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-rw-r--r--Documentation/ABI/testing/sysfs-bus-usb26
1 files changed, 26 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index 00a84326325f..f9937add033d 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -13,3 +13,29 @@ Description:
13 13
14 The autosuspend delay for newly-created devices is set to 14 The autosuspend delay for newly-created devices is set to
15 the value of the usbcore.autosuspend module parameter. 15 the value of the usbcore.autosuspend module parameter.
16
17What: /sys/bus/usb/devices/.../power/level
18Date: March 2007
19KernelVersion: 2.6.21
20Contact: Alan Stern <stern@rowland.harvard.edu>
21Description:
22 Each USB device directory will contain a file named
23 power/level. This file holds a power-level setting for
24 the device, one of "on", "auto", or "suspend".
25
26 "on" means that the device is not allowed to autosuspend,
27 although normal suspends for system sleep will still
28 be honored. "auto" means the device will autosuspend
29 and autoresume in the usual manner, according to the
30 capabilities of its driver. "suspend" means the device
31 is forced into a suspended state and it will not autoresume
32 in response to I/O requests. However remote-wakeup requests
33 from the device may still be enabled (the remote-wakeup
34 setting is controlled separately by the power/wakeup
35 attribute).
36
37 During normal use, devices should be left in the "auto"
38 level. The other levels are meant for administrative uses.
39 If you want to suspend a device immediately but leave it
40 free to wake up in response to I/O requests, you should
41 write "0" to power/autosuspend.