Enabling -Wformat-truncation yields the following warning:

../drivers/gpu/drm/nouveau/nouveau_backlight.c: In function 
‘nouveau_backlight_init’:
../drivers/gpu/drm/nouveau/nouveau_backlight.c:56:69: error: ‘%d’ directive 
output may be truncated writing between 1 and 10 bytes into a region of size 3 
[-Werror=format-truncation=]
   56 |                 snprintf(backlight_name, BL_NAME_SIZE, 
"nv_backlight%d", nb);
      |                                                                     ^~
In function ‘nouveau_get_backlight_name’,
    inlined from ‘nouveau_backlight_init’ at 
../drivers/gpu/drm/nouveau/nouveau_backlight.c:351:7:
../drivers/gpu/drm/nouveau/nouveau_backlight.c:56:56: note: directive argument 
in the range [1, 2147483647]
   56 |                 snprintf(backlight_name, BL_NAME_SIZE, 
"nv_backlight%d", nb);
      |                                                        ^~~~~~~~~~~~~~~~
../drivers/gpu/drm/nouveau/nouveau_backlight.c:56:17: note: ‘snprintf’ output 
between 14 and 23 bytes into a destination of size 15
   56 |                 snprintf(backlight_name, BL_NAME_SIZE, 
"nv_backlight%d", nb);
      |                 
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Silence the warning by checking the snprintf() return value.

Signed-off-by: Jani Nikula <jani.nik...@intel.com>

---

Cc: Karol Herbst <kher...@redhat.com>
Cc: Lyude Paul <ly...@redhat.com>
Cc: Danilo Krummrich <d...@redhat.com>
Cc: dri-de...@lists.freedesktop.org
Cc: nouv...@lists.freedesktop.org
---
 drivers/gpu/drm/nouveau/nouveau_backlight.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_backlight.c 
b/drivers/gpu/drm/nouveau/nouveau_backlight.c
index d47442125fa1..1d77a5f280c5 100644
--- a/drivers/gpu/drm/nouveau/nouveau_backlight.c
+++ b/drivers/gpu/drm/nouveau/nouveau_backlight.c
@@ -49,13 +49,18 @@ nouveau_get_backlight_name(char 
backlight_name[BL_NAME_SIZE],
                           struct nouveau_backlight *bl)
 {
        const int nb = ida_alloc_max(&bl_ida, 99, GFP_KERNEL);
+       int ret;
 
        if (nb < 0)
                return false;
        if (nb > 0)
-               snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", nb);
+               ret = snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight%d", 
nb);
        else
-               snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight");
+               ret = snprintf(backlight_name, BL_NAME_SIZE, "nv_backlight");
+
+       if (ret >= BL_NAME_SIZE)
+               return false;
+
        bl->id = nb;
        return true;
 }
-- 
2.39.2

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