[alsa-devel] [PATCH 7/8] ASoC: wm8998: Initial WM8998 codec driver

[Mark Brown]

On Tue, Apr 21, 2015 at 01:33:55PM +0100, Richard Fitzgerald wrote:

> +static int wm8998_in1mux_ev(struct snd_soc_dapm_widget *w,
> +				struct snd_kcontrol *kcontrol,
> +				int event)
> +{
> +	struct snd_soc_codec *codec = snd_soc_dapm_to_codec(w->dapm);
> +	struct arizona *arizona = dev_get_drvdata(codec->dev->parent);
> +	unsigned int left_mux, right_mux, in1mode, old;
> +
> +	switch (event) {
> +	case SND_SOC_DAPM_PRE_PMU:
> +		/* Validate the mux configuration */
> +		left_mux = snd_soc_read(codec, ARIZONA_ADC_DIGITAL_VOLUME_1L) &
> +				  ARIZONA_IN1L_SRC_MASK;
> +		right_mux = snd_soc_read(codec, ARIZONA_ADC_DIGITAL_VOLUME_1R) &
> +				  ARIZONA_IN1R_SRC_MASK;
> +
> +		/* Only IN1A can be digital, IN1B is always analogue */
> +		in1mode = (arizona->pdata.inmode[0] & 2)
> +				<< (ARIZONA_IN1_MODE_SHIFT - 1);
> +
> +		if (in1mode != 0) {
> +			/* if IN1A is digital, the only valid mux configs
> +			 * are both channels A or both channels B.
> +			 */
> +			if (left_mux != right_mux) {
> +				dev_err(arizona->dev,
> +					"IN1=DMIC and IN1L Mux != IN1R Mux");
> +				return -EINVAL;
> +			}

This (or at least some of it) seems like something we should be doing by
registering different widgets and routing at device probe time.

> +		old = snd_soc_read(codec, ARIZONA_IN1L_CONTROL) &
> +					ARIZONA_IN1_MODE_MASK;

> +		if (old != in1mode)
> +			snd_soc_update_bits(codec, ARIZONA_IN1L_CONTROL,
> +						ARIZONA_IN1_MODE_MASK, in1mode);

Why bother with the read into old here?  Suppressing redundant updates
is part of the point of snd_soc_update_bits().
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