Merge branch 'pci/misc'

- Fix whitespace issues (Li Jun)

- Fix pci_acpi_preserve_config() memory leak (Nirmoy Das)

- Add sysfs 'serial_number' file to expose the Device Serial Number
  (Matthew Wood)

* pci/misc:
  PCI/sysfs: Expose PCI device serial number
  PCI/ACPI: Fix pci_acpi_preserve_config() memory leak

3 files changed, 34 insertions, 2 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 69f952fffec7..92debe879ffb 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -612,3 +612,12 @@ Description:
 
 		  # ls doe_features
 		  0001:01        0001:02        doe_discovery
+
+What:		/sys/bus/pci/devices/.../serial_number
+Date:		December 2025
+Contact:	Matthew Wood <thepacketgeek@gmail.com>
+Description:
+		This is visible only for PCI devices that support the serial
+		number extended capability. The file is read only and due to
+		the possible sensitivity of accessible serial numbers, admin
+		only.
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index ddb25960ea47..9369377725fa 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -122,6 +122,8 @@ phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
 
 bool pci_acpi_preserve_config(struct pci_host_bridge *host_bridge)
 {
+	bool ret = false;
+
 	if (ACPI_HANDLE(&host_bridge->dev)) {
 		union acpi_object *obj;
 
@@ -135,11 +137,11 @@ bool pci_acpi_preserve_config(struct pci_host_bridge *host_bridge)
 					      1, DSM_PCI_PRESERVE_BOOT_CONFIG,
 					      NULL, ACPI_TYPE_INTEGER);
 		if (obj && obj->integer.value == 0)
-			return true;
+			ret = true;
 		ACPI_FREE(obj);
 	}
 
-	return false;
+	return ret;
 }
 
 /* _HPX PCI Setting Record (Type 0); same as _HPP */
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 50a2250acc2b..af74cf02bb90 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -30,6 +30,7 @@
 #include <linux/msi.h>
 #include <linux/of.h>
 #include <linux/aperture.h>
+#include <linux/unaligned.h>
 #include "pci.h"
 
 #ifndef ARCH_PCI_DEV_GROUPS
@@ -719,6 +720,22 @@ static ssize_t boot_vga_show(struct device *dev, struct device_attribute *attr,
 }
 static DEVICE_ATTR_RO(boot_vga);
 
+static ssize_t serial_number_show(struct device *dev,
+				  struct device_attribute *attr, char *buf)
+{
+	struct pci_dev *pci_dev = to_pci_dev(dev);
+	u64 dsn;
+	u8 bytes[8];
+
+	dsn = pci_get_dsn(pci_dev);
+	if (!dsn)
+		return -EIO;
+
+	put_unaligned_be64(dsn, bytes);
+	return sysfs_emit(buf, "%8phD\n", bytes);
+}
+static DEVICE_ATTR_ADMIN_RO(serial_number);
+
 static ssize_t pci_read_config(struct file *filp, struct kobject *kobj,
 			       const struct bin_attribute *bin_attr, char *buf,
 			       loff_t off, size_t count)
@@ -1729,6 +1746,7 @@ late_initcall(pci_sysfs_init);
 
 static struct attribute *pci_dev_dev_attrs[] = {
 	&dev_attr_boot_vga.attr,
+	&dev_attr_serial_number.attr,
 	NULL,
 };
 
@@ -1741,6 +1759,9 @@ static umode_t pci_dev_attrs_are_visible(struct kobject *kobj,
 	if (a == &dev_attr_boot_vga.attr && pci_is_vga(pdev))
 		return a->mode;
 
+	if (a == &dev_attr_serial_number.attr && pci_get_dsn(pdev))
+		return a->mode;
+
 	return 0;
 }