Saturday, July 4, 2009

(Not) blaming HAL

I still see bugreports that blame HAL for various things including my mouse buttons don't work", "the pointer jumps", and various other things. In none of these cases HAL is at fault. From the X server's point-of-view, HAL is merely a replacement for the xorg.conf.

The simple tasks HAL does for us in the X server is:

  1. List all input devices (the equivalent to the InputDevice sections in the xorg.conf).

  2. Nominate the appropriate driver for each input device (the equivalent to the Driver "..." line in each InputDevice section).

  3. Provide user-configured extra options such as the keyboard layout (the equivalent to the Option "Foo" "bar" lines).

Note that 2 and 3 are a result of your local configuration files and not some random guesses.

So whenever it's unclear if a problem is in fact caused by HAL ask yourself: if you had a xorg.conf, could this problem be fixed by editing it? If not, then you need to report the bug against the input driver or the X server. Here's Fedora's rough checklist for reporting input bugs.

That HAL is being replaced by libudev is a completely different issue as well.

libudev, not DeviceKit.


bmillemathias said...

Hi Peter,

Just to let you know DeviceKit won't replace Hal, DK was just a test project but its maintainer said it's a dead-end now (but note DK-Power or DK-Disk still remain).
So hal should be replaced by libudev.


boulabiar said...

According to Kay Sievers from SUSE:
(linux hotplug mailing-list)

1."The plain DeviceKit daemon was a temporary thing until libudev/gudev
was ready to do event multiplexing. It didn't do anything substantial
but pass an udev event to multiple listeners - the same what libudev/gudev does now. The DeviceKit daemon will not be in the final setups. Only udev will provide the device events."

But this doesn't mean that component specific subsystems will disappear :

2."There are still all the subsystem specific high-level interfaces for desktop stuff. See DeviceKit-disks, DevicKit-power, NetworkManager, PulseAudio, ... - all use libudev/gudev now instead if HAL."

So I am forced now to use libudev for my project.
I still don't understand why there won't be a simple DBus interface for device hotplug signals.