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

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

[Daniel Vetter]

On Sun, Jan 20, 2013 at 4:08 PM, Rob Clark <robdclark@gmail.com> 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.  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?

Definitely in favour of this. Also, I think the arm world _really_
needs something like Wu Fenggungs 0-day kernel testing/building
machines, which checks every commit pushed to around a 150 git kernel
maintainer repos with randconfigs, sparse (and iirc other static
checkers like cocinelle), and test-boots them on kvm. It's not just
that every driver seems to need it's own special defconfig/platform to
even be selectable in Kconfig, they also seem to randomly (and often)
break compilation if you're on the wrong tree or don't have the
exactly required golden config ...

I don't have any issues with compile-testing on different
architectures. But this kind of pain makes larger subsystem reworks
like the drm kms locking rework I've just done unnecessarily
cumbersome.

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

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

[Thierry Reding]

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On Sun, Jan 20, 2013 at 04:42:55PM +0100, Daniel Vetter wrote:
> On Sun, Jan 20, 2013 at 4:08 PM, Rob Clark <robdclark@gmail.com> 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.  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?
> 
> Definitely in favour of this. Also, I think the arm world _really_
> needs something like Wu Fenggungs 0-day kernel testing/building
> machines, which checks every commit pushed to around a 150 git kernel
> maintainer repos with randconfigs, sparse (and iirc other static
> checkers like cocinelle), and test-boots them on kvm. It's not just
> that every driver seems to need it's own special defconfig/platform to
> even be selectable in Kconfig, they also seem to randomly (and often)
> break compilation if you're on the wrong tree or don't have the
> exactly required golden config ...

That's true. Unfortunately due to the many repositories involved there
seem to be quite a few dependencies involved to get all the pieces to
build properly. linux-next is usually in pretty good shape, however.
I've been running an automated build over at least all ARM defconfigs in
linux-next for a few days and sent out patches for build failures. But
I'm not sure if I can keep that up, or at least not on a daily basis.

Obviously it doesn't help the DRM problem all that much. But I agree
with Rob that the only thing that will really help is multi-platform
support.

Thierry

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