Re: keymap rule selection for non-DMI platforms

[Daniel Drake <dsd@xxxxxxxxxx>]

On Tue, Aug 16, 2011 at 8:34 PM, Kay Sievers <kay.sievers@xxxxxxxx> wrote:
> Reading such things from /proc is kinda taboo from code we maintain in
> udev. All things not related to processes really do not belong into
> /proc and udev code should never get into the way of possibly
> deprecating these things in the long run, even when they might never
> happen. I know, there is sometimes no other simple option, but we
> generally prefer the inconvenience it causes, over adding hacks to
> upstream code, to make a move to a generally useful solution (which
> isn't /proc/*) more attractive.

I agree that the use of /proc is strange, but just to make sure you
understand: /proc/device-tree is a standard upstream kernel thing and
has been for a long time. It is not some OLPC-specific oddity to
access our manufacturing data. It is *the* way to access device tree
info on ARM, PPC, SPARC (and x86). And device tree is specifically
built as a way of identifying hardware info which the silicon can't
tell you. udev implementing support for device tree will solve OLPC's
keyboard identification issue, but you'll also solve a whole class of
problems for the wide range of platforms that use device tree (and
those that will soon use it).

> I guess one sensible option is to register the /sys/class/dmi
> interface to ARM too, even when it's not called that way for ARM
> hardware. 'Desktop Management Interface' makes not much sense anyway,
> not even for x86, but hey it's only 3 characters, whatever they mean.
> :)

I think you're too late to suggest a new solution to this problem.
This is exactly what device tree is for, and Linux has been steadily
going in this direction for a while.

However, the location inside of /proc is certainly something that can
be criticised.

> The alternative is to replace /sys/class/dmi with some completely arch
> and platform independent interface and export there what dmi currently
> supports and plug-in the other platforms.

Device tree is already arch and platform independent, but I'm not sure
how you would make DMI info look like a device tree. Despite both
being able to provide identification info, they are quite different
beasts.

Daniel
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