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Re: /proc/acpi/video

On Sat, 29 Oct 2011 15:01:12 +0000 (UTC), Camaleón writes:
> I'm running a Debian stock kernel (3.0.0-1) and neither have that entry 
> under "/proc/acpi" but can control the brigthness of my netbook either 
> from GNOME or using the hotkeys.
>
> Maybe this Ubuntu debug guide for backlight can give you any hints:
>
> https://wiki.ubuntu.com/Kernel/Debugging/Backlight
>
> Specifically this statement:
>
> ***
> The /proc/acpi/video interface
>
> Warning /!\ This actually is deprecated and would also only be working if 
> the ACPI backlight driver is active. It will be described only for 
> completeness. The ACPI backlight driver also exposes itself through the 
> new sysfs interface. 
> ***

Hrm... Nice article. Here are my evaluations:

1) I first tried to disable ACPI brightness switch. No matter what I
   give as kernel parameter, e.g.,

     acpi.brightness_switch_enabled=0
     acpi_backlight=vendor
     acpi_backlight=video

   /sys/module/video/parameters/brightness_switch_enabled is always set
   to Y. Moreover, actually nothing changes with above 3 parameters, as
   far as I observe.

3) When I set acpi to off, everything works fine.

> Besides, review your kernel config, just in case:
>
> grep -i -e backlight -e acpi /boot/config-3*

$ grep -i -e backlight -e acpi /boot/config-3.0.0 | grep -v ^#
CONFIG_ACPI=y
CONFIG_ACPI_SLEEP=y
CONFIG_ACPI_PROCFS=y
CONFIG_ACPI_AC=m
CONFIG_ACPI_BATTERY=m
CONFIG_ACPI_BUTTON=m
CONFIG_ACPI_VIDEO=m
CONFIG_ACPI_FAN=m
CONFIG_ACPI_DOCK=y
CONFIG_ACPI_PROCESSOR=m
CONFIG_ACPI_HOTPLUG_CPU=y
CONFIG_ACPI_PROCESSOR_AGGREGATOR=m
CONFIG_ACPI_THERMAL=m
CONFIG_ACPI_BLACKLIST_YEAR=0
CONFIG_ACPI_PCI_SLOT=m
CONFIG_ACPI_CONTAINER=m
CONFIG_ACPI_SBS=m
CONFIG_X86_ACPI_CPUFREQ=m
CONFIG_X86_POWERNOW_K7_ACPI=y
CONFIG_HOTPLUG_PCI_ACPI=m
CONFIG_HOTPLUG_PCI_ACPI_IBM=m
CONFIG_PNPACPI=y
CONFIG_ATA_ACPI=y
CONFIG_FB_BACKLIGHT=y
CONFIG_FB_NVIDIA_BACKLIGHT=y
CONFIG_FB_RADEON_BACKLIGHT=y
CONFIG_FB_ATY128_BACKLIGHT=y
CONFIG_FB_ATY_BACKLIGHT=y
CONFIG_BACKLIGHT_LCD_SUPPORT=y
CONFIG_BACKLIGHT_CLASS_DEVICE=y
CONFIG_BACKLIGHT_PROGEAR=m
CONFIG_LEDS_TRIGGER_BACKLIGHT=m
CONFIG_DRM_NOUVEAU_BACKLIGHT=y
CONFIG_THINKPAD_ACPI=m
CONFIG_THINKPAD_ACPI_ALSA_SUPPORT=y
CONFIG_THINKPAD_ACPI_VIDEO=y
CONFIG_THINKPAD_ACPI_HOTKEY_POLL=y
CONFIG_ACPI_WMI=m
CONFIG_ACPI_ASUS=m
CONFIG_ACPI_TOSHIBA=m

Any other ideas? What else should I debug?


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