xf86drm: Add a human readable representation for format modifiers

Introduces two new methods to retrieve a human readable representation of a
format modifier:

drmGetFormatModifierName() - returns a format modifier as a string,
from a token modifier
drmGetFormatModifierVendor() - returns the vendor as a string, from a
token modifier

and the fourcc_mod_get_vendor macro that returns the vendor.

New format modifiers added in drm_fourcc.h uapi kernel header should be
sync'ed up with libdrm and should include a human readable
representation for that format modifier, in order to display it
correctly as a string.

That happens with the help of a python script that reads up drm_fourcc
header file and outputs a static table comprised of token modifiers
alongside a vendor table (Suggested-by Simon Ser <contact@emersion.fr>).

The reason for doing it in libdrm is to have a unified place instead of each
user of libdrm having a way to keep track of the format modifiers.

With this patch, modetest has also been modified to make use of it.

Signed-off-by: Marius Vlad <marius.vlad@collabora.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/xf86drm.h b/xf86drm.h
index 9fc06ab8..930d2f40 100644
--- a/xf86drm.h
+++ b/xf86drm.h
@@ -944,6 +944,17 @@ extern int drmSyncobjTransfer(int fd,
 			      uint32_t src_handle, uint64_t src_point,
 			      uint32_t flags);
 
+extern char *
+drmGetFormatModifierVendor(uint64_t modifier);
+
+extern char *
+drmGetFormatModifierName(uint64_t modifier);
+
+#ifndef fourcc_mod_get_vendor
+#define fourcc_mod_get_vendor(modifier) \
+       (((modifier) >> 56) & 0xff)
+#endif
+
 #if defined(__cplusplus)
 }
 #endif