Re: [RFC][PATCH 04/15] videobuf2: add queue memory consistency parameter

[Hans Verkuil]

On 12/17/19 4:20 AM, Sergey Senozhatsky wrote:
> Preparations for future V4L2_FLAG_MEMORY_NON_CONSISTENT support.
> 
> Extend vb2_core_reqbufs() with queue memory consistency flag.
> API permits queue's consistency attribute adjustment only if
> the queue has no allocated buffers, not busy, and does not have
> buffers waiting to be de-queued.

Actually, you can call vb2_core_reqbufs() when buffers are allocated:
it will free the old buffers, then allocate the new ones. So drop the
'has no allocated buffers' bit.

> 
> If user-space attempts to allocate a buffer with consistency
> requirements which don't match queue's consistency model such
> allocation requests will be failed.

Is this last paragraph right? I don't see any code for that.

BTW, a general comment about patches 4-6: I prefer if you changes
this to two patches: one that adds videobuf2-core.c support for
this for reqbufs and create_bufs, then another that wires up the
new V4L2 flag in videobuf2-v4l2.c.

It's easier to review that way.

Regards,

	Hans

> 
> Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
> ---
>  drivers/media/common/videobuf2/videobuf2-core.c | 17 +++++++++++++----
>  drivers/media/common/videobuf2/videobuf2-v4l2.c |  4 ++--
>  drivers/media/dvb-core/dvb_vb2.c                |  2 +-
>  include/media/videobuf2-core.h                  |  3 ++-
>  4 files changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> index 4489744fbbd9..668c56df13f6 100644
> --- a/drivers/media/common/videobuf2/videobuf2-core.c
> +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> @@ -664,8 +664,16 @@ int vb2_verify_memory_type(struct vb2_queue *q,
>  }
>  EXPORT_SYMBOL(vb2_verify_memory_type);
>  
> +static void __set_queue_consistency(struct vb2_queue *q, bool consistent_mem)
> +{
> +	if (consistent_mem)
> +		q->dma_attrs &= ~DMA_ATTR_NON_CONSISTENT;
> +	else
> +		q->dma_attrs |= DMA_ATTR_NON_CONSISTENT;
> +}
> +
>  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> -		unsigned int *count)
> +		bool consistent_mem, unsigned int *count)
>  {
>  	unsigned int num_buffers, allocated_buffers, num_planes = 0;
>  	unsigned plane_sizes[VB2_MAX_PLANES] = { };
> @@ -720,6 +728,7 @@ int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
>  	num_buffers = min_t(unsigned int, num_buffers, VB2_MAX_FRAME);
>  	memset(q->alloc_devs, 0, sizeof(q->alloc_devs));
>  	q->memory = memory;
> +	__set_queue_consistency(q, consistent_mem);
>  
>  	/*
>  	 * Ask the driver how many buffers and planes per buffer it requires.
> @@ -2498,7 +2507,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>  	fileio->memory = VB2_MEMORY_MMAP;
>  	fileio->type = q->type;
>  	q->fileio = fileio;
> -	ret = vb2_core_reqbufs(q, fileio->memory, &fileio->count);
> +	ret = vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  	if (ret)
>  		goto err_kfree;
>  
> @@ -2555,7 +2564,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
>  
>  err_reqbufs:
>  	fileio->count = 0;
> -	vb2_core_reqbufs(q, fileio->memory, &fileio->count);
> +	vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  
>  err_kfree:
>  	q->fileio = NULL;
> @@ -2575,7 +2584,7 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
>  		vb2_core_streamoff(q, q->type);
>  		q->fileio = NULL;
>  		fileio->count = 0;
> -		vb2_core_reqbufs(q, fileio->memory, &fileio->count);
> +		vb2_core_reqbufs(q, fileio->memory, true, &fileio->count);
>  		kfree(fileio);
>  		dprintk(3, "file io emulator closed\n");
>  	}
> diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> index 2fccfe2a57f8..f1e88c9398c7 100644
> --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> @@ -695,7 +695,7 @@ int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
>  	int ret = vb2_verify_memory_type(q, req->memory, req->type);
>  
>  	fill_buf_caps(q, &req->capabilities);
> -	return ret ? ret : vb2_core_reqbufs(q, req->memory, &req->count);
> +	return ret ? ret : vb2_core_reqbufs(q, req->memory, true, &req->count);
>  }
>  EXPORT_SYMBOL_GPL(vb2_reqbufs);
>  
> @@ -945,7 +945,7 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
>  		return res;
>  	if (vb2_queue_is_busy(vdev, file))
>  		return -EBUSY;
> -	res = vb2_core_reqbufs(vdev->queue, p->memory, &p->count);
> +	res = vb2_core_reqbufs(vdev->queue, p->memory, true, &p->count);
>  	/* If count == 0, then the owner has released all buffers and he
>  	   is no longer owner of the queue. Otherwise we have a new owner. */
>  	if (res == 0)
> diff --git a/drivers/media/dvb-core/dvb_vb2.c b/drivers/media/dvb-core/dvb_vb2.c
> index 6974f1731529..e60063652164 100644
> --- a/drivers/media/dvb-core/dvb_vb2.c
> +++ b/drivers/media/dvb-core/dvb_vb2.c
> @@ -342,7 +342,7 @@ int dvb_vb2_reqbufs(struct dvb_vb2_ctx *ctx, struct dmx_requestbuffers *req)
>  
>  	ctx->buf_siz = req->size;
>  	ctx->buf_cnt = req->count;
> -	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, &req->count);
> +	ret = vb2_core_reqbufs(&ctx->vb_q, VB2_MEMORY_MMAP, true, &req->count);
>  	if (ret) {
>  		ctx->state = DVB_VB2_STATE_NONE;
>  		dprintk(1, "[%s] count=%d size=%d errno=%d\n", ctx->name,
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index 026004180440..810af5cf5742 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -726,6 +726,7 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
>   * vb2_core_reqbufs() - Initiate streaming.
>   * @q:		pointer to &struct vb2_queue with videobuf2 queue.
>   * @memory:	memory type, as defined by &enum vb2_memory.
> + * @consistent_mem:	memory consistency model.
>   * @count:	requested buffer count.
>   *
>   * Videobuf2 core helper to implement VIDIOC_REQBUF() operation. It is called
> @@ -750,7 +751,7 @@ void vb2_core_querybuf(struct vb2_queue *q, unsigned int index, void *pb);
>   * Return: returns zero on success; an error code otherwise.
>   */
>  int vb2_core_reqbufs(struct vb2_queue *q, enum vb2_memory memory,
> -		unsigned int *count);
> +		bool consistent_mem, unsigned int *count);
>  
>  /**
>   * vb2_core_create_bufs() - Allocate buffers and any required auxiliary structs
>