Re: [RFC PATCH v4 09/38] NTB: core: Add mw_set_trans_ranges() for subrange programming

Frank Li
2026-01-19T20:07:18Z

On Sun, Jan 18, 2026 at 10:54:11PM +0900, Koichiro Den wrote:
> At the BAR level, multiple MWs may be packed into a single BAR. In
> addition, a single MW may itself be subdivided into multiple address
> subranges, each of which can be mapped independently by the underlying
> NTB hardware.
>
> Introduce an optional ntb_dev_ops callback, .mw_set_trans_ranges(), to
> describe and program such layouts explicitly. The helper allows an NTB
> driver to provide, for each MW, a list of contiguous subranges that
> together cover the MW address space.
>
> Signed-off-by: Koichiro Den <den@valinux.co.jp>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>
> include/linux/ntb.h | 46 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 46 insertions(+)
>
> diff --git a/include/linux/ntb.h b/include/linux/ntb.h
> index 8ff9d663096b..84908753f446 100644
> --- a/include/linux/ntb.h
> +++ b/include/linux/ntb.h
> @@ -206,6 +206,11 @@ static inline int ntb_ctx_ops_is_valid(const struct ntb_ctx_ops *ops)
> 1;
> }
>
> +struct ntb_mw_subrange {
> + dma_addr_t addr;
> + resource_size_t size;
> +};
> +
> /**
> * struct ntb_dev_ops - ntb device operations
> * @port_number: See ntb_port_number().
> @@ -218,6 +223,7 @@ static inline int ntb_ctx_ops_is_valid(const struct ntb_ctx_ops *ops)
> * @mw_count: See ntb_mw_count().
> * @mw_get_align: See ntb_mw_get_align().
> * @mw_set_trans: See ntb_mw_set_trans().
> + * @mw_set_trans_ranges:See ntb_mw_set_trans_ranges().
> * @mw_clear_trans: See ntb_mw_clear_trans().
> * @peer_mw_count: See ntb_peer_mw_count().
> * @peer_mw_get_addr: See ntb_peer_mw_get_addr().
> @@ -276,6 +282,9 @@ struct ntb_dev_ops {
> resource_size_t *size_max);
> int (*mw_set_trans)(struct ntb_dev *ntb, int pidx, int widx,
> dma_addr_t addr, resource_size_t size);
> + int (*mw_set_trans_ranges)(struct ntb_dev *ntb, int pidx, int widx,
> + unsigned int num_ranges,
> + const struct ntb_mw_subrange *ranges);
> int (*mw_clear_trans)(struct ntb_dev *ntb, int pidx, int widx);
> int (*peer_mw_count)(struct ntb_dev *ntb);
> int (*peer_mw_get_addr)(struct ntb_dev *ntb, int widx,
> @@ -350,6 +359,7 @@ static inline int ntb_dev_ops_is_valid(const struct ntb_dev_ops *ops)
> ops->mw_get_align &&
> (ops->mw_set_trans ||
> ops->peer_mw_set_trans) &&
> + /* ops->mw_set_trans_ranges && */
> /* ops->mw_clear_trans && */
> ops->peer_mw_count &&
> ops->peer_mw_get_addr &&
> @@ -860,6 +870,42 @@ static inline int ntb_mw_set_trans(struct ntb_dev *ntb, int pidx, int widx,
> return ntb->ops->mw_set_trans(ntb, pidx, widx, addr, size);
> }
>
> +/**
> + * ntb_mw_set_trans_ranges() - set the translations of an inbound memory
> + * window, composed of multiple subranges.
> + * @ntb: NTB device context.
> + * @pidx: Port index of peer device.
> + * @widx: Memory window index.
> + * @num_ranges: The number of ranges described by @ranges array.
> + * @ranges: Array of subranges. The subranges are interpreted in ascending
> + * window offset order (i.e. ranges[0] maps the first part of the MW,
> + * ranges[1] the next part, ...).
> + *
> + * Return: Zero on success, otherwise an error number. If the driver does
> + * not implement the callback, return -EOPNOTSUPP.
> + */
> +static inline int ntb_mw_set_trans_ranges(struct ntb_dev *ntb, int pidx, int widx,
> + unsigned int num_ranges,
> + const struct ntb_mw_subrange *ranges)
> +{
> + if (!num_ranges || !ranges)
> + return -EINVAL;
> +
> + if (ntb->ops->mw_set_trans_ranges)
> + return ntb->ops->mw_set_trans_ranges(ntb, pidx, widx,
> + num_ranges, ranges);
> +
> + /*
> + * Fallback for drivers that only support the legacy single-range
> + * translation API.
> + */
> + if (num_ranges == 1)
> + return ntb_mw_set_trans(ntb, pidx, widx,
> + ranges[0].addr, ranges[0].size);
> +
> + return -EOPNOTSUPP;
> +}
> +
> /**
> * ntb_mw_clear_trans() - clear the translation address of an inbound memory
> * window
> --
> 2.51.0
>