Re: [PATCH 2/2] media: v4l2-mem2mem: add a list for buf used by hw
From: Randy Li
Date: Tue Jul 11 2023 - 04:55:07 EST
On 2023/7/8 03:20, Nicolas Dufresne wrote:
Le mardi 04 juillet 2023 à 12:00 +0800, Hsia-Jun Li a écrit :
From: "Hsia-Jun(Randy) Li" <randy.li@xxxxxxxxxxxxx>
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.
That's an interesting proposal. I didn't like leaving decoded frames into the
rdy_queue, but removing them required me to have my own list, so that I can
clean it up if some buffers are never displayed.
We'll see if we can use this into wave5.
Signed-off-by: Hsia-Jun(Randy) Li <randy.li@xxxxxxxxxxxxx>
---
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.
What's the threading protection around this one ?
I mentioned that in commit message.
"
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.
"
Also, would it be possible to
opt-in that the driver cleanup that list automatically after streamoff has been
executed ?
I think that is what streamoff purposes to do, or we don't have a method
to let the hardware(firmware) release all its buffers.
One thing the doc is missing, is that HW buffer are actually flagged as ACTIVE
buffer vb2, there is a strong link between the two concept, and the doc should
take care.
I would like to complete the doc if people are not against about this idea.
And I would put all necessary information in one place.
* @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;
};