Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Low] The newly added dma-buf API `dma_buf_get_pci_tph()` and its corresponding `get_pci_tph` callback are missing from the centralized dma-buf locking convention documentation. --
commit aa25de1b77cd2b1778e96e6bffe1b1b6ce39fd9c Author: Zhiping Zhang <[email protected]> dma-buf: add optional get_pci_tph() callback This commit adds an optional get_pci_tph callback to dma_buf_ops and a corresponding wrapper function dma_buf_get_pci_tph() for importers. These allow importers to retrieve PCIe TLP Processing Hint (TPH) metadata for peer-to-peer DMA. Both the callback and the wrapper require the dma-buf reservation lock to be held. > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c > index d504c636dc294..7a4c9b0d5dab4 100644 > --- a/drivers/dma-buf/dma-buf.c > +++ b/drivers/dma-buf/dma-buf.c [ ... ] > @@ -1144,6 +1144,31 @@ void dma_buf_unpin(struct dma_buf_attachment *attach) > } > EXPORT_SYMBOL_NS_GPL(dma_buf_unpin, "DMA_BUF"); > > +/** > + * dma_buf_get_pci_tph - Retrieve PCIe TLP Processing Hint (TPH) metadata > + * @dmabuf: DMA buffer to query > + * @extended: false for 8-bit ST, true for 16-bit Extended ST > + * @steering_tag: returns the raw steering tag for the requested namespace > + * @ph: returns the TPH processing hint > + * > + * Wrapper for the optional &dma_buf_ops.get_pci_tph callback. > + * > + * Must be called with &dma_buf.resv held. Returns -EOPNOTSUPP if the > + * exporter does not implement the callback or has no metadata for the > + * requested namespace. > + */ > +int dma_buf_get_pci_tph(struct dma_buf *dmabuf, bool extended, > + u16 *steering_tag, u8 *ph) > +{ > + dma_resv_assert_held(dmabuf->resv); [Severity: Low] This isn't a bug, but should dma_buf_get_pci_tph() be added to the list of functions in the "DOC: locking convention" block earlier in this file? The centralized documentation block serves as a single source of truth for importers by listing all functions that require the dma-buf reservation lock, such as dma_buf_pin() and dma_buf_vmap(). Adding this new function to that list would help keep the locking documentation complete. > + > + if (!dmabuf->ops->get_pci_tph) > + return -EOPNOTSUPP; > + > + return dmabuf->ops->get_pci_tph(dmabuf, extended, steering_tag, ph); > +} > +EXPORT_SYMBOL_NS_GPL(dma_buf_get_pci_tph, "DMA_BUF"); [ ... ] > diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h > index d1203da56fc5f..53b2686ad8fc6 100644 > --- a/include/linux/dma-buf.h > +++ b/include/linux/dma-buf.h [ ... ] > @@ -113,6 +113,26 @@ struct dma_buf_ops { > */ > void (*unpin)(struct dma_buf_attachment *attach); > > + /** > + * @get_pci_tph: > + * > + * Retrieve PCIe TLP Processing Hint (TPH) steering metadata for > + * this buffer so an importer can program a matching ST/PH hint on > + * outbound TLPs targeting the exporter for peer-to-peer DMA. > + * > + * @dmabuf: DMA buffer for which to retrieve TPH metadata > + * @extended: false for 8-bit ST, true for 16-bit Extended ST > + * @steering_tag: Returns the raw TPH steering tag for the requested > + * namespace > + * @ph: Returns the TPH processing hint (2-bit value) > + * > + * Optional callback for dma_buf_get_pci_tph(). Called with > + * &dma_buf.resv held. Returns 0 on success or -EOPNOTSUPP when > + * the exporter has no metadata for the requested namespace. > + */ > + int (*get_pci_tph)(struct dma_buf *dmabuf, bool extended, > + u16 *steering_tag, u8 *ph); [Severity: Low] Similarly, should &dma_buf_ops.get_pci_tph() be appended to the list of callbacks in the same "DOC: locking convention" block? The existing documentation explicitly calls out exporter callbacks that are invoked with the locked dma-buf reservation, so updating it here would keep the locking contract documentation consistent. -- Sashiko AI review · https://sashiko.dev/#/patchset/[email protected]?part=2
