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

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Date: Tue, 4 Jun 2024 09:10:35 -0500
From: David Lechner <dlechner@...libre.com>
To: Nuno Sá <noname.nuno@...il.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 6/4/24 6:19 AM, Nuno Sá wrote:
> 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...

Well, you do this every day. :-)

For someone who never wrote an IIO driver, it could be helpful.

> 
>> +	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
> 

I think I like that better too.