Well, this won't work for me. I don't have a NVidia. But I will search the web if there is a module for my Intel Skylake graphics. Although my brightness script actually works perfect. The only drawback currently: a few apps (e.g. chromium) reset the brightness to max upon their startup. Thanks anyway! Christian On Sun, 2016-11-20 at 03:08 -0600, David C. Rankin wrote: > On 11/19/2016 03:38 AM, Christian Klaue wrote: > > I am having exactly the same problem with my HP. I went as far as > > decompiling the ACPI bios. When I tried to compile it again, it > > threw a > > huge amount of errors. So I gave up. I didn't find any solution for > > my > > problem. I even tried other distros. I am still kind of convinced > > the > > error is in the ACPI module(s) of your UEFI. If you try to blame HP > > (as > > many people on their forum did before) they will ask you to test on > > Windows. Unfortunately there it works. The newest BIOS update > > doesn't > > fix the problem for my toy. > > > > I am lucky to have an OLED. Please keep me updated if you find a > > solution. > > Christian, > > You may be in luck. I did find a solution and now my backlight > functions as > it should using the nvidiabl kernel module (and a small helper script > that I > autostart in KDE, but you could just as easily start it in .xinitrc > for any > desktop) Basically, you have to use either of the following two > packages to > build a kernel module that will work with the proprietary nvidia > driver: > > nvidia-bl > https://aur.archlinux.org/packages/nvidia-bl/ > > nvidiabl > https://aur.archlinux.org/packages/nvidiabl/ > > I built them both, but haven't tried nvidia-bl, (even though it was > easier > to build and should do the same thing) > > To build nvidiabl, just follow the notes on its aur page and it > builds fine. > nvidia-bl, builds without issue, just download the tarball, unpack > it, and > then a makepkg -s is all that is needed. > > Both provide the kernel module: > > /usr/lib/modules/extramodules-4.8-ARCH/nvidiabl.ko > > Just build, then 'modprobe nvidiabl', and you will have backlight > control > through: > > /sys/class/backlight/nvidia_backlight/brightness > > The kicker is that nothing talks to nvidia_backlight by default, > instead all > the normal backlight controls use: > > /sys/class/backlight/acpi_video0/brightness > > The way to get your controls to work is to watch the > acpi_video0/brightness > values and automatically set nvidia_backlight/brightness any time the > earlier > one changes value. This is where the helper script comes into play > (actually 2 > short scripts -- the second just to ease the sudo redirection issue) > > The first script just maps values (0-20) from > acpi_video0/brightness into a > range of (0-127) for nvidia_backlight/brightness (it calls the second > script > as a helper). Just launch the first script in whatever desktop you > are using, > and your backlight keys should work. If not, then you just have to > copy > whatever value you want for your backlight/brightness to > nvidia_backlight/brightness, e.g. > > # echo 90 > /sys/class/backlight/nvidia_backlight/brightness > > Put both scripts in the same directory. You will need to configure > sudo > without a password for this to work when called as your normal user > (as when > using the laptop keys). The first is a quick modification of the > xbacklight > script. It reads the xbacklight value from acpi_video0 and then does > a rough > scale for what the nvidia_backlight value should be. Give it some > name like > nvbackligh.sh: > > #!/bin/sh > > path=/sys/class/backlight/acpi_video0 > dest=/sys/class/backlight/nvidia_backlight > dmax=$(<$dest/max_brightness) > > luminance() { > read -r level < "$path"/actual_brightness > factor=$((dmax / max)) > nvbrt=$((level * factor)) > case "$nvbrt" in > [0-9] ) printf "%d" $nvbrt;; > [0-9][0-9] ) printf "%d" $nvbrt;; > [1][0-1][0-9] ) printf "%d" $nvbrt;; > [1][2][0-9] ) printf "127";; > default ) printf "error: in value conversion\n" > exit 1;; > esac > } > > read -r max < "$path"/max_brightness > > inotifywait -me modify --format '' "$path"/actual_brightness | while > read; do > if [ $UID -eq 0 ]; then > echo $(luminance) > "$dest"/brightness > else > sudo ./nvhelper.sh $(luminance) # helper script > fi > printf "luminance %s\n" "$(luminance)" > done > > The second just echos the luminance value into > nvidia_backlight/brightness > which gets around sudo only applying to the echo and not the > redirection. An > alternative is calling it with 'su -c' (which you can configure pam > to allow > without a password if you are a member of the wheel group and you > uncomment > the first two lines in /etc/pam.d/su). The helper script nvhelper.sh > is: > > #!/bin/sh > [ $1 -lt 0 -o $1 -gt 127 ] && exit 1 ## check value out of range > echo $1 > /sys/class/backlight/nvidia_backlight/brightness > > If you try the aur nvidia-bl package and it works. Let me know, it > is a > simpler package to build. I'll try and get time to try it over the > next week > or so. > > So now, after a couple of days relearning xrandr, backlight, the > sysfs and > what goes with what in the nvidia driver, that xrandr is a software > pixel > darkening scheme, we came to understand the kernel model approach is > the > correct approach for backlight control here...and it is working > perfectly. > > (Now, if I could just get this damn HP laptop to boot grub without > having to > boot from USB and then boot grub on the hard drive, I'd be in great > shape. Let > me know if you have any questions. >
