Comment 6 for bug 935778

Seth Forshee <email address hidden> writes:

> It's hard to tell much from your ACPI tables, essentially they just seem
> to be handing everything off to the embedded controller. We'll have to
> experiment a little.

[...]

On first boot.

| root@ornery:/sys/class/backlight# ls -l
| total 0
| lrwxrwxrwx 1 root root 0 Feb 21 18:33 acpi_video0 -> ../../devices/pci0000:00/0000:00:02.0/backlight/acpi_video0
| lrwxrwxrwx 1 root root 0 Feb 21 18:33 intel_backlight -> ../../devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight
| lrwxrwxrwx 1 root root 0 Feb 21 18:33 toshiba -> ../../devices/LNXSYSTM:00/device:00/TOS6208:00/backlight/toshiba
| root@ornery:/sys/class/backlight#

Default levels (maximum brightness) after first boot:

| root@ornery:/sys/class/backlight# for i in *; do for j in brightness actual_brightness max_brightness; do echo -n ${i}/${j}: ; cat ${i}/${j}; done; echo; done
| acpi_video0/brightness:7
| acpi_video0/actual_brightness:7
| acpi_video0/max_brightness:7
|
| intel_backlight/brightness:4539
| intel_backlight/actual_brightness:4539
| intel_backlight/max_brightness:4539
|
| toshiba/brightness:7
| toshiba/actual_brightness:7
| toshiba/max_brightness:7
|
| root@ornery:/sys/class/backlight#

After pressing 'Fn-F6' (decrease brightness):

| root@ornery:/sys/class/backlight# for i in *; do for j in brightness actual_brightness max_brightness; do echo -n ${i}/${j}: ; cat ${i}/${j}; done; echo; done
| acpi_video0/brightness:5
| acpi_video0/actual_brightness:5
| acpi_video0/max_brightness:7
|
| intel_backlight/brightness:4539
| intel_backlight/actual_brightness:2723
| intel_backlight/max_brightness:4539
|
| toshiba/brightness:7
| toshiba/actual_brightness:5
| toshiba/max_brightness:7
|
| root@ornery:/sys/class/backlight#

I put the brightness back to maxmium, and then suspended and resumed. I
then tried 'Fn-F6' (decrease brightness) again:

| root@ornery:/sys/class/backlight# for i in *; do for j in brightness actual_brightness max_brightness; do echo -n ${i}/${j}: ; cat ${i}/${j}; done; echo; done
| acpi_video0/brightness:5
| acpi_video0/actual_brightness:5
| acpi_video0/max_brightness:7
|
| intel_backlight/brightness:4539
| intel_backlight/actual_brightness:4539
                                    ^^^^
| intel_backlight/max_brightness:4539
|
| toshiba/brightness:7
| toshiba/actual_brightness:5
| toshiba/max_brightness:7
|
| root@ornery:/sys/class/backlight#

Interesting, let's try setting that manually:

| root@ornery:/sys/class/backlight# echo 2723 > intel_backlight/brightness

And the brightness decreases...

| root@ornery:/sys/class/backlight# for i in *; do for j in brightness actual_brightness max_brightness; do echo -n ${i}/${j}: ; cat ${i}/${j}; done; echo; done
| acpi_video0/brightness:5
| acpi_video0/actual_brightness:5
| acpi_video0/max_brightness:7
|
| intel_backlight/brightness:2723
| intel_backlight/actual_brightness:2723
| intel_backlight/max_brightness:4539
|
| toshiba/brightness:7
| toshiba/actual_brightness:5
| toshiba/max_brightness:7
|
| root@ornery:/sys/class/backlight#

Please let me know if this is enough, or if you need more information.

--
James