netdev - [RFC PATCH v4 09/38] NTB: core: Add mw_set_trans

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Message-ID: <20260118135440.1958279-10-den@valinux.co.jp>
Date: Sun, 18 Jan 2026 22:54:11 +0900
From: Koichiro Den <den@...inux.co.jp>
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Subject: [RFC PATCH v4 09/38] NTB: core: Add mw_set_trans_ranges() for subrange programming

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@...inux.co.jp>
---
 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