[jarkko-tpmdd:v4l2-loopback 2/2] drivers/media/v4l2-core/v4l2-loopback.c:1276:49: warning: '%s' directive output may be truncated writing up to 63 bytes into a region of size 32

[jarkko-tpmdd:v4l2-loopback 2/2] drivers/media/v4l2-core/v4l2-loopback.c:1276:49: warning: '%s' directive output may be truncated writing up to 63 bytes into a region of size 32

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd.git v4l2-loopback
head:   a3f82e653c46a6e972edb5f623ab83190db10758
commit: a3f82e653c46a6e972edb5f623ab83190db10758 [2/2] media: v4l2-loopback
config: loongarch-allyesconfig (https://download.01.org/0day-ci/archive/20241212/202412121623.9I5dRbb9-lkp@intel.com/config)
compiler: loongarch64-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241212/202412121623.9I5dRbb9-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/202412121623.9I5dRbb9-lkp@intel.com/

All warnings (new ones prefixed by >>):

   drivers/media/v4l2-core/v4l2-loopback.c: In function 'inner_try_setfmt':
   drivers/media/v4l2-core/v4l2-loopback.c:748:14: warning: variable 'buf' set but not used [-Wunused-but-set-variable]
     748 |         char buf[5];
         |              ^~~
   drivers/media/v4l2-core/v4l2-loopback.c: In function 'vidioc_s_fmt_out':
   drivers/media/v4l2-core/v4l2-loopback.c:1576:14: warning: variable 'buf' set but not used [-Wunused-but-set-variable]
    1576 |         char buf[5];
         |              ^~~
   drivers/media/v4l2-core/v4l2-loopback.c: In function 'vidioc_querycap':
>> drivers/media/v4l2-core/v4l2-loopback.c:1276:49: warning: '%s' directive output may be truncated writing up to 63 bytes into a region of size 32 [-Wformat-truncation=]
    1276 |         snprintf(cap->card, sizeof(cap->card), "%s", dev->vdev->name);
         |                                                 ^~
   drivers/media/v4l2-core/v4l2-loopback.c:1276:9: note: 'snprintf' output between 1 and 64 bytes into a destination of size 32
    1276 |         snprintf(cap->card, sizeof(cap->card), "%s", dev->vdev->name);
         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


vim +1276 drivers/media/v4l2-core/v4l2-loopback.c

  1261	
  1262	/* V4L2 ioctl caps and params calls */
  1263	/* returns device capabilities
  1264	 * called on VIDIOC_QUERYCAP
  1265	 */
  1266	static int vidioc_querycap(struct file *file, void *priv,
  1267				   struct v4l2_capability *cap)
  1268	{
  1269		struct v4l2_loopback_device *dev = v4l2l_getdevice(file);
  1270		int device_nr =
  1271			((struct v4l2l_private *)video_get_drvdata(dev->vdev))
  1272				->device_nr;
  1273		__u32 capabilities = V4L2_CAP_STREAMING | V4L2_CAP_READWRITE;
  1274	
  1275		strscpy(cap->driver, "v4l2 loopback", sizeof(cap->driver));
> 1276		snprintf(cap->card, sizeof(cap->card), "%s", dev->vdev->name);
  1277		snprintf(cap->bus_info, sizeof(cap->bus_info),
  1278			 "platform:v4l2loopback-%03d", device_nr);
  1279	
  1280		if (dev->announce_all_caps) {
  1281			capabilities |= V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_VIDEO_OUTPUT;
  1282		} else {
  1283			if (dev->ready_for_capture) {
  1284				capabilities |= V4L2_CAP_VIDEO_CAPTURE;
  1285			}
  1286			if (dev->ready_for_output) {
  1287				capabilities |= V4L2_CAP_VIDEO_OUTPUT;
  1288			}
  1289		}
  1290	
  1291		dev->vdev->device_caps = cap->device_caps = cap->capabilities = capabilities;
  1292		cap->capabilities |= V4L2_CAP_DEVICE_CAPS;
  1293		memset(cap->reserved, 0, sizeof(cap->reserved));
  1294		return 0;
  1295	}
  1296	

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