Hi Thierry,
Thanks for the set. A few comments below.
On Fri, Oct 14, 2016 at 02:08:14PM +0200, Thierry Escande wrote:
> From: Pawel Osciak <posciak@xxxxxxxxxxxx>
>
> When this flag is set for CAPTURE queues by the driver on calling
> vb2_queue_init(), it forces the buffers on the queue to be
> allocated/mapped with DMA_BIDIRECTIONAL direction flag, instead of
> DMA_FROM_DEVICE. This allows the device not only to write to the
> buffers, but also read out from them. This may be useful e.g. for codec
> hardware, which may be using CAPTURE buffers as reference to decode
> other buffers.
Just out of curiosity --- when do you return these buffers back to the user?
Once they're no longer needed as reference frames?
>
> This flag is ignored for OUTPUT queues, as we don't want to allow HW to
> be able to write to OUTPUT buffers.
>
> Signed-off-by: Pawel Osciak <posciak@xxxxxxxxxxxx>
> Tested-by: Pawel Osciak <posciak@xxxxxxxxxxxx>
> Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
> Signed-off-by: Thierry Escande <thierry.escande@xxxxxxxxxxxxx>
> ---
> drivers/media/v4l2-core/videobuf2-v4l2.c | 8 ++++++--
> include/media/videobuf2-core.h | 4 ++++
> 2 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-v4l2.c b/drivers/media/v4l2-core/videobuf2-v4l2.c
> index fde1e2d..9255291 100644
> --- a/drivers/media/v4l2-core/videobuf2-v4l2.c
> +++ b/drivers/media/v4l2-core/videobuf2-v4l2.c
> @@ -659,8 +659,12 @@ int vb2_queue_init(struct vb2_queue *q)
> * queues will always initialize waiting_for_buffers to false.
> */
> q->quirk_poll_must_check_waiting_for_buffers = true;
> - q->dma_dir = V4L2_TYPE_IS_OUTPUT(q->type)
> - ? DMA_TO_DEVICE : DMA_FROM_DEVICE;
> +
> + if (V4L2_TYPE_IS_OUTPUT(q->type))
> + q->dma_dir = DMA_TO_DEVICE;
> + else
> + q->dma_dir = q->use_dma_bidirectional
> + ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE;
>
> return vb2_core_queue_init(q);
> }
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 38410dd..e613c74 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -433,6 +433,9 @@ struct vb2_buf_ops {
> * @quirk_poll_must_check_waiting_for_buffers: Return POLLERR at poll when QBUF
> * has not been called. This is a vb1 idiom that has been adopted
> * also by vb2.
> + * @use_dma_bidirectional: use DMA_BIDIRECTIONAL for CAPTURE buffers; this
> + * allows HW to read from the CAPTURE buffers in
> + * addition to writing; ignored for OUTPUT queues
> * @lock: pointer to a mutex that protects the vb2_queue struct. The
> * driver can set this to a mutex to let the v4l2 core serialize
> * the queuing ioctls. If the driver wants to handle locking
> @@ -500,6 +503,7 @@ struct vb2_queue {
> unsigned fileio_write_immediately:1;
> unsigned allow_zero_bytesused:1;
> unsigned quirk_poll_must_check_waiting_for_buffers:1;
> + unsigned use_dma_bidirectional:1;
This field is in the same struct as dma_dir which it directly affects.
How about adding a macro instead to give you the queue DMA direction
instead?
E.g.
#define vb2_dma_dir(q) \
(V4L2_TYPE_IS_OUTPUT((q)->type) ? DMA_TO_DEVICE : \
(q)->use_dma_bidirectional ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE)
I would call this capture_dma_bidirectional as it only affects capture. Or
simply choose DMA_BIDIRECTIONAL whenever the flag is set.
I wonder what others think.
>
> struct mutex *lock;
> void *owner;
--
Kind regards,
Sakari Ailus
e-mail: sakari.ailus@xxxxxx XMPP: sailus@xxxxxxxxxxxxxx
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