[PATCH] drm/amd: Fix the size of a buffer in amdgpu_vcn_idle_work_handler()

[Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>]

In order to be sure that fw_name is not truncated, this buffer should be
at least 41 bytes long.

Let the compiler compute the correct length by itself.

When building with W=1, this fixes the following warnings:

  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c: In function ‘amdgpu_vcn_early_init’:
  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:95:58: error: ‘snprintf’ output may be truncated before the last format character [-Werror=format-truncation=]
     95 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
        |                                                          ^
  drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c:95:9: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 40
     95 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
        |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes: 69939009bde7 ("drm/amd: Load VCN microcode during early_init")
Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
index c93f3a4c0e31..f8cd55a0d1f0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vcn.c
@@ -88,7 +88,7 @@ static void amdgpu_vcn_idle_work_handler(struct work_struct *work);
 int amdgpu_vcn_early_init(struct amdgpu_device *adev)
 {
 	char ucode_prefix[30];
-	char fw_name[40];
+	char fw_name[sizeof(ucode_prefix) + sizeof("amdgpu/.bin") - 1];
 	int r;
 
 	amdgpu_ucode_ip_version_decode(adev, UVD_HWIP, ucode_prefix, sizeof(ucode_prefix));
-- 
2.34.1