linux-kernel - Re: [PATCH 1/5] iio: adc: ad7192: use devm_regulator_get_enable_read

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Date: Mon, 3 Jun 2024 21:10:56 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
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 1/5] iio: adc: ad7192: use
 devm_regulator_get_enable_read_voltage

On Mon, 3 Jun 2024 08:36:51 -0500
David Lechner <dlechner@...libre.com> wrote:

> On 6/1/24 7:48 AM, Jonathan Cameron wrote:
> > On Fri, 31 May 2024 16:19:32 -0500
> > David Lechner <dlechner@...libre.com> wrote:
> >   
> >> This makes use of the new devm_regulator_get_enable_read_voltage()
> >> function to reduce boilerplate code.
> >>
> >> Error messages have changed slightly since there are now fewer places
> >> where we print an error. The rest of the logic of selecting which
> >> supply to use as the reference voltage remains the same.
> >>
> >> Also 1000 is replaced by MILLI in a few places for consistency.
> >>
> >> Signed-off-by: David Lechner <dlechner@...libre.com>  
> > Ouch diff didn't like this one much and it is a bit hard to read.
> > 
> > One case where I think this has an unintended side effect.
> > See below.
> >   
> 
> ...
> 
> >> @@ -1219,74 +1211,54 @@ static int ad7192_probe(struct spi_device *spi)
> >>  	 * Newer firmware should provide a zero volt fixed supply if wired to
> >>  	 * ground.
> >>  	 */
> >> -	aincom = devm_regulator_get_optional(&spi->dev, "aincom");
> >> -	if (IS_ERR(aincom)) {
> >> -		if (PTR_ERR(aincom) != -ENODEV)
> >> -			return dev_err_probe(&spi->dev, PTR_ERR(aincom),
> >> -					     "Failed to get AINCOM supply\n");
> >> -
> >> +	ret = devm_regulator_get_enable_read_voltage(&spi->dev, "aincom");
> >> +	if (ret == -ENODEV)
> >>  		st->aincom_mv = 0;
> >> -	} else {
> >> -		ret = regulator_enable(aincom);
> >> -		if (ret)
> >> -			return dev_err_probe(&spi->dev, ret,
> >> -					     "Failed to enable specified AINCOM supply\n");
> >> +	else if (ret < 0)
> >> +		return dev_err_probe(&spi->dev, ret, "Failed to get AINCOM voltage\n");
> >> +	else
> >> +		st->aincom_mv = ret / MILLI;
> >>  
> >> -		ret = devm_add_action_or_reset(&spi->dev, ad7192_reg_disable, aincom);
> >> +	/* AVDD can optionally be used as reference voltage */
> >> +	ret = devm_regulator_get_enable_read_voltage(&spi->dev, "avdd");
> >> +	if (ret == -EINVAL) {
> >> +		/*
> >> +		 * We get -EINVAL if avdd is a supply with unknown voltage. We
> >> +		 * still need to enable it since it is also a power supply.
> >> +		 */
> >> +		ret = devm_regulator_get_enable(&spi->dev, "avdd");  
> > 
> > What happens if the entry simply isn't there in the DT.
> > Previously I think the regulator framework would supply a stub whereas
> > the devm_regulator_get_enable_read_voltage() returns -ENODEV so isn't
> > caught by the handling and I think it should be.  
> 
> Ah, yes so:
> 
> if (ret == -EINVAL || ret == -ENODEV) {
> 
Yes I think.