linux-kernel - Re: [Regression] 2.6.37-rc1: Lenovo T61 mute button does not work

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Message-ID: <1291172324.14274.33.camel@nayuki>
Date:	Tue, 30 Nov 2010 21:58:44 -0500
From:	Calvin Walton <calvin.walton@...il.com>
To:	Lukas Hejtmanek <xhejtman@....muni.cz>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [Regression] 2.6.37-rc1: Lenovo T61 mute button does not work

On Tue, 2010-11-30 at 19:53 +0100, Lukas Hejtmanek wrote:
> Hi,
> 
> in 2.6.26, mute button worked as expected on my ThinkPad T61 - it toggled
> mute with mixer applet notification. In 2.6.37-rc1, it only mutes without any
> event to any mixer applet.

The mute button on this series of Thinkpads is a little weird (I have an
R61i, which is the same iirc) - the behaviour of the button depends on
the ACPI firmware. With no operating system running, it behaves as a
persistent hardware mute. Windows apparently uses a proprietary driver
to control the volume - part of this functionality has been added to the
Linux thinkpad_acpi driver, but it's not fully enabled yet.

By default on this series of laptops, Linux runs with the ACPI
_OSI(Linux) exported - when the bios of this laptop model sees that it's
running on Linux, it disables the hardware mute functionality and the
mute button acts as a standard keyboard key.

Search your dmesg for lines containing '_OSI(Linux)' - it should say
that a BIOS query was honoured. Make sure you do not have 'acpi_osi="!
Linux"' on your kernel command line.

-- 
Calvin Walton <calvin.walton@...il.com>

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