Re: [PATCH] iio: adc: Revoke valid channel for error path

Nuno Sá
2025-04-17T10:06:50Z

On Tue, 2025-04-15 at 14:20 -0400, Gabriel Shahrouzi wrote:
> According to the datasheet on page 9 under the channel selection table,
> all devices (AD7816/7/8) are able to use the channel marked as 7. This
> channel is used for diagnostic purposes by routing the internal 1.23V
> bandgap source through the MUX to the input of the ADC.
>
> Replace checking for string equality with checking for the same chip ID
> to reduce time complexity.
>
> Group invalid channels for all devices together because they are
> processed the same way.
>
> Fixes: 7924425db04a ("staging: iio: adc: new driver for AD7816 devices")
> Cc: stable@vger.kernel.org
> Signed-off-by: Gabriel Shahrouzi <gshahrouzi@gmail.com>
> ---
>  drivers/staging/iio/adc/ad7816.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/staging/iio/adc/ad7816.c
> b/drivers/staging/iio/adc/ad7816.c
> index 6c14d7bcdd675..d880fe0257697 100644
> --- a/drivers/staging/iio/adc/ad7816.c
> +++ b/drivers/staging/iio/adc/ad7816.c
> @@ -186,17 +186,12 @@ static ssize_t ad7816_store_channel(struct device *dev,
>   if (ret)
>   return ret;
>
> - if (data > AD7816_CS_MAX && data != AD7816_CS_MASK) {
> - dev_err(&chip->spi_dev->dev, "Invalid channel id %lu for
> %s.\n",
> - data, indio_dev->name);
> - return -EINVAL;
> - } else if (strcmp(indio_dev->name, "ad7818") == 0 && data > 1) {
> - dev_err(&chip->spi_dev->dev,
> - "Invalid channel id %lu for ad7818.\n", data);
> - return -EINVAL;
> - } else if (strcmp(indio_dev->name, "ad7816") == 0 && data > 0) {
> + if (data != AD7816_CS_MASK &&
> +     (data > AD7816_CS_MAX ||
> +     (chip->id == ID_AD7818 && data > 1) ||
> +     (chip->id == ID_AD7816 && data > 0))) {
>   dev_err(&chip->spi_dev->dev,
> - "Invalid channel id %lu for ad7816.\n", data);
> + "Invalid channel id %lu for %s.\n", data, indio_dev-
> >name);
>   return -EINVAL;
>   }

Hmm, maybe I'm missing something but the code just looks the same as before
(from a functionality point of view)? I'm really not seeing any fix...

Having said the above, not sure if grouping helps with readability. But I do
agree with moving from string comparison to use chip->id. And we also have
redundants 'else'

- Nuno Sá