PCI: create function symlinks in /sys/bus/pci/slots/N/

Create convenience symlinks in sysfs, linking slots to device
functions, and vice versa. These links make it easier for users to
figure out which devices actually live in what slots.

For example:

sapphire:/sys/bus/pci/slots # ls
1  10  2  3  4  5  6  7  8  9

sapphire:/sys/bus/pci/slots # ls -l 3
total 0
-r--r--r-- 1 root root 65536 Aug 18 14:10 address
lrwxrwxrwx 1 root root     0 Aug 18 14:10 function0 ->
../../../../devices/pci0000:23/0000:23:01.0
lrwxrwxrwx 1 root root     0 Aug 18 14:10 function1 ->
../../../../devices/pci0000:23/0000:23:01.1

sapphire:/sys/bus/pci/slots # ls -l 3/function0/slot
lrwxrwxrwx 1 root root 0 Aug 18 14:13 3/function0/slot ->
../../../bus/pci/slots/3

The original form of this patch was written by Matthew Wilcox,
and was enhanced to include links from the sysfs slots/ directory
pointing back at the device functions.

Cc: willy@linux.intel.com
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 40 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 25be3250f7d6..428676cfa61e 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -133,6 +133,46 @@ Description:
                 The symbolic link points to the PCI device sysfs entry of the
                 Physical Function this device associates with.
 
+
+What:           /sys/bus/pci/slots/...
+Date:           April 2005 (possibly older)
+KernelVersion:  2.6.12 (possibly older)
+Contact:        linux-pci@vger.kernel.org
+Description:
+                When the appropriate driver is loaded, it will create a
+                directory per claimed physical PCI slot in
+                /sys/bus/pci/slots/.  The names of these directories are
+                specific to the driver, which in turn, are specific to the
+                platform, but in general, should match the label on the
+                machine's physical chassis.
+
+                The drivers that can create slot directories include the
+                PCI hotplug drivers, and as of 2.6.27, the pci_slot driver.
+
+                The slot directories contain, at a minimum, a file named
+                'address' which contains the PCI bus:device:function tuple.
+                Other files may appear as well, but are specific to the
+                driver.
+
+What:           /sys/bus/pci/slots/.../function[0-7]
+Date:           March 2010
+KernelVersion:  2.6.35
+Contact:        linux-pci@vger.kernel.org
+Description:
+                If PCI slot directories (as described above) are created,
+                and the physical slot is actually populated with a device,
+                symbolic links in the slot directory pointing to the
+                device's PCI functions are created as well.
+
+What:           /sys/bus/pci/devices/.../slot
+Date:           March 2010
+KernelVersion:  2.6.35
+Contact:        linux-pci@vger.kernel.org
+Description:
+                If PCI slot directories (as described above) are created,
+                a symbolic link pointing to the slot directory will be
+                created as well.
+
 What:           /sys/bus/pci/slots/.../module
 Date:           June 2009
 Contact:        linux-pci@vger.kernel.org