State of X in experimental

What happened since last month? The video drivers we were previously lacking were built against X Server 1.9, with a tiny exception: xserver-xorg-video-nouveau. This one is particularly annoying because the ABI is not stable, and it requires a particular version of the kernel to be usable. The same seems to happen with the nouveau part of the libdrm library. As a consequence, I’ve demoted it from Depends to Recommends for the xserver-xorg-video-all metapackage.

The same happened to the xserver-xorg-input-wacom driver (for the xserver-xorg-input-all metapackage this time), since it isn’t maintained by debian-x@, and since it didn’t look too bad to have it only recommended (after all, we’re only targeting experimental right now).

In addition, all drivers were updated to the last upstream releases.

Bottom-line, the following is now possible on (at least) both amd64 and i386 architectures:

apt-get install -t experimental xserver-xorg

As a side note: Intel users probably want to upgrade their libdrm-intel1 package to 2.4.22-2 (in experimental as well), they could run into X.Org Bug #31443 otherwise.

Dependency handling for X packages in Debian

Previously, dependencies were quite fun:

• Drivers used to provide a given virtual package: xserver-xorg-input-$ABI and xserver-xorg-video-$ABI. One shall note that the ABI is evolving independently for input and video drivers, see SET_ABI_VERSION in server’s hw/xfree86/common/xf86Module.h for curious people.

• The xserver-xorg metapackage depended on xserver-xorg-core (the server itself) with a minimal version, and on those virtual packages. More precisely, for example in the input case: xserver-xorg-input-all | xserver-xorg-input-$ABI so that by default one gets everything for autodetection to work, but one can pick a specific driver instead.

• The drivers only depended on the server, with a minimal version as well.

So what did we do to ensure the server and drivers were all using the same ABI? When the server was updated to a new ABI, one had to add the previous virtual packages to Conflicts (and keep a list of all of them, yay!).

Needless to say, asking a package manager to upgrade at a same time many packages (several dozens for all drivers) declaring conflicts, especially during a mass dist-upgrade from a stable release to the next stable was no fun.

So what’s the current situation now?

• xserver-xorg depends on a minimal server version, and on drivers. The alternatives are now written like this: xserver-xorg-input-all | xorg-driver-input. Notice there’s no ABI mentioned here anymore. It’s just about having the server, at least an input driver, and at least a video driver.

• xserver-xorg-core now provides an input ABI and a video ABI. In experimental for example: xorg-input-abi-11.0, xorg-video-abi-8.0

• Drivers now depend on the ABI they were built against. For example, xserver-xorg-input-evdev in experimental depend on xorg-input-abi-11.0

So one might think everything is now fine, except there are some conflicts still declared, to ensure one can transition from packages using the former (bad) logic to the new state of affairs. And those conflicts were still causing headaches to package managers. Fortunately, David Kalnischkies came up with a proposal to replace Conflicts with Breaks, which turned out to ease things. Yatta!

All of that is implemented in experimental. squeeze is the transition period where the metapackage stills the depends on xserver-xorg-{input,video}-$ABI virtual packages, but where drivers now depend on the appropriate server ABI. (Thanks to Alexander Kurtz for his feedback.)