[RFC 2/2] ASoC: rt5670: Add LED trigger support

[Mark Brown]

On Tue, Feb 23, 2021 at 02:59:17PM +0100, Hans de Goede wrote:
> On 2/23/21 2:45 PM, Mark Brown wrote:
> > On Mon, Feb 15, 2021 at 03:24:19PM +0100, Hans de Goede wrote:

> > Why just these particular controls - what if a system has separate mutes
> > for speakers or something?

> These are the main volume controls, which are always in the output / input
> path independent on if we are outputting to e.g. speakers or the headphones.

> We want to use the main volume control for this, because there always is
> only 1 output mute LED and 1 input mute LED. Well at least that is the assumption
> the current ledtrig-audio.c code has.

> The idea is to only turn the single LED on if we are sure there will be not
> sound output on any of the outputs, which is why we tie the LED to the
> mute switch on the main volume control.

Right, so that might work well on your particular system with your
particular configuration but will it work well on other systems with
different hardware?  It's not clear to me that it makes sense to go
through all the drivers picking controls that might be used for this
purpose - it seems both time consuming and error prone.  Consider a
mostly digital device which has an ADC/DAC per input/output rather than
a central ADC/DAC with analogue muxing for example, or a system with
multiple DACs available for mixing together or analogue bypassess.  
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