* with acpi_backlight=vendor added (Fn key combination does not work):
[ 5.613] (--) intel(0): found backlight control interface /sys/class/backlight/samsung
* without acpi_backlight=vendor, as it is in the referred /proc/cmdline (Fn key combination works):
[ 5.097] (--) intel(0): found backlight control interface /sys/class/backlight/acpi_video0
The weird thing is that acpi_backlight=verdor worked when BIOS was in UEFI mode. I've changed this to CSM mode after some research about the infamous firmware bug:
Unfortunately I cannot provide more info for the UEFI mode.
The main advantage of using the samsung interface is that the minimum brightness threshold is lesser than in the native acpi_video interface, the former allows to dim completely the screen with the corresponding gaining in power saving.
FWIW
Mine is a different Samsung machine (NP900x3d), my Ubuntu version is 12.10. I've tried with/without acpi_backlight= vendor .
More precisely this is my current boot command line:
luis@sams9:~$ cat /proc/cmdline /boot/vmlinuz- 3.5.0-26- generic root=... ro quiet splash i915.i915_ enable_ rc6=1 i915.i915_ enable_ fbc=1 i915.lvds_ downclock= 1 vt.handoff=7
BOOT_IMAGE=
(The i915* options are my own customizations)
The output:
* with acpi_backlight= vendor added (Fn key combination does not work):
[ 5.613] (--) intel(0): found backlight control interface /sys/class/ backlight/ samsung
* without acpi_backlight= vendor, as it is in the referred /proc/cmdline (Fn key combination works):
[ 5.097] (--) intel(0): found backlight control interface /sys/class/ backlight/ acpi_video0
The weird thing is that acpi_backlight= verdor worked when BIOS was in UEFI mode. I've changed this to CSM mode after some research about the infamous firmware bug:
http:// mjg59.dreamwidt h.org/22855. html
Unfortunately I cannot provide more info for the UEFI mode.
The main advantage of using the samsung interface is that the minimum brightness threshold is lesser than in the native acpi_video interface, the former allows to dim completely the screen with the corresponding gaining in power saving.