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    SubjectRe: acpi 'video' driver, and issues with 'brightness_switch_enabled=0'
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    On Wed, 2009-04-29 at 11:08 +0800, Zhang Rui wrote:
    > On Tue, 2009-04-28 at 17:58 +0800, Maxim Levitsky wrote:
    > > 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.
    > >
    > so if you kill acpid, and run "cat /proc/acpi/event", there are some
    > ACPI video events popping up when you press the hotkeys, right?
    If 'video' acpi driver is loader, otherwise no events

    >
    > this is bad, because these events are "Used to notify OSPM that the
    > output device brightness should be increased/decreased by one level.
    > Used to notify OSPM that the user pressed a button or key that is
    > associated with cycling brightness." according to the ACPI spec.
    > So, if BIOS changes the brightness for OS, it should not issue an event
    > any more.

    >
    > > >
    > > > > 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.
    > >
    > well, this is rather a hardware problem to me.
    > Because OS should change the brightness upon such a notification, either
    > in ACPI video driver, or in user space.
    > IMO, if BIOS doesn't want OS to change the backlight, it should not
    > issue such events at all.
    >
    > > 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.
    > >
    > /sys/class/backlight/acpi_video0/brightness doesn't reflect the actual
    > brightness level, gdm should use actual_brightness instead.
    >
    > But if gdm uses the sysfs backlight I/F, the value of these two files
    > should be the same.
    If it sets the brightness that is.
    /sys/class/backlight/acpi_video0/brightness reflects last value written
    to it.
    >
    > can you do this test please?
    > 1. attach the output of "grep . /sys/class/backlight/acpi_video0/*"
    > 2. press the hotkey
    > 3. redo step 1.


    maxim@maxim-laptop:~$ grep . /sys/class/backlight/acpi_video0/*
    /sys/class/backlight/acpi_video0/actual_brightness:3
    /sys/class/backlight/acpi_video0/bl_power:0
    /sys/class/backlight/acpi_video0/brightness:7
    /sys/class/backlight/acpi_video0/max_brightness:9
    maxim@maxim-laptop:~$ grep . /sys/class/backlight/acpi_video0/*
    /sys/class/backlight/acpi_video0/actual_brightness:2
    /sys/class/backlight/acpi_video0/bl_power:0
    /sys/class/backlight/acpi_video0/brightness:7
    /sys/class/backlight/acpi_video0/max_brightness:9
    maxim@maxim-laptop:~$



    Note the above with brightness_switch_enabled=0, and with hal
    laptop_panel.brightness_in_hardware=true

    Which makes it ignore key-presses.

    And thus everyting almost work, but OSD of gpm doesn't reflect the
    current brightness (it uses /sys/class/backlight/acpi_video0/brightness
    it seems)

    >
    > >
    > > >
    > > > what's the model name of your laptop?
    > > acer aspire 5720G
    >
    > hah, I know this laptop.
    > > > 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.
    > And I know you're good at reporting bugs. :p
    And like to make linux better in any way I can

    >
    > why not move this discussion to the bugzilla so that I can better track
    > this bug?

    done: http://bugzilla.kernel.org/show_bug.cgi?id=13210

    >
    > thanks,
    > rui
    >
    >

    Best regards,
    Maxim Levitsky

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