Re: [RFC][PATCHv2 11/12] videobuf2: add begin/end cpu_access callbacks to dma-sg

[Hans Verkuil]

On 2/4/20 3:56 AM, Sergey Senozhatsky wrote:
> Provide begin_cpu_access() and end_cpu_access() dma_buf_ops
> callbacks for cache synchronisation on exported buffers.
> 
> V4L2_FLAG_MEMORY_NON_CONSISTENT has no effect on dma-sg buffers.
> dma-sg allocates memory using the page allocator directly, so
> there is no memory consistency guarantee.

This should also be a comment in the code.

Regards,

	Hans

> 
> Change-Id: Ia0d9d72a8c2a9fe3264ac148f59201573289ed2c
> Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
> ---
>  .../media/common/videobuf2/videobuf2-dma-sg.c | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> index 6db60e9d5183..bfc99a0cb7b9 100644
> --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> @@ -470,6 +470,26 @@ static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
>  	vb2_dma_sg_put(dbuf->priv);
>  }
>  
> +static int vb2_dma_sg_dmabuf_ops_begin_cpu_access(struct dma_buf *dbuf,
> +					enum dma_data_direction direction)
> +{
> +	struct vb2_dma_sg_buf *buf = dbuf->priv;
> +	struct sg_table *sgt = buf->dma_sgt;
> +
> +	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
> +	return 0;
> +}
> +
> +static int vb2_dma_sg_dmabuf_ops_end_cpu_access(struct dma_buf *dbuf,
> +					enum dma_data_direction direction)
> +{
> +	struct vb2_dma_sg_buf *buf = dbuf->priv;
> +	struct sg_table *sgt = buf->dma_sgt;
> +
> +	dma_sync_sg_for_device(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);
> +	return 0;
> +}
> +
>  static void *vb2_dma_sg_dmabuf_ops_vmap(struct dma_buf *dbuf)
>  {
>  	struct vb2_dma_sg_buf *buf = dbuf->priv;
> @@ -488,6 +508,8 @@ static const struct dma_buf_ops vb2_dma_sg_dmabuf_ops = {
>  	.detach = vb2_dma_sg_dmabuf_ops_detach,
>  	.map_dma_buf = vb2_dma_sg_dmabuf_ops_map,
>  	.unmap_dma_buf = vb2_dma_sg_dmabuf_ops_unmap,
> +	.begin_cpu_access = vb2_dma_sg_dmabuf_ops_begin_cpu_access,
> +	.end_cpu_access = vb2_dma_sg_dmabuf_ops_end_cpu_access,
>  	.vmap = vb2_dma_sg_dmabuf_ops_vmap,
>  	.mmap = vb2_dma_sg_dmabuf_ops_mmap,
>  	.release = vb2_dma_sg_dmabuf_ops_release,
>