Add an optional dma_buf_ops.get_tph callback and a dma_buf_get_tph() wrapper for importers.
8-bit ST and 16-bit Extended ST are distinct PCIe TPH namespaces, so the importer requests the namespace it can emit and the exporter returns the matching ST/PH tuple or -EOPNOTSUPP. dma_buf_get_tph() is the importer entry point. It returns -EOPNOTSUPP when the exporter lacks the callback and requires dmabuf->resv to be held while the callback runs. The first user is VFIO_DEVICE_FEATURE_DMA_BUF_TPH in vfio-pci, with mlx5 as the first importer. Signed-off-by: Zhiping Zhang <[email protected]> --- drivers/dma-buf/dma-buf.c | 25 +++++++++++++++++++++++++ include/linux/dma-buf.h | 21 +++++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index d504c636dc29..aff79ea12e43 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_tph - Retrieve TPH metadata from an exporter + * @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_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_tph(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph) +{ + dma_resv_assert_held(dmabuf->resv); + + if (!dmabuf->ops->get_tph) + return -EOPNOTSUPP; + + return dmabuf->ops->get_tph(dmabuf, extended, steering_tag, ph); +} +EXPORT_SYMBOL_NS_GPL(dma_buf_get_tph, "DMA_BUF"); + /** * dma_buf_map_attachment - Returns the scatterlist table of the attachment; * mapped into _device_ address space. Is a wrapper for map_dma_buf() of the diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h index d1203da56fc5..6a54e0f251a2 100644 --- a/include/linux/dma-buf.h +++ b/include/linux/dma-buf.h @@ -113,6 +113,25 @@ struct dma_buf_ops { */ void (*unpin)(struct dma_buf_attachment *attach); + /** + * @get_tph: + * @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) + * + * Return TPH metadata for the namespace selected by @extended. Return + * 0 on success, or -EOPNOTSUPP if no metadata is available. + * + * This callback is optional. Importers must not call it directly; + * the dma_buf_get_tph() wrapper is the only entry point and handles + * the NULL-callback case. The callback is invoked with + * &dma_buf.resv held. + */ + int (*get_tph)(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph); + /** * @map_dma_buf: * @@ -563,6 +582,8 @@ void dma_buf_detach(struct dma_buf *dmabuf, struct dma_buf_attachment *attach); int dma_buf_pin(struct dma_buf_attachment *attach); void dma_buf_unpin(struct dma_buf_attachment *attach); +int dma_buf_get_tph(struct dma_buf *dmabuf, bool extended, + u16 *steering_tag, u8 *ph); struct dma_buf *dma_buf_export(const struct dma_buf_export_info *exp_info); -- 2.53.0-Meta
