[Nouveau] nouveau exposes backlight controls in presence of ACPI
skeggsb at gmail.com
Tue Nov 2 15:37:51 PDT 2010
On Tue, 2010-11-02 at 15:51 +0100, Aaron Sowry wrote:
> > However. There's also the platform-specific modules (thinkpad etc) that
> > will provide their own backlight methods if the standard ACPI mechanism
> > isn't available. I didn't see any immediately obvious way of knowing
> > whether or not they were being provided.
> > I'm not too certain the best way to deal with this, any ideas? :)
> See attached patch, which prevents nouveau registering a backlight control if ACPI already provides one. If there are no glaring errors in the code/implementation then I would like to submit it.
This is much like what I intended to commit. I guess it doesn't hurt to
do so, it doesn't help with all cases yet but if it fixes issues for
some people, why not.
> Dealing with platform-specific modules is tricky because it looks like nouveau initialises itself quite early on in the boot process:
> [aaron at jules ~]$ dmesg | grep ACPI
> [ 3.359377] nouveau 0000:01:00.0: power state changed by ACPI to D0
> [ 3.359560] nouveau 0000:01:00.0: power state changed by ACPI to D0
> [ 4.860678] [drm] nouveau 0000:01:00.0: Detected ACPI backlight support, not registering control
> [ 14.206997] ACPI: WMI: Skipping duplicate GUID 05901221-D566-11D1-B2F0-00A0C9062910
> [ 14.207693] ACPI: WMI: Mapper loaded
> [ 17.686907] thinkpad_acpi: ThinkPad ACPI Extras v0.24
> [ 17.689517] thinkpad_acpi: This ThinkPad has standard ACPI backlight brightness control, supported by the ACPI video driver
> [ 17.756039] thinkpad_acpi: Standard ACPI backlight interface available, not loading native one.
> My suggestion would be that it is the responsibility of user-space to select an appropriate ACPI backlight control.
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