[PATCH] remoteproc: mtk_scp: remove unnecessary checking

[PATCH] remoteproc: mtk_scp: remove unnecessary checking

[Dan Carpenter]

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 a zero return is sort of questionable.  Just
delete this impossible code.

Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
 drivers/remoteproc/mtk_scp.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index 10e3f9eb8cd2..9b624948a572 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c
@@ -1127,11 +1127,9 @@ 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);
+		snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
 	else
-		ret = snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
-	if (ret <= 0)
-		return ERR_PTR(ret);
+		snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
 
 	/* Not using strchr here, as strlen of a const gets optimized by compiler */
 	soc = &compatible[strlen("mediatek,")];
-- 
2.51.0

Re: [PATCH] remoteproc: mtk_scp: remove unnecessary checking

[kernel test robot]

Hi Dan,

kernel test robot noticed the following build warnings:

[auto build test WARNING on remoteproc/rproc-next]
[also build test WARNING on next-20251023]
[cannot apply to linus/master v6.18-rc2]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dan-Carpenter/remoteproc-mtk_scp-remove-unnecessary-checking/20251022-200619
base:   https://git.kernel.org/pub/scm/linux/kernel/git/remoteproc/linux.git rproc-next
patch link:    https://lore.kernel.org/r/aPi6eBlFLH43A4C0%40stanley.mountain
patch subject: [PATCH] remoteproc: mtk_scp:  remove unnecessary checking
config: arm-randconfig-003-20251023 (https://download.01.org/0day-ci/archive/20251023/202510231714.dlrsh9El-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 8.5.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251023/202510231714.dlrsh9El-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202510231714.dlrsh9El-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/remoteproc/mtk_scp.c: In function 'scp_rproc_init':
>> drivers/remoteproc/mtk_scp.c:1130:56: warning: '%1d' directive output may be truncated writing between 1 and 10 bytes into a region of size 2 [-Wformat-truncation=]
      snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
                                                           ^~~
   drivers/remoteproc/mtk_scp.c:1130:50: note: directive argument in the range [0, 1073741824]
      snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
                                                     ^~~~~~~~~~
   drivers/remoteproc/mtk_scp.c:1130:3: note: 'snprintf' output between 7 and 16 bytes into a destination of size 7
      snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +1130 drivers/remoteproc/mtk_scp.c

  1096	
  1097	/**
  1098	 * scp_get_default_fw_path() - Get default SCP firmware path
  1099	 * @dev:     SCP Device
  1100	 * @core_id: SCP Core number
  1101	 *
  1102	 * This function generates a path based on the following format:
  1103	 *     mediatek/(soc_model)/scp(_cX).img; for multi-core or
  1104	 *     mediatek/(soc_model)/scp.img for single core SCP HW
  1105	 *
  1106	 * Return: A devm allocated string containing the full path to
  1107	 *         a SCP firmware or an error pointer
  1108	 */
  1109	static const char *scp_get_default_fw_path(struct device *dev, int core_id)
  1110	{
  1111		struct device_node *np = core_id < 0 ? dev->of_node : dev->parent->of_node;
  1112		const char *compatible, *soc;
  1113		char scp_fw_file[7];
  1114		int ret;
  1115	
  1116		/* Use only the first compatible string */
  1117		ret = of_property_read_string_index(np, "compatible", 0, &compatible);
  1118		if (ret)
  1119			return ERR_PTR(ret);
  1120	
  1121		/* If the compatible string's length is implausible bail out early */
  1122		if (strlen(compatible) < strlen("mediatek,mtXXXX-scp"))
  1123			return ERR_PTR(-EINVAL);
  1124	
  1125		/* If the compatible string starts with "mediatek,mt" assume that it's ok */
  1126		if (!str_has_prefix(compatible, "mediatek,mt"))
  1127			return ERR_PTR(-EINVAL);
  1128	
  1129		if (core_id >= 0)
> 1130			snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);
  1131		else
  1132			snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
  1133	
  1134		/* Not using strchr here, as strlen of a const gets optimized by compiler */
  1135		soc = &compatible[strlen("mediatek,")];
  1136	
  1137		return devm_kasprintf(dev, GFP_KERNEL, "mediatek/%.*s/%s.img",
  1138				      (int)strlen("mtXXXX"), soc, scp_fw_file);
  1139	}
  1140	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: [PATCH] remoteproc: mtk_scp: remove unnecessary checking

[Zhongqiu Han]

On 10/22/2025 7:05 PM, Dan Carpenter wrote:
> 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 a zero return is sort of questionable.  Just
> delete this impossible code.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
>   drivers/remoteproc/mtk_scp.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
> index 10e3f9eb8cd2..9b624948a572 100644
> --- a/drivers/remoteproc/mtk_scp.c
> +++ b/drivers/remoteproc/mtk_scp.c
> @@ -1127,11 +1127,9 @@ 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);
> +		snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id);

Hello Dan Carpenter,

The patch looks fine to me functionally. However, one concern beyond the
current scope: if core_id >= 10 in future extensions, the
snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp_c%1d", core_id) may
cause truncation.

scp_add_multi_core
       |
       v
scp_rproc_init
       |
       v
scp_get_default_fw_path
     char scp_fw_file[7];


To guard against this, maybe should we consider adding:

if (ret >= ARRAY_SIZE(scp_fw_file))
     return ERR_PTR(-ENAMETOOLONG);

or just expand the scp_fw_file[7] array?

Thank you~


>   	else
> -		ret = snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
> -	if (ret <= 0)
> -		return ERR_PTR(ret);
> +		snprintf(scp_fw_file, ARRAY_SIZE(scp_fw_file), "scp");
>   
>   	/* Not using strchr here, as strlen of a const gets optimized by compiler */
>   	soc = &compatible[strlen("mediatek,")];


-- 
Thx and BRs,
Zhongqiu Han