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    SubjectRe: acpi 'video' driver, and issues with 'brightness_switch_enabled=0'
    On Tue, 2009-04-28 at 01:57 +0800, Maxim Levitsky wrote:
    > I have a notebook which handles brightness keys in hardware, but tells
    > loudly when it does so.
    if you boot into console mode w/o ACPI video driver, does the brightness
    still change when you press the hotkeys?

    > Currently, acpi 'video' also sets the brightness, which result in double
    > setting, and on top of that it emits a key that makes gpm set brightness
    > again.
    we need to support the brightness control in console mode.
    and "brightness_switch_enabled" should be cleared in graphics mode to
    prevent the ACPI video driver action upon hotkey events.

    > And (yes...) on top of that keyboard emits a brightness up/down even,
    > which (you guessed...) sets brightness again.
    > I found out that it is possible to tell gnome-power-manager not to set
    > brightness, but yet in kernel driver still sets it.
    > I found out even earlier that I can use brightness_switch_enabled=0,
    > which supposed to make inkernel driver not touch the brightness.
    > But I found out that this driver won't update the brightness, in /sys
    > interface when I set this param.
    No, when "brightness_switch_enabled" is cleared, gdm should still use
    the ACPI backlight sysfs I/F if available to change the backlight,
    i.e. /sys/class/backlight/acpi_video0/...

    what's the model name of your laptop?
    are you using Intel graphics?
    please attach the output of acpidump and lspci.
    It would be great if you can file a bug report about this issue at


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