On Sun, Jan 18, 2026 at 10:54:13PM +0900, Koichiro Den wrote: > 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 <[email protected]> > --- > 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)
I remember if there are inline, needn't __maybe_unused. Reviewed-by: Frank Li <[email protected]> > +{ > + 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. > -- > 2.51.0 >
