[Intel-gfx] Legacy backlight control with KMS and BACKLIGHT property

Jesse Barnes jbarnes at virtuousgeek.org
Fri Aug 14 19:56:39 CEST 2009

On Fri, 14 Aug 2009 19:54:05 +0200
Matthias Hopf <mhopf at suse.de> wrote:

> Currently with KMS legacy backlight control isn't working at all.
> Also, the driver doesn't expose the BACKLIGHT RandR property in any
> case, so xbacklight doesn't work with KMS.
> I've been working on a patch as a quick-hack for this (attached;
> please DON'T apply), and am finally understanding enough to actually
> implement this correctly together with GregKH.
> What we're supposing is
> - a kernel driver for the /sys/class/backlight/ api for the legacy
> method
> - support in the driver to actually open this one (trivial)
> - support for the BACKLIGHT property in KMS case, *only* using the
>   kernel api method for now (will need some abstraction)

This sounds like the correct approach.  We have an RFE open on this too:

> Also I noted that the BACKLIGHT property is
> - not preceeded with _
> - not yet documented in randrproto.txt
> I suggest that I add this in randrproto.txt, as it seems plausible to
> me to actually make this a known property.
> Does this sound reasonable?

Yeah, sounds good to me.

Jesse Barnes, Intel Open Source Technology Center

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