On Tue, Jul 04, 2023 at 12:00:38PM +0800, Hsia-Jun Li wrote:
> 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.
Could you describe in what case such a list would be useful for a
mem2mem driver?
>
> 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;
> + }
> }
src and dst would be referenced unitialized below if neither of the
above ifs hits...
Best regards,
Tomasz
>
> 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
>
