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

Takashi Iwai tiwai at suse.de
Mon Sep 24 10:09:00 CEST 2012

At Sat, 22 Sep 2012 20:54:11 +0200,
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.

Such a hardware mute isn't always related with the codec itself.
For example, Lenovo laptops have controls of the sound in the ACPI
over the sound chip.  OTOH, some machines (like HP laptops) use EAPD
for controlling the mute LED.  This is bound with the Master switch in
the recent driver.

So, without knowing the hardware detail, it's hard to tell more.


> 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.
> Kind regards,
> Arnout

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