[media] media: v4l2-mem2mem: extend m2m APIs for more accurate buffer management

this add functions for:
  - remove buffers from src/dst queue by index
  - remove exact buffer from src/dst queue

also extends m2m API to iterate over a list of src/dst buffers
in safely and non-safely manner.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 6bc27e7..f62e68a 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -126,6 +126,43 @@ void *v4l2_m2m_buf_remove(struct v4l2_m2m_queue_ctx *q_ctx)
 }
 EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove);
 
+void v4l2_m2m_buf_remove_by_buf(struct v4l2_m2m_queue_ctx *q_ctx,
+				struct vb2_v4l2_buffer *vbuf)
+{
+	struct v4l2_m2m_buffer *b;
+	unsigned long flags;
+
+	spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
+	b = container_of(vbuf, struct v4l2_m2m_buffer, vb);
+	list_del(&b->list);
+	q_ctx->num_rdy--;
+	spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove_by_buf);
+
+struct vb2_v4l2_buffer *
+v4l2_m2m_buf_remove_by_idx(struct v4l2_m2m_queue_ctx *q_ctx, unsigned int idx)
+
+{
+	struct v4l2_m2m_buffer *b, *tmp;
+	struct vb2_v4l2_buffer *ret = NULL;
+	unsigned long flags;
+
+	spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
+	list_for_each_entry_safe(b, tmp, &q_ctx->rdy_queue, list) {
+		if (b->vb.vb2_buf.index == idx) {
+			list_del(&b->list);
+			q_ctx->num_rdy--;
+			ret = &b->vb;
+			break;
+		}
+	}
+	spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_buf_remove_by_idx);
+
 /*
  * Scheduling handlers
  */