PCI: add remove_id sysfs entry

This adds a remove_id sysfs entry to allow users of new_id to later
remove the added dynid.  One use case is management tools that want to
dynamically bind/unbind devices to pci-stub driver while devices are
assigned to KVM guests.  Rather than having to track which driver was
originally bound to the driver, a mangement tool can simply:

Guest uses device

Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index e638e15a8895..3d29793a0ea2 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -41,6 +41,22 @@ Description:
                 for the device and attempt to bind to it.  For example:
                 # echo "8086 10f5" > /sys/bus/pci/drivers/foo/new_id
 
+What:           /sys/bus/pci/drivers/.../remove_id
+Date:           February 2009
+Contact:        Chris Wright <chrisw@sous-sol.org>
+Description:
+                Writing a device ID to this file will remove an ID
+                that was dynamically added via the new_id sysfs entry.
+                The format for the device ID is:
+                VVVV DDDD SVVV SDDD CCCC MMMM.  That is Vendor ID, Device
+                ID, Subsystem Vendor ID, Subsystem Device ID, Class,
+                and Class Mask.  The Vendor ID and Device ID fields are
+                required, the rest are optional.  After successfully
+                removing an ID, the driver will no longer support the
+                device.  This is useful to ensure auto probing won't
+                match the driver to the device.  For example:
+                # echo "8086 10f5" > /sys/bus/pci/drivers/foo/remove_id
+
 What:           /sys/bus/pci/devices/.../vpd
 Date:           February 2008
 Contact:        Ben Hutchings <bhutchings@solarflare.com>