[Linaro-mm-sig] Re: [RFC PATCH 1/2] dma-buf: Add support for private interconnects

On Thu, 2025-09-25 at 15:08 +0200, Thomas Hellström wrote:

Add a function to the dma_buf_attach_ops to indicate whether the connection is a private interconnect. If so the function returns the address to an interconnect-defined structure that can be used for further negotiating.

Also add a field to the dma_buf_attachment that indicates whether a private interconnect is used by the attachment.

Signed-off-by: Thomas Hellström thomas.hellstrom@linux.intel.com

include/linux/dma-buf.h | 15 +++++++++++++++  1 file changed, 15 insertions(+)

diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d58e329ac0e7..e7191edb2125 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -475,6 +475,19 @@ struct dma_buf_attach_ops {   * point to the new location of the DMA-buf.   */   void (*move_notify)(struct dma_buf_attachment *attach);

• /**

• * @supports_interconnect: [optional] - Does the driver
  

support a local interconnect?

• *
  

• * Does the importer support a private interconnect? The
  

interconnect is

• * identified using a unique address defined by the exporter
  

and declared

• * in a protocol header.
  

Actually we'd probably want to use something like a

struct dma_buf_interconnect { const char *name; };

Here, and for globally known interconnects have them instantiated somewhere common since there could be multiple exporters.

(RFC: Should this be a struct instead).

• *
  

• * Return: A pointer to the interconnect-private attach_ops
  

structure if supported,

• * %NULL otherwise.
  

• */
  

• const void *(*supports_interconnect)(struct

dma_buf_attachment *attach,

• 			     const void
  

*interconnect);

And similarly for stricter type-checking the return value could be a struct dma_buf_interconnect_attach_ops { };

which is subclassed for each interconnect-private attach ops.

};    /** @@ -484,6 +497,7 @@ struct dma_buf_attach_ops {   * @node: list of dma_buf_attachment, protected by dma_resv lock of the dmabuf.   * @peer2peer: true if the importer can handle peer resources without pages.   * @priv: exporter specific attachment data.

• • @interconnect: Private interconnect to use if any, NULL

otherwise.   * @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. @@ -503,6 +517,7 @@ struct dma_buf_attachment {   struct list_head node;   bool peer2peer;   const struct dma_buf_attach_ops *importer_ops;

• const void *interconnect;

const struct dma_buf_interconnect *interconnect;

void *importer_priv;   void *priv;  };

/Thomas