Re: [PATCH v2 1/7] regulator: devres: add API for reference voltage supplies

[David Lechner]

On Mon, Apr 29, 2024 at 6:40 PM David Lechner <dlechner@xxxxxxxxxxxx> wrote:
>
> A common use case for regulators is to supply a reference voltage to an
> analog input or output device. This adds a new devres API to get,
> enable, and get the voltage in a single call. This allows eliminating
> boilerplate code in drivers that use reference supplies in this way.
>
> Signed-off-by: David Lechner <dlechner@xxxxxxxxxxxx>
> ---
>
> v2 changes:
> * removed dev_err_probe() on error return
> * dropped optional version of the function since there is no more
>   difference after dev_err_probe() is removed
> * renamed function to devm_regulator_get_enable_read_voltage()
> * added unwinding on error paths
> ---
>  Documentation/driver-api/driver-model/devres.rst |  1 +
>  drivers/regulator/devres.c                       | 59 ++++++++++++++++++++++++
>  include/linux/regulator/consumer.h               |  7 +++
>  3 files changed, 67 insertions(+)
>
> diff --git a/Documentation/driver-api/driver-model/devres.rst b/Documentation/driver-api/driver-model/devres.rst
> index 7be8b8dd5f00..18caebad7376 100644
> --- a/Documentation/driver-api/driver-model/devres.rst
> +++ b/Documentation/driver-api/driver-model/devres.rst
> @@ -433,6 +433,7 @@ REGULATOR
>    devm_regulator_bulk_put()
>    devm_regulator_get()
>    devm_regulator_get_enable()
> +  devm_regulator_get_enable_read_voltage()
>    devm_regulator_get_enable_optional()
>    devm_regulator_get_exclusive()
>    devm_regulator_get_optional()
> diff --git a/drivers/regulator/devres.c b/drivers/regulator/devres.c
> index 90bb0d178885..4f290b9b559b 100644
> --- a/drivers/regulator/devres.c
> +++ b/drivers/regulator/devres.c
> @@ -145,6 +145,65 @@ struct regulator *devm_regulator_get_optional(struct device *dev,
>  }
>  EXPORT_SYMBOL_GPL(devm_regulator_get_optional);
>
> +/**
> + * devm_regulator_get_enable_read_voltage - Resource managed regulator get and
> + *                                          enable that returns the voltage
> + * @dev: device to supply
> + * @id:  supply name or regulator ID.
> + *
> + * Get and enable regulator for duration of the device life-time.
> + * regulator_disable() and regulator_put() are automatically called on driver
> + * detach. See regulator_get_optional(), regulator_enable(), and
> + * regulator_get_voltage() for more information.
> + *
> + * This is a convenience function for supplies that provide a reference voltage
> + * where the consumer driver just needs to know the voltage and keep the
> + * regulator enabled.
> + *
> + * In cases where the supply is not strictly required, callers can check for
> + * -ENODEV error and handle it accordingly.
> + *
> + * Returns: voltage in microvolts on success, or an error code on failure.
> + */
> +int devm_regulator_get_enable_read_voltage(struct device *dev, const char *id)
> +{
> +       struct regulator *r;
> +       int ret;
> +
> +       /*
> +        * Since we need a real voltage, we use devm_regulator_get_optional()
> +        * rather than getting a dummy regulator with devm_regulator_get() and
> +        * then letting regulator_get_voltage() fail with -EINVAL. This way, the
> +        * caller can handle the -ENODEV error code if needed instead of the
> +        * ambiguous -EINVAL.
> +        */
> +       r = devm_regulator_get_optional(dev, id);
> +       if (IS_ERR(r))
> +               return PTR_ERR(r);
> +
> +       ret = regulator_enable(r);
> +       if (ret)
> +               goto err_regulator_put;
> +
> +       ret = devm_add_action_or_reset(dev, regulator_action_disable, r);
> +       if (ret)
> +               goto err_regulator_put;
> +
> +       ret = regulator_get_voltage(r);
> +       if (ret < 0)
> +               goto err_release_action;
> +
> +       return 0;

Oof. Apparently I didn't test this as well as I should have after
adding the unwinding. This obviously should return ret, not 0.

I did more extensive testing today, including faking error returns to
test unwinding to make sure I didn't miss anything else.

> +
> +err_release_action:
> +       devm_release_action(dev, regulator_action_disable, r);
> +err_regulator_put:
> +       devm_regulator_put(r);
> +
> +       return ret;
> +}
> +EXPORT_SYMBOL_GPL(devm_regulator_get_enable_read_voltage);
> +