[Intel-gfx] [PATCH] drm/i915: do not expose a dysfunctional backlight interface to userspace

[Chris Wilson]

On Mon,  3 Sep 2012 16:25:12 +0300, Jani Nikula <jani.nikula at intel.com> wrote:
> Previously intel_panel_setup_backlight() would create a sysfs backlight
> interface with max brightness of 1 if it was unable to figure out the max
> backlight brightness. This rendered the backlight interface useless.
> 
> Do not create a dysfunctional backlight interface to begin with.
> 
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

> ---
> 
> See https://bugzilla.redhat.com/show_bug.cgi?id=752595
> 
> There's still a bug somewhere in the userspace as well; it should always
> prefer the platform backlight interface over the raw one. This patch might
> have the effect of hiding that particular userspace issue, but we shouldn't
> be exporting a backlight interface that's useless no matter what.

It was fixed. UXA uses a hardcoded set of preferred platform drivers,
SNA looks at all the backlights under /sys/class/backlight and sorts
them by type. We still have the issue of multi-panel or just multiple
backlight interfaces and choosing the wrong one randomly. libbacklight's
idea was to expose some more details through the kernel to be able to
link device + connector to a particular backlight interface. However,
userspace has the Option "Backlight" for fine tuning.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre