linux-kernel - Re: [PATCH 2/5] iio: adc: ad7266: use devm_regulator_get_enable_read

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Date: Tue, 04 Jun 2024 13:19:30 +0200
From: Nuno Sá <noname.nuno@...il.com>
To: David Lechner <dlechner@...libre.com>, Jonathan Cameron
 <jic23@...nel.org>
Cc: Marcelo Schmitt <marcelo.schmitt1@...il.com>, Nuno Sá
 <nuno.sa@...log.com>, Michael Hennerich <Michael.Hennerich@...log.com>,
 Mark Brown <broonie@...nel.org>, Liam Girdwood <lgirdwood@...il.com>,
 linux-iio@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] iio: adc: ad7266: use
 devm_regulator_get_enable_read_voltage

On Fri, 2024-05-31 at 16:19 -0500, David Lechner wrote:
> This makes use of the new devm_regulator_get_enable_read_voltage()
> function to reduce boilerplate code.
> 
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
>  drivers/iio/adc/ad7266.c | 37 ++++++++++---------------------------
>  1 file changed, 10 insertions(+), 27 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7266.c b/drivers/iio/adc/ad7266.c
> index 353a97f9c086..026db1bedc0a 100644
> --- a/drivers/iio/adc/ad7266.c
> +++ b/drivers/iio/adc/ad7266.c
> @@ -25,7 +25,6 @@
>  
>  struct ad7266_state {
>  	struct spi_device	*spi;
> -	struct regulator	*reg;
>  	unsigned long		vref_mv;
>  
>  	struct spi_transfer	single_xfer[3];
> @@ -377,11 +376,6 @@ static const char * const ad7266_gpio_labels[] = {
>  	"ad0", "ad1", "ad2",
>  };
>  
> -static void ad7266_reg_disable(void *reg)
> -{
> -	regulator_disable(reg);
> -}
> -
>  static int ad7266_probe(struct spi_device *spi)
>  {
>  	struct ad7266_platform_data *pdata = spi->dev.platform_data;
> @@ -396,28 +390,17 @@ static int ad7266_probe(struct spi_device *spi)
>  
>  	st = iio_priv(indio_dev);
>  
> -	st->reg = devm_regulator_get_optional(&spi->dev, "vref");
> -	if (!IS_ERR(st->reg)) {
> -		ret = regulator_enable(st->reg);
> -		if (ret)
> -			return ret;
> -
> -		ret = devm_add_action_or_reset(&spi->dev, ad7266_reg_disable, st-
> >reg);
> -		if (ret)
> -			return ret;
> -
> -		ret = regulator_get_voltage(st->reg);
> -		if (ret < 0)
> -			return ret;
> -
> -		st->vref_mv = ret / 1000;
> -	} else {
> -		/* Any other error indicates that the regulator does exist */
> -		if (PTR_ERR(st->reg) != -ENODEV)
> -			return PTR_ERR(st->reg);
> -		/* Use internal reference */
> +	/*
> +	 * Use external reference from vref if present, otherwise use 2.5V
> +	 * internal reference.
> +	 */

Not sure the comment brings any added value. The code is fairly self explanatory
IMO...

> +	ret = devm_regulator_get_enable_read_voltage(&spi->dev, "vref");
> +	if (ret == -ENODEV)
>  		st->vref_mv = 2500;
> -	}
> +	else if (ret < 0)
> +		return ret;
> +	else

I think it would be better (as that is the typical pattern) to first check for
errors. Also the 'return' in the middle of the else if () is a bit weird to me...
Maybe something like this?

if (ret < 0 && ret != -ENODEV)
	return ret;
if (ret == -ENODEV)
	st->vref_mv = 2500;
else
	st->vref_mv = ret / 1000;

or even replacing the if() else by
st->vref_mv = ret == -ENODEV ? 2500 : ret / 1000;

- Nuno Sá