[PATCH v3 0/1] PCI/sysfs: Expose PCIe device serial number

[PATCH v3 0/1] PCI/sysfs: Expose PCIe device serial number

[Matthew Wood]

Add a single sysfs read-only interface for reading PCIe device serial
numbers from userspace, using the same hexadecimal 1-byte dashed
formatting as lspci serial number capability output:

    more /sys/devices/pci0000:c0/0000:c0:01.1/0000:c1:00.0/0000:c2:1f.0/0000:cc:00.0/device_serial_number
    00-80-ee-00-00-00-41-80

If a device doesn't support the serial number capability, the
device_serial_number sysfs attribute will not be visible.

Comparing serial number format to lspci output:

    sudo lspci -vvv -s cc:00.0
        cc:00.0 Serial Attached SCSI controller: Broadcom / LSI PCIe Switch management endpoint (rev b0)
            Subsystem: Broadcom / LSI Device 0144
            ...
            Capabilities: [100 v1] Device Serial Number 00-80-ee-00-00-00-41-80
            ...

This PCIe device sysfs attribute eliminates the need for parsing lspci
output (e.g. regexp) for userspace applications that utilize serial
numbers.


Matthew Wood (1):
  PCI/sysfs: Expose PCIe device serial number

 Documentation/ABI/testing/sysfs-bus-pci |  7 +++++++
 drivers/pci/pci-sysfs.c                 | 27 ++++++++++++++++++++++---
 2 files changed, 31 insertions(+), 3 deletions(-)

-- 
2.50.0

[PATCH v3 1/1] PCI/sysfs: Expose PCIe device serial number

[Matthew Wood]

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@gmail.com>
---
 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@gmail.com>
+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);
+
 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 = {
-- 
2.50.0

Re: [PATCH v3 1/1] PCI/sysfs: Expose PCIe device serial number

[Mario Limonciello]

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@gmail.com>
> ---
>   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@gmail.com>
> +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 = {

Re: [PATCH v3 1/1] PCI/sysfs: Expose PCIe device serial number

[Matthew Wood]

On Wed, Jul 16, 2025 at 10:02 AM Mario Limonciello <superm1@kernel.org> wrote:
>
> 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@gmail.com>
> > ---
> >   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@gmail.com>
> > +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.

That makes sense, thanks for the suggestion.

>
> Also, as this is a "device" attribute is it really necessary to encode
> the extra word and "number"?

Another good point. I will remove the device_ prefix however I think
"serial_number" is helpful to keep as "serial" alone is too easy to
conflate with any of the other usages of the serial word.

>
> > +
> >   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 = {
>