Hi Ben,
I'm bringing you into the loop here. Maybe you can help as kernel maintainer (or know someone we could ask). On Thu, 17 Oct 2019 11:26:05 +0200 Rado S <d-eb...@q3co.de> wrote: > =- Michael Biebl wrote on Wed 16.Oct'19 at 13:06:29 +0200 -= > > > >>> # cat /sys/class/backlight/intel_backlight/brightness > > >>> 1500 > > > > > > I get 79560. > > > > > >> and change it via > > >>> # echo 2000 > /sys/class/backlight/intel_backlight/brightness > > > > > > Setting it via intel to 66666 makes it darker. > > > > > >> What's the output you get for your dell_backlight? > > > > > >>From dell_backlight I get: > > > # cat dell_backlight/brightness > > > 6 > > > > > > But when setting it, it says: > > > > > > # echo 5 > dell_backlight/brightness > > > -ksh: echo: write to 1 failed [Input/output error] > > > {...} > > > What next? > > > > Dunno. You'll probably need to ask someone who is familiar with > > Dell hardware. I have no idea why these Dell laptops provide a > > dell_backlight device and what this device supposed to control. > > Apparently it can't be used to change the brightness despite it > > exposing the brightness attribute. > > For the record: > the dell value for brightness reflects the scale given in the BIOS > menu: (0-7) > > The dell vostro works OK: > despite having an Intel GM45 it has no intel_backlight device at > the same place as the others. > Instead it has acpi_video0 which scales like the dell_backlight > (values 0-7) rather than the intel_backlight (*1000). > At Installation time xorg also decided not to use a gpu specific > driver (xorg-video-intel) with the vostro for the acpi_video0, which > in return made X operate slow compared to the older dells, which > still do use the xorg-video-intel (or radeon). > > Which components of the installer decide whether to use xorg-drivers > and which devices to create for backlight handling? > > Is this still systemd or again a kernel issue? Tbh, I don't know. Ben, maybe you can help here: If a backlight device exposes a brightness attribute, is it safe to assume that this property is writable? If not, is there a way to determine whether it is writable? Regards, Michael -- Why is it that all of the instruments seeking intelligent life in the universe are pointed away from Earth?
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