[alsa-devel] [PATCH 10/10] ASoC: dapm: Implement mixer input auto-disable

[Mark Brown]

On Mon, Jul 29, 2013 at 05:14:04PM +0200, Lars-Peter Clausen wrote:

> -	ucontrol->value.integer.value[0] =
> -		(snd_soc_read(codec, reg) >> shift) & mask;
> +	mutex_lock_nested(&card->dapm_mutex, SND_SOC_DAPM_CLASS_RUNTIME);
> +	if (dapm_kcontrol_is_powered(kcontrol))
> +		val = (snd_soc_read(codec, reg) >> shift) & mask;
> +	else
> +		val = dapm_kcontrol_get_value(kcontrol);
> +	mutex_unlock(&card->dapm_mutex);
> +

My first thought looking at this is that I would expect this to be
encapsulated in kcntrol_get_value(), though at the minute it's actually
only returning the virtual value which makes sense for the existing use.  

Equally well I'd expect the value to always be a functioning cache of
the real value so I think what I'm really saying here is that I don't
think we should really be checking if the control is powered at all.  We
do need the I/O path but the power isn't the reason for it, the fact
that we have the value stashed locally is.

Another thing that's bothering me here is that this only works for mono
controls but many of the uses are stereo mutes and/or volumes.  We'd
need to add back the support for those.
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