For a while I have been pondering over a problem that arises when your functionally written program has some state with cross references for example a list of users, each of which uses a number of computers, and a list of computers, each having an owner. Implicit referencing For doing queries on such data, it would be convenient if every reference is just the referenced object itself. Although we would visualize this as a graph, semantically, it is more like an infinite tree. This is possible in Haskell, due to laziness, and if you create the data structure cleverly, it even uses constant memory, no matter how deep you enter this infinite tree (a recent post of mine talks about this). A possible data definition would be:

data User = User  
	userName :: String,
	uses :: [Computer]
	 
data Computer = Computer  
	computerName :: String,
	owner :: User -- references the Users
	 
data State = State [User] [Computer]

testState = let user = User "Conrad" [computer]
                computer = Computer "Z3" user 
            in State [user] [computer]

Explicit referencing But such a representation is very unsuitable for updates (at least I can t think if a nice way of updating such a graph without breaking the internal cross-references) and serialization, which is a must for a HAppS based application. So what one would probably start with is this data structure:

data User = User  
	userId :: Int,
	userName :: String,
	uses :: [Int] -- references the Computers
	 
data Computer = Computer  
	computerId :: Int,
	computerName :: String,
	owner :: Int -- references the Users
	 
data State = State [User] [Computer]

testState = State
		[User 0 "Conrad" [1]]
		[Computer 1 "Z3" 0]

I think the semantics of this are clear. Note that the referencing is currently not type-safe, but this can be provided by phantom types. Maybe I ll write more about that later. Now imaging you want to display the information about the first computer with your web application. You extract the information with let State _ cs = testState in head cs and pass that to your templating engine. But what if your template wants to display the name of the owner? It only has access to his userId. You would either need to know what information the template will ever need, extract that from the state beforehand and pass it along, or give the template access to the whole state. In that case, though, there has to be lookup-logic in your output code, which is also not nice. Woudln t it be nice if you could, in your application logic, work with the explicit references, which are easy to modify and store, but somehow turn that into the implicit referencing? Duplicated representation One way would be to have two unrelated sets of data structures, ExplicitState, ExplicitUser, ExplicitComputer, which use explicit identifiers to reference each other, and ImplicitState,... which are defined as the first representation of our state. It is then mostly trivial to write a function that converts ExplicitState to ImplicitState. The big disadvantage of this is that you have to maintain these two different hierarchies. It also means that every function on the state has to be defined twice, which often almost identical code. Clearly, this is not desirable. Annotated representation It would be more elegant if the state is stored in one data type that, controlled by a type parameter, comes in the one or the other representation. To do that, we need two types: One that contains a value, and one that contains just a reference:

newtype Id v = Id v deriving (Show, Typeable, Data)
newtype Ref v = Ref Int deriving (Show, Typeable, Data)

Then we need to adjust our data definitions, to make use of these. (I ll leave out the names, to keep the code smaller)

data User ref = User  
	userId :: Int,
	uses :: [ref (Computer ref)]
	 
data Computer ref = Computer  
	computerId :: Int,
	owner :: ref (User ref)
	 
data State ref = State [User ref] [Computer ref]

Here we introduce a type parameter ref , which will later be either Id or Ref. Note that now a reference also states the object it is a reference for, which greatly increases type safety. Functions on these data types that don t work with the references will be polymorphic in the ref type parameter, so only need to be written once. A User Id is a complete user with all related data, while User Ref is a user with only references. And a Ref (User Ref) is reference to a user, which contains references... Not so kind kinds Did you notice the lack of a deriving clause? Our data structures have the relatively peculiar kind ((* -> *) -> *), which makes it hard for the compiler to derive instances for things like Show. But we already know that we will only use Id or Ref for the type variable, so we can use ghc s StandaloneDeriving language extension and have these instances created:

deriving instance Show (User Id)
deriving instance Show (User Ref)
deriving instance Show (Computer Id)
deriving instance Show (Computer Ref)
deriving instance Show (State Id)
deriving instance Show (State Ref)

Toggling a type parameter The next step is to write the conversion function. It will have type

unrefState :: State Ref -> State Id

For that, and for later, we need lookup functions:

unrefUserRef :: State Id -> Ref (User Ref) -> Id (User Id)
unrefUserRef (State l _) (Ref i) = Id $ fromJust $
	find (\u@(User i' _) -> i == i') l 
unrefComputerRef :: State Id -> Ref (Computer Ref) -> Id (Computer Id)
unrefComputerRef (State _ l) (Ref i) = Id $ fromJust $
	find (\u@(Computer i' _) -> i == i') l 

These expect a State (with implicit referencing) and a reference, and look up this reference. The function unrefState then looks like this:

unrefState :: State Ref -> State Id
unrefState (State us cs) =
	let unrefState = State (map (unrefUser unrefState) us)
	                       (map (unrefComp unrefState) cs)
	in unrefState
  where unrefUser :: State Id -> User Ref -> User Id
        unrefUser s (User i refs) = User i (map (unrefComputerRef s) refs)

	unrefComp :: State Id -> Computer Ref -> Computer Id
	unrefComp s (Computer i ref) = Computer i (unrefUserRef s ref)

Note how we tie the knot in the let expression. This is the trick that ensures constant memory consumption, because every reference points back to the same place in memory. Satisfied already? So what do we have? We have no duplication of data types, we can write general functions, and we can resolve the explicit referencing. We can also easily write functions like unrefUser :: State Ref -> User Ref -> User Id, which transform just a part of the state. But writing unrefState is very tedious when the State becomes more complex. Each of the other unrefSomething functions are very similar, but need to be written anyways. This is unsatisfactory. What we want, is a generic function, something like

gunref :: State Ref -> a Ref -> a Id

which, given a state with explicit references, replaces all explicit references in the first argument (which could be State Ref or User Ref or anything like that) with implicit ones. This function can not exist, because we would not know anything about a and b. But maybe we can do this:

gunref :: (Data (a Id), Data (a Ref)) =>  State Ref -> a Ref -> a Id

Typeable and Data Before being able to do so, we need to derive Data for our types. We can start with

deriving instance Data (User Id)
deriving instance Data (User Ref)
deriving instance Data (Computer Id)
deriving instance Data (Computer Ref)
deriving instance Data (State Id)
deriving instance Data (State Ref

but that will complain about missing Typeable instances. Unfortunately, ghc s deriver for Typeable (even the stand-alone-one), does not handle our peculiar kind, so we need to do it by hand. With some help from quicksilver on #haskell, I got it to work:

instance Typeable1 ref => Typeable (User ref) where
	typeOf _ = mkTyConApp (mkTyCon "User")     [typeOf1 (undefined :: ref ())]
instance Typeable1 ref => Typeable (Computer ref) where 
	typeOf _ = mkTyConApp (mkTyCon "Computer") [typeOf1 (undefined :: ref ())]
instance Typeable1 ref => Typeable (State ref) where 
	typeOf _ = mkTyConApp (mkTyCon "State")    [typeOf1 (undefined :: ref ())]

everywhere is not enough Turning to the documentation of Data.Generics, I notice with some disappointment that there is no function that is able to change a type they all seem to replace a value by another value of the same type. But the functions gfoldl and gunfold sounded like they could be used for this. Warning: What comes now is a very non-haskellish hack that subverts the type system, just to get the job done. Please read it with a healthy portion of distrust. If you know of a cleaner way of doing that, please tell me! Wrapped Data I want to do some heavy type hackery, so I need to disable haskell s type system. There is Data.Dynamic, but not even that is enough, as we need to carry a type s Data instance around as well. So let s wrap that up:

data AData where AData :: Data a => a -> AData
instance Show AData where show (AData a) = "<" ++ show (typeOf a) ++ ">"

fromADataE :: forall b. Data b => AData -> b
fromADataE (AData d) = case cast d of
	Just v -> v
	Nothing -> error $ "Type error, trying to convert " ++
			   show (typeOf d) ++ " to  " ++
			   show (typeOf (undefined :: b)) ++ "."

There is also a function that converts an AData back to a normal type, if possible. If it s not possible, then there is a bug in our code, so we give an informative error message. AData transformers Similar to everywhere, we want to have transformers that combinable. They need to have the change to convert an arbitrary value, but also signal that they could not convert something (and this something has to be recursed into). I came up with this:

type ADataT = AData -> Maybe AData

extADT :: forall a b. (Data a, Data b) => ADataT -> (a -> b) -> ADataT
extADT at t a@(AData v) = case cast v of 
		Just x ->  Just (AData (t x))
		Nothing -> at a

doNothing :: ADataT
doNothing = const Nothing

ADataT is the type for such a transformer. doNothing will not transform anything, and extADT can be used to add any function to the list of tried transformers, in the spirit of extT. The ugly part To apply such a transformer, I want to use this function, which I ll describe in the code comments:

everywhereADT :: forall a b. (Data a, Data b) => ADataT -> a -> b

-- first check if we can transform this value already
everywhereADT f v = case f (AData v) of
        -- if so, coerce it to the users  requested type, which hopefully goes well
	Just r ->  fromADataE r 
	-- if not, we need to recurse into the data structure
	Nothing -> recursed

	-- for that, we first need to figure out the arguments to the 
        -- constructor. We store them in the untyped list
  where args :: [AData]
        (Const args) = gfoldl k z v
	-- gfoldl lets us have a look at each argument. We wrap it in AData
        -- and append it to the list
	k (Const args) arg = Const (AData arg : args)
	z start = Const []

	-- We need the data constructor of the input data type. If the user did not want
        -- it to be transformed, it will be the same
	c = toConstr v

	-- To give better error messages, we make sure that the outmost type constructor
        -- of the requested type actually has the data constructor we were given. Otherwise
        -- gunfold will complain in a non-helpful way
	input_type = dataTypeRep (constrType c)
	output_type = dataTypeRep (dataTypeOf (undefined :: b))

	recursed = if input_type /= output_type
                   then error $ "Can not convert <" ++ show input_type ++ ">"++
                                            " to <" ++ show output_type ++ ">."
	-- the types match, so we assemble the output type, using gunfold
                   else snd (gunfold k' z' c)
	k' :: forall b r . Data b => ([AData], b -> r) -> ([AData],r)

	-- we start by reversing the input list
	z' start = (reverse args,start)
	
	-- then we call us recursively on the argument and feed the result
        -- to the output constructor
	k' ((AData a) : args, append) = (args, append (everywhereADT f a))

-- Used for folding (we don t need to retain the original constructor)
data Const a b = Const a 

What a beast! But surprisingly, it works. Here are some examples. Note that I always have to specify the requested output type:

bool2Int :: Bool -> Int
bool2Int False = 0
bool2Int True = 1

*Main> everywhereADT (doNothing  extADT  bool2Int) True :: Int
1
*Main> everywhereADT (doNothing  extADT  bool2Int) True :: ()
*** Exception: Type error, trying to convert Int to  ().
*Main> everywhereADT (doNothing  extADT  bool2Int) (True,False) :: (Int,Int)
(1,0)
*Main> everywhereADT (doNothing  extADT  bool2Int) ([True,False],True,()) :: ([Int],Int,())
([1,0],1,())
*Main> everywhereADT (doNothing  extADT  bool2Int) ([True,False],True,()) :: [()]
*** Exception: Can not convert  to .
*Main> everywhereADT (doNothing  extADT  bool2Int) [True] :: [Bool]
[*** Exception: Type error, trying to convert Int to  Bool.

I hope this code does not inflict too much pain on any Haskell-loving reader. I know I violated the language, but I didn t know how to do it better (at least not without using Template Haskell). I also know that this is not very good performance wide: Every single value in the input will be deconstructed, type-compared several times and re-assembled. If that is an issue, then this function should only be used for prototyping. Almost done To apply this to our state, we only need to glue it to our lookup functions from above:

gunref :: (Data (a Id), Data (a Ref)) =>  State Ref -> a Ref -> a Id
gunref s w = let unrefState = gunref' unrefState s
             in gunref' unrefState w

gunref' :: (Data (a Id), Data (a Ref)) =>  State Id -> a Ref -> a Id
gunref' unrefState = everywhereADT unref'
  where unref' = doNothing  extADT 
		 unrefUserRef unrefState  extADT 
		 unrefComputerRef unrefState

Now we have a generic unreferencer. I set the type a bit more specific than necessary, to make it safe to use (under the assumption that the list of lookup functions is complete and will not leave any Ref in the output).

*Main> testState 
State [User  userId = 0, uses = [Ref 1] ] [Computer  computerId = 1, owner = Ref 0 ]
*Main> gunref testState testState 
State [User  userId = 0, uses = [Id (Computer  computerId = 1, owner = Id (User  userId = 0,
uses = [Id (Computer  computerId = 1, owner = Id (User  userId = 0, uses = ..

Oh, and by the way, if you want to test this code, you ll need at least:

 -# LANGUAGE DeriveDataTypeable, FlexibleInstances, GADTs,
             FlexibleContexts, StandaloneDeriving, ScopedTypeVariables #- 

Since it took me more than one hour to figure out (and the documentation wasn't too helpful), here's how to enumerate audio devices in GStreamer:

import gst
sink=gst.element_factory_make("pulsesink","mysink")sink.probe_property_name("device")
devs = sink.probe_get_values_name("device")

Note that for some drivers (such as pulse) you explicitely need to call probe first, before you can get values. Also note that the ALSA module apparently only enumerates hardware devices, which probably is a bug in the module (according to Lennart's blog, you should use snd_device_name_hint which seems to be the only function to get all the ALSA devices, including software devices such as dmix or the pulse linking module).

So I replaced my Latitude D410 with a shiny new Latitude E4300 (Intel Core 2 Duo SP9400 2.4 Ghz with 4 Gb RAM). Here are some notes about this laptop that might be interesting for others. SSD disk I now use an SSD drive for my main disk (Dell Ultra Performance SSD, it s the second generation of Samsung SSD) and I m satisfied with that choice, I can boot (an unmodified Debian desktop install) from the SSD in less than 30 seconds while the same system booting from a traditional hard-disk takes more than 45 seconds. X server The Intel GM45 graphic card is not auto-recognized by Xorg 7.3 (or rather by xserver-xorg-video-intel 2.3.2 which is in lenny) so you end up with the vesa driver by default. It s possible to force the usage of the intel driver by adding a Driver intel line in the device section of xorg.conf but I have opted to use Xorg 7.4 (available in experimental). With this version, I can successfully use the DVI output in the associated dock and I have working suspend/resume. It does create some interesting problems however since that version of the xserver relies on HAL to detect the keyboard layout and doesn t use the Keyboard section of xorg.conf. You have to create /etc/hal/fdi/policy/10-keymap.fdi by using /usr/share/hal/fdi/policy/10osvendor/10-keymap.fdi as template and reload HAL then restart X. Wifi support The Intel 5100 Wifi chipset requires Linux 2.6.27 at least for the new iwlagn driver. This driver also needs a new firmware (the iwlwifi-5000 one) that is not yet integrated in the non-free package firmware-iwlwifi (see #497717). Sound support It works ok with alsa and the version integrated in linux 2.6.27 but it still has some rough edges when used in combination with the dock. Using the output jack connector on the dock doesn t stop the output in the integrated loudspeakers and the volume on that connector is so low that you could think that it doesn t work at all if you don t pay attention. Using the microphone works fine. For reference, if you play in the mixer, Front mic means the microphone connected on the dock while Mic means the one connected on the laptop. Each Analog loopback X option goes pairwise with the corresponding Input source X setting. In order for the recording to work, I have to set Digital Input Source to Analog Input , Digital must be activated and Input source 1 defines the default input used for the recording. Bluetooth support Contrary to the previous laptop, Dell offered no choice on the bluetooth chipset, they only propose the Dell 365 Bluetooth Card so I took it but it doesn t seem to work out of the box. In fact I can t even see it with lspci or lsusb so I wonder if they did something wrong during the assembly. Googling on the topic didn t gave me any good result, let me a comment if you know how to get this working. Update: so apparently the bluetooth component is there (ID 0a5c:4500 Broadcom Corp.), it just appears as an USB hub so it s somewhat difficult to guess that it s effectively a bluetooth card. Freezes, in particular with an amd64 installation I first installed the system in 64 bits mode (amd64 architecture) but I had very regular freezes of the system (I couldn t finish a single kernel compilation for example). Since I switched to an i386 installation, the system is more stable but I still get an occasional freeze every other day. It might be that a more recent kernel fixes this or maybe it will be fixed with a future Dell Bios update we ll see, but it s my biggest complaint with this laptop so far. Links Lucas Nussbaum bought the same laptop, you might want to read his remarks as well. More details Load the full article only if you want to see the lspci and lsusb output on this laptop.


rhertzog@rivendell:~$ lspci -nnk
00:00.0 Host bridge [0600]: Intel Corporation Mobile 4 Series Chipset Memory Controller Hub [8086:2a40] (rev 07)
Kernel driver in use: agpgart-intel
Kernel modules: intel-agp
00:02.0 VGA compatible controller [0300]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a42] (rev 07)
00:02.1 Display controller [0380]: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller [8086:2a43] (rev 07)
00:19.0 Ethernet controller [0200]: Intel Corporation 82567LM Gigabit Network Connection [8086:10f5] (rev 03)
Kernel driver in use: e1000e
Kernel modules: e1000e
00:1a.0 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #4 [8086:2937] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1a.1 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #5 [8086:2938] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1a.2 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #6 [8086:2939] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1a.7 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #2 [8086:293c] (rev 03)
Kernel driver in use: ehci_hcd
Kernel modules: ehci-hcd
00:1b.0 Audio device [0403]: Intel Corporation 82801I (ICH9 Family) HD Audio Controller [8086:293e] (rev 03)
Kernel driver in use: HDA Intel
Kernel modules: snd-hda-intel
00:1c.0 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 1 [8086:2940] (rev 03)
Kernel driver in use: pcieport-driver
Kernel modules: shpchp
00:1c.1 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 2 [8086:2942] (rev 03)
Kernel driver in use: pcieport-driver
Kernel modules: shpchp
00:1c.3 PCI bridge [0604]: Intel Corporation 82801I (ICH9 Family) PCI Express Port 4 [8086:2946] (rev 03)
Kernel driver in use: pcieport-driver
Kernel modules: shpchp
00:1d.0 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #1 [8086:2934] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1d.1 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #2 [8086:2935] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1d.2 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB UHCI Controller #3 [8086:2936] (rev 03)
Kernel driver in use: uhci_hcd
Kernel modules: uhci-hcd
00:1d.7 USB Controller [0c03]: Intel Corporation 82801I (ICH9 Family) USB2 EHCI Controller #1 [8086:293a] (rev 03)
Kernel driver in use: ehci_hcd
Kernel modules: ehci-hcd
00:1e.0 PCI bridge [0604]: Intel Corporation 82801 Mobile PCI Bridge [8086:2448] (rev 93)
00:1f.0 ISA bridge [0601]: Intel Corporation ICH9M-E LPC Interface Controller [8086:2917] (rev 03)
00:1f.2 RAID bus controller [0104]: Intel Corporation Mobile 82801 SATA RAID Controller [8086:282a] (rev 03)
Kernel driver in use: ahci
Kernel modules: ahci
00:1f.3 SMBus [0c05]: Intel Corporation 82801I (ICH9 Family) SMBus Controller [8086:2930] (rev 03)
Kernel driver in use: i801_smbus
Kernel modules: i2c-i801
02:01.0 FireWire (IEEE 1394) [0c00]: Ricoh Co Ltd R5C832 IEEE 1394 Controller [1180:0832] (rev 05)
Kernel driver in use: firewire_ohci
Kernel modules: firewire-ohci
02:01.1 SD Host controller [0805]: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter [1180:0822] (rev 22)
02:01.2 System peripheral [0880]: Ricoh Co Ltd R5C843 MMC Host Controller [1180:0843] (rev 12)
0c:00.0 Network controller [0280]: Intel Corporation Wireless WiFi Link 5100 [8086:4232]
Kernel driver in use: iwlagn
Kernel modules: iwlagn
$ lsusb
Bus 008 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 019: ID 046d:c03d Logitech, Inc. M-BT69a Pilot Optical Mouse
Bus 004 Device 018: ID 0424:2228 Standard Microsystems Corp. 9-in-2 Card Reader
Bus 004 Device 017: ID 0424:2602 Standard Microsystems Corp.
Bus 004 Device 016: ID 0424:2502 Standard Microsystems Corp.
Bus 004 Device 007: ID 045e:00dd Microsoft Corp.
Bus 004 Device 006: ID 0c45:63fe Microdia
Bus 004 Device 004: ID 413c:2513 Dell Computer Corp.
Bus 004 Device 003: ID 413c:2513 Dell Computer Corp.
Bus 004 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 005: ID 413c:8162 Dell Computer Corp.
Bus 001 Device 004: ID 413c:8161 Dell Computer Corp.
Bus 001 Device 003: ID 0a5c:4500 Broadcom Corp.
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 002: ID 0a5c:5800 Broadcom Corp.
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
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I have finally bought an EeePC 901, mainly to use for travelling.

I had been holding off for some weeks because I had hoped (in vain) that the Linux version with 20GB SSD and without a Windows XP license would become available here in Australia.

Anyway, I decided to try putting brand new Ubuntu Intrepid Ibex on it and I must say it worked really well. Here is what I did:

• Downloaded the standard Intrepid i386 Desktop CD and put it on a USB memory stick using UNetbootin.
• Installed with the following disk layout: / on 4GB SSD, 1GB swap and 7GB /home on 8GB SSD. (I setup a 1GB swap partition for hibernation and also used ext3 even though some sources say that the flash memory may die during the lifetime of the box.)
• One issue I noticed was that my static IP configuration did get lost between reboots. Eventually I created a new connection from scratch and that worked fine.
• After installation, I added the Ubuntu EeePC kernel and assorted tools which resolved the WLAN problem (even though I have not actually connected to any access points yet) and got all of the Hot Keys to work.
• I thought the screen was a bit dark, so I looked around and found that using the following command makes it much brighter: setpci -s 00:02.1 f4.b=ff. (This may fry the screen apparently, so use at own risk.)
  
• Also, the sound volume was very low. Appending the following to /etc/modprobe.d/alsa-base fixed this: options snd-hda-intel model=auto
  

Everything else is pretty much ok. Apart from smaller fonts and makingg windows go above the top panel (with: gconftool-2 --set /apps/compiz/plugins/move/allscreens/options/constrain_y --type bool 0), I have not really made any changes.

I am typing this on the little keyboard of the 901 and it is actually quite usable even though I would not want to type pages and pages on it. (Somehow the Blogger editor behaves a bit funny, but I guess this has nothing to do with the hardware but if anything with Firefox 3.)

So far, I think this is an excellent little machine - it even plays Big Buck Bunny in 720p without any problems. ;-)

Xorg 1.4 in experimental is supposed to have input device hotplugging.Does anyone have a Howto for Debian? I tried it, but I couldn't get it to hot-plug my USB mouse, so I'm back to using the regular mouse driver for it again, using the /dev/input/mice in-kernel-hack for hotplugging.P.S. on a recent kernel, you might want to add

blacklist snd_pcsp

to a custom file in /etc/modutils/, in order to avoid your PC speaker showing up as regular audio device. You don't want your regular apps to consider your legacy PC speaker as audio device usually.P.S. No, my blog doesn't have comments. Just send me an email (you know, 'legacy' email) via erich AT debian org.

Risto Suominen contacted me recently, after seeing my Ubuntu wiki page where I try to document what works and what doesn't using ALSA on PowerPC hardware. He has developed a patch against the snd-powermac driver that mainly support 603, 604 and G3 PowerMac hardware, to implement better support for several old Mac models. He was wondering where he could find testers for his work, so I offered to blog about it here. You can find his diff and patching instructions on his website. You can contact Risto to report on your testing's result using firstname.lastname@gmail.com

Today was a good day — at least if I average all the things happened today. And since Twitter.com is currently down and there’s no way all those things fit in 140 characters, I decided to pack them in a “short” blog post:

• This afternoon one backplane of our newest backup server caught fire. :-( No collateral damages though. :-) The machine is currently at the manufacturer and should be back on Monday.
• My EeePC (more about it in an upcoming blog post) recently overheated and switched off. It looked as if it since then didn’t turn off correctly anymore, but power and the fan stayed on although the operating system was shut down. Today I found out with help of the debian-eeepc-devel mailing list that my EeePC wasn’t damaged but the snd_hda_intel driver caused the machine to not shut down correctly. One rmmod line into /etc/default/halt and it shuts down perfectly and fast again. :-) See also the hint in the Debian Wiki.
• Even more: I’m sure that it not even has been turned by being hit by something through its neopren bag inside my backpack as I initially expected. It turned out that I must have not noticed that it wasn’t properly shut down and put it in the neopren case in that condition :-( since the power button simply doesn’t work when the lid is close. The good news: It doesn’t seem to have carried away any damage. :-)
• I had the same problem as Beat had: I couldn’t import certificates into my Nokia E51 mobile phone. I already tried to import the PEM and the DER versions of the CAcert root certificates but it just didn’t work. After Beat found out (Kudos to maol who pointed me to Beat’s blog posting), which certificate format is necessary, I found out that while the CAcert PEM certificates have the correct Content-Type header (application/x-x509-ca-cert) the DER certificates have not — they are served as text/plain. Downloading them to my server, adding the right content type to the config and downloading them from there again with the mobile phone worked fine and I now don’t need to acknowledge anymore the certificate of my IMAP server each time I want to read my e-mails on the mobile phone. :-)
• One more EeePC thing. During a discussion on the debian-eeepc-devel mailing list, I noted that the maximum summed up resolution of the internal and external display seems to be 800×800, but it turned out that you can configure that in your xorg.conf. :-) The screen section of my xorg.conf now looks like this:

  Section "Screen"
          Identifier      "Default Screen"
          Monitor         "Configured Monitor"
          SubSection "Display"
                  Virtual         2048 2048
          EndSubSection
  EndSection
  

  See also the xorg.conf in the Debian Wiki.

So if I sum up the smileys in this blog posting, I get 5 happy ones and only 2 sad ones. I think being happy outrun being unhappy today. ;-) Now I want to dive into my bath tub to get this smell of burning servers off me and my cloths. ;-)

Instructions how to use etchanhalf kernels are available too, please report problems to the mailinglist mentioned there.

I still have oldworld powerpc hardware to give away, if someone wants to have those for testing the new snd-powermac driver or whatever, please contact me. Appearantly my mail didn't make it to the powerpc list when I originally sent it, so I've just resend it.

Today I will switch the second PCs of my parents to Debian etch. They seem to like it and "Gnome is not really different than Windows" ;-)

2.6.24 has been uploaded on Saturday and passed NEW on Monday. It will be soonest available for all archs. If we don't get enough test coverage or things go bad 2.6.22 will be the fallback for Etch+half. The images install in Lenny/testing just fine. So please give it a spin. Known Issues are still missing VServer and Xen images, bnx2 + snd-cs46xx disabled due to firmware issue and ACPI userland still relying on old interfaces (for example #462305). For more adventurous souls the kernel buildserver will continue to track latest Linus git daily snapshot (enhanced ext4 should land soon). 2.6.24 will also soon be pushed to Testing. I repeat this is not the real Etch+half kernel yet as there will be some config changes for it, but it is pretty close. Thanks for your 2.6.24-rc7 feedback.

Yesterday I bought a laptop for a friend, who also asked me to install Linux on it. Since she's not computer-savvy at all, I opted for an Ubuntu. I provide here a short description of the hardware and what to expect regarding compatibility for anyone about to buy one of these. Hardware description

Model	HP 530
Part No.	GU322AA
CPU	Intel(R) Core(TM) Duo CPU T2300 @ 1.66GHz (stepping 12) - 2 MiB cache
CPU flags	fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx constant_tsc pni monitor est tm2 xtpr
Screen	330 mm x 250 mm viewable area, "glossy" wide-screen. 1280x800 pixels.
Video	Intel Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller
Audio	Intel 82801G (ICH7 Family) HDA
USB	Intel 82801G (ICH7 Family) USB2 EHCI Controller
Ethernet	Intel 82562ET/EZ/GT/GZ - PRO/100 VE (LOM) Ethernet Controller Mobile
WiFi	Intel Corporation PRO/Wireless 3945ABG Network Connection
Optical media	Optiarc DVD RW AD-7560A
Hard disk	Fujitsu MHY2120BH, 112GiB, max UDMA/100

Problems The only problems I had with the hardware were related to the sound card and the lid. The sound card had exactly the same problem as my Dell Inspiron 6400: it won't turn off the internal speakers when you plug something in the audio output jack. This is easily solved adding the following to /etc/modprobe.d/options: options snd-hda-intel enable=yes model=laptop The problem with the lid is that the screen didn't turn off when the lid closed. Just one time it did work, and stopped doing so after a reboot. Looking with acpi_listen, it seems that the acpi event isn't even generated. I don't know if this is a hardware or software problem. Also, some not very nice things should be noted about it: it has no independent media buttons for volume, suspend, etc.; only the WiFi transmitter kill and the power button, the rest needed a key chord. It has only two USB ports, which nowadays is incredibly few. No LEDs for hard dist, scroll lock or num lock. The audio jacks are on the front, which makes them very unsuitable for any straight plug. Although seldom used, it is nice to have the ability to turn the screen 180 , but this one can't do it. Finally, the battery is tiny: only four cells amounting 2 Ah of capacity. The power consumption seems a little better than my Dell: running on batteries, with low brightness, an idle GNOME desktop gave a reading of 820mA. Watching a movie from optical media in full screen ranged from 1 A to 1.3 A depending on the spinning of the media and the codec. Burning a DVD at 2x took 1.15 A The good After installing a Ubuntu 7.10, almost everything Just Worked . Of course it warned me about the non-free ipw3945 driver, but in seconds network-manager had connected to my home WLAN. Network manager could be a little more smart and turn off the WiFi transmitter when it's disabled by the user, but I guess that's not only an Ubuntu problem :). Most media keys worked out of the box, the WiFi kill switch worked OK, as did suspend to ram and to disk. Video acceleration and obligatory eye candy worked automatically. No problems either with burning a DVD, listening to music, watching a movie or connecting to my home network. The external aspect is not bad, the screen looks good, and the touch pad is very nice: just a matrix of dots over a surface that doesn't show any other sign of being an input method. In conclusion, it shows that it is a very cheap machine, but the drawbacks seem very few comparing to the good price. Tags: Planet Lugfi, Planet Debian, Tecnolog a

I recently bought a Fujitsu-Siemens LIFEBOOK S-4572 (sub)notebook on eBay for less than 150 Euros, a really great little machine. It's a Pentium III, 750 MHz, 256 MB RAM (the chipset cannot handle more than that unfortunately), 12.1" screen, ethernet, 2x USB 1.1, CD-ROM/DVD reader + CD-ROM writer, PCMCIA, IrDA, modem, and a 15 GB hard drive. No floppy, no serial ports, no parallel port. There's no wireless builtin, but I use a cheapo PCMCIA adapter. The greatest feature compared to all other laptops I previously owned is that the battery life is really great, it lasts almost 3 hours (compare that to 45 minutes on my current "main" laptop). I'm running Debian unstable on the box (of course). Here's the Linux support status as far as I have tested things: Networking Works out of the box using the e100 driver. Sound Works out of the box using the snd_intel8x0 driver. X11 Works out of the box, using either the vesa or the ati driver (at a max. resolution of 1024x768). Touchpad Works out of the box. Using the Option "SHMConfig" "on" line in /etc/X11/xorg.conf's InputDevice section (using the synaptics driver) also works fine and allows you to scroll using the touchpad, e.g. in a browser. More info in the SynapticsTouchpad page on the Debian wiki. CDROM, DVD Reading CD-ROMs and DVDs as well as burning CD-ROMs works fine. I don't think the drive is capable of writing DVDs. External VGA Displaying the screen contents on an external VGA monitor (or beamer) works just fine, switching is done using Fn+F10. PCMCIA Works fine, tested using the Sitecom WL-112 wireless card. The driver installation for that is straight-forward, too:

$ apt-get install rt2500-source
$ m-a a-i rt2500-source
$ dpkg -i /usr/src/rt2500*deb

Special keys All the Fn-keys work fine (brightness, volume, etc.). There are five other special keys (for starting a browser or something) which I haven't tested, but I don't really care... USB Works fine, but it's only USB 1.1, so some higher-speed devices will not work (DVB-T USB devices for example; PCMCIA DVB-T adapters might work). IrDA, Modem Untested, I don't care. Powersaving, Suspend to RAM It seems this CPU (Pentium III, Coppermine) doesn't support frequency scaling, so cpufreq-set doesn't work. I'm using laptop-mode-tools to improve battery life a bit more, though. Also, Suspend-to-RAM works fine out of the box:

$ apt-get install hibernate
$ hibernate-ram

I haven't tested Suspend-to-Disk yet, but I'm not sure it'll work anyway, as I'm using a dm-crypt'ed disk (+ LVM), as with all my boxes. lspci

00:00.0 Host bridge [0600]: Intel Corporation 82440MX Host Bridge [8086:7194] (rev 01)
00:00.1 Multimedia audio controller [0401]: Intel Corporation 82440MX AC'97 Audio Controller [8086:7195]
00:00.2 Modem [0703]: Intel Corporation 82440MX AC'97 Modem Controller [8086:7196]
00:07.0 Bridge [0680]: Intel Corporation 82440MX ISA Bridge [8086:7198] (rev 01)
00:07.1 IDE interface [0101]: Intel Corporation 82440MX EIDE Controller [8086:7199]
00:07.2 USB Controller [0c03]: Intel Corporation 82440MX USB Universal Host Controller [8086:719a]
00:07.3 Bridge [0680]: Intel Corporation 82440MX Power Management Controller [8086:719b]
00:12.0 Ethernet controller [0200]: Intel Corporation 82557/8/9 [Ethernet Pro 100] [8086:1229] (rev 09)
00:13.0 CardBus bridge [0607]: O2 Micro, Inc. OZ6933/711E1 CardBus/SmartCardBus Controller [1217:6933] (rev 02)
00:13.1 CardBus bridge [0607]: O2 Micro, Inc. OZ6933/711E1 CardBus/SmartCardBus Controller [1217:6933] (rev 02)
00:14.0 VGA compatible controller [0300]: ATI Technologies Inc Rage Mobility P/M [1002:4c52] (rev 64)
01:00.0 Network controller [0280]: RaLink RT2500 802.11g Cardbus/mini-PCI [1814:0201] (rev 01)

Other resources

• Linux on a Fujitsu Siemens S-4572 notebook
• Linux on the Fujitsu-Siemens LifeBook S-4572 Laptop
• LCO's Notebook: Fujitsu-Siemens S Series Lifebook S-4572
• FreeBSD on the Fujitsu-Siemens Lifebook S-4572
• Gentoo on Fujitsu Siemens s4572

I'm really considering making this my "main" box even though it's a bit older/slower, as my current laptop with 45 minutes battery life is a major pain when travelling...

I'm a happy NSLU2 user since a few months now, and I'm using it for all kinds of things, e.g. as a 24/7 remote ssh server at home (using DynDNS and the ddclient Debian package), as IRC logger (screen + irssi), etc. etc. I was considering multiple options as to where/how to install the slug (USB thumb drive, Compact Flash, disk drive, ...) but I settled with a full Debian install on an 1 GB USB thumb drive for now. I implemented some measures to maximize the life time of the USB thumb drive, maybe I'll post some info on that later... One new thing I've been trying lately is to use the slug as an audio player. As it doesn't come with an integrated sound card, you have to use an external USB audio device. I've got mine (see photo) from eBay for ca. 5 Euro (+ shipping) and it works out of the box with Linux 2.6.18 using the snd_usb_audio kernel module. You simply attach it via USB (the module is automatically loaded) and then attach external speakers to it. Here's an lsusb of the device:

Bus 001 Device 011: ID 1130:f211 Tenx Technology, Inc.

One problem with playing audio on the slug is the slow CPU. At 266 MHz (and without FPU!) playing audio with "normal" audio players such as mplayer or mpg321 is not possible. But there are several ways to make the slug play your favorite music. Here's a list of players I tested and a status report of whether they work at all. If yes, I listed a rough percentage of CPU load resulting from playing the music.

• MP3:
  • mplayer, mpg321, aplay, playsound, and splay don't work.
  • $ madplay foo.mp3: 17% CPU load
    

Ogg vorbis:

• mplayer, aplay, playsound, and ogg123 don't work.

• $ apt-get install libvorbisidec-dev
  $ cd /usr/share/doc/libvorbisidec-dev/examples
  $ make
  $ cat foo.ogg   ./ivorbisfile_example   aplay -f cd
  

  Result: 40% CPU load

MOD, XM, S3M, IT, etc.:

• $ mikmod foo.mod: 10% CPU load (even with compressed MOD files)

WAV:

• $ mplayer foo.wav: 10% CPU load
• $ aplay foo.wav: 10% CPU load
• $ playsound foo.wav: 10% CPU load

FLAC:

• $ flac123 foo.flac: 17% CPU load

SPEEX:

• $ speexdec foo.spx: doesn't work, 100% CPU load. Any known alternatives?

AU:

• $ cat foo.au > /dev/dsp: 3% CPU load (but sounds crappy)
• $ cat foo.au > /dev/audio: 3% CPU load (sounds better)
• $ mplayer foo.au: 5% CPU load
• $ aplay foo.au: 5% CPU load
• $ playsound foo.au: 5% CPU load

AIFF:

• $ sox foo.aiff -t wav - aplay: 50% CPU load (a bit stupid, but it works)

Streaming MP3:

• $ mplayer http://www.example.com/foo.mp3: doesn't work, 100% CPU load.
• $ wget http://www.example.com/foo.mp3 -O - madplay - : 17% CPU load

Streaming Ogg Vorbis:

• $ cd /usr/share/doc/libvorbisidec-dev/examples
$ wget http://www.example.com/foo.ogg -O - ./ivorbisfile_example aplay -f cd: 40% CPU load

The SlugAsAudioPlayer page in the NSLU2-Linux wiki might have further information on this topic. Feel free to add comments if you know of other audio types which can be played on an NSLU2.

I took some days off-line so the iBook story hasn’t progressed very much. On the other hand I’ve spent some time with my family and finaly finished Neil Stephenson’s Quicksilver. Sound Had some problems with the internal soundcard. I’m not quite sure what the porblem was, but the right module is snd_powermac and not anything like snd_aoa. Probaly did something else wrong along the way too. The fun part would be playing music throug AirTunes. raop-play claims to solve this problem. They got debian packages for i386 and a nice debian/ in the source tar-ball. The build-deps is missing fluid and libglib2.0-dev but other than that it builds nicely — but no sound… Nearly giving up I looked at the alsapcm module not part of the debian package, just to see how it worked in theory. And suddenly I could play music with mplayer -ao alsa:device=hw=1.0 music.ogg. Problem is that raop-play isn’t endian safe, but the alsapcm module forces use of little endian somewhere before the real raop-play. Afterward I’ve tested raop-play on amd64 where it works nicely. Java Java seems to be a problem. None of the packages of ibm-jre packages I’m seem to be able to find is supported by java-package. My Bank uses java, so that is kind of a show stopper, but I havn’t really looked into it yet. Flash, Youtube and the like Flash isn’t really a showstopper, but it would be nice to be able to see all the funny video clips people are refering to. None of the free flash plugins seems to work (swfdec, libfalsh-mozplugin), but youtube-dl and mplayer do the job. Futher work… Java is a major show stopper. I can’t switch for real without java support in my browser. The other problems is something I can live with. I migth even prefer to use AirTunes from my amd64 server instead of my laptop so I will probally ITP raop-play soon. Some people have asked why I want to switch away from wonderfull OS X. I’ll try to wirte something up one of the days - and no it’s is not anything personal against mac fans.

Life sometimes goes in a funny direction, like a full circle d j vu: 20 years ago, I was studying Technology of Computerized Systems (a combination of electronics and programming). Now, 20 years later, I'm starting a dream job as the Business Development Manager of Artec Group and their core business is you guessed it exactly that. The really cool thing about Artec, from a Free Software advocate's point of view, is that they contribute firmware and drivers for their products to LinuxBIOS and the Linux kernel. At this point, my initial tasks will focus on marketing and selling Artec's flagship OEM product, the ThinCan. What is the ThinCan? Actually, you're already familiar with one iteration of the product: the Linutop is a branded ThinCan, delivered with a custom hardware configuration, plus custom casing artwork designed by Fr d ric Baille of Linutop SARL and loaded with Fred's favorite Xubuntu configuration. In the Linutop's case, their business model is to fill the market niche for a simple Internet surfing platform that fits 80% of average people's daily computing needs, so the hardware configuration they ordered reflects that. Still, as several readers of this blog noticed, the "Linutop" could make a fantastic thin client and, sure enough, that was the main purpose behind the ThinCan's original design; it sells well in the Fortune-500 market as an RDP client running under Windows CE. However, until recently, there simply wasn't much demand for a contemporary X11 terminal solution based on the ThinCan. That is, until LTSP took off, thanks to the contributions of Edubuntu and similar educational Linux distributions. Sure enough, someone spotted the opportunity and contacted Artec to order a branded ThinCan iteration with Etherboot and PXE support, which they call the Linuterm. By the way, for those who need a really cheap OEM thin client, I've got a great spring clearance offer for you:

Artec has about 500 pieces left of their older DBE60 ThinCan model, based on the AMD Geode SC2200, and we're selling them at 100 euro / piece, plus VAT and shipping.

The DBE60 is configured with three USB 1.1 ports, one parallel printer port, one 100baseT Ethernet port, one VGA port (up to 1024x768 @ 16bpp 60-85Hz or 1280x1024 @ 8bpp 60-75Hz) and one 1/8" stereo audio output jack. Its BIOS provides Etherboot support and its motherboard is populated with 64MB of RAM and 32MB of Stratoflash. It comes delivered with a European AC adapter. The Geode SC2200 is fully supported by the Linux kernel with the sole exception of a missing ALSA snd-scx200, but this could easily be ported from AMD's deprecated OSS driver and X.org support is provided by the "nsc" driver.

Minimum order size is 10 pieces. Contact me via my full name (unaccented, with one hyphen and one dot) at artecgroup.com quoting this special offer.

PS: someone was asking if that DBE60 special is also available in the aforementioned Fortune-500 configuration. It indeed is: add 16 euro / piece for the Windows CE 4.1 license with an RDP client.