[PATCH 0/3] xfree86: Configure input devices by properties

Michael Thayer Michael.Thayer at Sun.COM
Mon Oct 5 02:57:48 PDT 2009

Dan Nicholson wrote:
> These patches add support in xorg.conf to apply input configuration to a
> class of devices by property. The idea is to offer similar property
> matching capabilities to the hal fdi system. Moving the configuration
> back into the ddx means that some day we can stop doing it from the
> config backend and asking users to adjust to it.
Sorry to be chipping in on this after you have written your patch, but
I'm really wondering whether xorg.conf is the right place to put this
sort of information.  It thought that the way things were currently
moving was that xorg.conf was being deprecated as far as possible, and
that nothing should go into xorg.conf which could reasonably be
auto-detected.  Things like the the mapping between the evdev driver and
/dev/input/event* (from the rule in your example) on Linux systems are
well-known, and I would have thought hardly something that need to be
specified in xorg.conf.

I should add that as someone who maintains a set of out-of-tree drivers
complete with installation scripts (no, I'm not quite an impartial
observer) I really like the fact that xorg.conf is being deprecated - to
install on older versions of X.Org/XFree86, I have to hack xorg.conf
using a script, which is not fun.  By way of comparison, hal can be
configured by simply dropping a file into a directory.  I don't know how
much out-of-tree drivers weigh in this though.

I'm afraid that I haven't yet thought this through enough to offer a
well-thought-out alternative, as I didn't want to wait too long before
starting a discussion.  I do have a couple of thoughts though - if
device names are to be mapped to X.Org drivers directly, as in your
example, then udev (or its equivalent, if any, on other systems) might
not be such a bad place after all, as that is where device names are
handled.  An alternative though, would be to hardcode the name(s) of the
kernel driver(s) which correspond to the X.Org driver in the driver
itself, and have the backend (udev or whatever) supply the kernel driver
name along with the path to the device node.  I am assuming that the
kernel driver names are relatively stable, and this seems to me like a
reasonably platform-independent way of doing things.

What other information is currently supplied via hal?  On my Ubuntu
system, the only other information that I see is Debian-specific stuff
relaying Debian keyboard configuration to X.Org.  Which really could be
in udev, as the people writing it are probably reasonably familiar with
it anyway.  I assume though, that there is other stuff which I'm not
aware of, and which doesn't belong as well in udev/whatever.

Sorry that was a bit long!  Interested to hear what you think about the


Sun Microsystems GmbH        Michael Thayer
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