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

[Greg KH]

On Fri, Aug 14, 2009 at 10:56:39AM -0700, Jesse Barnes wrote:
> 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:
> http://bugs.freedesktop.org/show_bug.cgi?id=20963

My question is, does this belong in the kernel side, to expose the
backlight through /sys/class/backlight/, or do we do this on the
userspace side in perhaps the xorg intel driver (where we can touch
pci config space just as easily)?

What does KMS expect to have happen?

thanks,

greg k-h