> > include/linux/dma-buf.h | 31 +++++++++++++++++++++++++++++++
> > 1 file changed, 31 insertions(+)
> >
> > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
> > index d1203da56fc5..8437dbe4a83e 100644
> > --- a/include/linux/dma-buf.h
> > +++ b/include/linux/dma-buf.h
> > @@ -113,6 +113,37 @@ struct dma_buf_ops {
> > */
> > void (*unpin)(struct dma_buf_attachment *attach);
> >
> > + /**
> > + * @get_tph:
> > + * @dmabuf: DMA buffer for which to retrieve TPH metadata
> > + * @extended: false to request the 8-bit ST namespace, true to request
> > + * the 16-bit Extended ST namespace
> > + * @steering_tag: Returns the raw TPH steering tag for the requested
> > + * namespace
> > + * @ph: Returns the TPH processing hint (2-bit value)
> > + *
> > + * Return the TPH (TLP Processing Hints) metadata associated with this
> > + * DMA buffer for the requested steering-tag namespace. 8-bit ST and
> > + * 16-bit Extended ST are distinct namespaces in the PCIe TPH ST table
> > + * and may both be present with different values, so the exporter must
> > + * select the value that matches @extended and must not substitute one
> > + * for the other.
> > + *
> > + * The exporter owns the completing address space for @dmabuf and
> > + * therefore decides whether it can derive meaningful TPH metadata for
> > + * that completer. The dma-buf core treats the returned ST/PH tuple as
> > + * opaque transport metadata; importers that support TPH place it on
> > + * outbound TLPs, while exporters that cannot derive a useful tuple
> > + * simply return -EOPNOTSUPP.
> > + *
> > + * Return 0 on success, or -EOPNOTSUPP if no metadata is available for
> > + * the requested namespace.
> > + *
> > + * This callback is optional.
> > + */
> > + int (*get_tph)(struct dma_buf *dmabuf, bool extended,
> > + u16 *steering_tag, u8 *ph);
> > +
>
> That needs a wrapper for importers to call which also handles if the callback
> isn't present.
>
> Regards,
> Christian.
>
agreed, will use a wrapper in next revision.
Thanks,
Zhiping
