Thinkpad T61 mute button no longer works in Hardy. It's back!

This problem is caused by thinkpad-acpi in 2.6.24 . This mailing list thread exposes the issue:
http://<email address hidden>/msg01060.html

It also affects the power button.

I misspoke it seems that this is a Lenovo firmware issue and thinkpad-acpi is not at fault. The link above exposes this (I just didn't read to the end of one of the mails):

There is another email on the issue here:
http://www.nabble.com/Backlight:-video-and-ibm-hotkey-report-the-same-event-td14385327.html

I take that back. The mute button work fine under Ubuntu Gutsy

So it's either thinkpad-acpi or acpi subsystem in 2.6.24.

So it's not thinkpad-acpi . The issue is very strange but basically any kernel past 2.6.22 displays it.

Now here is the kicker. The mute button actually mutes the. But the software (Gnome or KDE) does not pick it up when running on a kernel past 2.6.22. So the mixers are not aware that things have been muted. So you have no visual that things are muted.

Had a discussion on ibm-acpi-devel but it's not archived SO I'll past my results here:

System:
       Thinkpad T61
       Vendor: LENOVO
       Firmware Version: 7LETA7WW (2.07)
       EC Version: 1.08

Here are my test results (These are kernel.org kernels):

kernel 2.6.22.15 (w/ thinkpad-acpi v0.14) = Works great Gnome can see
                                                                      mute button pressed

Kernel 2.6.22.15 (with thinkpad-acpi v0.19) = Works great Gnome can see
                                                                        mute button pressed

kernel 2.6.23.13 (w/ thinkpad-acpi v0.16) = Gnome does NOT see mute is pressed
                                                              Mute button is not recogonized when try to
                                                               associate it with a keyboard action
                                                               using gnome-keybing-properties

kernel 2.6.24-rc7 (w/ thinkpad-acpi v0.17) = Gnome does NOT see mute is pressed
                                                              Mute button is not recogonized when try to
                                                              associate it with a keyboard action using
                                                               gnome-keybing-properties

Kernel 2.6.24-rc7 (with thinkpad-acpi v0.19) = Gnome does NOT see mute is pressed
                                                              Mute button is not recogonized when try to
                                                              associate it with a keyboard action using
                                                               gnome-keybing-properties

OK so the simple solution for this issue is to put ' acpi_osi=Linux' on the kernel command line. I am working with the thinkpad-acpi maintainer (who is working with the acpi maintainer) to get a proper in kernel fix.

soultion to this problem is adding acpi_osi=Linux to command line. Later Kernels will have a proper fix integrated or Lenovo will fix there firmware. Whichever comes first.