[RFC PATCH v4 11/38] NTB: core: Add .get_dma_dev() to ntb_dev_ops
From: Koichiro Den <hidden>
Date: 2026-01-18 13:55:16
Also in:
dmaengine, linux-devicetree, linux-doc, linux-iommu, linux-kselftest, linux-pci, linux-renesas-soc, lkml
Subsystem:
ntb driver core, the rest · Maintainers:
Jon Mason, Dave Jiang, Allen Hubbe, Linus Torvalds
Not all NTB implementations are able to naturally do DMA mapping through the NTB PCI device itself (e.g. due to IOMMU topology or non-PCI backing devices). Add an optional .get_dma_dev() callback and helper so clients can use the appropriate struct device for DMA API allocations and mappings. Signed-off-by: Koichiro Den <redacted> --- include/linux/ntb.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/include/linux/ntb.h b/include/linux/ntb.h
index aa888219732a..7ac8cb13e90d 100644
--- a/include/linux/ntb.h
+++ b/include/linux/ntb.h@@ -262,6 +262,7 @@ struct ntb_mw_subrange { * @msg_clear_mask: See ntb_msg_clear_mask(). * @msg_read: See ntb_msg_read(). * @peer_msg_write: See ntb_peer_msg_write(). + * @get_dma_dev: See ntb_get_dma_dev(). * @get_private_data: See ntb_get_private_data(). */ struct ntb_dev_ops {
@@ -339,6 +340,7 @@ struct ntb_dev_ops { int (*msg_clear_mask)(struct ntb_dev *ntb, u64 mask_bits); u32 (*msg_read)(struct ntb_dev *ntb, int *pidx, int midx); int (*peer_msg_write)(struct ntb_dev *ntb, int pidx, int midx, u32 msg); + struct device *(*get_dma_dev)(struct ntb_dev *ntb); void *(*get_private_data)(struct ntb_dev *ntb); };
@@ -405,6 +407,7 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops) !ops->peer_msg_write == !ops->msg_count && /* Miscellaneous optional callbacks */ + /* ops->get_dma_dev && */ /* ops->get_private_data && */ 1; }
@@ -1614,6 +1617,21 @@ static inline int ntb_peer_msg_write(struct ntb_dev *ntb, int pidx, int midx, return ntb->ops->peer_msg_write(ntb, pidx, midx, msg); } +/** + * ntb_get_dma_dev() - get the device suitable for DMA mapping + * @ntb: NTB device context. + * + * Retrieve a struct device which is suitable for DMA mapping. + * + * Return: Pointer to struct device. + */ +static inline struct device __maybe_unused *ntb_get_dma_dev(struct ntb_dev *ntb) +{ + if (!ntb->ops->get_dma_dev) + return ntb->dev.parent; + return ntb->ops->get_dma_dev(ntb); +} + /** * ntb_get_private_data() - get private data specific to the hardware driver * @ntb: NTB device context.
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2.51.0