Re: [PATCH v2] remoteproc: mtk_scp: change the snprintf() checking

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Mon, Oct 27, 2025 at 10:08:51AM +0300, Dan Carpenter wrote:
> The snprintf() calls here work but they have several minor style issues:
> 
> 1) It uses ARRAY_SIZE() which is the number of elements in an array.
>    Since were talking about char that works, but it's more common to
>    use sizeof() which is the number of bytes.
> 2) The printf format is "%1d".  The "1" ensures we always print at
>    least 1 character but since numbers all have at least 1 digit this
>    can be removed.
> 3) The kernel implementation of snprintf() cannot return negative error
>    codes.  Also these particular calls to snprintf() can't return zero
>    and the code to handle that zero return is sort of questionable.
> 4) In the current kernel the only "core_id" we print is "0" but if it
>    was more than 9 then the output would be truncated so GCC complains.
>    Add an "a >= sizeof(scp_fw_file)" check for output which is too long.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
> v2: The v1 introduced a W=1 warning because of the truncation issue.
>     It's a false positive because GCC assumes that "core_id" can be
>     every possible value of int but actually it can only be zero.  And
>     also generally, in the kernel, truncating is fine and it is fine
>     here too.
> 
>     But let's use that as an opportunity to do more cleanups.
> 
>  drivers/remoteproc/mtk_scp.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
> index 10e3f9eb8cd2..db8fd045468d 100644
> --- a/drivers/remoteproc/mtk_scp.c
> +++ b/drivers/remoteproc/mtk_scp.c
> @@ -1127,11 +1127,11 @@ static const char *scp_get_default_fw_path(struct device *dev, int core_id)
>  		return ERR_PTR(-EINVAL);
>  
>  	if (core_id >= 0)
> -		ret = snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
> +		ret = snprintf(scp_fw_file, sizeof(scp_fw_file), "scp_c%d", core_id);
>  	else
> -		ret = snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
> -	if (ret <= 0)
> -		return ERR_PTR(ret);
> +		ret = snprintf(scp_fw_file, sizeof(scp_fw_file), "scp");
> +	if (ret >= sizeof(scp_fw_file))
> +		return ERR_PTR(-ENAMETOOLONG);
>

Applied.

Thanks,
Mathieu
  
>  	/* Not using strchr here, as strlen of a const gets optimized by compiler */
>  	soc = &compatible[strlen("mediatek,")];
> -- 
> 2.51.0
>