[alsa-devel] HD Audio with 'mute light'

David Henningsson david.henningsson at canonical.com
Mon Sep 24 10:12:19 CEST 2012

On 09/22/2012 08:54 PM, Arnout Engelen wrote:
> Hi,
> I've got a laptop with a HD Audio onboard sound card: the CX20590.
> It seems like this card has a sort of 'hardware mute state': the 'mute button'
> has a light, and when this light is on, no sound is heard, regardless of
> whether or not the channel is muted in the ALSA mixer.
> The hardware mute button switches the 'hardware mute state', and also sends a
> keyboard event which I can use to also update the ALSA mixer mute.
> This doesn't, however, work the other way around: I haven't found any way yet
> to manipulate the 'hardware mute state' from software.
> Looking with hda_analyzer, I notice this card has a 'Vendor Defined Widget'.
> Might this be something that could be used to manipulate the hardware mute
> state? I can use hda-verb but I wouldn't know how to discover which verb to
> use. Anything else to try?
> Attached is the codec info.

We generally recommend people to submit the entire alsa-info, rather 
than just the codec info (which, btw, was an empty attachment). In 
particular; if you're having a thinkpad, the mute LED is controlled 
through thinkpad-acpi, and if you're having an HP, it's usually 
connected to the codec in a way hinted by BIOS. Given that you have a 
conexant codec, I'm guessing it's a thinkpad.

David Henningsson, Canonical Ltd.

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