usb: interface authorization: Documentation part

[deliverable/linux.git] / Documentation / usb / authorization.txt

diff --git a/Documentation/usb/authorization.txt b/Documentation/usb/authorization.txt
index c069b6884c779ffc855133f634cf6b640a81da00..020cec5585ce17369e99baf9265a076debcaf594 100644 (file)
--- a/Documentation/usb/authorization.txt
+++ b/Documentation/usb/authorization.txt
@@ -3,6 +3,9 @@ Authorizing (or not) your USB devices to connect to the system
 
 (C) 2007 Inaky Perez-Gonzalez <inaky@linux.intel.com> Intel Corporation
 
+Interface authorization part:
+       (C) 2015 Stefan Koch <skoch@suse.de> SUSE LLC
+
 This feature allows you to control if a USB device can be used (or
 not) in a system. This feature will allow you to implement a lock-down
 of USB devices, fully controlled by user space.
@@ -90,3 +93,34 @@ etc, but you get the idea. Anybody with access to a device gadget kit
 can fake descriptors and device info. Don't trust that. You are
 welcome.
 
+
+Interface authorization
+-----------------------
+There is a similar approach to allow or deny specific USB interfaces.
+That allows to block only a subset of an USB device.
+
+Authorize an interface:
+$ echo 1 > /sys/bus/usb/devices/INTERFACE/authorized
+
+Deauthorize an interface:
+$ echo 0 > /sys/bus/usb/devices/INTERFACE/authorized
+
+The default value for new interfaces
+on a particular USB bus can be changed, too.
+
+Allow interfaces per default:
+$ echo 1 > /sys/bus/usb/devices/usbX/interface_authorized_default
+
+Deny interfaces per default:
+$ echo 0 > /sys/bus/usb/devices/usbX/interface_authorized_default
+
+Per default the interface_authorized_default bit is 1.
+So all interfaces would authorized per default.
+
+Note:
+If a deauthorized interface will be authorized so the driver probing must
+be triggered manually by writing INTERFACE to /sys/bus/usb/drivers_probe
+
+For drivers that need multiple interfaces all needed interfaces should be
+authroized first. After that the drivers should be probed.
+This avoids side effects.