On 07/08/2012 11:48 PM, Damjan wrote:
>> I saw a number of discussion on new thinkpad led and caused me to
>> re-think about my previous patch.
>>
>> The previous patches add interfaces to control hardware mute via BIOS
>> functions; however there are nobody to control it and the problem of
>> out-of-sync between hardware mute and software mute will still exist.
>>
>> Will it be a better idea to disable hardware mute?
>
> Hardware mute is a much needed functionality. There are tons of
> situations where you can't be sure what software is running (if it is)
> and you want to be absolutely sure that you mute the mic and speakers
> without even looking at the screen.
>
>
Hi Damjan,
I think you are referring to the below mute button (from thinkpad-acpi.txt)
===============================================================
ThinkPads have a built-in amplifier and muting circuit that drives the
console headphone and speakers. This circuit is after the main AC97
or HDA mixer in the audio path, and under exclusive control of the
firmware.
ThinkPads have three special hotkeys to interact with the console
audio control: volume up, volume down and mute.
It is worth noting that the normal way the mute function works (on
ThinkPads that do not have a "mute LED") is:
1. Press mute to mute. It will *always* mute, you can press it as
many times as you want, and the sound will remain mute.
2. Press either volume key to unmute the ThinkPad (it will _not_
change the volume, it will just unmute).
...
===============================================================
Disabling function only works on the mute button with LED as below:
===============================================================
The newer Lenovo models only have firmware mute control, and depend on
the main HDA mixer to do volume control (which is done by the operating
system). In this case, the volume keys are filtered out for unmute
key press (there are some firmware bugs in this area) and delivered as
normal key presses to the operating system (thinkpad-acpi is not
involved).
===============================================================
New ACPI thinkpad methods such as "GSMS" or "SHDA" can be used as
detection of mute LED because it makes sense to me that BIOS includes
the new interfaces only when the hardware is present. I have a x200 that
has no mute led, and I will also test patches on it to make sure the
original function does not break.
Thanks for highlighting the information to me. I will remember to check
systems with two different designs.
Best Regards,
Alex Hung
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