen to be compatible with GitLab regarding the content of tarballs but not on archive naming. From a simplicity point of view, it would be nice if everyone used PROJECT-TAG.ARCHIVE for the archive filename and PROJECT-TAG/ for the pathname within the archive. This aspect will probably need more discussion. Side note on git archive output: It seems different versions of git archive produce different results for the same repository. The version of git in Debian 11, Trisquel 11 and Ubuntu 22.04 behave the same. The version of git in Debian 12, AlmaLinux/RockyLinux 8/9, Alpine, ArchLinux, macOS homebrew, and upcoming Ubuntu 24.04 behave in another way. Hopefully this will not change that often, but this would invalidate reproducibility of these tarballs in the future, forcing you to use an old git release to reproduce the source-only tarball. Alas, GitLab and most other sites appears to be using modern git so the download tarballs from them would not match my tarballs even though the content would. Side note on ChangeLog: ChangeLog files were traditionally manually curated files with version history for a package. In recent years, several projects moved to dynamically generate them from git history (using tools like git2cl or gitlog-to-changelog). This has consequences for reproducibility of tarballs: you need to have the entire git history available! The gitlog-to-changelog tool also output different outputs depending on the time zone of the person using it, which arguable is a simple bug that can be fixed. However this entire approach is incompatible with rebuilding the full tarball from the minimal source-only tarball. It seems Libntlm s ChangeLog file died on the surgery table here. So how would a distribution build these minimal source-only tarballs? I happen to help on the libntlm package in Debian. It has historically used the generated tarballs as the source code to build from. This means that code coming from gnulib is vendored in the tarball. When a security problem is discovered in gnulib code, the security team needs to patch all packages that include that vendored code and rebuild them, instead of merely patching the gnulib package and rebuild all packages that rely on that particular code. To change this, the Debian libntlm package needs to Build-Depends on Debian s gnulib package. But there was one problem: similar to most projects that use gnulib, Libntlm depend on a particular git commit of gnulib, and Debian only ship one commit. There is no coordination about which commit to use. I have adopted gnulib in Debian, and add a git bundle to the *_all.deb binary package so that projects that rely on gnulib can pick whatever commit they need. This allow an no-network GNULIB_URL and GNULIB_REVISION approach when running Libntlm s ./bootstrap with the Debian gnulib package installed. Otherwise libntlm would pick up whatever latest version of gnulib that Debian happened to have in the gnulib package, which is not what the Libntlm maintainer intended to be used, and can lead to all sorts of version mismatches (and consequently security problems) over time. Libntlm in Debian is developed and tested on Salsa and there is continuous integration testing of it as well, thanks to the Salsa CI team. Side note on git bundles: unfortunately there appears to be no reproducible way to export a git repository into one or more files. So one unfortunate consequence of all this work is that the gnulib *.orig.tar.gz tarball in Debian is not reproducible any more. I have tried to get Git bundles to be reproducible but I never got it to work see my notes in gnulib s debian/README.source on this aspect. Of course, source tarball reproducibility has nothing to do with binary reproducibility of gnulib in Debian itself, fortunately. One open question is how to deal with the increased build dependencies that is triggered by this approach. Some people are surprised by this but I don t see how to get around it: if you depend on source code for tools in another package to build your package, it is a bad idea to hide that dependency. We ve done it for a long time through vendored code in non-minimal tarballs. Libntlm isn t the most critical project from a bootstrapping perspective, so adding git and gnulib as Build-Depends to it will probably be fine. However, consider if this pattern was used for other packages that uses gnulib such as coreutils, gzip, tar, bison etc (all are using gnulib) then they would all Build-Depends on git and gnulib. Cross-building those packages for a new architecture will therefor require git on that architecture first, which gets circular quick. The dependency on gnulib is real so I don t see that going away, and gnulib is a Architecture:all package. However, the dependency on git is merely a consequence of how the Debian gnulib package chose to make all gnulib git commits available to projects: through a git bundle. There are other ways to do this that doesn t require the git tool to extract the necessary files, but none that I found practical ideas welcome! Finally some brief notes on how this was implemented. Enabling bootstrappable source-only minimal tarballs via gnulib s ./bootstrap is achieved by using the GNULIB_REVISION mechanism, locking down the gnulib commit used. I have always disliked git submodules because they add extra steps and has complicated interaction with CI/CD. The reason why I gave up git submodules now is because the particular commit to use is not recorded in the git archive output when git submodules is used. So the particular gnulib commit has to be mentioned explicitly in some source code that goes into the git archive tarball. Colin Watson added the GNULIB_REVISION approach to ./bootstrap back in 2018, and now it no longer made sense to continue to use a gnulib git submodule. One alternative is to use ./bootstrap with --gnulib-srcdir or --gnulib-refdir if there is some practical problem with the GNULIB_URL towards a git bundle the GNULIB_REVISION in bootstrap.conf. The srcdist make rule is simple:

git archive --prefix=libntlm-v1.8/ -o libntlm-v1.8.tar.gz HEAD

Making the make dist generated tarball reproducible can be more complicated, however for Libntlm it was sufficient to make sure the modification times of all files were set deterministically to the timestamp of the last commit in the git repository. Interestingly there seems to be a couple of different ways to accomplish this, Guix doesn t support minimal source-only tarballs but rely on a .tarball-timestamp file inside the tarball. Paul Eggert explained what TZDB is using some time ago. The approach I m using now is fairly similar to the one I suggested over a year ago. If there are problems because all files in the tarball now use the same modification time, there is a solution by Bruno Haible that could be implemented. Side note on git tags: Some people may wonder why not verify a signed git tag instead of verifying a signed tarball of the git archive. Currently most git repositories uses SHA-1 for git commit identities, but SHA-1 is not a secure hash function. While current SHA-1 attacks can be detected and mitigated, there are fundamental doubts that a git SHA-1 commit identity uniquely refers to the same content that was intended. Verifying a git tag will never offer the same assurance, since a git tag can be moved or re-signed at any time. Verifying a git commit is better but then we need to trust SHA-1. Migrating git to SHA-256 would resolve this aspect, but most hosting sites such as GitLab and GitHub does not support this yet. There are other advantages to using signed tarballs instead of signed git commits or git tags as well, e.g., tar.gz can be a deterministically reproducible persistent stable offline storage format but .git sub-directory trees or git bundles do not offer this property. Doing continous testing of all this is critical to make sure things don t regress. Libntlm s pipeline definition now produce the generated libntlm-*.tar.gz tarballs and a checksum as a build artifact. Then I added the 000-reproducability job which compares the checksums and fails on mismatches. You can read its delicate output in the job for the v1.8 release. Right now we insists that builds on Trisquel 11 match Ubuntu 22.04, that PureOS 10 builds match Debian 11 builds, that AlmaLinux 8 builds match RockyLinux 8 builds, and AlmaLinux 9 builds match RockyLinux 9 builds. As you can see in pipeline job output, not all platforms lead to the same tarballs, but hopefully this state can be improved over time. There is also partial reproducibility, where the full tarball is reproducible across two distributions but not the minimal tarball, or vice versa. If this way of working plays out well, I hope to implement it in other projects too. What do you think? Happy Hacking!

While the work to analyze the xz backdoor is in progress, several ideas have been suggested to improve the software supply chain ecosystem. Some of those ideas are good, some of the ideas are at best irrelevant and harmless, and some suggestions are plain bad. I d like to attempt to formalize two ideas, which have been discussed before, but the context in which they can be appreciated have not been as clear as it is today.

1. Reproducible tarballs. The idea is that published source tarballs should be possible to reproduce independently somehow, and that this should be continuously tested and verified preferrably as part of the upstream project continuous integration system (e.g., GitHub action or GitLab pipeline). While nominally this looks easy to achieve, there are some complex matters in this, for example: what timestamps to use for files in the tarball? I ve brought up this aspect before.
2. Minimal source tarballs without generated vendor files. Most GNU Autoconf/Automake-based tarballs pre-generated files which are important for bootstrapping on exotic systems that does not have the required dependencies. For the bootstrapping story to succeed, this approach is important to support. However it has become clear that this practice raise significant costs and risks. Most modern GNU/Linux distributions have all the required dependencies and actually prefers to re-build everything from source code. These pre-generated extra files introduce uncertainty to that process.

My strawman proposal to improve things is to define new tarball format *-src.tar.gz with at least the following properties:

1. The tarball should allow users to build the project, which is the entire purpose of all this. This means that at least all source code for the project has to be included.
2. The tarballs should be signed, for example with PGP or minisign.
3. The tarball should be possible to reproduce bit-by-bit by a third party using upstream s version controlled sources and a pointer to which revision was used (e.g., git tag or git commit).
4. The tarball should not require an Internet connection to download things.
   • Corollary: every external dependency either has to be explicitly documented as such (e.g., gcc and GnuTLS), or included in the tarball.
   • Observation: This means including all *.po gettext translations which are normally downloaded when building from version controlled sources.
5. The tarball should contain everything required to build the project from source using as much externally released versioned tooling as possible. This is the minimal property lacking today.
   • Corollary: This means including a vendored copy of OpenSSL or libz is not acceptable: link to them as external projects.
   • Open question: How about non-released external tooling such as gnulib or autoconf archive macros? This is a bit more delicate: most distributions either just package one current version of gnulib or autoconf archive, not previous versions. While this could change, and distributions could package the gnulib git repository (up to some current version) and the autoconf archive git repository and packages were set up to extract the version they need (gnulib s ./bootstrap already supports this via the gnulib-refdir parameter), this is not normally in place.
   • Suggested Corollary: The tarball should contain content from git submodule s such as gnulib and the necessary Autoconf archive M4 macros required by the project.
6. Similar to how the GNU project specify the ./configure interface we need a documented interface for how to bootstrap the project. I suggest to use the already well established idiom of running ./bootstrap to set up the package to later be able to be built via ./configure. Of course, some projects are not using the autotool ./configure interface and will not follow this aspect either, but like most build systems that compete with autotools have instructions on how to build the project, they should document similar interfaces for bootstrapping the source tarball to allow building.

If tarballs that achieve the above goals were available from popular upstream projects, distributions could more easily use them instead of current tarballs that include pre-generated content. The advantage would be that the build process is not tainted by unnecessary files. We need to develop tools for maintainers to create these tarballs, similar to make dist that generate today s foo-1.2.3.tar.gz files. I think one common argument against this approach will be: Why bother with all that, and just use git-archive outputs? Or avoid the entire tarball approach and move directly towards version controlled check outs and referring to upstream releases as git URL and commit tag or id. One problem with this is that SHA-1 is broken, so placing trust in a SHA-1 identifier is simply not secure. Another counter-argument is that this optimize for packagers benefits at the cost of upstream maintainers: most upstream maintainers do not want to store gettext *.po translations in their source code repository. A compromise between the needs of maintainers and packagers is useful, so this *-src.tar.gz tarball approach is the indirection we need to solve that. Update: In my experiment with source-only tarballs for Libntlm I actually did use git-archive output. What do you think?

My effort to improve transparency and confidence of public apt archives continues. I started to work on this in Apt Archive Transparency in which I mention the debdistget project in passing. Debdistget is responsible for mirroring index files for some public apt archives. I ve realized that having a publicly auditable and preserved mirror of the apt repositories is central to being able to do apt transparency work, so the debdistget project has become more central to my project than I thought. Currently I track Trisquel, PureOS, Gnuinos and their upstreams Ubuntu, Debian and Devuan. Debdistget download Release/Package/Sources files and store them in a git repository published on GitLab. Due to size constraints, it uses two repositories: one for the Release/InRelease files (which are small) and one that also include the Package/Sources files (which are large). See for example the repository for Trisquel release files and the Trisquel package/sources files. Repositories for all distributions can be found in debdistutils archives GitLab sub-group. The reason for splitting into two repositories was that the git repository for the combined files become large, and that some of my use-cases only needed the release files. Currently the repositories with packages (which contain a couple of months worth of data now) are 9GB for Ubuntu, 2.5GB for Trisquel/Debian/PureOS, 970MB for Devuan and 450MB for Gnuinos. The repository size is correlated to the size of the archive (for the initial import) plus the frequency and size of updates. Ubuntu s use of Apt Phased Updates (which triggers a higher churn of Packages file modifications) appears to be the primary reason for its larger size. Working with large Git repositories is inefficient and the GitLab CI/CD jobs generate quite some network traffic downloading the git repository over and over again. The most heavy user is the debdistdiff project that download all distribution package repositories to do diff operations on the package lists between distributions. The daily job takes around 80 minutes to run, with the majority of time is spent on downloading the archives. Yes I know I could look into runner-side caching but I dislike complexity caused by caching. Fortunately not all use-cases requires the package files. The debdistcanary project only needs the Release/InRelease files, in order to commit signatures to the Sigstore and Sigsum transparency logs. These jobs still run fairly quickly, but watching the repository size growth worries me. Currently these repositories are at Debian 440MB, PureOS 130MB, Ubuntu/Devuan 90MB, Trisquel 12MB, Gnuinos 2MB. Here I believe the main size correlation is update frequency, and Debian is large because I track the volatile unstable. So I hit a scalability end with my first approach. A couple of months ago I solved this by discarding and resetting these archival repositories. The GitLab CI/CD jobs were fast again and all was well. However this meant discarding precious historic information. A couple of days ago I was reaching the limits of practicality again, and started to explore ways to fix this. I like having data stored in git (it allows easy integration with software integrity tools such as GnuPG and Sigstore, and the git log provides a kind of temporal ordering of data), so it felt like giving up on nice properties to use a traditional database with on-disk approach. So I started to learn about Git-LFS and understanding that it was able to handle multi-GB worth of data that looked promising. Fairly quickly I scripted up a GitLab CI/CD job that incrementally update the Release/Package/Sources files in a git repository that uses Git-LFS to store all the files. The repository size is now at Ubuntu 650kb, Debian 300kb, Trisquel 50kb, Devuan 250kb, PureOS 172kb and Gnuinos 17kb. As can be expected, jobs are quick to clone the git archives: debdistdiff pipelines went from a run-time of 80 minutes down to 10 minutes which more reasonable correlate with the archive size and CPU run-time. The LFS storage size for those repositories are at Ubuntu 15GB, Debian 8GB, Trisquel 1.7GB, Devuan 1.1GB, PureOS/Gnuinos 420MB. This is for a couple of days worth of data. It seems native Git is better at compressing/deduplicating data than Git-LFS is: the combined size for Ubuntu is already 15GB for a couple of days data compared to 8GB for a couple of months worth of data with pure Git. This may be a sub-optimal implementation of Git-LFS in GitLab but it does worry me that this new approach will be difficult to scale too. At some level the difference is understandable, Git-LFS probably store two different Packages files around 90MB each for Trisquel as two 90MB files, but native Git would store it as one compressed version of the 90MB file and one relatively small patch to turn the old files into the next file. So the Git-LFS approach surprisingly scale less well for overall storage-size. Still, the original repository is much smaller, and you usually don t have to pull all LFS files anyway. So it is net win. Throughout this work, I kept thinking about how my approach relates to Debian s snapshot service. Ultimately what I would want is a combination of these two services. To have a good foundation to do transparency work I would want to have a collection of all Release/Packages/Sources files ever published, and ultimately also the source code and binaries. While it makes sense to start on the latest stable releases of distributions, this effort should scale backwards in time as well. For reproducing binaries from source code, I need to be able to securely find earlier versions of binary packages used for rebuilds. So I need to import all the Release/Packages/Sources packages from snapshot into my repositories. The latency to retrieve files from that server is slow so I haven t been able to find an efficient/parallelized way to download the files. If I m able to finish this, I would have confidence that my new Git-LFS based approach to store these files will scale over many years to come. This remains to be seen. Perhaps the repository has to be split up per release or per architecture or similar. Another factor is storage costs. While the git repository size for a Git-LFS based repository with files from several years may be possible to sustain, the Git-LFS storage size surely won t be. It seems GitLab charges the same for files in repositories and in Git-LFS, and it is around $500 per 100GB per year. It may be possible to setup a separate Git-LFS backend not hosted at GitLab to serve the LFS files. Does anyone know of a suitable server implementation for this? I had a quick look at the Git-LFS implementation list and it seems the closest reasonable approach would be to setup the Gitea-clone Forgejo as a self-hosted server. Perhaps a cloud storage approach a la S3 is the way to go? The cost to host this on GitLab will be manageable for up to ~1TB ($5000/year) but scaling it to storing say 500TB of data would mean an yearly fee of $2.5M which seems like poor value for the money. I realized that ultimately I would want a git repository locally with the entire content of all apt archives, including their binary and source packages, ever published. The storage requirements for a service like snapshot (~300TB of data?) is today not prohibitly expensive: 20TB disks are $500 a piece, so a storage enclosure with 36 disks would be around $18.000 for 720TB and using RAID1 means 360TB which is a good start. While I have heard about ~TB-sized Git-LFS repositories, would Git-LFS scale to 1PB? Perhaps the size of a git repository with multi-millions number of Git-LFS pointer files will become unmanageable? To get started on this approach, I decided to import a mirror of Debian s bookworm for amd64 into a Git-LFS repository. That is around 175GB so reasonable cheap to host even on GitLab ($1000/year for 200GB). Having this repository publicly available will make it possible to write software that uses this approach (e.g., porting debdistreproduce), to find out if this is useful and if it could scale. Distributing the apt repository via Git-LFS would also enable other interesting ideas to protecting the data. Consider configuring apt to use a local file:// URL to this git repository, and verifying the git checkout using some method similar to Guix s approach to trusting git content or Sigstore s gitsign. A naive push of the 175GB archive in a single git commit ran into pack size limitations: remote: fatal: pack exceeds maximum allowed size (4.88 GiB) however breaking up the commit into smaller commits for parts of the archive made it possible to push the entire archive. Here are the commands to create this repository: git init
git lfs install
git lfs track 'dists/**' 'pool/**'
git add .gitattributes
git commit -m"Add Git-LFS track attributes." .gitattributes
time debmirror --method=rsync --host ftp.se.debian.org --root :debian --arch=amd64 --source --dist=bookworm,bookworm-updates --section=main --verbose --diff=none --keyring /usr/share/keyrings/debian-archive-keyring.gpg --ignore .git .
git add dists project
git commit -m"Add." -a
git remote add origin git@gitlab.com:debdistutils/archives/debian/mirror.git
git push --set-upstream origin --all
for d in pool//; do
echo $d;
time git add $d;
git commit -m"Add $d." -a
git push
done The resulting repository size is around 27MB with Git LFS object storage around 174GB. I think this approach would scale to handle all architectures for one release, but working with a single git repository for all releases for all architectures may lead to a too large git repository (>1GB). So maybe one repository per release? These repositories could also be split up on a subset of pool/ files, or there could be one repository per release per architecture or sources. Finally, I have concerns about using SHA1 for identifying objects. It seems both Git and Debian s snapshot service is currently using SHA1. For Git there is SHA-256 transition and it seems GitLab is working on support for SHA256-based repositories. For serious long-term deployment of these concepts, it would be nice to go for SHA256 identifiers directly. Git-LFS already uses SHA256 but Git internally uses SHA1 as does the Debian snapshot service. What do you think? Happy Hacking!

Last week we held our promised miniDebConf in Santa Fe City, Santa Fe province, Argentina just across the river from Paran , where I have spent almost six beautiful months I will never forget. Around 500 Kilometers North from Buenos Aires, Santa Fe and Paran are separated by the beautiful and majestic Paran river, which flows from Brazil, marks the Eastern border of Paraguay, and continues within Argentina as the heart of the litoral region of the country, until it merges with the Uruguay river (you guessed right the river marking the Eastern border of Argentina, first with Brazil and then with Uruguay), and they become the R o de la Plata. This was a short miniDebConf: we were lent the APUL union s building for the weekend (thank you very much!); during Saturday, we had a cycle of talks, and on sunday we had more of a hacklab logic, having some unstructured time to work each on their own projects, and to talk and have a good time together. We were five Debian people attending: santiago debacle eamanu dererk gwolf @debian.org. My main contact to kickstart organization was Mart n Bayo. Mart n was for many years the leader of the Technical Degree on Free Software at Universidad Nacional del Litoral, where I was also a teacher for several years. Together with Leo Mart nez, also a teacher at the tecnicatura, they contacted us with Guillermo and Gabriela, from the APUL non-teaching-staff union of said university. We had the following set of talks (for which there is a promise to get electronic record, as APUL was kind enough to record them! of course, I will push them to our usual conference video archiving service as soon as I get them)

Hour	Title (Spanish)	Title (English)	Presented by
10:00-10:25	Introducci n al Software Libre	Introduction to Free Software	Mart n Bayo
10:30-10:55	Debian y su comunidad	Debian and its community	Emanuel Arias
11:00-11:25	Por qu sigo contribuyendo a Debian despu s de 20 a os?	Why am I still contributing to Debian after 20 years?	Santiago Ruano
11:30-11:55	Mi identidad y el proyecto Debian: Qu es el llavero OpenPGP y por qu ?	My identity and the Debian project: What is the OpenPGP keyring and why?	Gunnar Wolf
12:00-13:00	Explorando las masculinidades en el contexto del Software Libre	Exploring masculinities in the context of Free Software	Gora Ortiz Fuentes - Jos Francisco Ferro
13:00-14:30	Lunch
14:30-14:55	Debian para el d a a d a	Debian for our every day	Leonardo Mart nez
15:00-15:25	Debian en las Raspberry Pi	Debian in the Raspberry Pi	Gunnar Wolf
15:30-15:55	Device Trees	Device Trees	Lisandro Dami n Nicanor Perez Meyer (videoconferencia)
16:00-16:25	Python en Debian	Python in Debian	Emmanuel Arias
16:30-16:55	Debian y XMPP en la medici n de viento para la energ a e lica	Debian and XMPP for wind measuring for eolic energy	Martin Borgert

As it always happens DebConf, miniDebConf and other Debian-related activities are always fun, always productive, always a great opportunity to meet again our decades-long friends. Lets see what comes next!

Contributing to Debian is part of Freexian s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

/usr-move, by Helmut Grohne Much of the work was spent on handling interaction with time time64 transition and sending patches for mitigating fallout. The set of packages relevant to debootstrap is mostly converted and the patches for glibc and base-files have been refined due to feedback from the upload to Ubuntu noble. Beyond this, he sent patches for all remaining packages that cannot move their files with dh-sequence-movetousr and packages using dpkg-divert in ways that dumat would not recognize.

Upcoming improvements to Salsa CI, by Santiago Ruano Rinc n Last month, Santiago Ruano Rinc n started the work on integrating sbuild into the Salsa CI pipeline. Initially, Santiago used sbuild with the unshare chroot mode. However, after discussion with josch, jochensp and helmut (thanks to them!), it turns out that the unshare mode is not the most suitable for the pipeline, since the level of isolation it provides is not needed, and some test suites would fail (eg: krb5). Additionally, one of the requirements of the build job is the use of ccache, since it is needed by some C/C++ large projects to reduce the compilation time. In the preliminary work with unshare last month, it was not possible to make ccache to work. Finally, Santiago changed the chroot mode, and now has a couple of POC (cf: 1 and 2) that rely on the schroot and sudo, respectively. And the good news is that ccache is successfully used by sbuild with schroot! The image here comes from an example of building grep. At the end of the build, ccache -s shows the statistics of the cache that it used, and so a little more than half of the calls of that job were cacheable. The most important pieces are in place to finish the integration of sbuild into the pipeline. Other than that, Santiago also reviewed the very useful merge request !346, made by IOhannes zm lnig to autodetect the release from debian/changelog. As agreed with IOhannes, Santiago is preparing a merge request to include the release autodetection use case in the very own Salsa CI s CI.

Packaging simplemonitor, by Carles Pina i Estany Carles started using simplemonitor in 2017, opened a WNPP bug in 2022 and started packaging simplemonitor dependencies in October 2023. After packaging five direct and indirect dependencies, Carles finally uploaded simplemonitor to unstable in February. During the packaging of simplemonitor, Carles reported a few issues to upstream. Some of these were to make the simplemonitor package build and run tests reproducibly. A reproducibility issue was reprotest overriding the timezone, which broke simplemonitor s tests. There have been discussions on resolving this upstream in simplemonitor and in reprotest, too. Carles also started upgrading or improving some of simplemonitor s dependencies.

Miscellaneous contributions

• Stefano Rivera spent some time doing admin on debian.social infrastructure. Including dealing with a spike of abuse on the Jitsi server.
• Stefano started to prepare a new release of dh-python, including cleaning out a lot of old Python 2.x related code. Thanks to Niels Thykier (outside Freexian) for spear-heading this work.
• DebConf 24 planning is beginning. Stefano discussed venues and finances with the local team and remotely supported a site-visit by Nattie (outside Freexian).
• Also in the DebConf 24 context, Santiago took part in discussions and preparations related to the Content Team.
• A JIT bug was reported against pypy3 in Debian Bookworm. Stefano bisected the upstream history to find the patch (it was already resolved upstream) and released an update to pypy3 in bookworm.
• Enrico participated in /usr-merge discussions with Helmut.
• Colin Watson backported a python-channels-redis fix to bookworm, rediscovered while working on debusine.
• Colin dug into a cluster of celery build failures and tracked the hardest bit down to a Python 3.12 regression, now fixed in unstable. celery should be back in testing once the 64-bit time_t migration is out of the way.
• Thorsten Alteholz uploaded a new upstream version of cpdb-libs. Unfortunately upstream changed the naming of their release tags, so updating the watch file was a bit demanding. Anyway this version 2.0 is a huge step towards introduction of the new Common Print Dialog Backends.
• Helmut send patches for 48 cross build failures.
• Helmut changed debvm to use mkfs.ext4 instead of genext2fs.
• Helmut sent a debci MR for improving collector robustness.
• In preparation for DebConf 25, Santiago worked on the Brest Bid.

Thrilled to share that a new version of prrd arrived at CRAN yesterday in a first update in two and a half years. prrd facilitates the parallel running [of] reverse dependency [checks] when preparing R packages. It is used extensively for releases I make of Rcpp, RcppArmadillo, RcppEigen, BH, and others. The key idea of prrd is simple, and described in some more detail on its webpage and its GitHub repo. Reverse dependency checks are an important part of package development that is easily done in a (serial) loop. But these checks are also generally embarassingly parallel as there is no or little interdependency between them (besides maybe shared build depedencies). See the (dated) screenshot (running six parallel workers, arranged in a split byobu session). This release, the first since 2021, brings a number of enhancments. In particular, the summary function is now improved in several ways. Josh also put in a nice PR that generalizes some setup defaults and values. The release is summarised in the NEWS entry:

Changes in prrd version 0.0.6 (2024-03-06)

• The summary function has received several enhancements:
  • Extended summary is only running when failures are seen.
  • The summariseQueue function now displays an anticipated completion time and remaining duration.
  • The use of optional package foghorn has been refined, and refactored, when running summaries.
• The dequeueJobs.r scripts can receive a date argument, the date can be parse via anydate if anytime ins present.
• The enqueeJobs.r now considers skipped package when running 'addfailed' while ensuring selecting packages are still on CRAN.
• The CI setup has been updated (twice),
• Enqueing and dequing functions and scripts now support relative directories, updated documentation (#18 by Joshua Ulrich).

Courtesy of my CRANberries, there is also a diffstat report for this release. If you like this or other open-source work I do, you can sponsor me at GitHub.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

Happy 2024! DAIS have continued their programme of posthumous Coil remasters and re-issues. Constant Shallowness Leads To Evil was remastered by Josh Bonati in 2021 and re-released in 2022 in a dizzying array of different packaging variants. The original releases in 2000 had barely any artwork, and given that void I think Nathaniel Young has done a great job of creating something compelling. A limited number of the original re-issue have special lenticular covers, although these were not sold by any distributors outside the US. I tried to find a copy on my trip to Portland in 2022, to no avail. Last year DAIS followed Constant with Queens Of The Circulating Library, same deal: limited lenticular covers, US only. Both are also available digital-only, e.g. on Bandcamp: Constant , Queens . The original, pre-remastered releases have been freely available on archive.org for a long time: Constant , Queens Both of these releases feel to me that they were made available by the group somewhat as an afterthought, having been produced primarily as part of their live efforts. (I'm speculating freely here, it might not be true). Live takes of some of this material exist in the form of Coil Presents Time Machines, which has not (yet) been reissued. In my opinion this is a really compelling recording. I vividly remember listening to this whilst trying to get an hour's rest in a hotel somewhere on a work trip. It took me to some strange places! I'll leave you from one of my favourite moments from "Colour Sound Oblivion", Coil's video collection of live backdrops. When this was performed live it was also called "Constant Shallowness Leads To Evil", although it's distinct from the material on the LP: also available on archive.org. A version of this Constant made it onto a Russian live bootleg, which is available on Spotify and Bandcamp complete with some John Balance banter: we only do this on religious holidays Constant Shallowness Leads to Evil by Coil

Review: Making Money, by Terry Pratchett

Series:	Discworld #36
Publisher:	Harper
Copyright:	October 2007
Printing:	November 2014
ISBN:	0-06-233499-9
Format:	Mass market
Pages:	473

Making Money is the 36th Discworld novel, the second Moist von Lipwig book, and a direct sequel to Going Postal. You could start the series with Going Postal, but I would not start here. The post office is running like a well-oiled machine, Adora Belle is out of town, and Moist von Lipwig is getting bored. It's the sort of boredom that has him picking his own locks, taking up Extreme Sneezing, and climbing buildings at night. He may not realize it, but he needs something more dangerous to do. Vetinari has just the thing. The Royal Bank of Ankh-Morpork, unlike the post office before Moist got to it, is still working. It is a stolid, boring institution doing stolid, boring things for rich people. It is also the battleground for the Lavish family past-time: suing each other and fighting over money. The Lavishes are old money, the kind of money carefully entangled in trusts and investments designed to ensure the family will always have money regardless of how stupid their children are. Control of the bank is temporarily in the grasp of Joshua Lavish's widow Topsy, who is not a true Lavish, but the vultures are circling. Meanwhile, Vetinari has grand city infrastructure plans, and to carry them out he needs financing. That means he needs a functional bank, and preferably one that is much less conservative. Moist is dubious about running a bank, and even more reluctant when Topsy Lavish sees him for exactly the con artist he is. His hand is forced when she dies, and Moist discovers he has inherited her dog, Mr. Fusspot. A dog that now owns 51% of the Royal Bank and therefore is the chairman of the bank's board of directors. A dog whose safety is tied to Moist's own by way of an expensive assassination contract. Pratchett knew he had a good story with Going Postal, so here he runs the same formula again. And yes, I was happy to read it again. Moist knows very little about banking but quite a lot about pretending something will work until it does, which has more to do with banking than it does with running a post office. The bank employs an expert, Mr. Bent, who is fanatically devoted to the gold standard and the correctness of the books and has very little patience for Moist. There are golem-related hijinks. The best part of this book is Vetinari, who is masterfully manipulating everyone in the story and who gets in some great lines about politics.

"We are not going to have another wretched empire while I am Patrician. We've only just got over the last one."

Also, Vetinari processing dead letters in the post office was an absolute delight. Making Money does have the recurring Pratchett problem of having a fairly thin plot surrounded by random... stuff. Moist's attempts to reform the city currency while staying ahead of the Lavishes is only vaguely related to Mr. Bent's plot arc. The golems are unrelated to the rest of the plot other than providing a convenient deus ex machina. There is an economist making water models in the bank basement with an Igor, which is a great gag but has essentially nothing to do with the rest of the book. One of the golems has been subjected to well-meaning older ladies and 1950s etiquette manuals, which I thought was considerably less funny (and somewhat creepier) than Pratchett did. There are (sigh) clowns, which continue to be my least favorite Ankh-Morpork world-building element. At least the dog was considerably less annoying than I was afraid it was going to be. This grab-bag randomness is a shame, since I think there was room here for a more substantial plot that engaged fully with the high weirdness of finance. Unfortunately, this was a bit like the post office in Going Postal: Pratchett dives into the subject just enough to make a few wry observations and a few funny quips, and then resolves the deeper issues off-camera. Moist tries to invent fiat currency, because of course he does, and Pratchett almost takes on the gold standard, only to veer away at the last minute into vigorous hand-waving. I suspect part of the problem is that I know a little bit too much about finance, so I kept expecting Pratchett to take the humorous social commentary a couple of levels deeper. On a similar note, the villains have great potential that Pratchett undermines by adding too much over-the-top weirdness. I wish Cosmo Lavish had been closer to what he appears to be at the start of the book: a very wealthy and vindictive man (and a reference to Cosimo de Medici) who doesn't have Moist's ability to come up with wildly risky gambits but who knows considerably more than he does about how banking works. Instead, Pratchett gives him a weird obsession that slowly makes him less sinister and more pathetic, which robs the book of a competent antagonist for Moist. The net result is still a fun book, and a solid Discworld entry, but it lacks the core of the best series entries. It felt more like a skit comedy show than a novel, but it's an excellent skit comedy show with the normal assortment of memorable Pratchettisms. Certainly if you've read this far, or even if you've only read Going Postal, you'll want to read Making Money as well. Followed by Unseen Academicals. The next Moist von Lipwig book is Raising Steam. Rating: 8 out of 10

Review: The Library of Broken Worlds, by Alaya Dawn Johnson

Publisher:	Scholastic Press
Copyright:	June 2023
ISBN:	1-338-29064-9
Format:	Kindle
Pages:	446

The Library of Broken Worlds is a young-adult far-future science fantasy. So far as I can tell, it's stand-alone, although more on that later in the review. Freida is the adopted daughter of Nadi, the Head Librarian, and her greatest wish is to become a librarian herself. When the book opens, she's a teenager in highly competitive training. Freida is low-wetware, without the advanced and expensive enhancements of many of the other students competing for rare and prized librarian positions, which she makes up for by being the most audacious. She doesn't need wetware to commune with the library material gods. If one ventures deep into their tunnels and consumes their crystals, direct physical communion is possible. The library tunnels are Freida's second home, in part because that's where she was born. She was created by the Library, and specifically by Iemaja, the youngest of the material gods. Precisely why is a mystery. To Nadi, Freida is her daughter. To Quinn, Nadi's main political rival within the library, Freida is a thing, a piece of the library, a secondary and possibly rogue AI. A disruptive annoyance. The Library of Broken Worlds is the sort of science fiction where figuring out what is going on is an integral part of the reading experience. It opens with a frame story of an unnamed girl (clearly Freida) waking the god Nameren and identifying herself as designed for deicide. She provokes Nameren's curiosity and offers an Arabian Nights bargain: if he wants to hear her story, he has to refrain from killing her for long enough for her to tell it. As one might expect, the main narrative doesn't catch up to the frame story until the very end of the book. The Library is indeed some type of library that librarians can search for knowledge that isn't available from more mundane sources, but Freida's personal experience of it is almost wholly religious and oracular. The library's material gods are identified as AIs, but good luck making sense of the story through a science fiction frame, even with a healthy allowance for sufficiently advanced technology being indistinguishable from magic. The symbolism and tone is entirely fantasy, and late in the book it becomes clear that whatever the material gods are, they're not simple technological AIs in the vein of, say, Banks's Ship Minds. Also, the Library is not solely a repository of knowledge. It is the keeper of an interstellar peace. The Library was founded after the Great War, to prevent a recurrence. It functions as a sort of legal system and grand tribunal in ways that are never fully explained. As you might expect, that peace is based more on stability than fairness. Five of the players in this far future of humanity are the Awilu, the most advanced society and the first to leave Earth (or Tierra as it's called here); the Mah m, who possess the material war god Nameren of the frame story; the Lunars and Martians, who dominate the Sol system; and the surviving Tierrans, residents of a polluted and struggling planet that is ruthlessly exploited by the Lunars. The problem facing Freida and her friends at the start of the book is a petition brought by a young Tierran against Lunar exploitation of his homeland. His name is Joshua, and Freida is more than half in love with him. Joshua's legal argument involves interpretation of the freedom node of the treaty that ended the Great War, a node that precedent says gives the Lunars the freedom to exploit Tierra, but which Joshua claims has a still-valid originalist meaning granting Tierrans freedom from exploitation. There is, in short, a lot going on in this book, and "never fully explained" is something of a theme. Freida is telling a story to Nameren and only explains things Nameren may not already know. The reader has to puzzle out the rest from the occasional hint. This is made more difficult by the tendency of the material gods to communicate only in visions or guided hallucinations, full of symbolism that the characters only partly explain to the reader. Nonetheless, this did mostly work, at least for me. I started this book very confused, but by about the midpoint it felt like the background was coming together. I'm still not sure I understand the aurochs, baobab, and cicada symbolism that's so central to the framing story, but it's the pleasant sort of stretchy confusion that gives my brain a good workout. I wish Johnson had explained a few more things plainly, particularly near the end of the book, but my remaining level of confusion was within my tolerances. Unfortunately, the ending did not work for me. The first time I read it, I had no idea what it meant. Lots of baffling, symbolic things happened and then the book just stopped. After re-reading the last 10%, I think all the pieces of an ending and a bit of an explanation are there, but it's absurdly abbreviated. This is another book where the author appears to have been finished with the story before I was. This keeps happening to me, so this probably says something more about me than it says about books, but I want books to have an ending. If the characters have fought and suffered through the plot, I want them to have some space to be happy and to see how their sacrifices play out, with more detail than just a few vague promises. If much of the book has been puzzling out the nature of the world, I would like some concrete confirmation of at least some of my guesswork. And if you're going to end the book on radical transformation, I want to see the results of that transformation. Johnson does an excellent job showing how brutal the peace of the powerful can be, and is willing to light more things on fire over the course of this book than most authors would, but then doesn't offer the reader much in the way of payoff. For once, I wish this stand-alone turned out to be a series. I think an additional book could be written in the aftermath of this ending, and I would definitely read that novel. Johnson has me caring deeply about these characters and fascinated by the world background, and I'd happily spend another 450 pages finding out what happens next. But, frustratingly, I think this ending was indeed intended to wrap up the story. I think this book may fall between a few stools. Science fiction readers who want mysterious future worlds to be explained by the end of the book are going to be frustrated by the amount of symbolism, allusion, and poetic description. Literary fantasy readers, who have a higher tolerance for that style, are going to wish for more focused and polished writing. A lot of the story is firmly YA: trying and failing to fit in, developing one's identity, coming into power, relationship drama, great betrayals and regrets, overcoming trauma and abuse, and unraveling lies that adults tell you. But this is definitely not a straight-forward YA plot or world background. It demands a lot from the reader, and while I am confident many teenage readers would rise to that challenge, it seems like an awkward fit for the YA marketing category. About 75% of the way in, I would have told you this book was great and you should read it. The ending was a let-down and I'm still grumpy about it. I still think it's worth your attention if you're in the mood for a sink-or-swim type of reading experience. Just be warned that when the ride ends, I felt unceremoniously dumped on the pavement. Content warnings: Rape, torture, genocide. Rating: 7 out of 10

Having had success running Trisquel on the ppc64 Talos II, I felt ready to get an arm64 machine running Trisquel. I have a Ampere Altra Developer Platform from ADLINK, which is a fairly powerful desktop machine. While there were some issues during installation, I m happy to say the machine is stable and everything appears to work fine.

ISO images for non-amd64 platforms are unfortunately still hidden from the main Trisquel download area, so you will have to use the following procedure to download and extract a netinst ISO image (using debian-installer) and write it to a USB memory device. Another unfortunate problem is that there are no OpenPGP signatures or hash checksums, but below I publish one checksum.

wget -q http://builds.trisquel.org/debian-installer-images/debian-installer-images_20210731+deb11u9+11.0trisquel15_arm64.tar.gz
tar xfa debian-installer-images_20210731+deb11u9+11.0trisquel15_arm64.tar.gz ./installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso
echo '311732519cc8c7c1bb2fe873f134fdafb211ef3bcb5b0d2ecdc6ea4e3b336357  installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso'   sha256sum -c
sudo wipefs -a /dev/sdX
sudo dd if=installer-arm64/20210731+deb11u9+11/images/netboot/mini.iso of=/dev/sdX conv=sync status=progress

Insert the USB stick in a USB slot in the machine, and power up. Press ESCAPE at the BIOS prompt and select the USB device as the boot device. The first problem that hit me was that translations didn t work, I selected Swedish but the strings were garbled. Rebooting and selecting the default English worked fine. For installation, you need Internet connectivity and I use the RJ45 port closest to VGA/serial which is available as enP5p1s0 in the installer. I wouldn t connect the BMC RJ45 port to anything unless you understand the security implications. During installation you have to create a EFI partition for booting, and I ended up with one 1GB EFI partition, one 512GB ext4 partition for / with discard/noatime options, and a 32GB swap partition. The installer did not know about any Trisquel mirrors, but only had the default archive.trisquel.org, so if you need to use a mirror, take a note of the necessary details. The installation asks me about which kernel to install, and I went with the default linux-generic which results in a 5.15 linux-libre kernel. At the end of installation, unfortunately grub failed with a mysterious error message: Unable to install GRUB in dummy. Executing 'grub-install dummy' failed. On another console there is a better error message: failed to register the EFI boot entry. There are some references to file descriptor issues. Perhaps I partitioned the disk in a bad way, or this is a real bug in the installer for this platform. I continued installation, and it appears the installer was able to write GRUB to the device, but not add the right boot menu. So I was able to finish the installation properly, and then reboot and manually type the following GRUB commands: linux (hd0,gpt2)/boot/vmlinuz initrd (hd0,gpt2)/boot/initrd.img boot. Use the GRUB ls command to find the right device. See images below for more information.

Booting and installing GRUB again manually works fine:

root@ampel:~# update-grub
Sourcing file  /etc/default/grub'
Sourcing file  /etc/default/grub.d/background.cfg'
Sourcing file  /etc/default/grub.d/init-select.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.15.0-91-generic
Found initrd image: /boot/initrd.img-5.15.0-91-generic
Found linux image: /boot/vmlinuz-5.15.0-58-generic
Found initrd image: /boot/initrd.img-5.15.0-58-generic
Warning: os-prober will not be executed to detect other bootable partitions.
Systems on them will not be added to the GRUB boot configuration.
Check GRUB_DISABLE_OS_PROBER documentation entry.
Adding boot menu entry for UEFI Firmware Settings ...
done
root@ampel:~# 

During installation I tend to avoid selecting any tasksel components, in part because it didn t use a local mirror to gain network speed, and in part because I don t want to generate OpenSSH keys in a possibly outdated environment that is harder to audit and reproducible rebuild than the finally installed system. When I selected the OpenSSH and GNOME tasksel, I get an error, but fortunately using apt get directly is simple.

root@ampel:~# tasksel
Tasksel GNOME failed:
tasksel: apt-get failed (100)
root@ampel:~# apt-get install trisquel-gnome ssh

Graphics in GNOME was slow using the built-in ASPEED AST2500 VGA controller with linux-libre 5.15. There are kernels labeled 64k but I haven t tested them, and I m not sure they would bring any significant advantage. I simply upgraded to a more recent linux-libre 6.2 kernel via the linux-image-generic-hwe-11.0 virtual package. After a reboot, graphics in GNOME is usable.

root@ampel:~# apt-get install linux-image-generic-hwe-11.0

There seems to be some issue with power-saving inside GNOME, since the machine becomes unresponsive after 20 minutes, and I m unable to make it resume via keyboard or power button. Disabling the inactivity power setting in GNOME works fine to resolve this. I will now put this machine to some more heavy use and see how it handles it. I hope to find more suitable arm64-based servers to complement my ppc64el-based servers in the future, as this ADLINK Ampere Altra Developer Platform with liquid-cooling is more of a toy than a serious server for use in a datacentre. Happy Trisquel-on-arm64 Hacking!

What is DNS-over-TLS and DNS-over-HTTPS Subverting private DNS for ad blocking Other uses for AdGuard DNS Going further Epilogue

Recently I noticed a new tool called licenserecon written by Peter Blackman, and I helped get licenserecon into Debian. The purpose of licenserecon is to reconcile licenses from debian/copyright against the output from licensecheck, a tool written by Jonas Smedegaard. It assumes DEP5 copyright files. You run the tool in a directory that has a debian/ sub-directory, and its output when it notices mismatches (this is for resolv-wrapper):

# sudo apt install licenserecon
jas@kaka:~/dpkg/resolv-wrapper$ lrc
Parsing Source Tree ....
Running licensecheck ....
d/copyright       licensecheck
BSD-3-Clauses     BSD-3-clause     src/resolv_wrapper.c
BSD-3-Clauses     BSD-3-clause     tests/dns_srv.c
BSD-3-Clauses     BSD-3-clause     tests/test_dns_fake.c
BSD-3-Clauses     BSD-3-clause     tests/test_res_query_search.c
BSD-3-Clauses     BSD-3-clause     tests/torture.c
BSD-3-Clauses     BSD-3-clause     tests/torture.h
jas@kaka:~/dpkg/resolv-wrapper$ 

Noticing one-character typos like this may not bring satisfaction except to the most obsessive-compulsive among us, however the tool has the potential of discovering more serious mistakes. Using it manually once in a while may be useful, however I tend to forget QA steps that are not automated. Could we add this to the Salsa CI/CD pipeline? I recently proposed a merge request to add a wrap-and-sort job to the Salsa CI/CD pipeline (disabled by default) and learned how easy it was to extend it. I think licenserecon is still a bit rough on the edges, and I haven t been able to successfully use it on any but the simplest packages yet. I wouldn t want to suggest it is added to the normal Salsa CI/CD pipeline, even if disabled. If you maintain a Debian package on Salsa and wish to add a licenserecon job to your pipeline, I wrote licenserecon.yml for you. The simplest way to use licenserecon.yml is to replace recipes/debian.yml@salsa-ci-team/pipeline as the Salsa CI/CD configuration file setting with debian/salsa-ci.yml@debian/licenserecon. If you use a debian/salsa-ci.yml file you may put something like this in it instead:

---
include:
  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/recipes/debian.yml
  - https://salsa.debian.org/debian/licenserecon/raw/main/debian/licenserecon.yml

Once you trigger the pipeline, this will result in a new job licenserecon that validates debian/copyright against licensecheck output on every build! I have added this to the libcpucycles package on Salsa and the pipeline contains a new job licenserecon whose output currently ends with:

$ cd $ WORKING_DIR /$ SOURCE_DIR 
$ lrc
Parsing Source Tree ....
Running licensecheck ....
No differences found
Cleaning up project directory and file based variables

If upstream releases a new version with files not matching our debian/copyright file, we will detect that on the next Salsa build job rather than months later when somebody happens to run the tools manually or there is some license conflict. Incidentally licenserecon is written in Pascal which brought back old memories with Turbo Pascal back in the MS-DOS days. Thanks Peter for licenserecon, and Jonas for licensecheck making this possible!

Last week marked a major milestone for me: the AMD driver-specific color management properties reached the upstream linux-next! And to celebrate, I m happy to share the slides notes from my 2023 XDC talk, The Rainbow Treasure Map along with the individual recording that just dropped last week on youtube talk about happy coincidences!

Steam Deck Rainbow: Treasure Map & Magic Frogs While I may be bubbly and chatty in everyday life, the stage isn t exactly my comfort zone (hallway talks are more my speed). But the journey of developing the AMD color management properties was so full of discoveries that I simply had to share the experience. Witnessing the fantastic work of Jeremy and Joshua bring it all to life on the Steam Deck OLED was like uncovering magical ingredients and whipping up something truly enchanting. For XDC 2023, we split our Rainbow journey into two talks. My focus, The Rainbow Treasure Map, explored the new color features we added to the Linux kernel driver, diving deep into the hardware capabilities of AMD/Steam Deck. Joshua then followed with The Rainbow Frogs and showed the breathtaking color magic released on Gamescope thanks to the power unlocked by the kernel driver s Steam Deck color properties.

Packing a Rainbow into 15 Minutes I had so much to tell, but a half-slot talk meant crafting a concise presentation. To squeeze everything into 15 minutes (and calm my pre-talk jitters a bit!), I drafted and practiced those slides and notes countless times. So grab your map, and let s embark on the Rainbow journey together! Intro: Hi, I m Melissa from Igalia and welcome to the Rainbow Treasure Map, a talk about advanced color management on Linux with AMD/SteamDeck. Useful links: First of all, if you are not used to the topic, you may find these links useful.

1. XDC 2022 - I m not an AMD expert, but - Melissa Wen
2. XDC 2022 - Is HDR Harder? - Harry Wentland
3. XDC 2022 Lightning - HDR Workshop Summary - Harry Wentland
4. Color management and HDR documentation for FOSS graphics - Pekka Paalanen et al.
5. Cinematic Color - 2012 SIGGRAPH course notes - Jeremy Selan
6. AMD Driver-specific Properties for Color Management on Linux (Part 1) - Melissa Wen

Context: When we talk about colors in the graphics chain, we should keep in mind that we have a wide variety of source content colorimetry, a variety of output display devices and also the internal processing. Users expect consistent color reproduction across all these devices. The userspace can use GPU-accelerated color management to get it. But this also requires an interface with display kernel drivers that is currently missing from the DRM/KMS framework. Since April, I ve been bothering the DRM community by sending patchsets from the work of me and Joshua to add driver-specific color properties to the AMD display driver. In parallel, discussions on defining a generic color management interface are still ongoing in the community. Moreover, we are still not clear about the diversity of color capabilities among hardware vendors. To bridge this gap, we defined a color pipeline for Gamescope that fits the latest versions of AMD hardware. It delivers advanced color management features for gamut mapping, HDR rendering, SDR on HDR, and HDR on SDR. AMD/Steam Deck hardware: AMD frequently releases new GPU and APU generations. Each generation comes with a DCN version with display hardware improvements. Therefore, keep in mind that this work uses the AMD Steam Deck hardware and its kernel driver. The Steam Deck is an APU with a DCN3.01 display driver, a DCN3 family. It s important to have this information since newer AMD DCN drivers inherit implementations from previous families but aldo each generation of AMD hardware may introduce new color capabilities. Therefore I recommend you to familiarize yourself with the hardware you are working on. The AMD display driver in the kernel space: It consists of three layers, (1) the DRM/KMS framework, (2) the AMD Display Manager, and (3) the AMD Display Core. We extended the color interface exposed to userspace by leveraging existing DRM resources and connecting them using driver-specific functions for color property management. Bridging DC color capabilities and the DRM API required significant changes in the color management of AMD Display Manager - the Linux-dependent part that connects the AMD DC interface to the DRM/KMS framework. The AMD DC is the OS-agnostic layer. Its code is shared between platforms and DCN versions. Examining this part helps us understand the AMD color pipeline and hardware capabilities, since the machinery for hardware settings and resource management are already there. The newest architecture for AMD display hardware is the AMD Display Core Next. In this architecture, two blocks have the capability to manage colors:

• Display Pipe and Plane (DPP) - for pre-blending adjustments;
• Multiple Pipe/Plane Combined (MPC) - for post-blending color transformations.

Let s see what we have in the DRM API for pre-blending color management. DRM plane color properties: This is the DRM color management API before blending. Nothing! Except two basic DRM plane properties: color_encoding and color_range for the input colorspace conversion, that is not covered by this work. In case you re not familiar with AMD shared code, what we need to do is basically draw a map and navigate there! We have some DRM color properties after blending, but nothing before blending yet. But much of the hardware programming was already implemented in the AMD DC layer, thanks to the shared code. Still both the DRM interface and its connection to the shared code were missing. That s when the search begins! AMD driver-specific color pipeline: Looking at the color capabilities of the hardware, we arrive at this initial set of properties. The path wasn t exactly like that. We had many iterations and discoveries until reached to this pipeline. The Plane Degamma is our first driver-specific property before blending. It s used to linearize the color space from encoded values to light linear values. We can use a pre-defined transfer function or a user lookup table (in short, LUT) to linearize the color space. Pre-defined transfer functions for plane degamma are hardcoded curves that go to a specific hardware block called DPP Degamma ROM. It supports the following transfer functions: sRGB EOTF, BT.709 inverse OETF, PQ EOTF, and pure power curves Gamma 2.2, Gamma 2.4 and Gamma 2.6. We also have a one-dimensional LUT. This 1D LUT has four thousand ninety six (4096) entries, the usual 1D LUT size in the DRM/KMS. It s an array of drm_color_lut that goes to the DPP Gamma Correction block. We also have now a color transformation matrix (CTM) for color space conversion. It s a 3x4 matrix of fixed points that goes to the DPP Gamut Remap Block. Both pre- and post-blending matrices were previously gone to the same color block. We worked on detaching them to clear both paths. Now each CTM goes on its own way. Next, the HDR Multiplier. HDR Multiplier is a factor applied to the color values of an image to increase their overall brightness. This is useful for converting images from a standard dynamic range (SDR) to a high dynamic range (HDR). As it can range beyond [0.0, 1.0] subsequent transforms need to use the PQ(HDR) transfer functions. And we need a 3D LUT. But 3D LUT has a limited number of entries in each dimension, so we want to use it in a colorspace that is optimized for human vision. It means in a non-linear space. To deliver it, userspace may need one 1D LUT before 3D LUT to delinearize content and another one after to linearize content again for blending. The pre-3D-LUT curve is called Shaper curve. Unlike Degamma TF, there are no hardcoded curves for shaper TF, but we can use the AMD color module in the driver to build the following shaper curves from pre-defined coefficients. The color module combines the TF and the user LUT values into the LUT that goes to the DPP Shaper RAM block. Finally, our rockstar, the 3D LUT. 3D LUT is perfect for complex color transformations and adjustments between color channels. 3D LUT is also more complex to manage and requires more computational resources, as a consequence, its number of entries is usually limited. To overcome this restriction, the array contains samples from the approximated function and values between samples are estimated by tetrahedral interpolation. AMD supports 17 and 9 as the size of a single-dimension. Blue is the outermost dimension, red the innermost. As mentioned, we need a post-3D-LUT curve to linearize the color space before blending. This is done by Blend TF and LUT. Similar to shaper TF, there are no hardcoded curves for Blend TF. The pre-defined curves are the same as the Degamma block, but calculated by the color module. The resulting LUT goes to the DPP Blend RAM block. Now we have everything connected before blending. As a conflict between plane and CRTC Degamma was inevitable, our approach doesn t accept that both are set at the same time. We also optimized the conversion of the framebuffer to wire encoding by adding support to pre-defined CRTC Gamma TF. Again, there are no hardcoded curves and TF and LUT are combined by the AMD color module. The same types of shaper curves are supported. The resulting LUT goes to the MPC Gamma RAM block. Finally, we arrived in the final version of DRM/AMD driver-specific color management pipeline. With this knowledge, you re ready to better enjoy the rainbow treasure of AMD display hardware and the world of graphics computing. With this work, Gamescope/Steam Deck embraces the color capabilities of the AMD GPU. We highlight here how we map the Gamescope color pipeline to each AMD color block. Future works: The search for the rainbow treasure is not over! The Linux DRM subsystem contains many hidden treasures from different vendors. We want more complex color transformations and adjustments available on Linux. We also want to expose all GPU color capabilities from all hardware vendors to the Linux userspace. Thanks Joshua and Harry for this joint work and the Linux DRI community for all feedback and reviews. The amazing part of this work comes in the next talk with Joshua and The Rainbow Frogs! Any questions?

---

References:

1. Slides of the talk The Rainbow Treasure Map.
2. Youtube video of the talk The Rainbow Treasure Map.
3. Patch series for AMD driver-specific color management properties (upstream Linux 6.8v).
4. SteamDeck/Gamescope color management pipeline
5. XDC 2023 website.
6. Igalia website.

My earlier work on Streamlined NTRU Prime has been progressing along. The IETF document on sntrup761 in SSH has passed several process points. GnuPG s libgcrypt has added support for sntrup761. The libssh support for sntrup761 is working, but the merge request is stuck mostly due to lack of time to debug why the regression test suite sporadically errors out in non-sntrup761 related parts with the patch. The foundation for lattice-based post-quantum algorithms has some uncertainty around it, and I have felt that there is more to the post-quantum story than adding sntrup761 to implementations. Classic McEliece has been mentioned to me a couple of times, and I took some time to learn it and did a cut n paste job of the proposed ISO standard and published draft-josefsson-mceliece in the IETF to make the algorithm easily available to the IETF community. A high-quality implementation of Classic McEliece has been published as libmceliece and I ve been supporting the work of Jan Moj to package libmceliece for Debian, alas it has been stuck in the ftp-master NEW queue for manual review for over two months. The pre-dependencies librandombytes and libcpucycles are available in Debian already. All that text writing and packaging work set the scene to write some code. When I added support for sntrup761 in libssh, I became familiar with the OpenSSH code base, so it was natural to return to OpenSSH to experiment with a new SSH KEX for Classic McEliece. DJB suggested to pick mceliece6688128 and combine it with the existing X25519+sntrup761 or with plain X25519. While a three-algorithm hybrid between X25519, sntrup761 and mceliece6688128 would be a simple drop-in for those that don t want to lose the benefits offered by sntrup761, I decided to start the journey on a pure combination of X25519 with mceliece6688128. The key combiner in sntrup761x25519 is a simple SHA512 call and the only good I can say about that is that it is simple to describe and implement, and doesn t raise too many questions since it is already deployed. After procrastinating coding for months, once I sat down to work it only took a couple of hours until I had a successful Classic McEliece SSH connection. I suppose my brain had sorted everything in background before I started. To reproduce it, please try the following in a Debian testing environment (I use podman to get a clean environment).

# podman run -it --rm debian:testing-slim
apt update
apt dist-upgrade -y
apt install -y wget python3 librandombytes-dev libcpucycles-dev gcc make git autoconf libz-dev libssl-dev
cd ~
wget -q -O- https://lib.mceliece.org/libmceliece-20230612.tar.gz   tar xfz -
cd libmceliece-20230612/
./configure
make install
ldconfig
cd ..
git clone https://gitlab.com/jas/openssh-portable
cd openssh-portable
git checkout jas/mceliece
autoreconf
./configure # verify 'libmceliece support: yes'
make # CC="cc -DDEBUG_KEX=1 -DDEBUG_KEXDH=1 -DDEBUG_KEXECDH=1"

You should now have a working SSH client and server that supports Classic McEliece! Verify support by running ./ssh -Q kex and it should mention mceliece6688128x25519-sha512@openssh.com. To have it print plenty of debug outputs, you may remove the # character on the final line, but don t use such a build in production. You can test it as follows:

./ssh-keygen -A # writes to /usr/local/etc/ssh_host_...
# setup public-key based login by running the following:
./ssh-keygen -t rsa -f ~/.ssh/id_rsa -P ""
cat ~/.ssh/id_rsa.pub > ~/.ssh/authorized_keys
adduser --system sshd
mkdir /var/empty
while true; do $PWD/sshd -p 2222 -f /dev/null; done &
./ssh -v -p 2222 localhost -oKexAlgorithms=mceliece6688128x25519-sha512@openssh.com date

On the client you should see output like this:

OpenSSH_9.5p1, OpenSSL 3.0.11 19 Sep 2023
...
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: mceliece6688128x25519-sha512@openssh.com
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:YognhWY7+399J+/V8eAQWmM3UFDLT0dkmoj3pIJ0zXs
...
debug1: Host '[localhost]:2222' is known and matches the ED25519 host key.
debug1: Found key in /root/.ssh/known_hosts:1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
...
debug1: Sending command: date
debug1: pledge: fork
debug1: permanently_set_uid: 0/0
Environment:
  USER=root
  LOGNAME=root
  HOME=/root
  PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin
  MAIL=/var/mail/root
  SHELL=/bin/bash
  SSH_CLIENT=::1 46894 2222
  SSH_CONNECTION=::1 46894 ::1 2222
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_channel_req: channel 0 rtype eow@openssh.com reply 0
Sat Dec  9 22:22:40 UTC 2023
debug1: channel 0: free: client-session, nchannels 1
Transferred: sent 1048044, received 3500 bytes, in 0.0 seconds
Bytes per second: sent 23388935.4, received 78108.6
debug1: Exit status 0

Notice the kex: algorithm: mceliece6688128x25519-sha512@openssh.com output. How about network bandwidth usage? Below is a comparison of a complete SSH client connection such as the one above that log in and print date and logs out. Plain X25519 is around 7kb, X25519 with sntrup761 is around 9kb, and mceliece6688128 with X25519 is around 1MB. Yes, Classic McEliece has large keys, but for many environments, 1MB of data for the session establishment will barely be noticeable.

./ssh -v -p 2222 localhost -oKexAlgorithms=curve25519-sha256 date 2>&1   grep ^Transferred
Transferred: sent 3028, received 3612 bytes, in 0.0 seconds
./ssh -v -p 2222 localhost -oKexAlgorithms=sntrup761x25519-sha512@openssh.com date 2>&1   grep ^Transferred
Transferred: sent 4212, received 4596 bytes, in 0.0 seconds
./ssh -v -p 2222 localhost -oKexAlgorithms=mceliece6688128x25519-sha512@openssh.com date 2>&1   grep ^Transferred
Transferred: sent 1048044, received 3764 bytes, in 0.0 seconds

So how about session establishment time?

date; i=0; while test $i -le 100; do ./ssh -v -p 2222 localhost -oKexAlgorithms=curve25519-sha256 date > /dev/null 2>&1; i= expr $i + 1 ; done; date
Sat Dec  9 22:39:19 UTC 2023
Sat Dec  9 22:39:25 UTC 2023
# 6 seconds
date; i=0; while test $i -le 100; do ./ssh -v -p 2222 localhost -oKexAlgorithms=sntrup761x25519-sha512@openssh.com date > /dev/null 2>&1; i= expr $i + 1 ; done; date
Sat Dec  9 22:39:29 UTC 2023
Sat Dec  9 22:39:38 UTC 2023
# 9 seconds
date; i=0; while test $i -le 100; do ./ssh -v -p 2222 localhost -oKexAlgorithms=mceliece6688128x25519-sha512@openssh.com date > /dev/null 2>&1; i= expr $i + 1 ; done; date
Sat Dec  9 22:39:55 UTC 2023
Sat Dec  9 22:40:07 UTC 2023
# 12 seconds

I never noticed adding sntrup761, so I m pretty sure I wouldn t notice this increase either. This is all running on my laptop that runs Trisquel so take it with a grain of salt but at least the magnitude is clear. Future work items include:

• Use a better hybrid mode combiner than SHA512? See for example KEM Combiners.
• Write IETF document describing the Classic McEliece SSH protocol
• Submit my patch to the OpenSSH community for discussion and feedback, please review meanwhile!
• Implement a mceliece6688128sntrup761x25519 multi-hybrid mode?
• Write a shell script a la sntrup761.sh to import a stripped-down mceliece6688128 implementation to avoid having OpenSSH depend on libmceliece?
• My kexmceliece6688128x25519.c is really just kexsntrup761x25519.c with the three calls to sntrup761 replaced with mceliece6688128. This should be parametrized to avoid cut n paste of code, if the OpenSSH community is interested.
• Consider if the behaviour of librandombytes related to closing of file descriptors is relevant to OpenSSH.

Happy post-quantum SSH ing! Update: Changing the mceliece6688128_keypair call to mceliece6688128f_keypair (i.e., using the fully compatible f-variant) results in McEliece being just as fast as sntrup761 on my machine. Update 2023-12-26: An initial IETF document draft-josefsson-ssh-mceliece-00 published.

I haven't done one of these in quite a while, long enough that I've already read and reviewed many of these books. John Joseph Adams (ed.) The Far Reaches (sff anthology)
Poul Anderson The Shield of Time (sff)
Catherine Asaro The Phoenix Code (sff)
Catherine Asaro The Veiled Web (sff)
Travis Baldree Bookshops & Bonedust (sff)
Sue Burke Semiosis (sff)
Jacqueline Carey Cassiel's Servant (sff)
Rob Copeland The Fund (nonfiction)
Mar Delaney Wolf Country (sff)
J.S. Dewes The Last Watch (sff)
J.S. Dewes The Exiled Fleet (sff)
Mike Duncan Hero of Two Worlds (nonfiction)
Mike Duncan The Storm Before the Storm (nonfiction)
Kate Elliott King's Dragon (sff)
Zeke Faux Number Go Up (nonfiction)
Nicola Griffith Menewood (sff)
S.L. Huang The Water Outlaws (sff)
Alaya Dawn Johnson The Library of Broken Worlds (sff)
T. Kingfisher Thornhedge (sff)
Naomi Kritzer Liberty's Daughter (sff)
Ann Leckie Translation State (sff)
Michael Lewis Going Infinite (nonfiction)
Jenna Moran Magical Bears in the Context of Contemporary Political Theory (sff collection)
Ari North Love and Gravity (graphic novel)
Ciel Pierlot Bluebird (sff)
Terry Pratchett A Hat Full of Sky (sff)
Terry Pratchett Going Postal (sff)
Terry Pratchett Thud! (sff)
Terry Pratchett Wintersmith (sff)
Terry Pratchett Making Money (sff)
Terry Pratchett Unseen Academicals (sff)
Terry Pratchett I Shall Wear Midnight (sff)
Terry Pratchett Snuff (sff)
Terry Pratchett Raising Steam (sff)
Terry Pratchett The Shepherd's Crown (sff)
Aaron A. Reed 50 Years of Text Games (nonfiction)
Dashka Slater Accountable (nonfiction)
Rory Stewart The Marches (nonfiction)
Emily Tesh Silver in the Wood (sff)
Emily Tesh Drowned Country (sff)
Valerie Vales Chilling Effect (sff)
Martha Wells System Collapse (sff)
Martha Wells Witch King (sff)

While the winter sets in, I have been mostly busy following up on job leads and applying to anything and everything. Something has to stick I am trying! Even out of industry. Debian: This weeks main focus was getting involved and familiar with Debian rust-packaging. It is really quite different from other teams! I was successful and the MR is https://salsa.debian.org/rust-team/debcargo-conf/-/merge_requests/566 if anyone on the rust team can take a gander, I will upload when merged. I will get a few more under my belt next week now that I understand the process. KDE neon: Unfortunately, I did not have much time for neon, but I did get some red builds fixed and started uploading the new signing key for mauikit* applications. KDE snaps: A big thank you to Josh and Albert for merging all my MR s and I have finished 23.08.3 releases to stable. I released a new Krita 5.2.1 with some runtime fixes, please update. Still no source of income so I must ask, if you have any spare change, please consider a donation. Thank you, Scarlett https://gofund.me/b74e4c6f

I hacked my coffee machine to let me turn it on from upstairs in bed :-). Read on for explanation, circuit diagrams, 3D models, firmware source code, and pictures.

• Background: the Morphy Richards filter coffee machine
• Planning
• Inside the Morphy Richards filter coffee machine
• Unexpected electrical hazard
• Design approach
• Implementation - hardware
• Implementation - software
• Results
• Epilogue
• Bonus pictures

Background: the Morphy Richards filter coffee machine I have a Morphy Richards filter coffee machine. It makes very good coffee. But the display and firmware are quite annoying:

• After it has finished making the coffee, it will keep the coffee warm using its hotplate, but only for 25 minutes. If you want to make a batch and drink it over the course of the morning that s far too short.
• It has a timer function. But it only has a 12 hour clock! You can t retire upstairs on a Friday night, having programmed the coffee machine to make you coffee at a suitable post-lie-in time. If you try, you are greeted with apparently-inexplicably-cold coffee.
• The buttons and UI are very confusing. For example, if it s just sitting there keeping the coffee warm, and you pour the last, you want to turn it off. So you press the power button. Then the display lights up as if you ve just turned it on! (The power LED is in the power button, which your finger is on.) If you know this you can get used to it, but it can confuse guests.

Also, I m lazy and wanted to be able to cause coffee to exist from upstairs in bed, without having to make a special trip down just to turn the machine on. Planning My original feeling was I can t be bothered dealing with the coffee machine innards so I thought I would make a mechanical contraption to physically press the coffee machine s on button. I could have my contraption press the button to turn the machine on (timed, or triggered remotely), and then periodically in pairs to reset the 25-minute keep-warm timer. But a friend pointed me at a blog post by Andy Bradford, where Andy recounts modifying his coffee machine, adding an ESP8266 and connecting it to his MQTT-based Home Assistant setup. I looked at the pictures and they looked very similar to my machine. I decided to take a look inside. Inside the Morphy Richards filter coffee machine My coffee machine seemed to be very similar to Andy s. His disassembly report was very helpful. Inside I found the high-voltage parts with the heating elements, and the front panel with the display and buttons. I spent a while poking about, masuring things, and so on. Unexpected electrical hazard At one point I wanted to use my storage oscilloscope to capture the duration and amplitude of the beep signal. I needed to connect the scope ground to the UI board s ground plane, but then when I switched the coffee machine on at the wall socket, it tripped the house s RCD. It turns out that the low voltage UI board is coupled to the mains. In my setting, there s an offset of about 8V between the UI board ground plane, and true earth. (In my house the neutral is about 2-3V away from true earth.) This alarmed me rather. To me, this means that my modifications needed to still properly electrically isolate everything connected to the UI board from anything external to the coffee machine s housing. In Andy s design, I think the internal UI board ground plane is directly brought out to an external USB-A connector. This means that if there were a neutral fault, the USB-A connector would be at live potential, possibly creating an electrocution or fire hazard. I made a comment in Andy Bradford s blog, reporting this issue, but it doesn t seem to have appeared. This is all quite alarming. I hope Andy is OK! Design approach I don t have an MQTT setup at home, or an installation of Home Assistant. I didn t feel like adding a lot of complicated software to my life, if I could avoid it. Nor did I feel like writing a web UI myself. I ve done that before, but I m lazy and in this case my requirements were quite modest. Also, the need for electrical isolation would further complicate any attempt to do something sophisticated (that could, for example, sense the state of the coffee machine). I already had a Tasmota-based cloud-free smart plug, which controls the fairy lights on our gazebo. We just operate that through its web UI. So, I decided I would add a small and stupid microcontroller. The microcontroller would be powered via a smart plug and an off-the-shelf USB power supply. The microcontroller would have no inputs. It would simply simulate an on button press once at startup, and thereafter two presses every 24 minutes. After the 4th double press the microcontroller would stop, leaving the coffee machine to time out itself, after a total period of about 2h. Implementation - hardware I used a DigiSpark board with an ATTiny85. One of the GPIOs is connected to an optoisolator, whose output transistor is wired across the UI board s on button. (click for diagram scans as pdfs). The DigiSpark has just a USB tongue, which is very wobbly in a normal USB socket. I designed a 3D printed case which also had an approximation of the rest of the USB A plug. The plug is out of spec; our printer won t go fine enough - and anyway, the shield is supposed to be metal, not fragile plastic. But it fit in the USB PSU I was using, satisfactorily if a bit stiffly, and also into the connector for programming via my laptop. Inside the coffee machine, there s the boundary between the original, coupled to mains, UI board, and the isolated low voltage of the microcontroller. I used a reasonably substantial cable to bring out the low voltage connection, past all the other hazardous innards, to make sure it stays isolated. I added a drain power supply resistor on another of the GPIOs. This is enabled, with a draw of about 30mA, when the microcontroller is soon going to off / on cycle the coffee machine. That reduces the risk that the user will turn off the smart plug, and turn off the machine, but that the microcontroller turns the coffee machine back on again using the remaining power from USB PSU. Empirically in my setup it reduces the time from smart plug off to microcontroller stops from about 2-3s to more like 1s. Optoisolator board (inside coffee machine) pictures (Click through for full size images.) Microcontroller board (in USB-plug-ish housing) pictures Implementation - software I originally used the Arduino IDE, writing my program in C. I had a bad time with that and rewrote it in Rust. The firmware is in a repository on Debian s gitlab Results I can now cause the coffee to start, from my phone. It can be programmed more than 12h in advance. And it stays warm until we ve drunk it. UI is worse There s one aspect of the original Morphy Richards machine that I haven t improved: the user interface is still poor. Indeed, it s now even worse: To turn the machine on, you probably want to turn on the smart plug instead. Unhappily, the power button for that is invisible in its installed location. In particular, in the usual case, if you want to turn it off, you should ideally turn off both the smart plug (which can be done with the button on it) and the coffee machine itself. If you forget to turn off the smart plug, the machine can end up being turned on, very briefly, a handful of times, over the next hour or two. Epilogue We had used the new features a handful of times when one morning the coffee machine just wouldn t make coffee. The UI showed it turning on, but it wouldn t get hot, so no coffee. I thought oh no, I ve broken it! But, on investigation, I found that the machine s heating element was open circuit (ie, completely broken). I didn t mess with that part. So, hooray! Not my fault. Probably, just being inverted a number of times and generally lightly jostled, had precipitated a latent fault. The machine was a number of years old. Happily I found a replacement, identical, machine, online. I ve transplanted my modification and now it all works well. Bonus pictures (Click through for full size images.)

edited 2023-11-26 14:59 UTC in an attempt to fix TOC links

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TL;DR: This blog post explores the color capabilities of AMD hardware and how they are exposed to userspace through driver-specific properties. It discusses the different color blocks in the AMD Display Core Next (DCN) pipeline and their capabilities, such as predefined transfer functions, 1D and 3D lookup tables (LUTs), and color transformation matrices (CTMs). It also highlights the differences in AMD HW blocks for pre and post-blending adjustments, and how these differences are reflected in the available driver-specific properties. Overall, this blog post provides a comprehensive overview of the color capabilities of AMD hardware and how they can be controlled by userspace applications through driver-specific properties. This information is valuable for anyone who wants to develop applications that can take advantage of the AMD color management pipeline. Get a closer look at each hardware block s capabilities, unlock a wealth of knowledge about AMD display hardware, and enhance your understanding of graphics and visual computing. Stay tuned for future developments as we embark on a quest for GPU color capabilities in the ever-evolving realm of rainbow treasures.

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Operating Systems can use the power of GPUs to ensure consistent color reproduction across graphics devices. We can use GPU-accelerated color management to manage the diversity of color profiles, do color transformations to convert between High-Dynamic-Range (HDR) and Standard-Dynamic-Range (SDR) content and color enhacements for wide color gamut (WCG). However, to make use of GPU display capabilities, we need an interface between userspace and the kernel display drivers that is currently absent in the Linux/DRM KMS API. In the previous blog post I presented how we are expanding the Linux/DRM color management API to expose specific properties of AMD hardware. Now, I ll guide you to the color features for the Linux/AMD display driver. We embark on a journey through DRM/KMS, AMD Display Manager, and AMD Display Core and delve into the color blocks to uncover the secrets of color manipulation within AMD hardware. Here we ll talk less about the color tools and more about where to find them in the hardware. We resort to driver-specific properties to reach AMD hardware blocks with color capabilities. These blocks display features like predefined transfer functions, color transformation matrices, and 1-dimensional (1D LUT) and 3-dimensional lookup tables (3D LUT). Here, we will understand how these color features are strategically placed into color blocks both before and after blending in Display Pipe and Plane (DPP) and Multiple Pipe/Plane Combined (MPC) blocks. That said, welcome back to the second part of our thrilling journey through AMD s color management realm!

AMD Display Driver in the Linux/DRM Subsystem: The Journey In my 2022 XDC talk I m not an AMD expert, but , I briefly explained the organizational structure of the Linux/AMD display driver where the driver code is bifurcated into a Linux-specific section and a shared-code portion. To reveal AMD s color secrets through the Linux kernel DRM API, our journey led us through these layers of the Linux/AMD display driver s software stack. It includes traversing the DRM/KMS framework, the AMD Display Manager (DM), and the AMD Display Core (DC) [1]. The DRM/KMS framework provides the atomic API for color management through KMS properties represented by struct drm_property. We extended the color management interface exposed to userspace by leveraging existing resources and connecting them with driver-specific functions for managing modeset properties. On the AMD DC layer, the interface with hardware color blocks is established. The AMD DC layer contains OS-agnostic components that are shared across different platforms, making it an invaluable resource. This layer already implements hardware programming and resource management, simplifying the external developer s task. While examining the DC code, we gain insights into the color pipeline and capabilities, even without direct access to specifications. Additionally, AMD developers provide essential support by answering queries and reviewing our work upstream. The primary challenge involved identifying and understanding relevant AMD DC code to configure each color block in the color pipeline. However, the ultimate goal was to bridge the DC color capabilities with the DRM API. For this, we changed the AMD DM, the OS-dependent layer connecting the DC interface to the DRM/KMS framework. We defined and managed driver-specific color properties, facilitated the transport of user space data to the DC, and translated DRM features and settings to the DC interface. Considerations were also made for differences in the color pipeline based on hardware capabilities.

Exploring Color Capabilities of the AMD display hardware Now, let s dive into the exciting realm of AMD color capabilities, where a abundance of techniques and tools await to make your colors look extraordinary across diverse devices. First, we need to know a little about the color transformation and calibration tools and techniques that you can find in different blocks of the AMD hardware. I borrowed some images from [2] [3] [4] to help you understand the information.

Predefined Transfer Functions (Named Fixed Curves): Transfer functions serve as the bridge between the digital and visual worlds, defining the mathematical relationship between digital color values and linear scene/display values and ensuring consistent color reproduction across different devices and media. You can learn more about curves in the chapter GPU Gems 3 - The Importance of Being Linear by Larry Gritz and Eugene d Eon. ITU-R 2100 introduces three main types of transfer functions:

• OETF: the opto-electronic transfer function, which converts linear scene light into the video signal, typically within a camera.
• EOTF: electro-optical transfer function, which converts the video signal into the linear light output of the display.
• OOTF: opto-optical transfer function, which has the role of applying the rendering intent .

AMD s display driver supports the following pre-defined transfer functions (aka named fixed curves):

• Linear/Unity: linear/identity relationship between pixel value and luminance value;
• Gamma 2.2, Gamma 2.4, Gamma 2.6: pure power functions;
• sRGB: 2.4: The piece-wise transfer function from IEC 61966-2-1:1999;
• BT.709: has a linear segment in the bottom part and then a power function with a 0.45 (~1/2.22) gamma for the rest of the range; standardized by ITU-R BT.709-6;
• PQ (Perceptual Quantizer): used for HDR display, allows luminance range capability of 0 to 10,000 nits; standardized by SMPTE ST 2084.

These capabilities vary depending on the hardware block, with some utilizing hardcoded curves and others relying on AMD s color module to construct curves from standardized coefficients. It also supports user/custom curves built from a lookup table.

1D LUTs (1-dimensional Lookup Table): A 1D LUT is a versatile tool, defining a one-dimensional color transformation based on a single parameter. It s very well explained by Jeremy Selan at GPU Gems 2 - Chapter 24 Using Lookup Tables to Accelerate Color Transformations It enables adjustments to color, brightness, and contrast, making it ideal for fine-tuning. In the Linux AMD display driver, the atomic API offers a 1D LUT with 4096 entries and 8-bit depth, while legacy gamma uses a size of 256.

3D LUTs (3-dimensional Lookup Table): These tables work in three dimensions red, green, and blue. They re perfect for complex color transformations and adjustments between color channels. It s also more complex to manage and require more computational resources. Jeremy also explains 3D LUT at GPU Gems 2 - Chapter 24 Using Lookup Tables to Accelerate Color Transformations

CTM (Color Transformation Matrices): Color transformation matrices facilitate the transition between different color spaces, playing a crucial role in color space conversion.

HDR Multiplier: HDR multiplier is a factor applied to the color values of an image to increase their overall brightness.

AMD Color Capabilities in the Hardware Pipeline First, let s take a closer look at the AMD Display Core Next hardware pipeline in the Linux kernel documentation for AMDGPU driver - Display Core Next In the AMD Display Core Next hardware pipeline, we encounter two hardware blocks with color capabilities: the Display Pipe and Plane (DPP) and the Multiple Pipe/Plane Combined (MPC). The DPP handles color adjustments per plane before blending, while the MPC engages in post-blending color adjustments. In short, we expect DPP color capabilities to match up with DRM plane properties, and MPC color capabilities to play nice with DRM CRTC properties. Note: here s the catch there are some DRM CRTC color transformations that don t have a corresponding AMD MPC color block, and vice versa. It s like a puzzle, and we re here to solve it!

AMD Color Blocks and Capabilities We can finally talk about the color capabilities of each AMD color block. As it varies based on the generation of hardware, let s take the DCN3+ family as reference. What s possible to do before and after blending depends on hardware capabilities describe in the kernel driver by struct dpp_color_caps and struct mpc_color_caps. The AMD Steam Deck hardware provides a tangible example of these capabilities. Therefore, we take SteamDeck/DCN301 driver as an example and look at the Color pipeline capabilities described in the file: driver/gpu/drm/amd/display/dcn301/dcn301_resources.c

/* Color pipeline capabilities */
dc->caps.color.dpp.dcn_arch = 1; // If it is a Display Core Next (DCN): yes. Zero means DCE.
dc->caps.color.dpp.input_lut_shared = 0;
dc->caps.color.dpp.icsc = 1; // Intput Color Space Conversion  (CSC) matrix.
dc->caps.color.dpp.dgam_ram = 0; // The old degamma block for degamma curve (hardcoded and LUT).  Gamma correction  is the new one.
dc->caps.color.dpp.dgam_rom_caps.srgb = 1; // sRGB hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.bt2020 = 1; // BT2020 hardcoded curve support (seems not actually in use)
dc->caps.color.dpp.dgam_rom_caps.gamma2_2 = 1; // Gamma 2.2 hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.pq = 1; // PQ hardcoded curve support
dc->caps.color.dpp.dgam_rom_caps.hlg = 1; // HLG hardcoded curve support
dc->caps.color.dpp.post_csc = 1; // CSC matrix
dc->caps.color.dpp.gamma_corr = 1; // New  Gamma Correction  block for degamma user LUT;
dc->caps.color.dpp.dgam_rom_for_yuv = 0;
dc->caps.color.dpp.hw_3d_lut = 1; // 3D LUT support. If so, it's always preceded by a shaper curve. 
dc->caps.color.dpp.ogam_ram = 1; //  Blend Gamma  block for custom curve just after blending
// no OGAM ROM on DCN301
dc->caps.color.dpp.ogam_rom_caps.srgb = 0;
dc->caps.color.dpp.ogam_rom_caps.bt2020 = 0;
dc->caps.color.dpp.ogam_rom_caps.gamma2_2 = 0;
dc->caps.color.dpp.ogam_rom_caps.pq = 0;
dc->caps.color.dpp.ogam_rom_caps.hlg = 0;
dc->caps.color.dpp.ocsc = 0;
dc->caps.color.mpc.gamut_remap = 1; // Post-blending CTM (pre-blending CTM is always supported)
dc->caps.color.mpc.num_3dluts = pool->base.res_cap->num_mpc_3dlut; // Post-blending 3D LUT (preceded by shaper curve)
dc->caps.color.mpc.ogam_ram = 1; // Post-blending regamma.
// No pre-defined TF supported for regamma.
dc->caps.color.mpc.ogam_rom_caps.srgb = 0;
dc->caps.color.mpc.ogam_rom_caps.bt2020 = 0;
dc->caps.color.mpc.ogam_rom_caps.gamma2_2 = 0;
dc->caps.color.mpc.ogam_rom_caps.pq = 0;
dc->caps.color.mpc.ogam_rom_caps.hlg = 0;
dc->caps.color.mpc.ocsc = 1; // Output CSC matrix.

I included some inline comments in each element of the color caps to quickly describe them, but you can find the same information in the Linux kernel documentation. See more in struct dpp_color_caps, struct mpc_color_caps and struct rom_curve_caps. Now, using this guideline, we go through color capabilities of DPP and MPC blocks and talk more about mapping driver-specific properties to corresponding color blocks.

DPP Color Pipeline: Before Blending (Per Plane) Let s explore the capabilities of DPP blocks and what you can achieve with a color block. The very first thing to pay attention is the display architecture of the display hardware: previously AMD uses a display architecture called DCE

• Display and Compositing Engine, but newer hardware follows DCN - Display Core Next.

The architectute is described by: dc->caps.color.dpp.dcn_arch

AMD Plane Degamma: TF and 1D LUT Described by: dc->caps.color.dpp.dgam_ram, dc->caps.color.dpp.dgam_rom_caps,dc->caps.color.dpp.gamma_corr AMD Plane Degamma data is mapped to the initial stage of the DPP pipeline. It is utilized to transition from scanout/encoded values to linear values for arithmetic operations. Plane Degamma supports both pre-defined transfer functions and 1D LUTs, depending on the hardware generation. DCN2 and older families handle both types of curve in the Degamma RAM block (dc->caps.color.dpp.dgam_ram); DCN3+ separate hardcoded curves and 1D LUT into two block: Degamma ROM (dc->caps.color.dpp.dgam_rom_caps) and Gamma correction block (dc->caps.color.dpp.gamma_corr), respectively. Pre-defined transfer functions:

• they are hardcoded curves (read-only memory - ROM);
• supported curves: sRGB EOTF, BT.709 inverse OETF, PQ EOTF and HLG OETF, Gamma 2.2, Gamma 2.4 and Gamma 2.6 EOTF.

The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. Setting TF = Identity/Default and LUT as NULL means bypass. References:

• [PATCH v3 04/32] drm/amd/display: add driver-specific property for plane degamma LUT
• [PATCH v3 05/32] drm/amd/display: add plane degamma TF driver-specific property
• [PATCH v3 19/32] drm/amd/display: add plane degamma TF and LUT support

AMD Plane 3x4 CTM (Color Transformation Matrix) AMD Plane CTM data goes to the DPP Gamut Remap block, supporting a 3x4 fixed point (s31.32) matrix for color space conversions. The data is interpreted as a struct drm_color_ctm_3x4. Setting NULL means bypass. References:

• [PATCH v3 30/32] drm/amd/display: add plane CTM driver-specific property
• [PATCH v3 31/32] drm/amd/display: add plane CTM support
• [PATCH v3 32/32] drm/amd/display: Add 3x4 CTM support for plane CTM

AMD Plane Shaper: TF + 1D LUT Described by: dc->caps.color.dpp.hw_3d_lut The Shaper block fine-tunes color adjustments before applying the 3D LUT, optimizing the use of the limited entries in each dimension of the 3D LUT. On AMD hardware, a 3D LUT always means a preceding shaper 1D LUT used for delinearizing and/or normalizing the color space before applying a 3D LUT, so this entry on DPP color caps dc->caps.color.dpp.hw_3d_lut means support for both shaper 1D LUT and 3D LUT. Pre-defined transfer function enables delinearizing content with or without shaper LUT, where AMD color module calculates the resulted shaper curve. Shaper curves go from linear values to encoded values. If we are already in a non-linear space and/or don t need to normalize values, we can set a Identity TF for shaper that works similar to bypass and is also the default TF value. Pre-defined transfer functions:

• there is no DPP Shaper ROM. Curves are calculated by AMD color modules. Check calculate_curve() function in the file amd/display/modules/color/color_gamma.c.
• supported curves: Identity, sRGB inverse EOTF, BT.709 OETF, PQ inverse EOTF, HLG OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 inverse EOTF.

The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. When setting Plane Shaper TF (!= Identity) and LUT at the same time, the color module will combine the pre-defined TF and the custom LUT values into the LUT that s actually programmed. Setting TF = Identity/Default and LUT as NULL works as bypass. References:

• [PATCH v3 10/32] drm/amd/display: add plane shaper LUT and TF
• [PATCH v3 23/32] drm/amd/display: add plane shaper LUT support
• [PATCH v3 24/32] drm/amd/display: add plane shaper TF support

AMD Plane 3D LUT Described by: dc->caps.color.dpp.hw_3d_lut The 3D LUT in the DPP block facilitates complex color transformations and adjustments. 3D LUT is a three-dimensional array where each element is an RGB triplet. As mentioned before, the dc->caps.color.dpp.hw_3d_lut describe if DPP 3D LUT is supported. The AMD driver-specific property advertise the size of a single dimension via LUT3D_SIZE property. Plane 3D LUT is a blog property where the data is interpreted as an array of struct drm_color_lut elements and the number of entries is LUT3D_SIZE cubic. The array contains samples from the approximated function. Values between samples are estimated by tetrahedral interpolation The array is accessed with three indices, one for each input dimension (color channel), blue being the outermost dimension, red the innermost. This distribution is better visualized when examining the code in [RFC PATCH 5/5] drm/amd/display: Fill 3D LUT from userspace by Alex Hung:

+	for (nib = 0; nib < 17; nib++)  
+		for (nig = 0; nig < 17; nig++)  
+			for (nir = 0; nir < 17; nir++)  
+				ind_lut = 3 * (nib + 17*nig + 289*nir);
+
+				rgb_area[ind].red = rgb_lib[ind_lut + 0];
+				rgb_area[ind].green = rgb_lib[ind_lut + 1];
+				rgb_area[ind].blue = rgb_lib[ind_lut + 2];
+				ind++;
+			 
+		 
+	 

In our driver-specific approach we opted to advertise it s behavior to the userspace instead of implicitly dealing with it in the kernel driver. AMD s hardware supports 3D LUTs with 17-size or 9-size (4913 and 729 entries respectively), and you can choose between 10-bit or 12-bit. In the current driver-specific work we focus on enabling only 17-size 12-bit 3D LUT, as in [PATCH v3 25/32] drm/amd/display: add plane 3D LUT support:

+		/* Stride and bit depth are not programmable by API yet.
+		 * Therefore, only supports 17x17x17 3D LUT (12-bit).
+		 */
+		lut->lut_3d.use_tetrahedral_9 = false;
+		lut->lut_3d.use_12bits = true;
+		lut->state.bits.initialized = 1;
+		__drm_3dlut_to_dc_3dlut(drm_lut, drm_lut3d_size, &lut->lut_3d,
+					lut->lut_3d.use_tetrahedral_9,
+					MAX_COLOR_3DLUT_BITDEPTH);

A refined control of 3D LUT parameters should go through a follow-up version or generic API. Setting 3D LUT to NULL means bypass. References:

• [PATCH v3 09/32] drm/amd/display: add plane 3D LUT driver-specific properties
• [PATCH v3 25/32] drm/amd/display: add plane 3D LUT support

AMD Plane Blend/Out Gamma: TF + 1D LUT Described by: dc->caps.color.dpp.ogam_ram The Blend/Out Gamma block applies the final touch-up before blending, allowing users to linearize content after 3D LUT and just before the blending. It supports both 1D LUT and pre-defined TF. We can see Shaper and Blend LUTs as 1D LUTs that are sandwich the 3D LUT. So, if we don t need 3D LUT transformations, we may want to only use Degamma block to linearize and skip Shaper, 3D LUT and Blend. Pre-defined transfer function:

• there is no DPP Blend ROM. Curves are calculated by AMD color modules;
• supported curves: Identity, sRGB EOTF, BT.709 inverse OETF, PQ EOTF, HLG inverse OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 EOTF.

The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. If plane_blend_tf_property != Identity TF, AMD color module will combine the user LUT values with pre-defined TF into the LUT parameters to be programmed. Setting TF = Identity/Default and LUT to NULL means bypass. References:

• [PATCH v3 11/32] drm/amd/display: add plane blend
• [PATCH v3 27/32] drm/amd/display: add plane blend LUT and TF support

MPC Color Pipeline: After Blending (Per CRTC)

DRM CRTC Degamma 1D LUT The degamma lookup table (LUT) for converting framebuffer pixel data before apply the color conversion matrix. The data is interpreted as an array of struct drm_color_lut elements. Setting NULL means bypass. Not really supported. The driver is currently reusing the DPP degamma LUT block (dc->caps.color.dpp.dgam_ram and dc->caps.color.dpp.gamma_corr) for supporting DRM CRTC Degamma LUT, as explaning by [PATCH v3 20/32] drm/amd/display: reject atomic commit if setting both plane and CRTC degamma.

DRM CRTC 3x3 CTM Described by: dc->caps.color.mpc.gamut_remap It sets the current transformation matrix (CTM) apply to pixel data after the lookup through the degamma LUT and before the lookup through the gamma LUT. The data is interpreted as a struct drm_color_ctm. Setting NULL means bypass.

DRM CRTC Gamma 1D LUT + AMD CRTC Gamma TF Described by: dc->caps.color.mpc.ogam_ram After all that, you might still want to convert the content to wire encoding. No worries, in addition to DRM CRTC 1D LUT, we ve got a AMD CRTC gamma transfer function (TF) to make it happen. Possible TF values are defined by enum amdgpu_transfer_function. Pre-defined transfer functions:

• there is no MPC Gamma ROM. Curves are calculated by AMD color modules.
• supported curves: Identity, sRGB inverse EOTF, BT.709 OETF, PQ inverse EOTF, HLG OETF, and Gamma 2.2, Gamma 2.4, Gamma 2.6 inverse EOTF.

The 1D LUT currently accepts 4096 entries of 8-bit. The data is interpreted as an array of struct drm_color_lut elements. When setting CRTC Gamma TF (!= Identity) and LUT at the same time, the color module will combine the pre-defined TF and the custom LUT values into the LUT that s actually programmed. Setting TF = Identity/Default and LUT to NULL means bypass. References:

• [PATCH v3 12/32] drm/amd/display: add CRTC gamma TF driver-specific property
• [PATCH v3 15/32] drm/amd/display: add CRTC gamma TF support

Others

AMD CRTC Shaper and 3D LUT We have previously worked on exposing CRTC shaper and CRTC 3D LUT, but they were removed from the AMD driver-specific color series because they lack userspace case. CRTC shaper and 3D LUT works similar to plane shaper and 3D LUT but after blending (MPC block). The difference here is that setting (not bypass) Shaper and Gamma blocks together are not expected, since both blocks are used to delinearize the input space. In summary, we either set Shaper + 3D LUT or Gamma.

Input and Output Color Space Conversion There are two other color capabilities of AMD display hardware that were integrated to DRM by previous works and worth a brief explanation here. The DC Input CSC sets pre-defined coefficients from the values of DRM plane color_range and color_encoding properties. It is used for color space conversion of the input content. On the other hand, we have de DC Output CSC (OCSC) sets pre-defined coefficients from DRM connector colorspace properties. It is uses for color space conversion of the composed image to the one supported by the sink. References:

• [PATCH] amd/display/dc: Fix COLOR_ENCODING and COLOR_RANGE doing nothing for DCN20+
• [PATCH v6 00/13] Enable Colorspace connector property in amdgpu

The search for rainbow treasures is not over yet If you want to understand a little more about this work, be sure to watch Joshua and I presented two talks at XDC 2023 about AMD/Steam Deck colors on Gamescope:

• The rainbow treasure map: advanced color management on Linux with AMD/Steam Deck
• Rainbow Frogs: HDR + Color Management in Gamescope/SteamOS

In the time between the first and second part of this blog post, Uma Shashank and Chaitanya Kumar Borah published the plane color pipeline for Intel and Harry Wentland implemented a generic API for DRM based on VKMS support. We discussed these two proposals and the next steps for Color on Linux during the Color Management workshop at XDC 2023 and I briefly shared workshop results in the 2023 XDC lightning talk session. The search for rainbow treasures is not over yet! We plan to meet again next year in the 2024 Display Hackfest in Coru a-Spain (Igalia s HQ) to keep up the pace and continue advancing today s display needs on Linux. Finally, a HUGE thank you to everyone who worked with me on exploring AMD s color capabilities and making them available in userspace.

Contributing to Debian is part of Freexian s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

Freexian Meetup, by Stefano Rivera, Utkarsh Gupta, et al. During DebConf, Freexian organized a meetup for its collaborators and those interested in learning more about Freexian and its services. It was well received and many people interested in Freexian showed up. Some developers who were interested in contributing to LTS came to get more details about joining the project. And some prospective customers came to get to know us and ask questions. Sadly, the tragic loss of Abraham shook DebConf, both individually and structurally. The meetup got rescheduled to a small room without video coverage. With that, we still had a wholesome interaction and here s a quick picture from the meetup taken by Utkarsh (which is also why he s missing!).

Debusine, by Rapha l Hertzog, et al. Freexian has been investing into debusine for a while, but development speed is about to increase dramatically thanks to funding from SovereignTechFund.de. Rapha l laid out the 5 milestones of the funding contract, and filed the issues for the first milestone. Together with Enrico and Stefano, they established a workflow for the expanded team. Among the first steps of this milestone, Enrico started to work on a developer-friendly description of debusine that we can use when we reach out to the many Debian contributors that we will have to interact with. And Rapha l started the design work of the autopkgtest and lintian tasks, i.e. what s the interface to schedule such tasks, what behavior and what associated options do we support? At this point you might wonder what debusine is supposed to be let us try to answer this: Debusine manages scheduling and distribution of Debian-related build and QA tasks to a network of worker machines. It also manages the resulting artifacts and provides the results in an easy to consume way. We want to make it easy for Debian contributors to leverage all the great QA tools that Debian provides. We want to build the next generation of Debian s build infrastructure, one that will continue to reliably do what it already does, but that will also enable distribution-wide experiments, custom package repositories and custom workflows with advanced package reviews. If this all sounds interesting to you, don t hesitate to watch the project on salsa.debian.org and to contribute.

lpr/lpd in Debian, by Thorsten Alteholz During Debconf23, Till Kamppeter presented CPDB (Common Print Dialog Backend), a new way to handle print queues. After this talk it was discussed whether the old lpr/lpd based printing system could be abandoned in Debian or whether there is still demand for it. So Thorsten asked on the debian-devel email list whether anybody uses it. Oddly enough, these old packages are still useful:

• Within a small network it is easier to distribute a printcap file, than to properly configure cups clients.
• One of the biggest manufacturers of WLAN router and DSL boxes only supports raw queues when attaching an USB printer to their hardware. Admittedly the CPDB still has problems with such raw queues.
• The Pharos printing system at MIT is still lpd-based.

As a result, the lpr/lpd stuff is not yet ready to be abandoned and Thorsten will adopt the relevant packages (or rather move them under the umbrella of the debian-printing team). Though it is not planned to develop new features, those packages should at least have a maintainer. This month Thorsten adopted rlpr, an utility for lpd printing without using /etc/printcap. The next one he is working on is lprng, a lpr/lpd printer spooling system. If you know of any other package that is also needed and still maintained by the QA team, please tell Thorsten.

/usr-merge, by Helmut Grohne Discussion about lifting the file move moratorium has been initiated with the CTTE and the release team. A formal lift is dependent on updating debootstrap in older suites though. A significant number of packages can automatically move their systemd unit files if dh_installsystemd and systemd.pc change their installation targets. Unfortunately, doing so makes some packages FTBFS and therefore patches have been filed. The analysis tool, dumat, has been enhanced to better understand which upgrade scenarios are considered supported to reduce false positive bug filings and gained a mode for local operation on a .changes file meant for inclusion in salsa-ci. The filing of bugs from dumat is still manual to improve the quality of reports. Since September, the moratorium has been lifted.

Miscellaneous contributions

• Rapha l updated Django s backport in bullseye-backports to match the latest security release that was published in bookworm. Tracker.debian.org is still using that backport.
• Helmut Grohne sent 13 patches for cross build failures.
• Helmut Grohne performed a maintenance upload of debvm enabling its use in autopkgtests.
• Helmut Grohne wrote an API-compatible reimplementation of autopkgtest-build-qemu. It is powered by mmdebstrap, therefore unprivileged, EFI-only and will soon be included in mmdebstrap.
• Santiago continued the work regarding how to make it easier to (automatically) test reverse dependencies. An example of the ongoing work was presented during the Salsa CI BoF at DebConf 23.
  In fact, omniorb-dfsg test pipelines as the above were used for the omniorb-dfsg 4.3.0 transition, verifying how the reverse dependencies (tango, pytango and omnievents) were built and how their autopkgtest jobs run with the to-be-uploaded omniorb-dfsg new release.
• Utkarsh and Stefano attended and helped run DebConf 23. Also continued winding up DebConf 22 accounting.
• Anton Gladky did some science team uploads to fix RC bugs.

Review: The Far Reaches, edited by John Joseph Adams

Publisher:	Amazon Original Stories
Copyright:	June 2023
ISBN:	1-6625-1572-3
ISBN:	1-6625-1622-3
ISBN:	1-6625-1503-0
ISBN:	1-6625-1567-7
ISBN:	1-6625-1678-9
ISBN:	1-6625-1533-2
Format:	Kindle
Pages:	219

Amazon has been releasing anthologies of original short SFF with various guest editors, free for Amazon Prime members. I previously tried Black Stars (edited by Nisi Shawl and Latoya Peterson) and Forward (edited by Blake Crouch). Neither were that good, but the second was much worse than the first. Amazon recently released a new collection, this time edited by long-standing SFF anthology editor John Joseph Adams and featuring a new story by Ann Leckie, which sounded promising enough to give them another chance. The definition of insanity is doing the same thing over and over again and expecting different results. As with the previous anthologies, each story is available separately for purchase or Amazon Prime "borrowing" with separate ISBNs. The sidebar cover is for the first in the sequence. Unlike the previous collections, which were longer novelettes or novellas, my guess is all of these are in the novelette range. (I did not do a word count.) If you're considering this anthology, read the Okorafor story ("Just Out of Jupiter's Reach"), consider "How It Unfolds" by James S.A. Corey, and avoid the rest. "How It Unfolds" by James S.A. Corey: Humans have invented a new form of physics called "slow light," which can duplicate any object that is scanned. The energy expense is extremely high, so the result is not a post-scarcity paradise. What the technology does offer, however, is a possible route to interstellar colonization: duplicate a team of volunteers and a ship full of bootstrapping equipment, and send copies to a bunch of promising-looking exoplanets. One of them might succeed. The premise is interesting. The twists Corey adds on top are even better. What can be duplicated once can be duplicated again, perhaps with more information. This is a lovely science fiction idea story that unfortunately bogs down because the authors couldn't think of anywhere better to go with it than relationship drama. I found the focus annoying, but the ideas are still very neat. (7) "Void" by Veronica Roth: A maintenance worker on a slower-than-light passenger ship making the run between Sol and Centauri unexpectedly is called to handle a dead body. A passenger has been murdered, two days outside the Sol system. Ace is in no way qualified to investigate the murder, nor is it her job, but she's watched a lot of crime dramas and she has met the victim before. The temptation to start poking around is impossible to resist. It's been a long time since I've read a story built around the differing experiences of time for people who stay on planets and people who spend most of their time traveling at relativistic speeds. It's a bit of a retro idea from an earlier era of science fiction, but it's still a good story hook for a murder mystery. None of the characters are that memorable and Roth never got me fully invested in the story, but this was still a pleasant way to pass the time. (6) "Falling Bodies" by Rebecca Roanhorse: Ira is the adopted son of a Genteel senator. He was a social experiment in civilizing the humans: rescue a human orphan and give him the best of Genteel society to see if he could behave himself appropriately. The answer was no, which is how Ira finds himself on Long Reach Station with a parole officer and a schooling opportunity, hopefully far enough from his previous mistakes for a second chance. Everyone else seems to like Rebecca Roanhorse's writing better than I do, and this is no exception. Beneath the veneer of a coming-of-age story with a twist of political intrigue, this is brutal, depressing, and awful, with an ending that needs a lot of content warnings. I'm sorry that I read it. (3) "The Long Game" by Ann Leckie: The Imperial Radch trilogy are some of my favorite science fiction novels of all time, but I am finding Leckie's other work a bit hit and miss. I have yet to read a novel of hers that I didn't like, but the short fiction I've read leans more heavily into exploring weird and alien perspectives, which is not my favorite part of her work. This story is firmly in that category: the first-person protagonist is a small tentacled alien creature, a bit like a swamp-dwelling octopus. I think I see what Leckie is doing here: balancing cynicism and optimism, exploring how lifespans influence thinking and planning, and making some subtle points about colonialism. But as a reading experience, I didn't enjoy it. I never liked any of the characters, and the conclusion of the story is the unsettling sort of main-character optimism that seems rather less optimistic to the reader. (4) "Just Out of Jupiter's Reach" by Nnedi Okorafor: K rm n scientists have found a way to grow living ships that can achieve a symbiosis with a human pilot, but the requirements for that symbiosis are very strict and hard to predict. The result was a planet-wide search using genetic testing to find the rare and possibly nonexistent matches. They found seven people. The deal was simple: spend ten years in space, alone, in her ship. No contact with any other human except at the midpoint, when the seven ships were allowed to meet up for a week. Two million euros a year, for as long as she followed the rules, and the opportunity to be part of a great experiment, providing data that will hopefully lead to humans becoming a spacefaring species. The core of this story is told during the seven days in the middle of the mission, and thus centers on people unfamiliar with human contact trying to navigate social relationships after five years in symbiotic ships that reshape themselves to their whims and personalities. The ships themselves link so that the others can tour, which offers both a good opportunity for interesting description and a concretized metaphor about meeting other people. I adore symbiotic spaceships, so this story had me at the premise. The surface plot is very psychological, and I didn't entirely click with it, but the sense of wonder vibes beneath that surface were wonderful. It also feels fresh and new: I've seen most of the ideas before, but not presented or written this way, or approached from quite this angle. Definitely the best story of the anthology. (8) "Slow Time Between the Stars" by John Scalzi: This, on the other hand, was a complete waste of time, redeemed only by being the shortest "story" in the collection. "Story" is generous, since there's only one character and a very dry, linear plot that exists only to make a philosophical point. "Speculative essay" may be closer. The protagonist is the artificial intelligence responsible for Earth's greatest interstellar probe. It is packed with a repository of all of human knowledge and the raw material to create life. Its mission is to find an exoplanet capable of sustaining that life, and then recreate it and support it. The plot, such as it is, follows the AI's decision to abandon that mission and cut off contact with Earth, for reasons that it eventually explains. Every possible beat of this story hit me wrong. The sense of wonder attaches to the most prosaic things and skips over the moments that could have provoked real wonder. The AI is both unbelievable and irritating, with all of the smug self-confidence of an Internet reply guy. The prose is overwrought in all the wrong places ("the finger of God, offering the spark to animate the dirt of another world" would totally be this AI's profile quote under their forum avatar). The only thing I liked about the story is the ethical point that it slowly meanders into, which I think I might agree with and at least find plausible. But it's delivered by the sort of character I would actively leave rooms to avoid, in a style that's about as engrossing as a tax form. Avoid. (2) Rating: 5 out of 10