media: v4l2-mem2mem: add v4l2_m2m_last_buf()

This can be used to mark the last queued source buffer as the last
buffer.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/v4l2-core/v4l2-mem2mem.c

@@ -129,6 +129,24 @@ void *v4l2_m2m_next_buf(struct v4l2_m2m_queue_ctx *q_ctx)
 }
 EXPORT_SYMBOL_GPL(v4l2_m2m_next_buf);
 
+void *v4l2_m2m_last_buf(struct v4l2_m2m_queue_ctx *q_ctx)
+{
+	struct v4l2_m2m_buffer *b;
+	unsigned long flags;
+
+	spin_lock_irqsave(&q_ctx->rdy_spinlock, flags);
+
+	if (list_empty(&q_ctx->rdy_queue)) {
+		spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
+		return NULL;
+	}
+
+	b = list_last_entry(&q_ctx->rdy_queue, struct v4l2_m2m_buffer, list);
+	spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
+	return &b->vb;
+}
+EXPORT_SYMBOL_GPL(v4l2_m2m_last_buf);
+
 void *v4l2_m2m_buf_remove(struct v4l2_m2m_queue_ctx *q_ctx)
 {
 	struct v4l2_m2m_buffer *b;

include/media/v4l2-mem2mem.h

@@ -449,6 +449,35 @@ static inline void *v4l2_m2m_next_dst_buf(struct v4l2_m2m_ctx *m2m_ctx)
 	return v4l2_m2m_next_buf(&m2m_ctx->cap_q_ctx);
 }
 
+/**
+ * v4l2_m2m_last_buf() - return last buffer from the list of ready buffers
+ *
+ * @q_ctx: pointer to struct @v4l2_m2m_queue_ctx
+ */
+void *v4l2_m2m_last_buf(struct v4l2_m2m_queue_ctx *q_ctx);
+
+/**
+ * v4l2_m2m_last_src_buf() - return last destination buffer from the list of
+ * ready buffers
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline void *v4l2_m2m_last_src_buf(struct v4l2_m2m_ctx *m2m_ctx)
+{
+	return v4l2_m2m_last_buf(&m2m_ctx->out_q_ctx);
+}
+
+/**
+ * v4l2_m2m_last_dst_buf() - return last destination buffer from the list of
+ * ready buffers
+ *
+ * @m2m_ctx: m2m context assigned to the instance given by struct &v4l2_m2m_ctx
+ */
+static inline void *v4l2_m2m_last_dst_buf(struct v4l2_m2m_ctx *m2m_ctx)
+{
+	return v4l2_m2m_last_buf(&m2m_ctx->cap_q_ctx);
+}
+
 /**
  * v4l2_m2m_for_each_dst_buf() - iterate over a list of destination ready
  * buffers