So, you've always been annoyed by the fact that you have to load all those laptop, i2c, hwmon, hdaps Linux kernel modules manually without having spiffy udev doing that work for you automagically? No more! I just sent a patch to LKML which adds DMI/SMBIOS-based module autoloading to the Linux kernel.

Hopefully this patch will be integrated into Linus' kernel shortly. As soon as that happens udev will automatically recognize your laptop/mainboard model and load the relevant modules.

Module maintainers, please add MODULE_ALIAS lines to your kernel modules to make sure that they are autoloaded using this new mechanism, as soon as it gets commited in Linus' kernel.

For a fully automatically configured system only ACPI-DSDT-based module autoloading is missing. I.e. load the "battery" module only when an ACPI battery is actually around.

Jeff now started to use lennartpoettering for tagging his blog stories... AWESOME!

One of the major construction sites in GNOME and all the other free desktop environments is the VFS abstraction. Recently, there has been some discussion about developing a replacement DVFS as replacement for the venerable Gnome-VFS system. Here are my 5 euro cent on this issue (Yepp, I am not fully up-to-date on the whole DVFS discussion, but during my flight from HEL to HAM I wrote this up, without being necesarily too well informed, lacking an Internet connection. Hence, if you find that I am an uniformed idiot, you're of course welcome to flame me!):

First of all, we have to acknowledge that Gnome-VFS never achieved any major adoption besides some core (not even all) GNOME applications. The reasons are many, among them: the API wasn't all fun, using Gnome-VFS added another dependency to applications, KDE uses a different abstraction (KIO), and many others. Adoption was suboptimal, and due to that user experience was suboptimal, too (to say the least).

One of the basic problems of Gnome-VFS is that it is a (somewhat) redundant abstraction layer over yet another abstraction layer. Gnome-VFS makes available an API that offers more or less the same functionality as the (most of the time) underlying POSIX API. The POSIX API is well accepted, relatively easy-to-use, portable and very well accepted. The same is not true for Gnome-VFS. Semantics of the translation between Gnome-VFS and POSIX are not always that clear. Paths understood by Gnome-VFS (URLs) follow a different model than those of the Linux kernel. Applications which understand Gnome-VFS can deal with FTP and HTTP resources, while the majority of the applications which do not link against Gnome-VFS does not understand it. Integration of Gnome-VFS-speaking and POSIX-speaking applications is difficult and most of the time only partially implementable.

So, in short: One one side we have that POSIX API which is a file system abstraction API. And a (kernel-based) virtual file system behind it. And on the other side we have the Gnome-VFS API which is also a file system abstraction API and a virtual file system behind it. Hence, why did we decide to standardize on Gnome-VFS, and not just on POSIX?

The major reason of course is that until recently accessing FTP, HTTP and other protocol shares through the POSIX API was not doable without special kernel patches. However, a while ago the FUSE system has been merged into the Linux kernel and has been made available for other operating systems as well, among them FreeBSD and MacOS X. This allows implementing file system drivers in userspace. Currently there are all kinds of these FUSE based file systems around, FTP and SSHFS are only two of them. My very own fusedav tool implements WebDAV for FUSE.

Another (*the* other?) major problem of the POSIX file system API is its synchronous design. While that is usually not a problem for local file systems and for high-speed network file systems such as NFS it becomes a problem for slow network FSs such as HTTP or FTP. Having the GUI block for various seconds while an application saves its documents is certainly not user friendly. But, can this be fixed? Yes, definitely, it can! Firstly, there already is the POSIX AIO interface -- which however is quite unfriendly to use (one reason is its use of Unix signals for notification of completed IO operations). Secondly, the (Linux) kernel people are working on a better asynchronous IO API (see the syslets/fibrils discussion). Unfortunately it will take a while before that new API will finally be available in upstream kernels. However, there's always the third solution: add an asynchronous API entirely in userspace. This is doable in a clean (and glib-ified) fashion: have a couple of worker threads which (synchronously) execute the various POSIX file system functions and add a nice, asynchronous API that can start and stop these threads, feed them operations to execute, and so on.

So, what's the grand solution I propose for the desktop VFS mess? First, kick Gnome-VFS entirely and don't replace it. Instead write a small D-Bus-accessible daemon that organizes a special directory ~/net/. Populate that directory with subdirectories for all WebDAV, FTP, NFS and SMB shares that can be found on the local network using both Avahi-based browsing and native SMB browsing. Now use the Linux automounting interface on top of that directory and automount the respective share every time someone wants to access it. For shares that are not announced via Avahi/Samba, add some D-Bus API (and a nice UI) for adding arbitrary shares. NFS and CIFS/SMB shares are mounted with the fast, optimized kernel filesystem implementation; WebDAV and FTP on the other hand are accessed via userspace FUSE-based file systems. The latter should also integrate with D-BUS in some way, to query the user nicely for access credentials and suchlike, with gnome-keyring support and everything.

~/net/ itself can -- but probably doesn't need to -- be a FUSE filesystem itself.

A shared library should be made available that will implement a few remaining things, that are not available in the POSIX file system API directly:

• As mentioned, some nice Glib-ish asynchronous POSIX file system API wrapper
• High-level file system operations such as copying, moving, deleting (trash!) which show a nice GUI when they are long-running operations.
• An API to translate and setup URL <-> filesystem mappings, i.e. something that translates ftp://test.local/a/certain/path/ to ~/net/ftp:test.local/a/certain/path and vice versa. (and probably also to a more user-friendly notation, maybe like "FTP Share on test.local" or similar). (Needs to communicate with the ~/net/ handling daemon to setup mappings if required)
• Meta data extraction. It makes sense to integrate that with extended attribute support (EA) in the kernel file system layer, which should be used more often anyway.
• Explicit mount operations (in contrast to implicit mounts, that are done through automounting) (this also needs to communicate with the ~/net/ daemon in some way)

Et voilá! Without a lot of new code you get a nice, asynchronous, modern, well integrated file system, that doesn't suck. (or at least, it doesn't suck as much as other solutions).

Also, this way we can escape the "abstraction trap". Let's KDE play the abstraction game, maybe they'll grow up eventually and learn that abstracting abstracted abstraction layers is child's play.

Yeah, sure, this proposed solution also has a few drawbacks, but be it that way. Here's a short incomprehensive list:

• The POSIX file system API sucks for file systems that don't have "inodes" or that are attached to a specific user sessions. -- Yes, sure, but both problems have been overcome by the FUSE project, at least partially.
• Not that portable -- Yes, but FUSE is now available for many systems besides Linux. The automount project is the bigger problem. But all you loose if you would run this proposed system on these (let's say "legacy") systems that don't have FUSE or automounting is access to FTP and WebDAV shares. So what? Local files can still be accessed.
• Translating between URLs and $HOME/net/ based paths sucks -- yepp, it does. But much less than not being able to access FTP/WebDAV shares from some apps but not from others, as we have it right now.
• Bah, you suck -- Yes, I do. On a straw, taking a nip from my caipirinha, right at the moment.

I guess I don't have to list all the advantages of this solution, do I?

BTW, pumping massive amounts of data through D-Bus sucks anyway.

And no, I am not going to hack on this. Too busy with other stuff.

The plane is now landing in HAM, that shall conclude our small rant.

Update: No, I didn't get a Caipirinha during my flight. That line I added in before publishing the blog story, which was when I was drinking my Caipirinha. In contrast to other people from the Free Software community I don't own my own private jet yet, with two stewardesses that might fix me a Caipirinha.

A while back there has been a lot of noise about the GNOME "platform" and what GNOME 3.0 should be. Personally -- while I certainly like the progress GNOME makes as a "platform" -- I must say that the platform is already quite good. In my opinion, what is lacking right now are more the tools and utilities that are shipped *with* the GNOME platform than the platform itself. More specifically there are a set of (rather small) tools I am really missing in the standard set of GNOME tools. So, here's my wishlist, in case anybody is interested to know:

<wishlist>

• A simple, usable VNC/RFB client as counterpart to the VNC server vino that has been shipped since early GNOME 2.0 times. Isn't it kind of awkward that we have been shipping a VNC server since ages, but no VNC client? What I want is a client (maybe called vinagre as a pun on vino) that is more than just a simple frontend to xvncviewer, but not necessarily too fancy. Something that integrates well into GNOME, i.e. uses D-Bus, gnome-keyring, avahi-ui. There seems to be a libvncclient library that might make the implementation of this tool easy.
• I am one of the (apparently not so few) people who run their GNOME session with LANG=de_DE and LC_MESSAGES=C, which enables german dates and everything else, but uses english messages. Right now it's a PITA to configure GNOME that way. It's not really documented how to do that, AFAIK. The best way to do this I found is to edit ~/.gnomerc and set the variables in there. A simple capplet which allows setting these environment variables from gnome-session would be a much better way to configure this. Nothing to fancy again. Just two drop down lists, to choose LANG and LC_MESSAGES and maybe a subset of the other i18n variables, and possibly G_FILENAME_ENCODING (although I might be the only one who still hasn't switched his $HOME to UTF-8)
• There's no world clock in GNOME. Sure, there are online tools for this, but I am not always online with my laptop.
• There is no simple tool to take photo snapshots or record short videos from webcams. I want to see something like camorama in gnome-media. Nothing too fancy again. No filters, no TV functionality. Just a small but useful GStreamer frontend.
• I'd like to see a simple BitTorrent client shipped with GNOME, which is integrated well into the rest of GNOME/Epiphany, so that downloading files from FTP or HTTP looks exactly like downloading them from Bittorrent.

</wishlist>

I'd love to see proper Avahi support in the Nokia N800 (just think of proper file manager integration of announced WebDAV shares!), but until now Nokia doesn't ship Avahi in Maemo. However, there's now a simple way to install at least basic Avahi support on the N800. The INdT includes Avahi in their Canola builds. Hence: just install Canola and your N800 will register itself via mDNS on your network.

In related news: I am happy to see that Avahi has apparently been included in the just announced GNOME Embedded Platform.

I have just released new versions of a few of my packages:

1. Avahi 0.6.18: The most interesting change is probably the addition of avahi-ui, our new GTK library which implements a standard dialog for browsing for Avahi services. A quick (albeit slightly out-of-date) introduction into avahi-ui (including screenshots) may be found in this old blog story of mine. If you are a developer of a GNOME application that acts as network client in some way, please consider adding support for avahi-ui to your project. Examples where adding support for avahi-ui makes sense are:
   • Mail applications such as Evolution may use it to browse for POP3, POP3S, IMAP, IMAPS and SMTP servers.
   • VNC applications may use it to browse for VNC/RFB servers
   • Database clients such as Glom may use it to browse for PostrgreSQL servers
   • FTP clients may use it to browse for FTP servers
   • RSS readers may use it to browse for local RSS feeds
   • And lots of others
   There are lots of other small and not so small changes in Avahi 0.6.18.
2. mod_dnssd 0.5: Mostly an update for Apache 2.2
3. mod_mime_xattr 0.4: dito

Does anybody know what's going on with LinuxTag? I submitted a presentation proposal a few months ago. I haven't yet received an email whether my talk has been accepted or not. According to their website notification emails should have been sent out on march 13th. Which is nearly a month ago now. When I login to the "virtual conference center" I see that my paper is still "In Review". They didn't respond to my emails (twice).

Does anyone have an idea what is going on?

Does anyone know what I can do to get psfrag work with PostScript files generated from Gnumeric (i.e. Cairo) charts?

Oh, and why does Gnumeric insist on using .ps as suffix for exported charts, although the files written are perfectly valid .eps files and presumably everyone uses them as such?

Thanks!

As it seems, the Avahi project has not been accepted as Google Summer of Code organization, much like the GStreamer project.

Grr, I cannot say I really understand why three wiki engines ^[1] got accepted, or a UI frontend for nmap - but not important infrastructure projects like GStreamer or Avahi. Mhmm, maybe I am just envious, and considering these two projects important is just hybris...

Anyway, we had already prepared a list of exciting ^[2] GSoC project ideas for Avahi. If anyone is interested to work on one of these there might be a small chance to get this done under the GNOME umbrella. Feel free to contact either me or Trent if you are interested!

Footnotes:

[1] If there is something we already have enough of in Free Software - then it is Wiki engines. just check the output of apt-cache search wiki | wc -l on a recent Debian system.

[2] In our definition of exciting, of course - which doesn't seem to be the same as Google's. Grrrh!

Finally, here's my linux.conf.au 2007 and FOMS 2007 recap. Maybe a little bit late, but better late then never.

FOMS was a very well organized conference with a packed schedule and a lot of high-profile attendees. To my surprise PulseAudio has been accepted by the attendees without any opposition (at least none was expressed aloud). After a few "discussions" on a few mailing lists (including GNOME MLs) and some personal emails I got, I had thought that more people were in opposition of the idea of having a userspace sound daemon for the desktop. Apparently, I was overly pessimistic. Good news, that!

During the FOMS conference we discussed the problems audio on Linux currently has. One of the major issues still is that we're lacking a cross-platform PCM audio API everyone agrees on. ALSA is Linux-specific and complicated to use. The only real contender is PortAudio. However, PortAudio has its share of problems and hasn't reach wide adoption yet. Right now most larger software projects implement an audio abstraction layer of some kind, and mostly in a very dirty, simplistic and limited fasion. MPlayer does, Xine does it, Flash does it. Everyone does it, and it sucks. (Note: this is only a very short overview why audio on Linux sucks right now. For a longer one, please have a look on the first 15mins of my PulseAudio talk at LCA, linked below.)

Several people were asking why not to make the PulseAudio API the new "standard" PCM API for Linux. Due to several reasons that would be a bad idea. First of all, the PulseAudio API cannot be used on anything else but PulseAudio. While PulseAudio has been ported to Win32, Vista already has a userspace desktop sound server, hence running PulseAudio on top of that doesn't make much sense. Thus the API is not exactly cross-platform. Secondly, I - as the guy who designed it - am not happy with the current PulseAudio API. While it is very powerful it is also very difficult to use and easy to misuse, mostly due to its fully asynchronous nature. In addition it is also not the exactly smallest API around.

So, what could be done about this? We agreed on a - maybe - controversional solution: defining yet another abstracted PCM audio API. Yes, fixing the problem that we have too many conflicting, competing sound systems by defining yet another API sounds like a paradoxon, but I do believe this is the right path to follow. Why? Because none of the currently available solutions is suitable for all application areas we have on Linux. Either the current APIs are not portable, or they are horribly difficult to use properly, or have a strange license, or are too simple in their functionality. MacOSX managed to establish a single audio API (CoreAudio) that makes almost everyone happy on that system - and we should be able to do same for Linux. Secondly, none of the current APIs has been designed with network sound servers in mind. However, proper networking support reflects back into the API, and in a non-trivial way. An API which works fine in networked environment needs to eliminate roundtrips where possible, be open for time interpolation and have a flexible buffering (besides other minor things). Thirdly none of the current APIs offers enough functionality to properly support all the needs of modern desktop sound systems, such as per-stream volumes, stream names and notifications about external state changes.

During FOMS and LCA, Mikko Leppanen (from Nokia), Jean-Marc Valin (from Xiph) and I sat down and designed a draft API for the functionality we would like to see in this API. For the time being we dubbed it libsydney, after the city where we started this project. I plan to make this the only supported audio API for PulseAudio, eventually. Thus, if you will code against PulseAudio you will get cross-platform support for free. In addition, because PulseAudio is now being integrated into the major distributions (at least Ubuntu and Fedora), this library will be made available on most systems through the backdoor.

So, what will this new API offer? Firstly, the buffering model is much more powerful than of any current sound API. The buffering model mostly follows PulseAudio's internal buffering model which (theoretically) can offer zero-latency streaming and has been pioneered by Jim Gettys' AF sound server. It allows you to seek around in the playback buffer very flexibly. This is very useful to allow very fast reaction to the user's playback control commands while still allowing large buffers, which are good to deal with high network lag. In addition it is very handy for the programmer, such as when implementing streaming clients where packets may arrive out-of-order. The API will emulate this buffering model on top of traditional audio devices, and when used on top of PulseAudio it will use its native implementation. The API will also clearly define which sound formats are guaranteed to be available, thus making it a lot easier to code without thinking of different hardware supporting different formats all the time. Of course, the API will be easier to use than PulseAudio's current API. It will be very portable, scaling from FPU-less architectures to pro-audio machines with a massive number of synchronised channels. There are several modes available to deal with XRUNs semi-automatically, one of them guaranteeing that the time axis stays linear and monotonical in all events.

The list of features of this new API is much longer, however, enough of these grand plans! We didn't write any real code for this yet. To make sure that this project is not another one of those which are announced grandiosely without ever producing any code I will stop listing features here now. We will eventually publish a first draft of our C API for public discussion. Stay tuned.

Side-by-side with libsydney I discussed an abstract API for desktop event sounds with Mikko (i.e. those annoying "bing" sounds when you click a button and the like). Dubbed libcanberra (named after the city which one of the developers visited after Sydney), this will hopefully be for the PulseAudio sample cache API what libsydney is for the PulseAudio streaming API: a total replacement.

As a by-product of the libsydney discussion Jean-Marc coded a fast C resampling library supporting both floating point and fixed point and being licensed under BSD. (In contrast to libsamplerate which is GPL and floating-point-only, but which probably has better quality). PulseAudio will make use of this new library, as will libsydney. And I sincerly hope that ALSA, GStreamer and other projects replace their crappy home-grown resamplers with this one!

For PulseAudio I was looking for a CODEC which we could use to encode audio if we have to transfer it over the network. Such a CODEC would need to have low CPU requirements and allow low-latency operation, while providing hifi audio. Compression ratio is not such a high requirement. Unfortunately, as it seems no such CODEC exists, especially not a "Free" one. However, the Xiph people recommended to hack up a special version of FLAC for this task. FLAC is fast, has (obviously) good quality and if hacked up could provide low-latency encoding. However, FLAC doesn't compress that well. Current PulseAudio thin-client installations require 170kB network bandwidth for each client if hifi audio is used. Encoding this in FLAC this could cut this in half. Not perfect, but better than nothing.

So, that was FOMS! FOMS is a definitely highly recommended conference. If you have the chance to attend next year, don't miss it! I've never been to a more productive, packed conference in my life!

At LCA I met fellow Avahi coder Trent Lloyd for the first time. Our talk about Avahi went very well. During my flights to and back from .au I hacked up avahi-ui which I also announced during that talk. Also, in related news, tedp started to work on an implementation of NAT-PMP (aka "reverse firewall piercing"; both client and server) for inclusion in Avahi. This will hopefully make the upcoming Wide-Area DNS support in Avahi much more useful.

linux.conf.au was a very exciting conference. As a speaker you're treated like a rock star, with stuff like the speakers dinner, the speakers adventure (climbing on top of Sydney's AMP tower) and the penguin dinner. Heck, the organizers even picked me up at the airport, something I really didn't expect when I landed in Sydney, which however is quite nice after a 27h flight.

Two talks I particularly enjoyed at LCA:

• nouveau - reverse engineered nvidia drivers (Ogg Theora)
• burning cpu and battery on the gnome desktop (Ogg Theora)

And just for the sake of completeness, here are the links to my presentations:

• The PulseAudio Sound Server (Ogg Theora; Slides)
• Using Avahi the "Right Way" (Ogg Theora; Slides)

Ok, that's it for now. Thanks go to Silvia Pfeiffer, the rest of the FOMS team and the Seven Team for organizing these two amazing conferences!