vo_gpu: hwdec_vaapi: handle lack of object size with AMD drivers

It turns out that the AMD driver doesn't bother to set the size
field in the descriptor for an exported VA surface. I guess they
assume the caller can always use lseek() and don't bother. So, we
need to use lseek() in these situations.

Modified-by: Niklas Haas <git@haasn.xyz>

Guarded this behind PL_API_VER >= 88 to prevent it from exploding on
older libplacebo versions, where vaapi support does not yet work
properly on AMD due to lack of DRM modifiers.

1 files changed, 26 insertions, 0 deletions

diff --git a/video/out/hwdec/hwdec_vaapi_vk.c b/video/out/hwdec/hwdec_vaapi_vk.c
index 7f09a7e895..1cee9e86b9 100644
--- a/video/out/hwdec/hwdec_vaapi_vk.c
+++ b/video/out/hwdec/hwdec_vaapi_vk.c
@@ -15,6 +15,9 @@
  * License along with mpv.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <errno.h>
+#include <unistd.h>
+
 #include "config.h"
 #include "hwdec_vaapi.h"
 #include "video/out/placebo/ra_pl.h"
@@ -41,6 +44,29 @@ static bool vaapi_vk_map(struct ra_hwdec_mapper *mapper)
         uint32_t size = p->desc.objects[id].size;
         uint32_t offset = p->desc.layers[n].offset[0];
 
+#if PL_API_VER >= 88
+        // AMD drivers do not return the size in the surface description, so we
+        // need to query it manually. The reason we guard this logic behind
+        // PL_API_VER >= 88 is that the same drivers also require DRM format
+        // modifier support in order to not produce corrupted textures, so
+        // having this #ifdef merely exists to protect users from combining
+        // too-new mpv with too-old libplacebo.
+        if (size == 0) {
+            size = lseek(fd, 0, SEEK_END);
+            if (size == -1) {
+                MP_ERR(mapper, "Cannot obtain size of object with fd %d: %s\n",
+                       fd, mp_strerror(errno));
+                return false;
+            }
+            off_t err = lseek(fd, 0, SEEK_SET);
+            if (err == -1) {
+                MP_ERR(mapper, "Failed to reset offset for fd %d: %s\n",
+                       fd, mp_strerror(errno));
+                return false;
+            }
+        }
+#endif
+
         struct pl_tex_params tex_params = {
             .w = mp_image_plane_w(&p->layout, n),
             .h = mp_image_plane_h(&p->layout, n),