Re: [PATCH] dma-buf: Add support for mapping buffers with DMA attributes

[Daniel Vetter]

On Mon, Aug 30, 2021 at 10:39:11AM +0800, guangming.cao@xxxxxxxxxxxx wrote:
> From: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>
> 
> When mapping the memory represented by a dma-buf into a device's
> address space, it might be desireable to map the memory with
> certain DMA attributes. Thus, introduce the dma_mapping_attrs
> field in the dma_buf_attachment structure so that when
> the memory is mapped with dma_buf_map_attachment, it is mapped
> with the desired DMA attributes.
> 
> Signed-off-by: Isaac J. Manjarres <isaacm@xxxxxxxxxxxxxx>
> Signed-off-by: Sandeep Patil <sspatil@xxxxxxxxxx>
> Signed-off-by: Guangming Cao <Guangming.Cao@xxxxxxxxxxxx>

Can you pls include the code that's going to use this here too?

At a glance all the attributes you might want to set are supposed to be
under the control of the exporter, not the importer.
-Daniel

> ---
>  drivers/dma-buf/heaps/cma_heap.c    | 6 ++++--
>  drivers/dma-buf/heaps/system_heap.c | 6 ++++--
>  include/linux/dma-buf.h             | 3 +++
>  3 files changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
> index 0c05b79870f9..2c9feb3bfc3e 100644
> --- a/drivers/dma-buf/heaps/cma_heap.c
> +++ b/drivers/dma-buf/heaps/cma_heap.c
> @@ -99,9 +99,10 @@ static struct sg_table *cma_heap_map_dma_buf(struct dma_buf_attachment *attachme
>  {
>  	struct dma_heap_attachment *a = attachment->priv;
>  	struct sg_table *table = &a->table;
> +	int attrs = attachment->dma_map_attrs;
>  	int ret;
>  
> -	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
> +	ret = dma_map_sgtable(attachment->dev, table, direction, attrs);
>  	if (ret)
>  		return ERR_PTR(-ENOMEM);
>  	a->mapped = true;
> @@ -113,9 +114,10 @@ static void cma_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
>  				   enum dma_data_direction direction)
>  {
>  	struct dma_heap_attachment *a = attachment->priv;
> +	int attrs = attachment->dma_map_attrs;
>  
>  	a->mapped = false;
> -	dma_unmap_sgtable(attachment->dev, table, direction, 0);
> +	dma_unmap_sgtable(attachment->dev, table, direction, attrs);
>  }
>  
>  static int cma_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
> diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
> index 23a7e74ef966..fc7b1e02988e 100644
> --- a/drivers/dma-buf/heaps/system_heap.c
> +++ b/drivers/dma-buf/heaps/system_heap.c
> @@ -130,9 +130,10 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac
>  {
>  	struct dma_heap_attachment *a = attachment->priv;
>  	struct sg_table *table = a->table;
> +	int attrs = attachment->dma_map_attrs;
>  	int ret;
>  
> -	ret = dma_map_sgtable(attachment->dev, table, direction, 0);
> +	ret = dma_map_sgtable(attachment->dev, table, direction, attrs);
>  	if (ret)
>  		return ERR_PTR(ret);
>  
> @@ -145,9 +146,10 @@ static void system_heap_unmap_dma_buf(struct dma_buf_attachment *attachment,
>  				      enum dma_data_direction direction)
>  {
>  	struct dma_heap_attachment *a = attachment->priv;
> +	int attrs = attachment->dma_map_attrs;
>  
>  	a->mapped = false;
> -	dma_unmap_sgtable(attachment->dev, table, direction, 0);
> +	dma_unmap_sgtable(attachment->dev, table, direction, attrs);
>  }
>  
>  static int system_heap_dma_buf_begin_cpu_access(struct dma_buf *dmabuf,
> diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> index efdc56b9d95f..4d650731766e 100644
> --- a/include/linux/dma-buf.h
> +++ b/include/linux/dma-buf.h
> @@ -379,6 +379,8 @@ struct dma_buf_attach_ops {
>   * @importer_ops: importer operations for this attachment, if provided
>   * dma_buf_map/unmap_attachment() must be called with the dma_resv lock held.
>   * @importer_priv: importer specific attachment data.
> + * @dma_map_attrs: DMA attributes to be used when the exporter maps the buffer
> + * through dma_buf_map_attachment.
>   *
>   * This structure holds the attachment information between the dma_buf buffer
>   * and its user device(s). The list contains one attachment struct per device
> @@ -399,6 +401,7 @@ struct dma_buf_attachment {
>  	const struct dma_buf_attach_ops *importer_ops;
>  	void *importer_priv;
>  	void *priv;
> +	unsigned long dma_map_attrs;
>  };
>  
>  /**
> -- 
> 2.17.1
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch