Documentation/ABI: document /sys/class/net/*/dev_port

The sysfs field was introduced 4 years ago along with fixes to various
drivers that erroneously used `dev_id' for that purpose, but it was not
properly documented anywhere.
See commit v3.14-rc3-739-g3f85944fe207.

Signed-off-by: Arseny Maslennikov <ar@cs.msu.ru>
Signed-off-by: Doug Ledford <dledford@redhat.com>

diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
index 2f1788111cd9cdec1aca6ccc42e873d30a59391d..ec2232f6a9494fa463a9c4694551049669d10f83 100644 (file)
--- a/Documentation/ABI/testing/sysfs-class-net
+++ b/Documentation/ABI/testing/sysfs-class-net
@@ -91,6 +91,24 @@ Description:
                stacked (e.g: VLAN interfaces) but still have the same MAC
                address as their parent device.
 
+What:          /sys/class/net/<iface>/dev_port
+Date:          February 2014
+KernelVersion: 3.15
+Contact:       netdev@vger.kernel.org
+Description:
+               Indicates the port number of this network device, formatted
+               as a decimal value. Some NICs have multiple independent ports
+               on the same PCI bus, device and function. This attribute allows
+               userspace to distinguish the respective interfaces.
+
+               Note: some device drivers started to use 'dev_id' for this
+               purpose since long before 3.15 and have not adopted the new
+               attribute ever since. To query the port number, some tools look
+               exclusively at 'dev_port', while others only consult 'dev_id'.
+               If a network device has multiple client adapter ports as
+               described in the previous paragraph and does not set this
+               attribute to its port number, it's a kernel bug.
+
 What:          /sys/class/net/<iface>/dormant
 Date:          March 2006
 KernelVersion: 2.6.17