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    SubjectRe: acpi 'video' driver, and issues with 'brightness_switch_enabled=0'
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    On Tue, 2009-04-28 at 10:43 +0800, Zhang Rui wrote:
    > 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?
    They always work.
    For s while, due to buggy ACPI table, acpi 'video' driver won't work, so
    I blacklisted it, and yet hw keys did work.

    >
    > > 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.
    How gnome power manager can do that, use /sys/module iface?

    >
    > > 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/...
    Indeed it does, but I don't like it, hardware already changed the
    brightness, but it receives another two events about brightness up/down.

    It (and I too) can change the brightness, but it doesn't update to
    reflect current brightness
    (/sys/class/backlight/acpi_video0/brightness) shows cached value from
    last time it was set.

    there is also the actual_brightness, but I think it isn't used by gpm.


    >
    > what's the model name of your laptop?
    acer aspire 5720G
    > are you using Intel graphics?
    no, nvidia 8400GS

    > please attach the output of acpidump and lspci.

    > It would be great if you can file a bug report about this issue at
    > bugzilla.kernel.org.
    No problem.
    >
    > thanks,
    > rui

    Thanks too,
    Best regards,
    Maxim Levitsky
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