[Intel-gfx] [RFC] [intel-gfx] :The backlight issue when KMS is used

Matthew Garrett mjg59 at srcf.ucam.org
Fri Apr 3 18:29:06 CEST 2009

On Fri, Apr 03, 2009 at 09:24:08AM -0700, Jesse Barnes wrote:
> I'd rather not have a native kernel backlight property (i.e. a property
> on the LVDS output) exposed at all.  I chatted with Matthew about this
> a little, and I think the best thing to do would be to have the i915
> driver register a backlight interface of its own if one doesn't already
> exist (e.g. in the case of a platform specific i2c interface and no
> ACPI backlight support).
> We might have to hack the backlight class code a little to prevent
> multiple registrations for the same device, but that shouldn't be too
> hard.
> Then whichever driver loads first (i915 or acpi video) would create a
> backlight interface if it could, and the userspace driver could use it;
> no need for new properties.

Right. I'd imagine it as i915 loading and calling is_acpi_backlight(). 
If that returns false, it should register a backlight device and also a 
notifier. If a machine-specific platform device (like thinkpad_acpi or 
dell_laptop or whatever) then loads, i915 should unregister its driver 
and leave it up to the machine-specific one. The DDX would then use the 
backlight device under all circumstances.

Matthew Garrett | mjg59 at srcf.ucam.org

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