[alsa-devel] [PATCH] ASoC: nau8825: erase pop noise by soft mute

[Mark Brown]

On Wed, Sep 14, 2016 at 03:47:32PM +0800, John Hsu wrote:

> + * Enable soft mute to gradually lower DAC volume to zero;
> + * Soft unmute will gradually increase DAC volume to volume setting.

> +		regmap_write(nau8825->regmap, NAU8825_REG_DAC_DGAIN_CTRL, 0);
> +		regmap_update_bits(nau8825->regmap, NAU8825_REG_MUTE_CTRL,
> +			NAU8825_DAC_SOFT_MUTE, NAU8825_DAC_SOFT_MUTE);

Why are we not just exposing soft mute as a userspace control like other
drivers do?  It seems like there's some weird interaction between
sidetones and the soft mute which this is trying to work around but
that's not really explained, it seems to be the main point here.
Basically I can't figure out what's intended here.

> +EXPORT_SYMBOL_GPL(nau8825_soft_mute);

Why is this exported, how will it be used?  The function seems to be
called from inside this driver as well...
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