linux-kernel - Re: acpi 'video' driver, and issues with 'brightness_switch

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Date:	Tue, 28 Apr 2009 12:58:51 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: acpi 'video' driver, and issues with
 'brightness_switch_enabled=0'

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

Download attachment "acpidump.bz2" of type "application/x-bzip" (42936 bytes)

Download attachment "lspci.bz2" of type "application/x-bzip" (8319 bytes)