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

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Message-ID: <fb712c034eda0d5d711a90a00b6382315fb5f929.camel@gmail.com>
Date: Thu, 17 Apr 2025 11:06:51 +0100
From: Nuno Sá <noname.nuno@...il.com>
To: Gabriel Shahrouzi <gshahrouzi@...il.com>, gregkh@...uxfoundation.org, 
	jic23@...nel.org, lars@...afoo.de, linux-iio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-staging@...ts.linux.dev, 
	Michael.Hennerich@...log.com, sonic.zhang@...log.com, vapier@...too.org
Cc: skhan@...uxfoundation.org, kernelmentees@...ts.linuxfoundation.org, 
	stable@...r.kernel.org
Subject: Re: [PATCH] iio: adc: Revoke valid channel for error path

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@...r.kernel.org
> Signed-off-by: Gabriel Shahrouzi <gshahrouzi@...il.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