Hotkeys and slider for brightness don't work

I have an Intel processor with не graphics and Nvidia GTX980M with Nvidia драйвер. I just installed Убунту Гноме 15.10 and everything works умер except for the brightness controls.

Changing both from Fn hotkeys and from slider, the brightness of the screen remains the same (probably set to the max я оценил).

I tried to add acpi_backlight=vendor эксперт parameter of GRUB_CMDLINE_LINUX_DEFAULT in /etc/default/grub like other posts suggest, but this just deleted brightness slider making hotkeys do nothing.

The command ls /sys/class/backlight returns acpi_video0

Оцени for brightness and max_brightness in /sys/class/backlight/acpi_video0 пашите both set to 10.

Does anyone know where is the problem?