On Mon, Oct 24, 2016 at 04:08:47PM +0300, Marta Lofstedt wrote:
Hi David,
I am currently investigating: https://bugs.freedesktop.org/show_bug.cgi?id=96572
Martin Peres suggested that your patches: https://lists.freedesktop.org/archives/dri-devel/2014-September/thread.html#... could solve the xf86-video-modesetting backlight issues.
I have rebased your patches and I am working on an IGT test for the functionality. With my i915 implementation and the small included bug-fix, I can update the drm BACKLIGHT property and the value is updated in the backlight class device. However, if I set the brigness value through the sysfs file of the backlight class device the drm BRIGHTNESS property does not update which would be confusing to users.
My understanding is that DRM properties are cached and, by design, do not have the capability to read the status from the driver.
What do we want to do about this?
Fix it I'd say. But right now there's no callback for drivers to return non-ATOMIC properties. Only old property values are cached like this. I guess we can add a get_property hook, which is optional, and which would fall back to the cached value if need. A bit a pain to wire up, but should get the job done. Maybe just start out with a callback for connectors only, instead of all kms objects which can have a property attached. -Daniel