vo_opengl: add KMS/DRM VAAPI hardware decoding interop

Just requires glueing it together with Bloat Super Glue (tm).

video/out/opengl/context_drm_egl.c

@@ -353,6 +353,9 @@ static int drm_egl_init(struct MPGLContext *ctx, int flags)
     void *(*gpa)(const GLubyte*) = (void *(*)(const GLubyte*))eglGetProcAddress;
     mpgl_load_functions(ctx->gl, gpa, egl_exts, ctx->vo->log);
 
+    ctx->native_display_type = "drm";
+    ctx->native_display = (void *)(intptr_t)p->kms->fd;
+
     // required by gbm_surface_lock_front_buffer
     eglSwapBuffers(p->egl.display, p->egl.surface);
 

video/out/opengl/hwdec_vaegl.c

@@ -65,6 +65,19 @@ static VADisplay *create_wayland_va_display(GL *gl)
 }
 #endif
 
+#if HAVE_VAAPI_DRM
+#include <va/va_drm.h>
+
+static VADisplay *create_drm_va_display(GL *gl)
+{
+    int drm_fd = (intptr_t)gl->MPGetNativeDisplay("drm");
+    // Note: yes, drm_fd==0 could be valid - but it's rare and doesn't fit with
+    //       our slightly crappy way of passing it through, so consider 0 not
+    //       valid.
+    return drm_fd ? vaGetDisplayDRM(drm_fd) : NULL;
+}
+#endif
+
 static VADisplay *create_native_va_display(GL *gl)
 {
     if (!gl->MPGetNativeDisplay)
@@ -79,6 +92,11 @@ static VADisplay *create_native_va_display(GL *gl)
     display = create_wayland_va_display(gl);
     if (display)
         return display;
+#endif
+#if HAVE_VAAPI_DRM
+    display = create_drm_va_display(gl);
+    if (display)
+        return display;
 #endif
     return display;
 }

wscript

@@ -705,7 +705,11 @@ video_output_features = [
         'desc': 'VAAPI (Wayland support)',
         'deps': [ 'vaapi', 'gl-wayland' ],
         'func': check_pkg_config('libva-wayland', '>= 0.36.0'),
-
+    }, {
+        'name': '--vaapi-drm',
+        'desc': 'VAAPI (DRM/EGL support)',
+        'deps': [ 'vaapi', 'egl-drm' ],
+        'func': check_pkg_config('libva-drm', '>= 0.36.0'),
     }, {
         'name': '--vaapi-glx',
         'desc': 'VAAPI GLX',