[PATCH v6 03/21] PCI/P2PDMA: Expose pci_p2pdma_map_type()

[Logan Gunthorpe]

pci_p2pdma_map_type() will be needed by the dma-iommu map_sg
implementation because it will need to determine the mapping type
ahead of actually doing the mapping to create the actual IOMMU mapping.

Prototypes for this helper are added to dma-map-ops.h as they are only
useful to dma map implementations and don't need to pollute the public
pci-p2pdma header

Signed-off-by: Logan Gunthorpe <logang at deltatee.com>
Acked-by: Bjorn Helgaas <bhelgaas at google.com>
Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>
Reviewed-by: Chaitanya Kulkarni <kch at nvidia.com>
---
 drivers/pci/p2pdma.c        | 25 +++++++++++++--------
 include/linux/dma-map-ops.h | 45 +++++++++++++++++++++++++++++++++++++
 2 files changed, 61 insertions(+), 9 deletions(-)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index c3a68e82cf36..8573bf9d651a 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -10,6 +10,7 @@
 
 #define pr_fmt(fmt) "pci-p2pdma: " fmt
 #include <linux/ctype.h>
+#include <linux/dma-map-ops.h>
 #include <linux/pci-p2pdma.h>
 #include <linux/module.h>
 #include <linux/slab.h>
@@ -20,13 +21,6 @@
 #include <linux/seq_buf.h>
 #include <linux/xarray.h>
 
-enum pci_p2pdma_map_type {
-	PCI_P2PDMA_MAP_UNKNOWN = 0,
-	PCI_P2PDMA_MAP_NOT_SUPPORTED,
-	PCI_P2PDMA_MAP_BUS_ADDR,
-	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
-};
-
 struct pci_p2pdma {
 	struct gen_pool *pool;
 	bool p2pmem_published;
@@ -842,8 +836,21 @@ void pci_p2pmem_publish(struct pci_dev *pdev, bool publish)
 }
 EXPORT_SYMBOL_GPL(pci_p2pmem_publish);
 
-static enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
-						    struct device *dev)
+/**
+ * pci_p2pdma_map_type - return the type of mapping that should be used for
+ *	a given device and pgmap
+ * @pgmap: the pagemap of a page to determine the mapping type for
+ * @dev: device that is mapping the page
+ *
+ * Returns one of:
+ *	PCI_P2PDMA_MAP_NOT_SUPPORTED - The mapping should not be done
+ *	PCI_P2PDMA_MAP_BUS_ADDR - The mapping should use the PCI bus address
+ *	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE - The mapping should be done normally
+ *		using the CPU physical address (in dma-direct) or an IOVA
+ *		mapping for the IOMMU.
+ */
+enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
+					     struct device *dev)
 {
 	enum pci_p2pdma_map_type type = PCI_P2PDMA_MAP_NOT_SUPPORTED;
 	struct pci_dev *provider = to_p2p_pgmap(pgmap)->provider;
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 0d5b06b3a4a6..d693a0e33bac 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -379,4 +379,49 @@ static inline void debug_dma_dump_mappings(struct device *dev)
 
 extern const struct dma_map_ops dma_dummy_ops;
 
+enum pci_p2pdma_map_type {
+	/*
+	 * PCI_P2PDMA_MAP_UNKNOWN: Used internally for indicating the mapping
+	 * type hasn't been calculated yet. Functions that return this enum
+	 * never return this value.
+	 */
+	PCI_P2PDMA_MAP_UNKNOWN = 0,
+
+	/*
+	 * PCI_P2PDMA_MAP_NOT_SUPPORTED: Indicates the transaction will
+	 * traverse the host bridge and the host bridge is not in the
+	 * allowlist. DMA Mapping routines should return an error when
+	 * this is returned.
+	 */
+	PCI_P2PDMA_MAP_NOT_SUPPORTED,
+
+	/*
+	 * PCI_P2PDMA_BUS_ADDR: Indicates that two devices can talk to
+	 * each other directly through a PCI switch and the transaction will
+	 * not traverse the host bridge. Such a mapping should program
+	 * the DMA engine with PCI bus addresses.
+	 */
+	PCI_P2PDMA_MAP_BUS_ADDR,
+
+	/*
+	 * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE: Indicates two devices can talk
+	 * to each other, but the transaction traverses a host bridge on the
+	 * allowlist. In this case, a normal mapping either with CPU physical
+	 * addresses (in the case of dma-direct) or IOVA addresses (in the
+	 * case of IOMMUs) should be used to program the DMA engine.
+	 */
+	PCI_P2PDMA_MAP_THRU_HOST_BRIDGE,
+};
+
+#ifdef CONFIG_PCI_P2PDMA
+enum pci_p2pdma_map_type pci_p2pdma_map_type(struct dev_pagemap *pgmap,
+					     struct device *dev);
+#else /* CONFIG_PCI_P2PDMA */
+static inline enum pci_p2pdma_map_type
+pci_p2pdma_map_type(struct dev_pagemap *pgmap, struct device *dev)
+{
+	return PCI_P2PDMA_MAP_NOT_SUPPORTED;
+}
+#endif /* CONFIG_PCI_P2PDMA */
+
 #endif /* _LINUX_DMA_MAP_OPS_H */
-- 
2.30.2