path: root/Documentation
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authorAlan Stern <stern@rowland.harvard.edu>2007-03-20 14:59:39 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2007-04-27 13:28:37 -0700
commit2add5229d77a3de08015feef437653e02372162f (patch)
tree436109572453656747d6e5b3aec14939b1202ec3 /Documentation
parent13f6be01db9ada144f28241f939f4f3f8ec8e40b (diff)
USB: add power/level sysfs attribute
This patch (as874) adds another piece to the user-visible part of the USB autosuspend interface. The new power/level sysfs attribute allows users to force the device on (with autosuspend off), force the device to sleep (with autoresume off), or return to normal automatic operation. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation')
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:
The autosuspend delay for newly-created devices is set to
the value of the usbcore.autosuspend module parameter.
+What: /sys/bus/usb/devices/.../power/level
+Date: March 2007
+KernelVersion: 2.6.21
+Contact: Alan Stern <stern@rowland.harvard.edu>
+ Each USB device directory will contain a file named
+ power/level. This file holds a power-level setting for
+ the device, one of "on", "auto", or "suspend".
+ "on" means that the device is not allowed to autosuspend,
+ although normal suspends for system sleep will still
+ be honored. "auto" means the device will autosuspend
+ and autoresume in the usual manner, according to the
+ capabilities of its driver. "suspend" means the device
+ is forced into a suspended state and it will not autoresume
+ in response to I/O requests. However remote-wakeup requests
+ from the device may still be enabled (the remote-wakeup
+ setting is controlled separately by the power/wakeup
+ attribute).
+ During normal use, devices should be left in the "auto"
+ level. The other levels are meant for administrative uses.
+ If you want to suspend a device immediately but leave it
+ free to wake up in response to I/O requests, you should
+ write "0" to power/autosuspend.