linux-kernel - Re: [PATCH v4 04/12] iio: adc: ad7192: handle regulator voltage error first

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Message-ID: <20210513163850.434d8994@jic23-huawei>
Date:   Thu, 13 May 2021 16:38:50 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandru Ardelean <aardelean@...iqon.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jonathan.Cameron@...wei.com, alexandru.tachici@...log.com,
        linux@...iqon.com
Subject: Re: [PATCH v4 04/12] iio: adc: ad7192: handle regulator voltage
 error first

On Thu, 13 May 2021 15:07:44 +0300
Alexandru Ardelean <aardelean@...iqon.com> wrote:

> This change fixes a corner-case, where for a zero regulator value, the
> driver would exit early, initializing the driver only partially.
> The driver would be in an unknown state.
> 
> This change reworks the code to check regulator_voltage() return value
> for negative (error) first, and return early. This is the more common
> idiom.
> 
> Also, this change is removing the 'voltage_uv' variable and using the 'ret'
> value directly. The only place where 'voltage_uv' is being used is to
> compute the internal reference voltage, and the type of this variable is
> 'int' (same are for 'ret'). Using only 'ret' avoids having to assign it on
> the error path.
> 
> Fixes: ab0afa65bbc7 ("staging: iio: adc: ad7192: fail probe on get_voltage")
> Cc: Alexandru Tachici <alexandru.tachici@...log.com>
> Signed-off-by: Alexandru Ardelean <aardelean@...iqon.com>

I've applied the first 4 patches to the fixes-togreg branch of iio.git and
cc'd stable.

Added note to the first 3 about the sign-off chain as its a bit unusual
for it to include loops ;)  I always debate if I should sign-off again
when this happens, but decide against.

Jonathan

> ---
>  drivers/iio/adc/ad7192.c | 11 ++++-------
>  1 file changed, 4 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
> index d3be67aa0522..1141cc13a124 100644
> --- a/drivers/iio/adc/ad7192.c
> +++ b/drivers/iio/adc/ad7192.c
> @@ -912,7 +912,7 @@ static int ad7192_probe(struct spi_device *spi)
>  {
>  	struct ad7192_state *st;
>  	struct iio_dev *indio_dev;
> -	int ret, voltage_uv = 0;
> +	int ret;
>  
>  	if (!spi->irq) {
>  		dev_err(&spi->dev, "no IRQ?\n");
> @@ -949,15 +949,12 @@ static int ad7192_probe(struct spi_device *spi)
>  		goto error_disable_avdd;
>  	}
>  
> -	voltage_uv = regulator_get_voltage(st->avdd);
> -
> -	if (voltage_uv > 0) {
> -		st->int_vref_mv = voltage_uv / 1000;
> -	} else {
> -		ret = voltage_uv;
> +	ret = regulator_get_voltage(st->avdd);
> +	if (ret < 0) {
>  		dev_err(&spi->dev, "Device tree error, reference voltage undefined\n");
>  		goto error_disable_avdd;
>  	}
> +	st->int_vref_mv = ret / 1000;
>  
>  	spi_set_drvdata(spi, indio_dev);
>  	st->chip_info = of_device_get_match_data(&spi->dev);