Hi, I posted my problem already on the linux_acpi mailing list but maybe this is a better place for it [1]. I am using a Asus Taichi31 with two screens (inside and outside on the lid). The /sys/class/backlight only shows a acpi_video0 and intel_backlight section one can manipulate for the "inner" display. The problem is: the outer display is working but the backlight is unchangeable set to off (besides that, one can very slightly see that it is indeed creating a picture). Do you have any suggestions how one could change that? Thanks a lot! Axel [1] http://marc.info/?l=linux-acpi&m=138938058419187&w=2
It's not clear to me how the 2nd display's backlight should be controlled. Please attach your acpidump, let's see what the firmware interface provides us: # acpidump > acpidump.txt
I think the main "confusion" is that this laptop actually contains two internal screens of the same type (2x model CMN N133HSG-WJ1). https://lh3.ggpht.com/-nnVyB5RUhRQ/UWKPw7GbdcI/AAAAAAAAPCU/kV_RmCfIIvw/s1600/asus_taichi_31_tablet.jpg I will add the acpidump asap in the evening, thank you Aaron.
Created attachment 121871 [details] acpidump The result of sudo acpidump > acidump.txt with mirrored screens set.
From the ACPI tables, there lists only one device that has backlight control method, so the problem is now: it's not clear how the 2nd screen is supposed be controlled regarding backlight to me. Jani & Daniel, Do you have any idea for the mirror screen backlight control problem? There is a link in comment #2 to show what the laptop looks like.
No idea at all ... atm we don't even link up backlights with outputs in any way, doing this is probably a requirement to get things going. Axel, can you please boot with drm.debug=0xe and attach the complete dmesg to this bug?
Created attachment 122131 [details] dmesg with drm.debug=0xe $ cat /proc/cmdline BOOT_IMAGE=/vmlinuz-3.13.0-031300rc7-generic root=UUID=0e7230c6-d126-4b9e-adf3-2cd0add113cd ro drm.debug=0xe
Created attachment 122141 [details] dmesg with drm.debug=0xe and acpi_backlight=vendor Maybe that is useful, too. $ cat /proc/cmdline BOOT_IMAGE=/vmlinuz-3.13.0-031300rc7-generic root=UUID=0e7230c6-d126-4b9e-adf3-2cd0add113cd ro drm.debug=0xe acpi_backlight=vendor $ ls /sys/class/backlight/ asus-nb-wmi intel_backlight $ ls /proc/acpi/ button/ wakeup
ping, anyone gets the time to take a look at the attached dmesg?
I am also still motivated to provide more feedback on it :)
We already track the issue at the fdo bugzilla, closing this one. https://bugs.freedesktop.org/show_bug.cgi?id=73156
(In reply to Axel from comment #7) > $ ls /sys/class/backlight/ > asus-nb-wmi intel_backlight What happens if you change backlight using the asus-nb-wmi interface directly, i.e. sudo sh -c "echo N > /sys/class/backlight/asus-nb-wmi/brightness" where N is a value between 0 and `cat /sys/class/backlight/asus-nb-wmi/max_brightness`? If possible, please reply to the bug at fdo.