media: h264: Sort p/b reflist using frame_num

In the reference list builder, frame_num refers to FrameNumWrap
in the spec, which is the same as the pic_num for frame decoding.
The same applies for long_term_pic_num and long_term_frame_idx.

Sort all type of references by frame_num so the sort can be reused
for fields reflist were the sorting is done using frame_num instead.
In short, pic_num is never actually used for building reference
lists.

Signed-off-by: Nicolas Dufresne <[e-mail]>
Reviewed-by: Sebastian Fricke <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/v4l2-core/v4l2-h264.c

···
 		if (!(dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_ACTIVE))
 			continue;
 
-		b->refs[i].pic_num = dpb[i].pic_num;
 		if (dpb[i].flags & V4L2_H264_DPB_ENTRY_FLAG_LONG_TERM)
 			b->refs[i].longterm = true;
 
···
 	}
 
 	/*
-	 * Short term pics in descending pic num order, long term ones in
-	 * ascending order.
+	 * For frames, short term pics are in descending pic num order and long
+	 * term ones in ascending order. For fields, the same direction is used
+	 * but with frame_num (wrapped). For frames, the value of pic_num and
+	 * frame_num are the same (see formula (8-28) and (8-29)). For this
+	 * reason we can use frame_num only and share this function between
+	 * frames and fields reflist.
 	 */
 	if (!builder->refs[idxa].longterm)
 		return builder->refs[idxb].frame_num <
 		       builder->refs[idxa].frame_num ?
 		       -1 : 1;
 
-	return builder->refs[idxa].pic_num < builder->refs[idxb].pic_num ?
+	return builder->refs[idxa].frame_num < builder->refs[idxb].frame_num ?
 	       -1 : 1;
 }
 
···
 			return 1;
 	}
 
-	/* Long term pics in ascending pic num order. */
+	/* Long term pics in ascending frame num order. */
 	if (builder->refs[idxa].longterm)
-		return builder->refs[idxa].pic_num <
-		       builder->refs[idxb].pic_num ?
+		return builder->refs[idxa].frame_num <
+		       builder->refs[idxb].frame_num ?
 		       -1 : 1;
 
 	poca = v4l2_h264_get_poc(builder, ptra);
···
 			return 1;
 	}
 
-	/* Long term pics in ascending pic num order. */
+	/* Long term pics in ascending frame num order. */
 	if (builder->refs[idxa].longterm)
-		return builder->refs[idxa].pic_num <
-		       builder->refs[idxb].pic_num ?
+		return builder->refs[idxa].frame_num <
+		       builder->refs[idxb].frame_num ?
 		       -1 : 1;
 
 	poca = v4l2_h264_get_poc(builder, ptra);

include/media/v4l2-h264.h

···
  * @refs.top_field_order_cnt: top field order count
  * @refs.bottom_field_order_cnt: bottom field order count
  * @refs.frame_num: reference frame number
- * @refs.pic_num: reference picture number
  * @refs.longterm: set to true for a long term reference
  * @refs: array of references
  * @cur_pic_order_count: picture order count of the frame being decoded
···
 		s32 top_field_order_cnt;
 		s32 bottom_field_order_cnt;
 		int frame_num;
-		u32 pic_num;
 		u16 longterm : 1;
 	} refs[V4L2_H264_NUM_DPB_ENTRIES];