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From: Jesse Barnes on 2 Jul 2010 19:20
On Tue, 22 Jun 2010 16:58:27 -0700
Bryan Freed <bfreed(a)chromium.org> wrote:

> drm/i915: Add a direct interface for pineview backlight support.
>
> This adds a Kconfig variable CONFIG_DRM_I915_DIRECT_BACKLIGHT to
> optionally include the new source file i915_backlight.c. This file
> registers a couple backlight set/get routines with the standard
> drivers/video/backlight interface to add a directory under
> /sys/class/backlight/.
>
> The big problem I see with this modification is that the i915 driver
> _already_ supports backlight level adjustment in i915_opregion.c.
> Unfortunately, that requires an IRQ to occur as the result of writing
> some ASLE (ACPI Source Language Event) register, and this requires
> BIOS support for the ACPI hook. It looks like we will not have such
> support in our initial custom BIOS.
>
> So I copy a small amount of code from i915_opregion.c to make backlight
> adjustment directly available to the backlight framework.
>
> Another problem is that I do not cover all the cases handled by the
> i915_opregion.c code. It would be too much untested code copying to
> do so. I enforce the lack of support by checking for IS_PINEVIEW()
> in i915_backlight_init().
>
> Review URL: http://codereview.chromium.org/2830015
> Signed-off-by: Bryan Freed <bfreed(a)chromium.org>

How does this compare to Matthew's native backlight support? AFAIK
that patch is still outstanding due to the need for some changes to the
backlight subsystem.

Matthew?

--
Jesse Barnes, Intel Open Source Technology Center
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