drm/fourcc: Add macros to determine the modifier vendor

When working with framebuffer modifiers, it can be useful to extract the
vendor identifier or check a modifier against a given vendor identifier.
Add one macro that extracts the vendor identifier and a helper to check
a modifier against a given vendor identifier.
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210610111236.3814211-1-thierry.reding@gmail.com

include/uapi/drm/drm_fourcc.h

@@ -373,6 +373,12 @@ extern "C" {
 
 #define DRM_FORMAT_RESERVED	      ((1ULL << 56) - 1)
 
+#define fourcc_mod_get_vendor(modifier) \
+	(((modifier) >> 56) & 0xff)
+
+#define fourcc_mod_is_vendor(modifier, vendor) \
+	(fourcc_mod_get_vendor(modifier) == DRM_FORMAT_MOD_VENDOR_## vendor)
+
 #define fourcc_mod_code(vendor, val) \
 	((((__u64)DRM_FORMAT_MOD_VENDOR_## vendor) << 56) | ((val) & 0x00ffffffffffffffULL))