PCI/P2PDMA: Introduce configfs/sysfs enable attribute helpers

Users of the P2PDMA infrastructure will typically need a way for the user
to tell the kernel to use P2P resources.  Typically this will be a simple
on/off boolean operation but sometimes it may be desirable for the user to
specify the exact device to use for the P2P operation.

Add new helpers for attributes which take a boolean or a PCI device.  Any
boolean as accepted by strtobool() turn P2P on or off (such as 'y', 'n',
'1', '0', etc).  Specifying a full PCI device name/BDF will select the
specific device.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index b6dfb6dc2e53..bca9bc3e5be7 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -32,6 +32,10 @@ void pci_p2pmem_free_sgl(struct pci_dev *pdev, struct scatterlist *sgl);
 void pci_p2pmem_publish(struct pci_dev *pdev, bool publish);
 int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
 		      enum dma_data_direction dir);
+int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
+			    bool *use_p2pdma);
+ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
+			       bool use_p2pdma);
 #else /* CONFIG_PCI_P2PDMA */
 static inline int pci_p2pdma_add_resource(struct pci_dev *pdev, int bar,
 		size_t size, u64 offset)
@@ -82,6 +86,17 @@ static inline int pci_p2pdma_map_sg(struct device *dev,
 {
 	return 0;
 }
+static inline int pci_p2pdma_enable_store(const char *page,
+		struct pci_dev **p2p_dev, bool *use_p2pdma)
+{
+	*use_p2pdma = false;
+	return 0;
+}
+static inline ssize_t pci_p2pdma_enable_show(char *page,
+		struct pci_dev *p2p_dev, bool use_p2pdma)
+{
+	return sprintf(page, "none\n");
+}
 #endif /* CONFIG_PCI_P2PDMA */