How to Fix it Yourself If what you, like me, need is simply for Bluetooth Audio to work with AAC in Debian s default desktop environment², then you ll need to rebuild the pipewire package to include the AAC codec. While the current version in Debian main has been built with AAC deliberately disabled, it is trivial to enable if you can install a version of the fdk-aac library. I preface this with the usual caveats when it comes to patent and licensing controversies. I am not a lawyer, building this package and/or using it could get you into legal trouble. These instructions have only been tested on an up-to-date copy of Debian 12.

1. Install pipewire s build dependencies

   sudo apt install build-essential devscripts
   sudo apt build-dep pipewire
   

2. Install libfdk-aac-dev

   sudo apt install libfdk-aac-dev
   

   If the above doesn t work you ll likely need to enable non-free and try again

   sudo sed -i 's/main/main non-free/g' /etc/apt/sources.list
   sudo apt update
   

   Alternatively, if you wish to ensure you are maximally license-compliant and patent un-infringing³, you can instead build fdk-aac-free which includes only those components of AAC that are known to be patent-free³. This is what should eventually end up in Debian to resolve this problem (see below).

   sudo apt install git-buildpackage
   mkdir fdk-aac-source
   cd fdk-aac-source
   git clone https://salsa.debian.org/multimedia-team/fdk-aac
   cd fdk-aac
   gbp buildpackage
   sudo dpkg -i ../libfdk-aac2_*deb ../libfdk-aac-dev_*deb
   

3. Get the pipewire source code

   mkdir pipewire-source
   cd pipewire-source
   apt source pipewire
   

   This will create a bunch of files within the pipewire-source directory, but you ll only need the pipewire-<version> folder, this contains all the files you ll need to build the package, with all the debian-specific patches already applied. Note that you don t want to run the apt source command as root, as it will then create files that your regular user cannot edit.
4. Fix the dependencies and build options To fix up the build scripts to use the fdk-aac library, you need to save the following as pipewire-source/aac.patch

   --- debian/control.orig
   +++ debian/control
   @@ -40,8 +40,8 @@
                modemmanager-dev,
                pkg-config,
                python3-docutils,
   -               systemd [linux-any]
   -Build-Conflicts: libfdk-aac-dev
   +               systemd [linux-any],
   +               libfdk-aac-dev
    Standards-Version: 4.6.2
    Vcs-Browser: https://salsa.debian.org/utopia-team/pipewire
    Vcs-Git: https://salsa.debian.org/utopia-team/pipewire.git
   --- debian/rules.orig
   +++ debian/rules
   @@ -37,7 +37,7 @@
    		-Dauto_features=enabled \
    		-Davahi=enabled \
    		-Dbluez5-backend-native-mm=enabled \
   -		-Dbluez5-codec-aac=disabled \
   +		-Dbluez5-codec-aac=enabled \
    		-Dbluez5-codec-aptx=enabled \
    		-Dbluez5-codec-lc3=enabled \
    		-Dbluez5-codec-lc3plus=disabled \
   

   Then you ll need to run patch from within the pipewire-<version> folder created by apt source:

   patch -p0 < ../aac.patch
   

5. Build pipewire

   cd pipewire-*
   debuild
   

   Note that you will likely see an error from debsign at the end of this process, this is harmless, you simply don t have a GPG key set up to sign your newly-built package⁴. Packages don t need to be signed to be installed, and debsign uses a somewhat non-standard signing process that dpkg does not check anyway.

1. Install libspa-0.2-bluetooth

   sudo dpkg -i libspa-0.2-bluetooth_*.deb
   

2. Restart PipeWire and/or Reboot

   sudo reboot
   

   Theoretically there s a set of services to restart here that would get pipewire to pick up the new library, probably just pipewire itself. But it s just as easy to restart and ensure everything is using the correct library.

Why This is a slightly unusual situation, as the fdk-aac library is licensed under what even the GNU project acknowledges is a free software license. However, this license explicitly informs the user that they need to acquire a patent license to use this software⁵:

3. NO PATENT LICENSE NO EXPRESS OR IMPLIED LICENSES TO ANY PATENT CLAIMS, including without limitation the patents of Fraunhofer, ARE GRANTED BY THIS SOFTWARE LICENSE. Fraunhofer provides no warranty of patent non-infringement with respect to this software. You may use this FDK AAC Codec software or modifications thereto only for purposes that are authorized by appropriate patent licenses.

To quote the GNU project:

Because of this, and because the license author is a known patent aggressor, we encourage you to be careful about using or redistributing software under this license: you should first consider whether the licensor might aim to lure you into patent infringement.

AAC is covered by a number of patents, which expire at some point in the 2030s⁶. As such the current version of the library is potentially legally dubious to ship with any other software, as it could be considered patent-infringing³.

Fedora s solution Since 2017, Fedora has included a modified version of the library as fdk-aac-free, see the announcement and the bugzilla bug requesting review. This version of the library includes only the AAC LC profile, which is believed to be entirely patent-free³. Based on this, there is an open bug report in Debian requesting that the fdk-aac package be moved to the main component and that the pipwire package be updated to build against it.

The Debian NEW queue To resolve these bugs, a version of fdk-aac-free has been uploaded to Debian by Jeremy Bicha. However, to make it into Debian proper, it must first pass through the ftpmaster s NEW queue. The current version of fdk-aac-free has been in the NEW queue since July 2023. Based on conversations in some of the bugs above, it s been there since at least 2022⁷. I hope this helps anyone stuck with AAC to get their hardware working for them while we wait for the package to eventually make it through the NEW queue. Discuss on Hacker News

1. Such as, for example, any Apple AirPods, which only support AAC AFAICT.
2. Which, as of Debian 12 is GNOME 3 under Wayland with PipeWire.
3. I m not a lawyer, I don t know what kinds of infringement might or might not be possible here, do your own research, etc. ^{2 3 4}
4. And if you DO have a key setup with debsign you almost certainly don t need these instructions.
5. This was originally phrased as explicitly does not grant any patent rights. It was pointed out on Hacker News that this is not exactly what it says, as it also includes a specific note that you ll need to acquire your own patent license. I ve now quoted the relevant section of the license for clarity.
6. Wikipedia claims the base patents expire in 2031, with the extensions expiring in 2038, but its source for these claims is some guy s spreadsheet in a forum. The same discussion also brings up Wikipedia s claim and casts some doubt on it, so I m not entirely sure what s correct here, but I didn t feel like doing a patent deep-dive today. If someone can provide a clear answer that would be much appreciated.
7. According to Jeremy B cha: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1021370#17

• The X- style prefixes for field names are now understood and handled. This means the language server now considers XC-Package-Type the same as Package-Type.

• More diagnostics:

  • Fields without values now trigger an error marker
  • Duplicated fields now trigger an error marker
  • Fields used in the wrong paragraph now trigger an error marker
  • Typos in field names or values now trigger a warning marker. For field names, X- style prefixes are stripped before typo detection is done.
  • The value of the Section field is now validated against a dataset of known sections and trigger a warning marker if not known.

• The "on-save trim end of line whitespace" now works. I had a logic bug in the server side code that made it submit "no change" edits to the editor.

• The language server now provides "hover" documentation for field names. There is a small screenshot of this below. Sadly, emacs does not support markdown or, if it does, it does not announce the support for markdown. For now, all the documentation is always in markdown format and the language server will tag it as either markdown or plaintext depending on the announced support.

• The language server now provides quick fixes for some of the more trivial problems such as deprecated fields or typos of fields and values.

• Added more known fields including the XS-Autobuild field for non-free packages along with a link to the relevant devref section in its hover doc.

• Releasing the power of collaboration: We ll work to remove bottlenecks and pave the way for smoother, more performant displays.
• Problem-solving powerhouse: Brainstorming sessions and collaborative coding will target issues like HDR, color management, variable refresh rates, and more.
• Building on past commitments: Let s solidify the progress made in recent years and push the boundaries even further.

How we executed a critical supply chain attack on PyTorch John Stawinski and Adnan Khan published a lengthy blog post detailing how they executed a supply-chain attack against PyTorch, a popular machine learning platform used by titans like Google, Meta, Boeing, and Lockheed Martin :

Our exploit path resulted in the ability to upload malicious PyTorch releases to GitHub, upload releases to [Amazon Web Services], potentially add code to the main repository branch, backdoor PyTorch dependencies the list goes on. In short, it was bad. Quite bad.

The attack pivoted on PyTorch s use of self-hosted runners as well as submitting a pull request to address a trivial typo in the project s README file to gain access to repository secrets and API keys that could subsequently be used for malicious purposes.

New Arch Linux forensic filesystem tool On our mailing list this month, long-time Reproducible Builds developer kpcyrd announced a new tool designed to forensically analyse Arch Linux filesystem images. Called archlinux-userland-fs-cmp, the tool is supposed to be used from a rescue image (any Linux) with an Arch install mounted to, [for example], /mnt. Crucially, however, at no point is any file from the mounted filesystem eval d or otherwise executed. Parsers are written in a memory safe language. More information about the tool can be found on their announcement message, as well as on the tool s homepage. A GIF of the tool in action is also available.

Issues with our SOURCE_DATE_EPOCH code? Chris Lamb started a thread on our mailing list summarising some potential problems with the source code snippet the Reproducible Builds project has been using to parse the SOURCE_DATE_EPOCH environment variable:

I m not 100% sure who originally wrote this code, but it was probably sometime in the ~2015 era, and it must be in a huge number of codebases by now. Anyway, Alejandro Colomar was working on the shadow security tool and pinged me regarding some potential issues with the code. You can see this conversation here.

Chris ends his message with a request that those with intimate or low-level knowledge of time_t, C types, overflows and the various parsing libraries in the C standard library (etc.) contribute with further info.

Distribution updates In Debian this month, Roland Clobus posted another detailed update of the status of reproducible ISO images on our mailing list. In particular, Roland helpfully summarised that all major desktops build reproducibly with bullseye, bookworm, trixie and sid provided they are built for a second time within the same DAK run (i.e. [within] 6 hours) . Additionally 7 of the 8 bookworm images from the official download link build reproducibly at any later time. In addition to this, three reviews of Debian packages were added, 17 were updated and 15 were removed this month adding to our knowledge about identified issues. Elsewhere, Bernhard posted another monthly update for his work elsewhere in openSUSE.

Community updates There were made a number of improvements to our website, including Bernhard M. Wiedemann fixing a number of typos of the term nondeterministic . [ ] and Jan Zerebecki adding a substantial and highly welcome section to our page about SOURCE_DATE_EPOCH to document its interaction with distribution rebuilds. [ ].
diffoscope is our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues. This month, Chris Lamb made a number of changes such as uploading versions 254 and 255 to Debian but focusing on triaging and/or merging code from other contributors. This included adding support for comparing eXtensible ARchive (.XAR/.PKG) files courtesy of Seth Michael Larson [ ][ ], as well considerable work from Vekhir in order to fix compatibility between various and subtle incompatible versions of the progressbar libraries in Python [ ][ ][ ][ ]. Thanks!

Reproducibility testing framework The Reproducible Builds project operates a comprehensive testing framework (available at tests.reproducible-builds.org) in order to check packages and other artifacts for reproducibility. In January, a number of changes were made by Holger Levsen:

• Debian-related changes:
  • Reduce the number of arm64 architecture workers from 24 to 16. [ ]
  • Use diffoscope from the Debian release being tested again. [ ]
  • Improve the handling when killing unwanted processes [ ][ ][ ] and be more verbose about it, too [ ].
  • Don t mark a job as failed if process marked as to-be-killed is already gone. [ ]
  • Display the architecture of builds that have been running for more than 48 hours. [ ]
  • Reboot arm64 nodes when they hit an OOM (out of memory) state. [ ]
• Package rescheduling changes:
  • Reduce IRC notifications to 1 when rescheduling due to package status changes. [ ]
  • Correctly set SUDO_USER when rescheduling packages. [ ]
  • Automatically reschedule packages regressing to FTBFS (build failure) or FTBR (build success, but unreproducible). [ ]
• OpenWrt-related changes:
  • Install the python3-dev and python3-pyelftools packages as they are now needed for the sunxi target. [ ][ ]
  • Also install the libpam0g-dev which is needed by some OpenWrt hardware targets. [ ]
• Misc:
  • As it s January, set the real_year variable to 2024 [ ] and bump various copyright years as well [ ].
  • Fix a large (!) number of spelling mistakes in various scripts. [ ][ ][ ]
  • Prevent Squid and Systemd processes from being killed by the kernel s OOM killer. [ ]
  • Install the iptables tool everywhere, else our custom rc.local script fails. [ ]
  • Cleanup the /srv/workspace/pbuilder directory on boot. [ ]
  • Automatically restart Squid if it fails. [ ]
  • Limit the execution of chroot-installation jobs to a maximum of 4 concurrent runs. [ ][ ]

Significant amounts of node maintenance was performed by Holger Levsen (eg. [ ][ ][ ][ ][ ][ ][ ] etc.) and Vagrant Cascadian (eg. [ ][ ][ ][ ][ ][ ][ ][ ]). Indeed, Vagrant Cascadian handled an extended power outage for the network running the Debian armhf architecture test infrastructure. This provided the incentive to replace the UPS batteries and consolidate infrastructure to reduce future UPS load. [ ] Elsewhere in our infrastructure, however, Holger Levsen also adjusted the email configuration for @reproducible-builds.org to deal with a new SMTP email attack. [ ]

Upstream patches The Reproducible Builds project tries to detects, dissects and fix as many (currently) unreproducible packages as possible. We endeavour to send all of our patches upstream where appropriate. This month, we wrote a large number of such patches, including:

• Bernhard M. Wiedemann:
  • cython (nondeterminstic path issue)
  • deluge (issue with modification time of .egg file)
  • gap-ferret, gap-semigroups & gap-simpcomp (nondeterministic config.log file)
  • grpc (filesystem ordering issue )
  • hub (random)
  • kubernetes1.22 & kubernetes1.23 (sort-related issue)
  • kubernetes1.24 & kubernetes1.25 (go -trimpath vs random issue)
  • libjcat (drop test files with random bytes)
  • luajit (Use new d option for deterministic bytecode output)
  • meson [ ][ ] (sort the results from Python filesystem call)
  • python-rjsmin (drop GCC instrumentation artifacts)
  • qt6-virtualkeyboard+others (bug parallelism/race)
  • SoapySDR (parallelism-related issue)
  • systemd (sorting problem)
  • warewulf (CPIO modification time issue, etc.)
• Chris Lamb:
  • #1060254 filed against mumble.
• James Addison:
  • guake ( Schroedinger file due to race condition)
  • qhelpgenerator-qt5 (timezone localization; fix also merged upstream for QT6)
  • sphinx (search index doctitle sorting)

Separate to this, Vagrant Cascadian followed up with the relevant maintainers when reproducibility fixes were not included in newly-uploaded versions of the mm-common package in Debian this was quickly fixed, however. [ ]

---

If you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

• IRC: #reproducible-builds on irc.oftc.net.
• Mailing list: rb-general@lists.reproducible-builds.org
• Mastodon: @reproducible_builds
• Twitter: @ReproBuilds

curl -L --remote-name-all $(curl -L "https://github.com/pypi-data/data/raw/main/links/dataset.txt")

1. project name, version and release date
2. file path, size and line count
3. hash of the file

describe select * from '*.parquet';
 
    column_name     column_type    null    
      varchar         varchar     varchar  
 
  project_name      VARCHAR       YES      
  project_version   VARCHAR       YES      
  project_release   VARCHAR       YES      
  uploaded_on       TIMESTAMP     YES      
  path              VARCHAR       YES      
  archive_path      VARCHAR       YES      
  size              UBIGINT       YES      
  hash              BLOB          YES      
  skip_reason       VARCHAR       YES      
  lines             UBIGINT       YES      
  repository        UINTEGER      YES      
 
  11 rows                       6 columns  
 

select
    path,
    hash,
    uploaded_on,
    repository
from '*.parquet'
where
    skip_reason == '' and
    lower(string_split(path, '/')[-1]) == 'pyproject.toml' and
    len(string_split(path, '/')) == 5
order by uploaded_on desc

url = f"https://raw.githubusercontent.com/pypi-data/pypi-mirror- repository /code/ path "

>>> results.backend.value_counts()
backend
setuptools        701550
poetry            380830
hatchling          56917
flit               36223
pdm                11437
maturin             9796
jupyter             1707
mesonpy              625
scikit               556
                   ...
postry                 1
tree                   1
setuptoos              1
neuron                 1
avalon                 1
maturimaturinn         1
jsonpath               1
ha                     1
pyo3                   1
Name: count, Length: 73, dtype: int64

• Setuptools: ~50%
• Poetry: ~33%
• Hatch: ~10%
• Flit: ~3%
• Other: ~4%

manifest-version: "0.1"
installations:
  - install:
      source: foo
      dest-dir: usr/bin

 
  "manifest-version": "0.1",
  "installations": [
      
       "install":  
         "source": "foo",
         "dest-dir": "usr/bin",
        
      
  ]
 

1. Most plugins would probably throw KeyError: X or ValueError style errors for quite a while. Worst case, they would end on my table because the user would have a hard time telling where debputy ends and where the plugins starts. "Best" case, I would teach debputy to say "This poor error message was brought to you by plugin foo. Go complain to them". Either way, it would be a bad user experience.
2. This even assumes plugin providers would actually bother writing manifest parsing code. If it is that difficult, then just providing a custom file in debian might tempt plugin providers and that would undermine the idea of having the manifest be the sole input for debputy.

1. It had to cover as many parsing errors as possible. An error case this code would handle for you, would be an error where I could ensure it sufficient degree of detail and context for the user.
2. It should be type-safe / provide typing support such that IDEs/mypy could help you when you work on the parsed result.
3. It had to support "normalization" of the input, such as

           # User provides
           - install: "foo"
           # Which is normalized into:
           - install:
               source: "foo"
4) It must be simple to tell  debputy  what input you expected.

# User provides
- install: "foo"
# Which is normalized into:
- install:
    source: "foo"

# Example input matching this typed dict.
#    
#       "source": ["foo"]
#       "into": ["pkg"]
#    
class InstallExamplesTargetFormat(TypedDict):
    # Which source files to install (dest-dir is fixed)
    sources: List[str]
    # Which package(s) that should have these files installed.
    into: NotRequired[List[str]]

# Example input matching this typed dict.
#    
#       "source": "foo"
#       "into": "pkg"
#    
#
class InstallExamplesManifestFormat(TypedDict):
    # Note that sources here is split into source (str) vs. sources (List[str])
    sources: NotRequired[List[str]]
    source: NotRequired[str]
    # We allow the user to write  into: foo  in addition to  into: [foo] 
    into: Union[str, List[str]]
FullInstallExamplesManifestFormat = Union[
    InstallExamplesManifestFormat,
    List[str],
    str,
]

def _handler(
    normalized_form: InstallExamplesTargetFormat,
) -> InstallRule:
    ...  # Do something with the normalized form and return an InstallRule.
concept_debputy_api.add_install_rule(
  keyword="install-examples",
  target_form=InstallExamplesTargetFormat,
  manifest_form=FullInstallExamplesManifestFormat,
  handler=_handler,
)

def normalize_into_list(x: Union[str, List[str]]) -> List[str]:
    return x if isinstance(x, list) else [x]

# Map from
class InstallExamplesManifestFormat(TypedDict):
    # Note that sources here is split into source (str) vs. sources (List[str])
    sources: NotRequired[List[str]]
    source: NotRequired[str]
    # We allow the user to write  into: foo  in addition to  into: [foo] 
    into: Union[str, List[str]]
# ... into
class InstallExamplesTargetFormat(TypedDict):
    # Which source files to install (dest-dir is fixed)
    sources: List[str]
    # Which package(s) that should have these files installed.
    into: NotRequired[List[str]]

# For all intents and purposes,  foo  is a string despite all the  Annotated  stuff.
foo: Annotated[str, "hello world"] = "my string here"

# Map from
#      
#        "source": "foo"  # (or "sources": ["foo"])
#        "into": "pkg"
#      
class InstallExamplesManifestFormat(TypedDict):
    # Note that sources here is split into source (str) vs. sources (List[str])
    sources: NotRequired[List[str]]
    source: NotRequired[
        Annotated[
            str,
            DebputyParseHint.target_attribute("sources")
        ]
    ]
    # We allow the user to write  into: foo  in addition to  into: [foo] 
    into: Union[str, List[str]]
# ... into
#      
#        "source": ["foo"]
#        "into": ["pkg"]
#      
class InstallExamplesTargetFormat(TypedDict):
    # Which source files to install (dest-dir is fixed)
    sources: List[str]
    # Which package(s) that should have these files installed.
    into: NotRequired[List[str]]

# Map from
class InstallExamplesManifestFormat(TypedDict):
    # Note that sources here is split into source (str) vs. sources (List[str])
    sources: NotRequired[List[str]]
    source: NotRequired[
        Annotated[
            str,
            DebputyParseHint.target_attribute("sources")
        ]
    ]
    # We allow the user to write  into: foo  in addition to  into: [foo] 
    into: Union[BinaryPackage, List[BinaryPackage]]
# ... into
class InstallExamplesTargetFormat(TypedDict):
    # Which source files to install (dest-dir is fixed)
    sources: List[str]
    # Which package(s) that should have these files installed.
    into: NotRequired[
        Annotated[
            List[BinaryPackage],
            DebputyParseHint.required_when_multi_binary()
        ]
    ]

Three tiers of emails The main reason my setup works for me, despite my receiving hundreds of spam messages every day, is that I split incoming emails into three tiers via procmail:

1. not spam: delivered to inbox
2. likely spam: quarantined in a soft_spam/ folder
3. definitely spam: silently deleted

I only ever have to review the likely spam tier for false positives, which is on the order of 10-30 spam emails a day. I never even see the the hundreds that are silently deleted due to a very high score. This is implemented based on a threshold in my .procmailrc:

# Use spamassassin to check for spam
:0fw: .spamassassin.lock
  /usr/bin/spamassassin
# Throw away messages with a score of > 12.0
:0
* ^X-Spam-Level: \*\*\*\*\*\*\*\*\*\*\*\*
/dev/null
:0:
* ^X-Spam-Status: Yes
$HOME/Mail/soft_spam/
# Deliver all other messages
:0:
$ DEFAULT 

I also use the following ~/.muttrc configuration to easily report false negatives/positives and examine my likely spam folder via a shortcut in mutt:

unignore X-Spam-Level
unignore X-Spam-Status
macro index S "c=soft_spam/\n" "Switch to soft_spam"
# Tell mutt about SpamAssassin headers so that I can sort by spam score
spam "X-Spam-Status: (Yes No), (hits score)=(-?[0-9]+\.[0-9])" "%3"
folder-hook =soft_spam 'push ol'
folder-hook =spam 'push ou'
# <Esc>d = de-register as non-spam, register as spam, move to spam folder.
macro index \ed "<enter-command>unset wait_key\n<pipe-entry>spamassassin -r\n<enter-command>set wait_key\n<save-message>=spam\n" "report the message as spam"
# <Esc>u = unregister as spam, register as non-spam, move to inbox folder.
macro index \eu "<enter-command>unset wait_key\n<pipe-entry>spamassassin -k\n<enter-command>set wait_key\n<save-message>=inbox\n" "correct the false positive (this is not spam)"

Custom SpamAssassin rules In addition to the default ruleset that comes with SpamAssassin, I've also accrued a number of custom rules over the years. The first set comes from the (now defunct) SpamAssassin Rules Emporium. The second set is the one that backs bugs.debian.org and lists.debian.org. Note this second one includes archived copies of some of the SARE rules and so I only use some of the rules in the common/ directory. Finally, I wrote a few custom rules of my own based on specific kinds of emails I have seen slip through the cracks. I haven't written any of those in a long time and I suspect some of my rules are now obsolete. You may want to do your own testing before you copy these outright. In addition to rules to match more spam, I've also written a ruleset to remove false positives in French emails coming from many of the above custom rules. I also wrote a rule to get a bonus to any email that comes with a patch:

describe FM_PATCH   Includes a patch
body FM_PATCH   /\bdiff -pruN\b/
score FM_PATCH  -1.0

since it's not very common in spam emails

SpamAssassin settings When it comes to my system-wide SpamAssassin configuration in /etc/spamassassin/, I enable the following plugins:

loadplugin Mail::SpamAssassin::Plugin::AntiVirus
loadplugin Mail::SpamAssassin::Plugin::AskDNS
loadplugin Mail::SpamAssassin::Plugin::ASN
loadplugin Mail::SpamAssassin::Plugin::AutoLearnThreshold
loadplugin Mail::SpamAssassin::Plugin::Bayes
loadplugin Mail::SpamAssassin::Plugin::BodyEval
loadplugin Mail::SpamAssassin::Plugin::Check
loadplugin Mail::SpamAssassin::Plugin::DKIM
loadplugin Mail::SpamAssassin::Plugin::DNSEval
loadplugin Mail::SpamAssassin::Plugin::FreeMail
loadplugin Mail::SpamAssassin::Plugin::FromNameSpoof
loadplugin Mail::SpamAssassin::Plugin::HashBL
loadplugin Mail::SpamAssassin::Plugin::HeaderEval
loadplugin Mail::SpamAssassin::Plugin::HTMLEval
loadplugin Mail::SpamAssassin::Plugin::HTTPSMismatch
loadplugin Mail::SpamAssassin::Plugin::ImageInfo
loadplugin Mail::SpamAssassin::Plugin::MIMEEval
loadplugin Mail::SpamAssassin::Plugin::MIMEHeader
loadplugin Mail::SpamAssassin::Plugin::OLEVBMacro
loadplugin Mail::SpamAssassin::Plugin::PDFInfo
loadplugin Mail::SpamAssassin::Plugin::Phishing
loadplugin Mail::SpamAssassin::Plugin::Pyzor
loadplugin Mail::SpamAssassin::Plugin::Razor2
loadplugin Mail::SpamAssassin::Plugin::RelayEval
loadplugin Mail::SpamAssassin::Plugin::ReplaceTags
loadplugin Mail::SpamAssassin::Plugin::Rule2XSBody
loadplugin Mail::SpamAssassin::Plugin::SpamCop
loadplugin Mail::SpamAssassin::Plugin::TextCat
loadplugin Mail::SpamAssassin::Plugin::TxRep
loadplugin Mail::SpamAssassin::Plugin::URIDetail
loadplugin Mail::SpamAssassin::Plugin::URIEval
loadplugin Mail::SpamAssassin::Plugin::VBounce
loadplugin Mail::SpamAssassin::Plugin::WelcomeListSubject
loadplugin Mail::SpamAssassin::Plugin::WLBLEval

Some of these require extra helper packages or Perl libraries to be installed. See the comments in the relevant *.pre files. My ~/.spamassassin/user_prefs file contains the following configuration:

required_hits   5
ok_locales en fr
# Bayes options
score BAYES_00 -4.0
score BAYES_40 -0.5
score BAYES_60 1.0
score BAYES_80 2.7
score BAYES_95 4.0
score BAYES_99 6.0
bayes_auto_learn 1
bayes_ignore_header X-Miltered
bayes_ignore_header X-MIME-Autoconverted
bayes_ignore_header X-Evolution
bayes_ignore_header X-Virus-Scanned
bayes_ignore_header X-Forwarded-For
bayes_ignore_header X-Forwarded-By
bayes_ignore_header X-Scanned-By
bayes_ignore_header X-Spam-Level
bayes_ignore_header X-Spam-Status

as well as manual score reductions due to false positives, and manual score increases to help push certain types of spam emails over the 12.0 definitely spam threshold. Finally, I have the FuzzyOCR package installed since it has occasionally flagged some spam that other tools had missed. It is a little resource intensive though and so you may want to avoid this one if you are filtering spam for other people. As always, feel free to leave a comment if you do something else that works well and that's not included in my setup. This is a work-in-progress.

Screentest is dead It was removed from Debian in May 2023 but had already missed two releases (Debian 11 "bullseye" and 12 "bookworm") due to release critical bugs. The stated reason for removal was:

The package is orphaned and its upstream is no longer developed. It depends on gtk2, has a low popcon and no reverse dependencies.

So I had little hope to see this program back in Debian. The git repository shows little activity, the last being two years ago. Interestingly, I do not quite remember what it was testing, but I do remember it to find dead pixels, confirm native resolution, and various pixel-peeping. Here's a screenshot of one of the screentest screens: Now, I think it's safe to assume this program is dead and buried, and anyways I'm running wayland now, surely there's something better? Well, no. Of course not. Someone would know about it and tell me before I go on a random coding spree in a fit of procrastination... riiight? At least, the Debconf video team didn't seem to know of any replacement. They actually suggested I just "invoke gstreamer directly" and "embrace the joy of shell scripting".

Screentest reborn So, I naively did exactly that and wrote a horrible shell script. Then I realized the next step was to write an command line parser and monitor geometry guessing, and thought "NOPE, THIS IS WHERE THE SHELL STOPS", and rewrote the whole thing in Python. Now, screentest lives as a ~400-line Python script, half of which is unit test data and command-line parsing.

Why screentest Some smarty pants is going to complain and ask why the heck one would need something like that (and, well, someone already did), so maybe I can lay down a list of use case:

• testing color output, in broad terms (answering the question of "is it just me or this project really yellow?")
• testing focus and keystone ("this looks blurry, can you find a nice sharp frame in that movie to adjust focus?")
• test for native resolution and sharpness ("does this projector really support 4k for 30$? that sounds like bullcrap")
• looking for dead pixels ("i have a new monitor, i hope it's intact")

What does screentest do? Screentest displays a series of "patterns" on screen. The list of patterns is actually hardcoded in the script, copy-pasted from this list from the videotestsrc gstreamer plugin, but you can pass any pattern supported by your gstreamer installation with --patterns. A list of patterns relevant to your installation is available with the gst-inspect-1.0 videotestsrc command. By default, screentest goes through all patterns. Each pattern runs indefinitely until the you close the window, then the next pattern starts. You can restrict to a subset of patterns, for example this would be a good test for dead pixels:

screentest --patterns black,white,red,green,blue

This would be a good sharpness test:

screentest --patterns pinwheel,spokes,checkers-1,checkers-2,checkers-4,checkers-8

A good generic test is the classic SMPTE color bars and is the first in the list, but you can run only that test with:

screentest --patterns smpte

(I will mention, by the way, that as a system administrator with decades of experience, it is nearly impossible to type SMPTE without first typing SMTP and re-typing it again a few times before I get it right. I fully expect this post to have numerous typos.)

Here's an example of the SMPTE pattern from Wikipedia: For multi-monitor setups, screentest also supports specifying which output to use as a native resolution, with --output. Failing that, it will try to look at the outputs and use the first it will find. If it fails to find anything, you can specify a resolution with --resolution WIDTHxHEIGHT. I have tried to make it go full screen by default, but stumbled a bug in Sway that crashes gst-launch. If your Wayland compositor supports it, you can possibly enable full screen with --sink waylandsink fullscreen=true. Otherwise it will create a new window that you will have to make fullscreen yourself. For completeness, there's also an --audio flag that will emit the classic "drone", a sine wave at 440Hz at 40% volume (the audiotestsrc gstreamer plugin. And there's a --overlay-name option to show the pattern name, in case you get lost and want to start with one of them again.

How this works Most of the work is done by gstreamer. The script merely generates a pipeline and calls gst-launch to show the output. That both limits what it can do but also makes it much easier to use than figuring out gst-launch. There might be some additional patterns that could be useful, but I think those are better left to gstreamer. I, for example, am somewhat nostalgic of the Philips circle pattern that used to play for TV stations that were off-air in my area. But that, in my opinion, would be better added to the gstreamer plugin than into a separate thing. The script shows which command is being ran, so it's a good introduction to gstreamer pipelines. Advanced users (and the video team) will possibly not need screentest and will design their own pipelines with their own tools. I've previously worked with ffmpeg pipelines (in another such procrastinated coding spree, video-proxy-magic), and I found gstreamer more intuitive, even though it might be slightly less powerful. In retrospect, I should probably have picked a new name, to avoid crashing the namespace already used by the project, which is now on GitHub. Who knows, it might come back to life after this blog post; it would not be the first time. For now, the project lives along side the rest of my scripts collection but if there's sufficient interest, I might move it to its own git repositories. Comments, feedback, contributions are as usual welcome. And naturally, if you know something better for this kind of stuff, I'm happy to learn more about your favorite tool! So now I have finally found something to test my projector, which will likely confirm what I've already known all along: that it's kind of a piece of crap and I need to get a proper one.

Pre-Debugging Steps: Before diving into an issue, it s crucial to perform two essential steps: 1) Check the latest changes: Ensure you re working with the latest AMD driver modifications located in the amd-staging-drm-next branch maintained by Alex Deucher. You may also find bug fixes for newer kernel versions on branches that have the name pattern drm-fixes-<date>. 2) Examine the issue tracker: Confirm that your issue isn t already documented and addressed in the AMD display driver issue tracker. If you find a similar issue, you can team up with others and speed up the debugging process.

Understanding the issue: Do you really need to change this? Where should you start looking for changes? 3) Is the issue in the AMD kernel driver or in the userspace?: Identifying the source of the issue is essential regardless of the GPU vendor. Sometimes this can be challenging so here are some helpful tips:

• Record the screen: Capture the screen using a recording app while experiencing the issue. If the bug appears in the capture, it s likely a userspace issue, not the kernel display driver.
• Analyze the dmesg log: Look for error messages related to the display driver in the dmesg log. If the error message appears before the message [drm] Display Core v... , it s not likely a display driver issue. If this message doesn t appear in your log, the display driver wasn t fully loaded and you will see a notification that something went wrong here.

4) AMD Display Manager vs. AMD Display Core: The AMD display driver consists of two components:

• Display Manager (DM): This component interacts directly with the Linux DRM infrastructure. Occasionally, issues can arise from misinterpretations of DRM properties or features. If the issue doesn t occur on other platforms with the same AMD hardware - for example, only happens on Linux but not on Windows - it s more likely related to the AMD DM code.
• Display Core (DC): This is the platform-agnostic part responsible for setting and programming hardware features. Modifications to the DC usually require validation on other platforms, like Windows, to avoid regressions.

5) Identify the DC HW family: Each AMD GPU has variations in its hardware architecture. Features and helpers differ between families, so determining the relevant code for your specific hardware is crucial.

• Find GPU product information in Linux/AMD GPU documentation
• Check the dmesg log for the Display Core version (since this commit in Linux kernel 6.3v). For example:
  • [drm] Display Core v3.2.241 initialized on DCN 2.1
  • [drm] Display Core v3.2.237 initialized on DCN 3.0.1

Investigating the relevant driver code: Keep from letting unrelated driver code to affect your investigation. 6) Narrow the code inspection down to one DC HW family: the relevant code resides in a directory named after the DC number. For example, the DCN 3.0.1 driver code is located at drivers/gpu/drm/amd/display/dc/dcn301. We all know that the AMD s shared code is huge and you can use these boundaries to rule out codes unrelated to your issue. 7) Newer families may inherit code from older ones: you can find dcn301 using code from dcn30, dcn20, dcn10 files. It s crucial to verify which hooks and helpers your driver utilizes to investigate the right portion. You can leverage ftrace for supplemental validation. To give an example, it was useful when I was updating DCN3 color mapping to correctly use their new post-blending color capabilities, such as:

• [PATCH] drm/amd/display: set stream gamut remap matrix to MPC for DCN3+

Additionally, you can use two different HW families to compare behaviours. If you see the issue in one but not in the other, you can compare the code and understand what has changed and if the implementation from a previous family doesn t fit well the new HW resources or design. You can also count on the help of the community on the Linux AMD issue tracker to validate your code on other hardware and/or systems. This approach helped me debug a 2-year-old issue where the cursor gamma adjustment was incorrect in DCN3 hardware, but working correctly for DCN2 family. I solved the issue in two steps, thanks for community feedback and validation:

• [PATCH] drm/amd/display: check attr flag before set cursor degamma on DCN3+
• [PATCH] drm/amd/display: enable cursor degamma for DCN3+ DRM legacy gamma

8) Check the hardware capability screening in the driver: You can currently find a list of display hardware capabilities in the drivers/gpu/drm/amd/display/dc/dcn*/dcn*_resource.c file. More precisely in the dcn*_resource_construct() function. Using DCN301 for illustration, here is the list of its hardware caps:

	/*************************************************
	 *  Resource + asic cap harcoding                *
	 *************************************************/
	pool->base.underlay_pipe_index = NO_UNDERLAY_PIPE;
	pool->base.pipe_count = pool->base.res_cap->num_timing_generator;
	pool->base.mpcc_count = pool->base.res_cap->num_timing_generator;
	dc->caps.max_downscale_ratio = 600;
	dc->caps.i2c_speed_in_khz = 100;
	dc->caps.i2c_speed_in_khz_hdcp = 5; /*1.4 w/a enabled by default*/
	dc->caps.max_cursor_size = 256;
	dc->caps.min_horizontal_blanking_period = 80;
	dc->caps.dmdata_alloc_size = 2048;
	dc->caps.max_slave_planes = 2;
	dc->caps.max_slave_yuv_planes = 2;
	dc->caps.max_slave_rgb_planes = 2;
	dc->caps.is_apu = true;
	dc->caps.post_blend_color_processing = true;
	dc->caps.force_dp_tps4_for_cp2520 = true;
	dc->caps.extended_aux_timeout_support = true;
	dc->caps.dmcub_support = true;
	/* Color pipeline capabilities */
	dc->caps.color.dpp.dcn_arch = 1;
	dc->caps.color.dpp.input_lut_shared = 0;
	dc->caps.color.dpp.icsc = 1;
	dc->caps.color.dpp.dgam_ram = 0; // must use gamma_corr
	dc->caps.color.dpp.dgam_rom_caps.srgb = 1;
	dc->caps.color.dpp.dgam_rom_caps.bt2020 = 1;
	dc->caps.color.dpp.dgam_rom_caps.gamma2_2 = 1;
	dc->caps.color.dpp.dgam_rom_caps.pq = 1;
	dc->caps.color.dpp.dgam_rom_caps.hlg = 1;
	dc->caps.color.dpp.post_csc = 1;
	dc->caps.color.dpp.gamma_corr = 1;
	dc->caps.color.dpp.dgam_rom_for_yuv = 0;
	dc->caps.color.dpp.hw_3d_lut = 1;
	dc->caps.color.dpp.ogam_ram = 1;
	// 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;
	dc->caps.color.mpc.num_3dluts = pool->base.res_cap->num_mpc_3dlut; //2
	dc->caps.color.mpc.ogam_ram = 1;
	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;
	dc->caps.dp_hdmi21_pcon_support = true;
	/* read VBIOS LTTPR caps */
	if (ctx->dc_bios->funcs->get_lttpr_caps)  
		enum bp_result bp_query_result;
		uint8_t is_vbios_lttpr_enable = 0;
		bp_query_result = ctx->dc_bios->funcs->get_lttpr_caps(ctx->dc_bios, &is_vbios_lttpr_enable);
		dc->caps.vbios_lttpr_enable = (bp_query_result == BP_RESULT_OK) && !!is_vbios_lttpr_enable;
	 
	if (ctx->dc_bios->funcs->get_lttpr_interop)  
		enum bp_result bp_query_result;
		uint8_t is_vbios_interop_enabled = 0;
		bp_query_result = ctx->dc_bios->funcs->get_lttpr_interop(ctx->dc_bios, &is_vbios_interop_enabled);
		dc->caps.vbios_lttpr_aware = (bp_query_result == BP_RESULT_OK) && !!is_vbios_interop_enabled;
	 

Keep in mind that the documentation of color capabilities are available at the Linux kernel Documentation.

Understanding the development history: What has brought us to the current state? 9) Pinpoint relevant commits: Use git log and git blame to identify commits targeting the code section you re interested in. 10) Track regressions: If you re examining the amd-staging-drm-next branch, check for regressions between DC release versions. These are defined by DC_VER in the drivers/gpu/drm/amd/display/dc/dc.h file. Alternatively, find a commit with this format drm/amd/display: 3.2.221 that determines a display release. It s useful for bisecting. This information helps you understand how outdated your branch is and identify potential regressions. You can consider each DC_VER takes around one week to be bumped. Finally, check testing log of each release in the report provided on the amd-gfx mailing list, such as this one Tested-by: Daniel Wheeler:

• RE: [PATCH 00/13] DC Patches for Dec 11, 2023

Reducing the inspection area: Focus on what really matters. 11) Identify involved HW blocks: This helps isolate the issue. You can find more information about DCN HW blocks in the DCN Overview documentation. In summary:

• Plane issues are closer to HUBP and DPP.
• Blending/Stream issues are closer to MPC, OPP and OPTC. They are related to DRM CRTC subjects.

This information was useful when debugging a hardware rotation issue where the cursor plane got clipped off in the middle of the screen. Finally, the issue was addressed by two patches:

• [PATCH 21/22] drm/amd/display: Fix rotated cursor offset calculation
• [PATCH] drm/amd/display: fix cursor offset on rotation 180

12) Issues around bandwidth (glitches) and clocks: May be affected by calculations done in these HW blocks and HW specific values. The recalculation equations are found in the DML folder. DML stands for Display Mode Library. It s in charge of all required configuration parameters supported by the hardware for multiple scenarios. See more in the AMD DC Overview kernel docs. It s a math library that optimally configures hardware to find the best balance between power efficiency and performance in a given scenario. Finding some clk variables that affect device behavior may be a sign of it. It s hard for a external developer to debug this part, since it involves information from HW specs and firmware programming that we don t have access. The best option is to provide all relevant debugging information you have and ask AMD developers to check the values from your suspicions.

• Do a trick: If you suspect the power setup is degrading performance, try setting the amount of power supplied to the GPU to the maximum and see if it affects the system behavior with this command: sudo bash -c "echo high > /sys/class/drm/card0/device/power_dpm_force_performance_level"

I learned it when debugging glitches with hardware cursor rotation on Steam Deck. My first attempt was changing the clock calculation. In the end, Rodrigo Siqueira proposed the right solution targeting bandwidth in two steps:

• Patch series to create a new internal commit sequence
• Enabling pipe split on DCN301

Checking implicit programming and hardware limitations: Bring implicit programming to the level of consciousness and recognize hardware limitations. 13) Implicit update types: Check if the selected type for atomic update may affect your issue. The update type depends on the mode settings, since programming some modes demands more time for hardware processing. More details in the source code:

/* Surface update type is used by dc_update_surfaces_and_stream
 * The update type is determined at the very beginning of the function based
 * on parameters passed in and decides how much programming (or updating) is
 * going to be done during the call.
 *
 * UPDATE_TYPE_FAST is used for really fast updates that do not require much
 * logical calculations or hardware register programming. This update MUST be
 * ISR safe on windows. Currently fast update will only be used to flip surface
 * address.
 *
 * UPDATE_TYPE_MED is used for slower updates which require significant hw
 * re-programming however do not affect bandwidth consumption or clock
 * requirements. At present, this is the level at which front end updates
 * that do not require us to run bw_calcs happen. These are in/out transfer func
 * updates, viewport offset changes, recout size changes and pixel
depth changes.
 * This update can be done at ISR, but we want to minimize how often
this happens.
 *
 * UPDATE_TYPE_FULL is slow. Really slow. This requires us to recalculate our
 * bandwidth and clocks, possibly rearrange some pipes and reprogram
anything front
 * end related. Any time viewport dimensions, recout dimensions,
scaling ratios or
 * gamma need to be adjusted or pipe needs to be turned on (or
disconnected) we do
 * a full update. This cannot be done at ISR level and should be a rare event.
 * Unless someone is stress testing mpo enter/exit, playing with
colour or adjusting
 * underscan we don't expect to see this call at all.
 */
enum surface_update_type  
UPDATE_TYPE_FAST, /* super fast, safe to execute in isr */
UPDATE_TYPE_MED,  /* ISR safe, most of programming needed, no bw/clk change*/
UPDATE_TYPE_FULL, /* may need to shuffle resources */
 ;

Using tools: Observe the current state, validate your findings, continue improvements. 14) Use AMD tools to check hardware state and driver programming: help on understanding your driver settings and checking the behavior when changing those settings.

• DC Visual confirmation: Check multiple planes and pipe split policy.
• DTN logs: Check display hardware state, including rotation, size, format, underflow, blocks in use, color block values, etc.
• UMR: Check ASIC info, register values, KMS state - links and elements (framebuffers, planes, CRTCs, connectors). Source: UMR project documentation

15) Use generic DRM/KMS tools:

• IGT test tools: Use generic KMS tests or develop your own to isolate the issue in the kernel space. Compare results across different GPU vendors to understand their implementations and find potential solutions. Here AMD also has specific IGT tests for its GPUs that is expect to work without failures on any AMD GPU. You can check results of HW-specific tests using different display hardware families or you can compare expected differences between the generic workflow and AMD workflow.
• drm_info: This tool summarizes the current state of a display driver (capabilities, properties and formats) per element of the DRM/KMS workflow. Output can be helpful when reporting bugs.

Don t give up! Debugging issues in the AMD display driver can be challenging, but by following these tips and leveraging available resources, you can significantly improve your chances of success. Worth mentioning: This blog post builds upon my talk, I m not an AMD expert, but presented at the 2022 XDC. It shares guidelines that helped me debug AMD display issues as an external developer of the driver. Open Source Display Driver: The Linux kernel/AMD display driver is open source, allowing you to actively contribute by addressing issues listed in the official tracker. Tackling existing issues or resolving your own can be a rewarding learning experience and a valuable contribution to the community. Additionally, the tracker serves as a valuable resource for finding similar bugs, troubleshooting tips, and suggestions from AMD developers. Finally, it s a platform for seeking help when needed. Remember, contributing to the open source community through issue resolution and collaboration is mutually beneficial for everyone involved.

# 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"

./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

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

./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

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

• 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.

Reproducible Builds Summit 2023 Between October 31st and November 2nd, we held our seventh Reproducible Builds Summit in Hamburg, Germany! Amazingly, the agenda and all notes from all sessions are all online many thanks to everyone who wrote notes from the sessions. As a followup on one idea, started at the summit, Alexander Couzens and Holger Levsen started work on a cache (or tailored front-end) for the snapshot.debian.org service. The general idea is that, when rebuilding Debian, you do not actually need the whole ~140TB of data from snapshot.debian.org; rather, only a very small subset of the packages are ever used for for building. It turns out, for amd64, arm64, armhf, i386, ppc64el, riscv64 and s390 for Debian trixie, unstable and experimental, this is only around 500GB ie. less than 1%. Although the new service not yet ready for usage, it has already provided a promising outlook in this regard. More information is available on https://rebuilder-snapshot.debian.net and we hope that this service becomes usable in the coming weeks. The adjacent picture shows a sticky note authored by Jan-Benedict Glaw at the summit in Hamburg, confirming Holger Levsen s theory that rebuilding all Debian packages needs a very small subset of packages, the text states that 69,200 packages (in Debian sid) list 24,850 packages in their .buildinfo files, in 8,0200 variations. This little piece of paper was the beginning of rebuilder-snapshot and is a direct outcome of the summit! The Reproducible Builds team would like to thank our event sponsors who include Mullvad VPN, openSUSE, Debian, Software Freedom Conservancy, Allotropia and Aspiration Tech.

Beyond Trusting FOSS presentation at SeaGL On November 4th, Vagrant Cascadian presented Beyond Trusting FOSS at SeaGL in Seattle, WA in the United States. Founded in 2013, SeaGL is a free, grassroots technical summit dedicated to spreading awareness and knowledge about free source software, hardware and culture. The summary of Vagrant s talk mentions that it will:

[ ] introduce the concepts of Reproducible Builds, including best practices for developing and releasing software, the tools available to help diagnose issues, and touch on progress towards solving decades-old deeply pervasive fundamental security issues Learn how to verify and demonstrate trust, rather than simply hoping everything is OK!

Germane to the contents of the talk, the slides for Vagrant s talk can be built reproducibly, resulting in a PDF with a SHA1 of cfde2f8a0b7e6ec9b85377eeac0661d728b70f34 when built on Debian bookworm and c21fab273232c550ce822c4b0d9988e6c49aa2c3 on Debian sid at the time of writing.

Human Factors in Software Supply Chain Security Marcel Fourn , Dominik Wermke, Sascha Fahl and Yasemin Acar have published an article in a Special Issue of the IEEE s Security & Privacy magazine. Entitled A Viewpoint on Human Factors in Software Supply Chain Security: A Research Agenda, the paper justifies the need for reproducible builds to reach developers and end-users specifically, and furthermore points out some under-researched topics that we have seen mentioned in interviews. An author pre-print of the article is available in PDF form.

Community updates On our mailing list this month:

• Julien Lepiller mentioned that they were interested in translating our website, and provided offered GNU Guix s translation framework (Weblate) as a potential model to emulate.
• Bernhard M. Wiedemann posted a positive LibreOffice success story documenting that, after some work:

  [ ] today I hold in my hands the first two bit-identical LibreOffice rpm packages. And this is the success I wanted to share with you all today [and] it makes me feel as if we can solve anything.

• kpcyrd reported on their excellent results with making esp32c3 microcontroller firmware reproducible with Rust, repro-env and Arch Linux:

  I chose the esp32c3 [board] because it has good Rust support from the esp-rs project, and you can get a dev board for about 6-8 . To document my build environment I used repro-env together with Arch Linux because its archive is very reliable and contains all the different Rust development tools I needed.

• Separate to their work on LibreOffice however, Bernhard M. Wiedemann also requested assistance with a number of packages that so far refuse to build reproducibly. He writes that the common theme around them is that they use scheme or lisp to produce binaries with a dump command and hopes that someone may be able to help.
• Finally, Fay Stegerman regrettably reports that she will no longer be able to work on Android reproducible builds nor update the Reproducible Builds community with the status of reproducibility within F-Droid.

openSUSE updates Bernhard M. Wiedemann has created a wiki page outlining an proposal to create a general-purpose Linux distribution which consists of 100% bit-reproducible packages albeit minus the embedded signature within RPM files. It would be based on openSUSE Tumbleweed or, if available, its Slowroll-variant. In addition, Bernhard posted another monthly update for his work elsewhere in openSUSE.

Reproducibility-related changes in Debian As recently reported in the most recent Debian Developer News, Paul Gevers has integrated a package s reproducibility status into the way Debian migrates packages into the next stable release. For the amd64, arm64, i386 and armhf architectures, data is collected from the Reproducible Builds testing framework is collected by this migration software even though, at the time of writing, it neither causes nor migration bonuses nor blocks migration. Indeed, the information only results are visible on Britney s excuses as well as on individual packages pages on tracker.debian.org.

Ubuntu Launchpad now supports .buildinfo files Back in 2017, Steve Langasek filed a bug against Ubuntu s Launchpad code hosting platform to report that .changes files (artifacts of building Ubuntu and Debian packages) reference .buildinfo files that aren t actually exposed by Launchpad itself. This was causing issues when attempting to process .changes files with tools such as Lintian. However, it was noticed last month that, in early August of this year, Simon Quigley had resolved this issue, and .buildinfo files are now available from the Launchpad system.

PHP reproducibility updates There have been two updates from the PHP programming language this month. Firstly, the widely-deployed PHPUnit framework for the PHP programming language have recently released version 10.5.0, which introduces the inclusion of a composer.lock file, ensuring total reproducibility of the shipped binary file. Further details and the discussion that went into their particular implementation can be found on the associated GitHub pull request. In addition, the presentation Leveraging Nix in the PHP ecosystem has been given in late October at the PHP International Conference in Munich by Pol Dellaiera. While the video replay is not yet available, the (reproducible) presentation slides and speaker notes are available.

diffoscope changes diffoscope is our in-depth and content-aware diff utility that can locate and diagnose reproducibility issues. This month, Chris Lamb made a number of changes, including:

• Improving DOS/MBR extraction by adding support for 7z. [ ]
• Adding a missing RequiredToolNotFound import. [ ]
• As a UI/UX improvement, try and avoid printing an extended traceback if diffoscope runs out of memory. [ ]
• Mark diffoscope as stable on PyPI.org. [ ]
• Uploading version 252 to Debian unstable. [ ]

Website updates A huge number of notes were added to our website that were taken at our recent Reproducible Builds Summit held between October 31st and November 2nd in Hamburg, Germany. In particular, a big thanks to Arnout Engelen, Bernhard M. Wiedemann, Daan De Meyer, Evangelos Ribeiro Tzaras, Holger Levsen and Orhun Parmaks z. In addition to this, a number of other changes were made, including:

• Chris Lamb migrated the website s homepage to a hero image [ ], improved the documentation related to SOURCE_DATE_EPOCH and CMake [ ], added iomart (ne Bytemark) and DigitalOcean to our sponsors page [ ] and dropped an unnecessary link on some horizontal navigation buttons [ ].
• Holger Levsen also made a large number of notes pages from our 2022 summit in Venice [ ], migrated the website s syntax highlighter from [Pygments]https://pygments.org/() to Rouge [ ], fixed some grammar on our donate page [ ][ ][ ] and did a lot of updates to the Hamburg Summit s general information page [ ][ ].

Upstream patches The Reproducible Builds project detects, dissects and attempts to fix as many currently-unreproducible packages as possible. We endeavour to send all of our patches upstream where appropriate. This month, we wrote a large number of such patches, including:

• Bernhard M. Wiedemann:
  • amber-cli (date-related issue)
  • bin86 (FTBFS-2038)
  • buildah (timestamp)
  • colord (CPU)
  • google-noto-fonts (file modification issue)
  • grub2 (directory-related metadata)
  • guile-fibers (parallelism issue)
  • guile-newt (parallelism issue)
  • gutenprint (embedded date/hostname)
  • hub (random build path)
  • ipxe (nondeterministic behavoiour)
  • joker / joker
  • kopete (undefined behaviour)
  • kraft (embedde hostname)
  • libcamera (signature)
  • libguestfs (embeds build host file)
  • llvm (toolchain/Rust-related issue)
  • nfdump (date-related issue)
  • ovmf (unknown cause)
  • quazip (missing fonts)
  • rdflib (nondeterminstic behaviour)
  • rpm (toolchain)
  • tigervnc (embedded an RSA signature)
  • whatsie (date-related issue)
  • xen (time-related issue)
• Cathy Hu:
  • policycoreutils (sort-related issue)
• Chris Lamb:
  • #1055919 filed against python-ansible-pygments.
  • #1055920 filed against bidict.
  • #1056117 filed against meson.
  • #1056118 filed against radsecproxy.
  • #1056119 filed against taffybar.
  • #1056398 filed against php-doc.
  • #1056571 filed against pelican.
  • #1056572 filed against maildir-utils.
  • #1056573 filed against openmrac-data.
  • #1056649 filed against vectorscan.
• Vagrant Cascadian:
  • #1055969 filed against kuttypy.

Reproducibility testing framework The Reproducible Builds project operates a comprehensive testing framework (available at tests.reproducible-builds.org) in order to check packages and other artifacts for reproducibility. In October, a number of changes were made by Holger Levsen:

• Debian-related changes:
  • Track packages marked as Priority: important in a new package set. [ ][ ]
  • Stop scheduling packages that fail to build from source in bookworm [ ] and bullseye. [ ].
  • Add old releases dashboard link in web navigation. [ ]
  • Permit re-run of the pool_buildinfos script to be re-run for a specific year. [ ]
  • Grant jbglaw access to the osuosl4 node [ ][ ] along with lynxis [ ].
  • Increase RAM on the amd64 Ionos builders from 48 GiB to 64 GiB; thanks IONOS! [ ]
  • Move buster to archived suites. [ ][ ]
  • Reduce the number of arm64 architecture workers from 24 to 16 in order to improve stability [ ], reduce the workers for amd64 from 32 to 28 and, for i386, reduce from 12 down to 8 [ ].
  • Show the entire build history of each Debian package. [ ]
  • Stop scheduling already tested package/version combinations in Debian bookworm. [ ]
• Snapshot service for rebuilders
  • Add an HTTP-based API endpoint. [ ][ ]
  • Add a Gunicorn instance to serve the HTTP API. [ ]
  • Add an NGINX config [ ][ ][ ][ ]
• System-health:
  • Detect failures due to HTTP 503 Service Unavailable errors. [ ]
  • Detect failures to update package sets. [ ]
  • Detect unmet dependencies. (This usually occurs with builds of Debian live-build.) [ ]
• Misc-related changes:
  • do install systemd-ommd on jenkins. [ ]
  • fix harmless typo in squid.conf for codethink04. [ ]
  • fixup: reproducible Debian: add gunicorn service to serve /api for rebuilder-snapshot.d.o. [ ]
  • Increase codethink04 s Squid cache_dir size setting to 16 GiB. [ ]
  • Don t install systemd-oomd as it unfortunately kills sshd [ ]
  • Use debootstrap from backports when commisioning nodes. [ ]
  • Add the live_build_debian_stretch_gnome, debsums-tests_buster and debsums-tests_buster jobs to the zombie list. [ ][ ]
  • Run jekyll build with the --watch argument when building the Reproducible Builds website. [ ]
  • Misc node maintenance. [ ][ ][ ]

Other changes were made as well, however, including Mattia Rizzolo fixing rc.local s Bash syntax so it can actually run [ ], commenting away some file cleanup code that is (potentially) deleting too much [ ] and fixing the html_brekages page for Debian package builds [ ]. Finally, diagnosed and submitted a patch to add a AddEncoding gzip .gz line to the tests.reproducible-builds.org Apache configuration so that Gzip files aren t re-compressed as Gzip which some clients can t deal with (as well as being a waste of time). [ ]

---

If you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

• IRC: #reproducible-builds on irc.oftc.net.
• Mailing list: rb-general@lists.reproducible-builds.org
• Mastodon: @reproducible_builds
• Twitter: @ReproBuilds

• SVK, a DVCS built on top of Subversion, allowing users to create local (offline) branches of remote Subversion repositories. It was also known for its powerful merging capabilities. I picked it at some point for my Debian work, mainly because I needed to interact with Subversion repositories.
• Arch (tla), later known as GNU arch. From what I remember, it was awful to use. You think Git is complex or confusing? Arch was way worse. It was forked as "Bazaar", but the fork was abandoned in favor of "Bazaar-NG", now known as "Bazaar" or "bzr", a much more user-friendly DVCS. The first release of Bzr actually precedes Git's by two weeks. I guess it was too new to be considered by Linus Torvalds for the Linux kernel needs.
• Monotone, which I don't know much about, but it was mentioned by Linus Torvalds two days before the initial Git commit of Git. As far as I know, it was too slow for the Linux kernel's needs. I'll note in passing that Monotone is the creation of Graydon Hoare, who also created Rust.
• Darcs, with its patch-based model, rather than the common snapshot-based model, allowed more flexible management of changes. This approach came, however, at the expense of performance.

• Make sure git is installed. Chances are you already have it.
• Install git-cinnabar where mach bootstrap would install it.

  $ mkdir -p ~/.mozbuild/git-cinnabar
  $ cd ~/.mozbuild/git-cinnabar
  $ curl -sOL https://raw.githubusercontent.com/glandium/git-cinnabar/master/download.py
  $ python3 download.py && rm download.py

• Add git-cinnabar to your PATH. Make sure to also set that wherever you keep your PATH up-to-date (.bashrc or wherever else).

  $ PATH=$PATH:$HOME/.mozbuild/git-cinnabar

• Enter your mozilla-central or mozilla-unified Mercurial working copy, we'll do an in-place conversion, so that you don't need to move your mozconfigs, objdirs and what not.
• Initialize the git repository from GitHub.

  $ git init
  $ git remote add origin https://github.com/mozilla/gecko-dev
  $ git remote update origin

• Switch to a Mercurial remote.

  $ git remote set-url origin hg::https://hg.mozilla.org/mozilla-unified
  $ git config --local remote.origin.cinnabar-refs bookmarks
  $ git remote update origin --prune

• Fetch your local Mercurial heads.

  $ git -c cinnabar.refs=heads fetch hg::$PWD refs/heads/default/*:refs/heads/hg/*

  This will create a bunch of hg/<sha1> local branches, not all relevant to you (some come from old branches on mozilla-central). Note that if you're using Mercurial MQ, this will not pull your queues, as they don't exist as heads in the Mercurial repo. You'd need to apply your queues one by one and run the command above for each of them.
  Or, if you have bookmarks for your local Mercurial work, you can use this instead:

  $ git -c cinnabar.refs=bookmarks fetch hg::$PWD refs/heads/*:refs/heads/hg/*

  This will create hg/<bookmark_name> branches.
• Now, make git know what commit your working tree is on.

  $ git reset $(git cinnabar hg2git $(hg log -r . -T ' node '))

  This will take a little moment because Git is going to scan all the files in the tree for the first time. On the other hand, it won't touch their content or timestamps, so if you had a build around, it will still be valid, and mach build won't rebuild anything it doesn't have to.

$ git branch <branch_name> $(git cinnabar hg2git <hg_sha1>)

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.

---

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.

• https://codeberg.org/pere/docbook-example/
• https://pere.codeberg.page/docbook-example/