linux-kernel - [PATCH 2/2] media: v4l2-mem2mem: add a list for buf used by hw

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Date:   Tue,  4 Jul 2023 12:00:38 +0800
From:   Hsia-Jun Li <randy.li@...aptics.com>
To:     linux-media@...r.kernel.org
Cc:     ayaka@...lik.info, hans.verkuil@...co.com, tfiga@...omium.org,
        mchehab@...nel.org, laurent.pinchart@...asonboard.com,
        hiroh@...omium.org, hverkuil@...all.nl,
        linux-kernel@...r.kernel.org, nicolas@...fresne.ca,
        "Hsia-Jun(Randy) Li" <randy.li@...aptics.com>
Subject: [PATCH 2/2] media: v4l2-mem2mem: add a list for buf used by hw

From: "Hsia-Jun(Randy) Li" <randy.li@...aptics.com>

Many drivers have to create its own buf_struct for a
vb2_queue to track such a state. Also driver has to
iterate over rdy_queue every times to find out a buffer
which is not sent to hardware(or firmware), this new
list just offers the driver a place to store the buffer
that hardware(firmware) has acknowledged.

One important advance about this list, it doesn't like
rdy_queue which both bottom half of the user calling
could operate it, while the v4l2 worker would as well.
The v4l2 core could only operate this queue when its
v4l2_context is not running, the driver would only
access this new hw_queue in its own worker.

Signed-off-by: Hsia-Jun(Randy) Li <randy.li@...aptics.com>
---
 drivers/media/v4l2-core/v4l2-mem2mem.c | 25 +++++++++++++++++--------
 include/media/v4l2-mem2mem.h           | 10 +++++++++-
 2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-mem2mem.c b/drivers/media/v4l2-core/v4l2-mem2mem.c
index c771aba42015..b4151147d5bd 100644
--- a/drivers/media/v4l2-core/v4l2-mem2mem.c
+++ b/drivers/media/v4l2-core/v4l2-mem2mem.c
@@ -321,15 +321,21 @@ static void __v4l2_m2m_try_queue(struct v4l2_m2m_dev *m2m_dev,
 		goto job_unlock;
 	}
 
-	src = v4l2_m2m_next_src_buf(m2m_ctx);
-	dst = v4l2_m2m_next_dst_buf(m2m_ctx);
-	if (!src && !m2m_ctx->out_q_ctx.buffered) {
-		dprintk("No input buffers available\n");
-		goto job_unlock;
+	if (list_empty(&m2m_ctx->out_q_ctx.hw_queue)) {
+		src = v4l2_m2m_next_src_buf(m2m_ctx);
+
+		if (!src && !m2m_ctx->out_q_ctx.buffered) {
+			dprintk("No input buffers available\n");
+			goto job_unlock;
+		}
 	}
-	if (!dst && !m2m_ctx->cap_q_ctx.buffered) {
-		dprintk("No output buffers available\n");
-		goto job_unlock;
+
+	if (list_empty(&m2m_ctx->cap_q_ctx.hw_queue)) {
+		dst = v4l2_m2m_next_dst_buf(m2m_ctx);
+		if (!dst && !m2m_ctx->cap_q_ctx.buffered) {
+			dprintk("No output buffers available\n");
+			goto job_unlock;
+		}
 	}
 
 	m2m_ctx->new_frame = true;
@@ -896,6 +902,7 @@ int v4l2_m2m_streamoff(struct file *file, struct v4l2_m2m_ctx *m2m_ctx,
 	INIT_LIST_HEAD(&q_ctx->rdy_queue);
 	q_ctx->num_rdy = 0;
 	spin_unlock_irqrestore(&q_ctx->rdy_spinlock, flags);
+	INIT_LIST_HEAD(&q_ctx->hw_queue);
 
 	if (m2m_dev->curr_ctx == m2m_ctx) {
 		m2m_dev->curr_ctx = NULL;
@@ -1234,6 +1241,8 @@ struct v4l2_m2m_ctx *v4l2_m2m_ctx_init(struct v4l2_m2m_dev *m2m_dev,
 
 	INIT_LIST_HEAD(&out_q_ctx->rdy_queue);
 	INIT_LIST_HEAD(&cap_q_ctx->rdy_queue);
+	INIT_LIST_HEAD(&out_q_ctx->hw_queue);
+	INIT_LIST_HEAD(&cap_q_ctx->hw_queue);
 	spin_lock_init(&out_q_ctx->rdy_spinlock);
 	spin_lock_init(&cap_q_ctx->rdy_spinlock);
 
diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h
index d6c8eb2b5201..2342656e582d 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -53,9 +53,16 @@ struct v4l2_m2m_dev;
  *	processed
  *
  * @q:		pointer to struct &vb2_queue
- * @rdy_queue:	List of V4L2 mem-to-mem queues
+ * @rdy_queue:	List of V4L2 mem-to-mem queues. If v4l2_m2m_buf_queue() is
+ *		called in struct vb2_ops->buf_queue(), the buffer enqueued
+ *		by user would be added to this list.
  * @rdy_spinlock: spin lock to protect the struct usage
  * @num_rdy:	number of buffers ready to be processed
+ * @hw_queue:	A list for tracking the buffer is occupied by the hardware
+ * 		(or device's firmware). A buffer could only be in either
+ * 		this list or @rdy_queue.
+ * 		Driver may choose not to use this list while uses its own
+ * 		private data to do this work.
  * @buffered:	is the queue buffered?
  *
  * Queue for buffers ready to be processed as soon as this
@@ -68,6 +75,7 @@ struct v4l2_m2m_queue_ctx {
 	struct list_head	rdy_queue;
 	spinlock_t		rdy_spinlock;
 	u8			num_rdy;
+	struct list_head	hw_queue;
 	bool			buffered;
 };
 
-- 
2.17.1