KMS backlight ABI proposition

[Jani Nikula]

On Mon, 20 Feb 2017, Dave Airlie <airlied at gmail.com> wrote:
> How do you tackle that end of the problem, how does the i915/drm core
> know when the driver for the one backlight it needs has appeared, and
> is working, by deferring this to userspace we let the system load all
> the drivers and the policy of picking the correct one is left there.

One of David's original ideas was to allow userspace to re-associate the
properties with the underlying backlight class implementations. The
kernel could make a best guess, and udev could handle the exceptions. I
wouldn't mind having the quirks managed there. I think udev rules could
handle the same backlight type priority ordering as we have now.

> I'm not saying this is pretty,and we have libbacklight to "solve" the
> problems for generic userspace, but any solution is going to a be a
> lot uglier than you think.

I have no illusions about this, but I'm really hoping we could hide a
good chunk of the ugliness under a fresh layer of paint in drm,
especially for the nowadays most common case of native backlights.


BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center