frontends/va: check number of temporal layers supported by encoder

Checks the encoder to determine the number of temporal layers supported,
and returns max_num_temporal_layers_minus1, along with setting the
corresponding control flag if multiple layers are supported.

Signed-off-by: Thong Thai <thong.thai@amd.com>
Reviewed-by: Boyuan Zhang <Boyuan.Zhang@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11850>

src/gallium/frontends/va/config.c

@@ -159,6 +159,15 @@ vlVaGetConfigAttributes(VADriverContextP ctx, VAProfile profile, VAEntrypoint en
          case VAConfigAttribRateControl:
             value = VA_RC_CQP | VA_RC_CBR | VA_RC_VBR;
             break;
+         case VAConfigAttribEncRateControlExt:
+            value = pscreen->get_video_param(pscreen, ProfileToPipe(profile),
+                                             PIPE_VIDEO_ENTRYPOINT_ENCODE,
+                                             PIPE_VIDEO_CAP_MAX_TEMPORAL_LAYERS);
+            if (value > 0) {
+               value -= 1;
+               value |= (1 << 8);   /* temporal_layer_bitrate_control_flag */
+            }
+            break;
          case VAConfigAttribEncPackedHeaders:
             value = VA_ENC_PACKED_HEADER_NONE;
             if (u_reduce_video_profile(ProfileToPipe(profile)) == PIPE_VIDEO_FORMAT_MPEG4_AVC ||