Hi 2023. július 11., kedd 11:42 keltezéssel, Hans de Goede <hdegoede@xxxxxxxxxx> írta: > [...] > >> > >> If settings below 60 are no good, then the correct way to handle > >> this is to limit the range to 0 - (255-60) and add / substract > >> 60 when setting / getting the brightness. > >> > >> E.g. do something like this: > >> > >> #define SCREENPAD_MIN_BRIGHTNESS 60 > >> #define SCREENPAD_MAX_BRIGHTNESS 255 > >> > >> props.max_brightness = SCREENPAD_MAX_BRIGHTNESS - > >> SCREENPAD_MIN_BRIGHTNESS; > >> > >> And in update_screenpad_bl_status() do: > >> > >> ctrl_param = bd->props.brightness + SCREENPAD_MIN_BRIGHTNESS; > >> > >> And when reading the brightness substract SCREENPAD_MIN_BRIGHTNESS, > >> clamping to a minimum value of 0. > >> > >> This avoids a dead-zone in the brightness range between 0-60 . > > > > Hi Hans, I think this is the wrong thing to do. > > > > The initial point of that first `brightness = 60;` is only to set it to > > an acceptable brightness on boot. We don't want to prevent the user > > from going below that brightness at all - this is just to ensure the > > screen is visible on boot if the brightness was under that value, and > > it is usually only under that value if it was set to off before > > shutdown/reboot. > > > > It's not to try and put the range between 60-255, it's just to make the > > screen visible on boot if it was off previously. The folks who have > > tested this have found that this is the desired behaviour they expect. > > I see. > > So if I understand things correctly then 60 is a good default, > but the screen can go darker and still be usable. > > But 1 leads to an unusable screen, so we still need > a SCREENPAD_MIN_BRIGHTNESS to avoid the screen being able > to go so dark that it is no longer usable and then still > move the range a bit, but just not by 60, but by some > other number (something in the 10-30 range I guess?) > > Combined with adding a: > > #define SCREENPAD_DEFAULT_BRIGHTNESS 60 > > And at boot when the read back brightness < > SCREENPAD_MIN_BRIGHTNESS set it to SCREENPAD_DEFAULT_BRIGHTNESS. > > We really want to avoid users to be able to set an unusable > low brightness level. As mentioned in the new panel brightness > API proposal: > > https://lore.kernel.org/dri-devel/b61d3eeb-6213-afac-2e70-7b9791c86d2e@xxxxxxxxxx/ > > "3. The meaning of 0 is not clearly defined, it can be either off, > or minimum brightness at which the display is still readable > (in a low light environment)" > > and the plan going forward is to: > > "Unlike the /sys/class/backlight/foo/brightness this brightness property > has a clear definition for the value 0. The kernel must ensure that 0 > means minimum brightness (so 0 should _never_ turn the backlight off). > If necessary the kernel must enforce a minimum value by adding > an offset to the value seen in the property to ensure this behavior." > > So I really want to see this new backlight driver implement the > new planned behavior for 0 from the start, with 0 meaning minimum > *usable* brightness. > > Regards, > > Hans Sorry for hijacking this thread, but then how can I turn backlight off? I quite liked how I was able to turn my laptop display (almost) completely off with the brightness hotkeys / brightness slider in gnome-shell, and I was quite annoyed when this was changed in gnome-settings-daemon and forced the minimum brightness to be 1% of max_brightness. (https://gitlab.gnome.org/GNOME/gnome-settings-daemon/-/merge_requests/17) Also, "minimum brightness at which the display is still readable" is not really well-defined, so it can (will) happen that the minimum brightness values don't match, so it is theoretically possible that I cannot set both my laptop panel and external monitor to the same desired brightness level. Or am I missing something? Regards, Barnabás Pőcze
