Re: [PATCH -next] pwm: lp3943: Fix an incorrect type in lp3943_pwm_parse_dt()

Uwe Kleine-König
2024-08-09T08:50:53Z

Hello Jiapeng,

On 8/9/24 10:05, Jiapeng Chong wrote:
> The return value from the call to of_property_count_u32_elems() is int.
> However, the return value is being assigned to an u32 variable
> 'num_outputs', so making 'num_outputs' an int.
>
> ./drivers/pwm/pwm-lp3943.c:238:6-17: WARNING: Unsigned expression compared with zero: num_outputs <= 0.

Which tool does emit this warning? My test build (with C=1 and W=1)
doesn't emit it.

> Reported-by: Abaci Robot <abaci@linux.alibaba.com>
> Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=9710
> Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>

This problem was introduced in a commit in next:

Fixes: d6a56f3bb650 ("pwm: lp3943: Use of_property_count_u32_elems() to
get property length")

Rob: I guess this wasn't the only conversion of this type. Maybe these
others suffer from the same problem?!

> ---
> drivers/pwm/pwm-lp3943.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/pwm/pwm-lp3943.c b/drivers/pwm/pwm-lp3943.c
> index f0e94c9e5956..90b0733c00c1 100644
> --- a/drivers/pwm/pwm-lp3943.c
> +++ b/drivers/pwm/pwm-lp3943.c
> @@ -218,8 +218,7 @@ static int lp3943_pwm_parse_dt(struct device *dev,
> struct lp3943_platform_data *pdata;
> struct lp3943_pwm_map *pwm_map;
> enum lp3943_pwm_output *output;
> - int i, err, count = 0;
> - u32 num_outputs;
> + int i, err, num_outputs, count = 0;
>
> if (!node)
> return -EINVAL;

Nitpick (maybe even a subjective one):
While touching num_outputs, its scope could be reduced to the for loop.

Best regards
Uwe