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!
