[PATCH -v2 1/3] PCI: introduce PCIe Device Serial Number Capability support

[Yijing Wang <wangyijing@huawei.com>]

Introduce PCIe Ext Capability Device Serial Number support,
so we can use the unique device serial number to identify
the physical device. During system suspend, if the PCIe
device was removed and inserted a new same device, after
system resume there is no good way to identify it, maybe
Device Serial Number is a good choice if device support.

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
---
 drivers/pci/pci.c   |   27 +++++++++++++++++++++++++++
 drivers/pci/probe.c |    2 ++
 include/linux/pci.h |    3 +++
 3 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e37fea6..2e855b5 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -2048,6 +2048,33 @@ void pci_free_cap_save_buffers(struct pci_dev *dev)
 }
 
 /**
+ * pci_device_serial_number - get device serial number
+ * @dev: the PCI device
+ *
+ * return the device serial number if device support,
+ * otherwise return 0.
+ */
+u64 pci_device_serial_number(struct pci_dev *dev)
+{
+	int pos;
+	u64 sn;
+	u32 lo, hi;
+
+	if (!pci_is_pcie(dev))
+		return 0;
+
+	pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DSN);
+	if (!pos)
+		return 0;
+
+	pci_read_config_dword(dev, pos + 4, &lo);
+	pci_read_config_dword(dev, pos + 8, &hi);
+	sn = ((u64)hi << 32) | lo;
+	return sn;
+}
+EXPORT_SYMBOL(pci_device_serial_number);
+
+/**
  * pci_configure_ari - enable or disable ARI forwarding
  * @dev: the PCI device
  *
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 46ada5c..c4c1a2b 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1322,6 +1322,8 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	/* Power Management */
 	pci_pm_init(dev);
 
+	dev->sn = pci_device_serial_number(dev);
+
 	/* Vital Product Data */
 	pci_vpd_pci22_init(dev);
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 0fd1f15..10d190b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -342,6 +342,7 @@ struct pci_dev {
 	struct list_head msi_list;
 	struct kset *msi_kset;
 #endif
+	u64 sn;		/* device serieal number, 0 if not support */
 	struct pci_vpd *vpd;
 #ifdef CONFIG_PCI_ATS
 	union {
@@ -995,6 +996,8 @@ ssize_t pci_read_vpd(struct pci_dev *dev, loff_t pos, size_t count, void *buf);
 ssize_t pci_write_vpd(struct pci_dev *dev, loff_t pos, size_t count, const void *buf);
 int pci_vpd_truncate(struct pci_dev *dev, size_t size);
 
+u64 pci_device_serial_number(struct pci_dev *dev);
+
 /* Helper functions for low-level code (drivers/pci/setup-[bus,res].c) */
 resource_size_t pcibios_retrieve_fw_addr(struct pci_dev *dev, int idx);
 void pci_bus_assign_resources(const struct pci_bus *bus);
-- 
1.7.1