tl;dr: acpi_backlight=vendor to kernel at boot (add in grub configuration) + modprobe -r samsung_laptop && systemctl restart gdm. (i discovered it with pf-kernel, need to try in stock kernel)
Well, i don't know if this is known, but i could not find it.
Maybe its a bug to be fixed that im not aware of.
Well, i had the common problem with the LCD brightness not responding. It used to decrease, but not increase. All of this running Gnome 3.
After days of fight what i did was download pf-kernel and configure it. I selected the "samsung_laptop" module as my common sense told me, and in case it was needed the Q10 Samsung or something like that module too.
I rebooted into the pf-kernel, with no luck, the same problem was still happening.
I decided to stop gdm and use startx to try some things.
First i modprobed the samsung_laptop module just in case, started X again, and it was the same.
And then i did modprobe -r samsung_laptop, restarted X... AND IT WORKS.
NOTE: The acpi_backlight=vendor is needed in the grub configuration to this to work.
Oddly, without the samsung_laptop module.
So i rebooted to try this again. Unloaded the module, did systemctl restart gdm, aand there it was working again.
So, it may be a problem with that module, or maybe its not needed after all, im not sure.
I'm kind of newbie in all of this, so if this is dumb or something im sorry but i think it may be helpful for somebody else in my situation.
By googling i only found scripts to make this work that i did not like.
Is neccesary that i place a bug report? Im not sure if that kernel module is made to fix this or if its for something else, so i dont know if the bug report makes sense.
Last edited by nlabrad (2012-12-27 18:07:52)
More history on what does what.
At first, i could only decrease the brightness 1 step, from the max to one below.
Then i put acpi_backlight=vendor in grub, and i could decrease the brightness to some value (which is not the real minimum), but could not increase it more than 2 steps over that minimum once decreased (like locked in the 2 lower values).
To manually change the brightness i echoed values to /sys/class/backlight/intel_backlight/brightness. The other one did not work (samsung...), but it wasn't what i wanted.
After changing kernel, unloading the kernel module samsung_laptop and restarting x it works.
Not sure if the kernel has something to do.
I can confirm that this works on the standard kernel and KDE on a Samsung QX142.
Thank you nlabrad!
Edit: Maybe you can make a note of this in the wiki?
Last edited by koz (2012-12-29 09:29:00)
Thank you! I am confirming that this solution works on Samsung NP300V5Z.
Did you ever had an issue with non-waking (on resume from suspend-to-ram) screen on your laptop, btw?
Please don't necrobump old threads: https://wiki.archlinux.org/index.php/Fo … Bumping.27