Yes we would need this. -Sameer -----Original Message----- From: wayland-devel <wayland-devel-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Pekka Paalanen Sent: Friday, April 29, 2022 2:37 PM To: Hans de Goede <hdegoede@xxxxxxxxxx> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>; Sebastian Wick <sebastian.wick@xxxxxxxxxx>; Martin Roukala <martin.roukala@xxxxxxxxx>; Christoph Grenz <christophg+lkml@xxxxxxxxxxxxx>; wayland <wayland-devel@xxxxxxxxxxxxxxxxxxxxx>; dri-devel@xxxxxxxxxxxxxxxxxxxxx; Daniel Vetter <daniel@xxxxxxxx>; Alex Deucher <alexdeucher@xxxxxxxxx>; Yusuf Khan <yusisamerican@xxxxxxxxx> Subject: Re: [RFC] drm/kms: control display brightness through drm_connector properties On Fri, 29 Apr 2022 08:59:24 +0000 Simon Ser <contact@xxxxxxxxxxx> wrote: > On Friday, April 29th, 2022 at 10:55, Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > > I believe that we can fix the new interface, the plan is for there > > to be some helper code to proxy the new connector properties to what > > is still a good old backlight-device internally in the kernel,. > > > > This proxy-ing code could take a minimum value below which it should > > not go when things are set through the properties and then if e.g. > > the /sys/class/backlight interface offers range of 0-65535 and the > > kms driver asks the proxying helper for a minimum of 500, show this > > as 0-65035 on the property, simply adding 500 before sending the > > value to the backlight-device on writes (and subtracting 500 on > > reads, clamping to 0 as lowest value reported on reads). > > > > This way apps using the new API can never go below 500 (in this > > example) and for old API users nothing changes. > > > > Given that Jani seems to be in favor of enforcing some minimal value > > inside the i915 code going forward and also what Alex said that the > > amdgpu code already enforces its own minimum if the video BIOS > > tables don't provide one, it seems that there is consensus that we > > want 0 to mean minimum brightness at which the screen is still > > somewhat readable and that we want to enforce this at the kernel level. > > > > Which also means the weird hint property which I came up with won't > > be necessary as we now have a clean definition of what brightness > > 0 is supposed to mean (in the new API) and any cases where this is > > not the case are kernel bugs and should be fixed in the kernel. > > Looks like a good approach to me from user-space PoV! Yes! Thanks, pq
