On 7/16/25 11:32 AM, Matthew Wood wrote:
Add a single sysfs read-only interface for reading PCIe device serial
numbers from userspace in a programmatic way. This device attribute
uses the same hexadecimal 1-byte dashed formatting as lspci serial number
capability output. If a device doesn't support the serial number
capability, the device_serial_number sysfs attribute will not be visible.
Signed-off-by: Matthew Wood <thepacketgeek@xxxxxxxxx>
---
Documentation/ABI/testing/sysfs-bus-pci | 7 +++++++
drivers/pci/pci-sysfs.c | 27 ++++++++++++++++++++++---
2 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 69f952fffec7..f7e84b3a4204 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -612,3 +612,10 @@ Description:
# ls doe_features
0001:01 0001:02 doe_discovery
+
+What: /sys/bus/pci/devices/.../device_serial_number
+Date: July 2025
+Contact: Matthew Wood <thepacketgeek@xxxxxxxxx>
+Description:
+ This is visible only for PCIe devices that support the serial
+ number extended capability. The file is read only.
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 268c69daa4d5..b7b52dea6e31 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -239,6 +239,22 @@ static ssize_t current_link_width_show(struct device *dev,
}
static DEVICE_ATTR_RO(current_link_width);
+static ssize_t device_serial_number_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct pci_dev *pci_dev = to_pci_dev(dev);
+ u64 dsn;
+
+ dsn = pci_get_dsn(pci_dev);
+ if (!dsn)
+ return -EIO;
+
+ return sysfs_emit(buf, "%02llx-%02llx-%02llx-%02llx-%02llx-%02llx-%02llx-%02llx\n",
+ dsn >> 56, (dsn >> 48) & 0xff, (dsn >> 40) & 0xff, (dsn >> 32) & 0xff,
+ (dsn >> 24) & 0xff, (dsn >> 16) & 0xff, (dsn >> 8) & 0xff, dsn & 0xff);
+}
+static DEVICE_ATTR_RO(device_serial_number);
The serial number /could/ be considered sensitive information. I think
it's better to use DEVICE_ATTR_ADMIN_RO.
Also, as this is a "device" attribute is it really necessary to encode
the extra word and "number"?
+
static ssize_t secondary_bus_number_show(struct device *dev,
struct device_attribute *attr,
char *buf)
@@ -660,6 +676,7 @@ static struct attribute *pcie_dev_attrs[] = {
&dev_attr_current_link_width.attr,
&dev_attr_max_link_width.attr,
&dev_attr_max_link_speed.attr,
+ &dev_attr_device_serial_number.attr,
NULL,
};
@@ -1749,10 +1766,14 @@ static umode_t pcie_dev_attrs_are_visible(struct kobject *kobj,
struct device *dev = kobj_to_dev(kobj);
struct pci_dev *pdev = to_pci_dev(dev);
- if (pci_is_pcie(pdev))
- return a->mode;
+ if (!pci_is_pcie(pdev))
+ return 0;
+
+ if (a == &dev_attr_device_serial_number.attr && !pci_get_dsn(pdev))
+ return 0;
+
+ return a->mode;
- return 0;
}
static const struct attribute_group pci_dev_group = {
