[PATCH 2/4] ASoC: cx20442: add bias control over a platform provided regulator

[Mark Brown]

On Sat, Dec 24, 2011 at 12:12:22AM +0100, Janusz Krzysztofik wrote:

> +	case SND_SOC_BIAS_ON:
> +	case SND_SOC_BIAS_PREPARE:
> +		if (IS_ERR(cx20442->por.regulator)) {
> +			err = PTR_ERR(cx20442->por.regulator);
> +		} else if (!cx20442->por.enabled) {
> +			err = regulator_enable(cx20442->por.regulator);
> +			if (!err)
> +				cx20442->por.enabled = true;
> +		}
> +		break;
> +	case SND_SOC_BIAS_STANDBY:
> +	case SND_SOC_BIAS_OFF:
> +		if (IS_ERR(cx20442->por.regulator)) {
> +			err = PTR_ERR(cx20442->por.regulator);
> +		} else if (cx20442->por.enabled) {
> +			err = regulator_disable(cx20442->por.regulator);
> +			if (!err)
> +				cx20442->por.enabled = false;
> +		}
> +	}
> +	mutex_unlock(&cx20442->por.lock);

You can avoid the mutex and simplify the code by relying on the fact
that the only possible transitions are:

   OFF <-> STANDBY <-> PREPARE <-> ON

which would look a lot more natural - you shouldn't need to remember if
the regulator is enabled, you should just turn it on in the STANDBY to
PREPARE transition and turn it off in the ON to PREPARE or PREPARE to
STANDBY transitions.