Re: [PATCH v2] iio: scd4x: check return of scd4x_write_and_fetch

From: Jonathan Cameron <jic23@kernel.org>
To: trix@redhat.com
Cc: roan@protonic.nl, lars@metafoo.de, nathan@kernel.org,
	ndesaulniers@google.com, linux-iio@vger.kernel.org,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH v2] iio: scd4x: check return of scd4x_write_and_fetch
Date: Sun, 20 Mar 2022 15:39:25 +0000	[thread overview]
Message-ID: <20220320153925.12bb01eb@jic23-huawei> (raw)
In-Reply-To: <20220301025223.223223-1-trix@redhat.com>

On Mon, 28 Feb 2022 18:52:23 -0800
trix@redhat.com wrote:

> From: Tom Rix <trix@redhat.com>
> 
> Clang static analysis reports this problem
> scd4x.c:474:10: warning: The left operand of '==' is a
>   garbage value
>   if (val == 0xff) {
>       ~~~ ^
> val is only set from a successful call to scd4x_write_and_fetch()
> So check it's return.
> 
> Fixes: 49d22b695cbb ("drivers: iio: chemical: Add support for Sensirion SCD4x CO2 sensor")
> Signed-off-by: Tom Rix <trix@redhat.com>

Hi Tom,

This looks good to me.  Timing was a bit unfortunate so now I'll queue this up for post
rc1.  Hence applied to my local copy of fixes-togreg (which includes the stuff that
should go in during the merge window) but not pushed out until I can rebase on rc1.

Thanks,

Jonathan

> ---
> v2: rework return on error logic to be similar to existing code
> 
>  drivers/iio/chemical/scd4x.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
> index 20d4e7584e923..37143b5526ee6 100644
> --- a/drivers/iio/chemical/scd4x.c
> +++ b/drivers/iio/chemical/scd4x.c
> @@ -471,12 +471,15 @@ static ssize_t calibration_forced_value_store(struct device *dev,
>  	ret = scd4x_write_and_fetch(state, CMD_FRC, arg, &val, sizeof(val));
>  	mutex_unlock(&state->lock);
>  
> +	if (ret)
> +		return ret;
> +
>  	if (val == 0xff) {
>  		dev_err(dev, "forced calibration has failed");
>  		return -EINVAL;
>  	}
>  
> -	return ret ?: len;
> +	return len;
>  }
>  
>  static IIO_DEVICE_ATTR_RW(calibration_auto_enable, 0);