linux-kernel - Re: [PATCH v3 04/12] iio: adc: ad7192: handle zero Avdd regulator value

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Date:   Thu, 13 May 2021 09:41:10 +0200
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Alexandru Ardelean <aardelean@...iqon.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     jic23@...nel.org, Jonathan.Cameron@...wei.com,
        alexandru.tachici@...log.com, linux@...iqon.com
Subject: Re: [PATCH v3 04/12] iio: adc: ad7192: handle zero Avdd regulator
 value

On 5/12/21 7:49 PM, Alexandru Ardelean 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.
>
> If the regulator value is zero, then the internal reference will be zero
> (though that value will be zero for anything less than 1 millivolt).
>
> 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>
> ---
>   drivers/iio/adc/ad7192.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
> index d3be67aa0522..9da394ad3868 100644
> --- a/drivers/iio/adc/ad7192.c
> +++ b/drivers/iio/adc/ad7192.c
> @@ -951,7 +951,7 @@ static int ad7192_probe(struct spi_device *spi)
>   
>   	voltage_uv = regulator_get_voltage(st->avdd);
>   
> -	if (voltage_uv > 0) {
> +	if (voltage_uv >= 0) {
>   		st->int_vref_mv = voltage_uv / 1000;
>   	} else {
>   		ret = voltage_uv;

More idiomatic would be to check for voltage_uv < 0.

     if (voltage_uv < 0) {
         ret = voltage_uv;
         dev_err(&spi->dev, "Device tree error, reference voltage 
undefined\n");
         goto error_disable_avdd;
     }

     st->int_vref_mv = voltage_uv / 1000;