Several device drivers read their Device Serial Number from the PCIe
extended config space.
Introduce a new helper function, pci_get_dsn(). This function reads the
eight bytes of the DSN and returns them as a u64. If the capability does not
exist for the device, the function returns 0.
Signed-off-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Jeff Kirsher <jeffrey.t.kirsher@xxxxxxxxx>
Cc: Michael Chan <michael.chan@xxxxxxxxxxxx>
---
drivers/pci/pci.c | 34 ++++++++++++++++++++++++++++++++++
include/linux/pci.h | 5 +++++
2 files changed, 39 insertions(+)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d828ca835a98..03f50e706c0d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -557,6 +557,40 @@ int pci_find_ext_capability(struct pci_dev *dev, int cap)
}
EXPORT_SYMBOL_GPL(pci_find_ext_capability);
+/**
+ * pci_get_dsn - Read and return the 8-byte Device Serial Number
+ * @dev: PCI device to query
+ *
+ * Looks up the PCI_EXT_CAP_ID_DSN and reads the 8 bytes of the Device Serial
+ * Number.
+ *
+ * Returns the DSN, or zero if the capability does not exist.
+ */
+u64 pci_get_dsn(struct pci_dev *dev)
+{
+ u32 dword;
+ u64 dsn;
+ int pos;
+
+ pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN);
+ if (!pos)
+ return 0;
+
+ /*
+ * The Device Serial Number is two dwords offset 4 bytes from the
+ * capability position. The specification says that the first dword is
+ * the lower half, and the second dword is the upper half.
+ */
+ pos += 4;
+ pci_read_config_dword(dev, pos, &dword);
+ dsn = (u64)dword;
+ pci_read_config_dword(dev, pos + 4, &dword);
+ dsn |= ((u64)dword) << 32;
+
+ return dsn;
+}
+EXPORT_SYMBOL_GPL(pci_get_dsn);
+
static int __pci_find_next_ht_cap(struct pci_dev *dev, int pos, int ht_cap)
{
int rc, ttl = PCI_FIND_CAP_TTL;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 3840a541a9de..d92cf2da1ae1 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1045,6 +1045,8 @@ int pci_find_ht_capability(struct pci_dev *dev, int ht_cap);
int pci_find_next_ht_capability(struct pci_dev *dev, int pos, int ht_cap);
struct pci_bus *pci_find_next_bus(const struct pci_bus *from);
+u64 pci_get_dsn(struct pci_dev *dev);
+
struct pci_dev *pci_get_device(unsigned int vendor, unsigned int device,
struct pci_dev *from);
struct pci_dev *pci_get_subsys(unsigned int vendor, unsigned int device,
@@ -1699,6 +1701,9 @@ static inline int pci_find_next_capability(struct pci_dev *dev, u8 post,
static inline int pci_find_ext_capability(struct pci_dev *dev, int cap)
{ return 0; }
+static inline u64 pci_get_dsn(struct pci_dev *dev)
+{ return 0; }
+
/* Power management related routines */
static inline int pci_save_state(struct pci_dev *dev) { return 0; }
static inline void pci_restore_state(struct pci_dev *dev) { }
--
2.25.0.368.g28a2d05eebfb
