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Subject[PATCH v6 04/13] 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, or the word 'auto' turn P2P on or off. Specifying a full
PCI device name/BDF will select the specific device.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
drivers/pci/p2pdma.c | 83 ++++++++++++++++++++++++++++++++++++++
include/linux/pci-p2pdma.h | 15 +++++++
2 files changed, 98 insertions(+)

diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
index 29bd40a87768..3da848f3fe72 100644
--- a/drivers/pci/p2pdma.c
+++ b/drivers/pci/p2pdma.c
@@ -9,6 +9,7 @@
*/

#define pr_fmt(fmt) "pci-p2pdma: " fmt
+#include <linux/ctype.h>
#include <linux/pci-p2pdma.h>
#include <linux/module.h>
#include <linux/slab.h>
@@ -856,3 +857,85 @@ int pci_p2pdma_map_sg(struct device *dev, struct scatterlist *sg, int nents,
return nents;
}
EXPORT_SYMBOL_GPL(pci_p2pdma_map_sg);
+
+/**
+ * pci_p2pdma_enable_store - parse a configfs/sysfs attribute store
+ * to enable p2pdma
+ * @page: contents of the value to be stored
+ * @p2p_dev: returns the PCI device that was selected to be used
+ * (if 'auto', 'none or a boolean isn't the store value)
+ * @use_p2pdma: returns whether to enable p2pdma or not
+ *
+ * Parses an attribute value to decide whether to enable p2pdma.
+ * The value can select a PCI device (using it's full BDF device
+ * name), a boolean, or 'auto'. 'auto' and a true boolean value
+ * have the same meaning. A false value disables p2pdma and
+ * a PCI device enables it to use a specific device as the
+ * backing provider.
+ *
+ * pci_p2pdma_enable_show() should be used as the show operation for
+ * the attribute.
+ *
+ * Returns 0 on success
+ */
+int pci_p2pdma_enable_store(const char *page, struct pci_dev **p2p_dev,
+ bool *use_p2pdma)
+{
+ struct device *dev;
+
+ dev = bus_find_device_by_name(&pci_bus_type, NULL, page);
+ if (dev) {
+ *use_p2pdma = true;
+ *p2p_dev = to_pci_dev(dev);
+
+ if (!pci_has_p2pmem(*p2p_dev)) {
+ pr_err("PCI device has no peer-to-peer memory: %s\n",
+ page);
+ pci_dev_put(*p2p_dev);
+ return -ENODEV;
+ }
+
+ return 0;
+ } else if (sysfs_streq(page, "auto")) {
+ *use_p2pdma = true;
+ return 0;
+ } else if ((page[0] == '0' || page[0] == '1') && !iscntrl(page[1])) {
+ /*
+ * If the user enters a PCI device that doesn't exist
+ * like "0000:01:00.1", we don't want strtobool to think
+ * it's a '0' when it's clearly not what the user wanted.
+ * So we require 0's and 1's to be exactly one character.
+ */
+ } else if (!strtobool(page, use_p2pdma)) {
+ return 0;
+ }
+
+ pr_err("No such PCI device: %.*s\n", (int)strcspn(page, "\n"), page);
+ return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_enable_store);
+
+/**
+ * pci_p2pdma_enable_show - show a configfs/sysfs attribute indicating
+ * whether p2pdma is enabled
+ * @page: contents of the stored value
+ * @p2p_dev: the selected p2p device (NULL if no device is selected)
+ * @use_p2pdma: whether p2pdme has been enabled
+ *
+ * Attributes that use pci_p2pdma_enable_store() should use this function
+ * to show the value of the attribute.
+ *
+ * Returns 0 on success
+ */
+ssize_t pci_p2pdma_enable_show(char *page, struct pci_dev *p2p_dev,
+ bool use_p2pdma)
+{
+ if (!use_p2pdma)
+ return sprintf(page, "none\n");
+
+ if (!p2p_dev)
+ return sprintf(page, "auto\n");
+
+ return sprintf(page, "%s\n", pci_name(p2p_dev));
+}
+EXPORT_SYMBOL_GPL(pci_p2pdma_enable_show);
diff --git a/include/linux/pci-p2pdma.h b/include/linux/pci-p2pdma.h
index 2f03dbbf5af6..377de4d73767 100644
--- a/include/linux/pci-p2pdma.h
+++ b/include/linux/pci-p2pdma.h
@@ -38,6 +38,10 @@ 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)
@@ -105,5 +109,16 @@ 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 */
#endif /* _LINUX_PCI_P2P_H */
--
2.19.0
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