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

[Thierry Reding]

On Sun, Jan 20, 2013 at 09:08:34AM -0600, 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.  And I think when tegra
> came in, it introduced some non-trivial plat dependencies.

I've talked to Stephen about this a few days ago and his (tentative)
plan is to support ARCH_MULTIPLATFORM in 3.9. I'm not sure if that's
soon enough for you. I think the one remaining platform dependency is
the tegra_periph_reset_{assert,deassert}() which should be gone with the
common clock framework changes which should go into 3.9. Stephen has
other work-in-progress patches for the rest, so I think chances are
actually pretty good to get this ready for 3.9.

> 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?

I imagine that on Tegra we could add dummy implementations for the reset
functions, which should allow it to build it for non-Tegra. However, I
don't think it's really worth the churn to do this now just to remove
them again in 3.9. The general direction would seem to be to require new
platforms to be multi-platform from the start, so any new drivers should
not cause the same pain anyway.

Thierry
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