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SubjectRe: [PATCH] iio: scd4x: check return of scd4x_write_and_fetch
On Sun, 27 Feb 2022 07:43:31 -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>

Good find, but I'd prefer a separate check on ret inline with what the
other error checking paths in that function are doing.

> ---
> drivers/iio/chemical/scd4x.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
> index 20d4e7584e923..b978330fb761c 100644
> --- a/drivers/iio/chemical/scd4x.c
> +++ b/drivers/iio/chemical/scd4x.c
> @@ -471,7 +471,7 @@ 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 (val == 0xff) {
> + if (!ret && val == 0xff) {
> dev_err(dev, "forced calibration has failed");
> return -EINVAL;
> }
Prefer

if (ret)
return ret;

if (val == 0xff) {
dev_err(dev, "...
return -EINVAL;
}

Thanks,

Jonathan

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