linux-kernel - [PATCH 1/2] PCI: endpoint: Add BAR subrange mapping support

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Message-ID: <20260105080214.1254325-2-den@valinux.co.jp>
Date: Mon,  5 Jan 2026 17:02:13 +0900
From: Koichiro Den <den@...inux.co.jp>
To: jingoohan1@...il.com,
	mani@...nel.org,
	lpieralisi@...nel.org,
	kwilczynski@...nel.org,
	robh@...nel.org,
	bhelgaas@...gle.com
Cc: Frank.Li@....com,
	linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] PCI: endpoint: Add BAR subrange mapping support

Extend the PCI endpoint core to support mapping subranges within a BAR.
Introduce a new 'submap' field and a 'use_submap' flag in struct
pci_epf_bar so an endpoint function driver can request inbound mappings
that cover only a portion of a BAR.

This provides the generic infrastructure needed to map multiple logical
regions into a single BAR at different offsets, without assuming a
controller-specific inbound address translation mechanism.

No controller-specific implementation is added in this commit.

Signed-off-by: Koichiro Den <den@...inux.co.jp>
---
 include/linux/pci-epf.h | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/include/linux/pci-epf.h b/include/linux/pci-epf.h
index 48f68c4dcfa5..164768db85f6 100644
--- a/include/linux/pci-epf.h
+++ b/include/linux/pci-epf.h
@@ -110,6 +110,24 @@ struct pci_epf_driver {
 
 #define to_pci_epf_driver(drv) container_of_const((drv), struct pci_epf_driver, driver)
 
+/**
+ * struct pci_epf_bar_submap - represents a BAR subrange for inbound mapping
+ * @phys_addr: physical address that should be mapped to the BAR subrange
+ * @size: the size of the subrange to be mapped
+ * @offset: The byte offset from the BAR base
+ *
+ * When pci_epf_bar.use_submap is set, an EPF driver may describe multiple
+ * independent mappings within a single BAR. An EPC driver can use these
+ * descriptors to set up the required address translation (e.g. multiple
+ * inbound iATU regions) without requiring the whole BAR to be mapped at
+ * once.
+ */
+struct pci_epf_bar_submap {
+	dma_addr_t	phys_addr;
+	size_t		size;
+	size_t		offset;
+};
+
 /**
  * struct pci_epf_bar - represents the BAR of EPF device
  * @phys_addr: physical address that should be mapped to the BAR
@@ -119,6 +137,9 @@ struct pci_epf_driver {
  *            requirement
  * @barno: BAR number
  * @flags: flags that are set for the BAR
+ * @use_submap: set true to request subrange mappings within this BAR
+ * @num_submap: number of entries in @submap
+ * @submap: array of subrange descriptors allocated by the caller
  */
 struct pci_epf_bar {
 	dma_addr_t	phys_addr;
@@ -127,6 +148,11 @@ struct pci_epf_bar {
 	size_t		mem_size;
 	enum pci_barno	barno;
 	int		flags;
+
+	/* Optional sub-range mapping */
+	bool		use_submap;
+	int		num_submap;
+	struct pci_epf_bar_submap	*submap;
 };
 
 /**
-- 
2.51.0