This patch enables mic-mute button on Lenovo X220 laptop. 

1. In order to get led indicator working, you need a patched version of 
thinkpad_acpi kernel module which will provide access to the sysfs file
to control the led. Linux kernel 3.2 does not support the led yet, for
future versions just check if the following file is exisiting:
    /sys/devices/platform/thinkpad_acpi/leds/tpacpi::micmute/brightness
If you don't care about led, the button will work without patching
the kernel.

2. The thinkpad_acpi extracted from Linux kernel 3.2 is available in
the 'src' directory. Just type ./build.sh and it will produce the 
patched module (if you have all required build tools and headers 
installed of course).

For different kernels, just apply 'thinkpad_acpi-micmute_led.patch'
patch. To avoid compiling the whole kernel, you may try to copy the 
thinkpad_acpi.c out of the kernel source tree to the 'src' directory,
apply patch, and build with ./build.sh

3. Install the builded module into the /lib/modules/... in place of
the original.

4. Now configure acpid to control alsa and the led when button is 
pressed. Place 'lenovo-micmute' into the '/etc/acpi/events' and
'lenovo-micmute.sh' into the '/etc/acpi'.

5. Thats all, restart acpid.
