thoughts on requiring multi-arch support for arm drm drivers?

[Rob Clark]

On Mon, Jan 21, 2013 at 9:47 AM, Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> Hi Rob,
>
> On Sunday 20 January 2013 09:08:34 Rob Clark wrote:
>> One thing I've run into in the past when trying to make changes in drm
>> core, and Daniel Vetter has mentioned the same, is that it is a bit of
>> a pain to compile test things for the arm drivers that do not support
>> CONFIG_ARCH_MULTIPLATFORM.  I went through a while back and fixed up
>> the low hanging fruit (basically the drivers that just needed a
>> Kconfig change).  But, IIRC some of the backlight related code in
>> shmob had some non-trivial plat dependencies.
>
> I've just compiled the shmob-drm driver without any error on x86_64. The CMA
> GEM helpers don't compile due to missing dma_(alloc|free)_writecombine though
> (but that would only be an issue if we require no arch dependency at all, not
> with multiarch).

ahh, ok.. maybe I should try again.  I'm pretty sure I was hitting
some issues around the backlight code before, but maybe that has been
fixed since then.

Anyways, if it builds for multi-platform, maybe you could send a patch
for the kconfig?

>> And I think when tegra came in, it introduced some non-trivial plat
>> dependencies.
>>
>> What do others think about requiring multiarch or no arch dependencies
>> for new drivers, and cleaning up existing drivers.  Even if it is at
>> reduced functionality (like maybe #ifdef CONFIG_ARCH_SHMOBILE for some
>> of the backlight code in shmob) or doesn't even work but is just for
>> the purpose of being able to compile test the rest of the code?
>>
>> Thoughts?
>
> That sounds good to me, but would result in many drivers being exposed on x86
> even though they're useless on that platform. Would it make sense to add a new
> CONFIG_COMPILE_TEST (or similar) Kconfig option used for compilation tests
> only ? The shmob driver would then depend on SUPERH || ARCH_MULTIPLATFORM ||
> COMPILE_TEST.
>

fwiw, CONFIG_OF seems to filter things out on x86..  but I could live
doing one arm build and one x86 build to compile test things.

CONFIG_COMPILE_TEST might be a good idea if we need stub fxn hacks to
build (ie. driver is known not to be functional).. sounds like that
will shortly not be an issue for tegra, and if shmobile already buids
on multiplatform, then maybe we won't need this.

BR,
-R

> I'm pretty sure I've seen a similar proposal quite recently but I can't
> remember where.
>
> --
> Regards,
>
> Laurent Pinchart
>