[RFC PATCH 2/4] v4l2-mem2mem: add v4l2_m2m_last_buf()

[Hans Verkuil]

From: Hans Verkuil <hans.verk...@cisco.com>

This can be used to mark the last queued source buffer as the last
buffer.

Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
---
 drivers/media/v4l2-core/v4l2-mem2mem.c | 18 ++++++++++++++++
 include/media/v4l2-mem2mem.h           | 29 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c 
b/drivers/media/v4l2-core/v4l2-mem2mem.c
index 725da74d15d8..3b5b610665f3 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/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;
diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index af48b1eca025..bbf300c7b12c 100644
--- a/include/media/v4l2-mem2mem.h
+++ 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
-- 
2.18.0