diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2009-12-08 15:49:48 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2009-12-23 11:34:09 -0800 |
| commit | baf67741bf52b985e318bed3c4acadcda5351e08 (patch) | |
| tree | 3f80d00eaf81b1a547b0bc2c55c14cdcd1f5bc0d /Documentation/ABI/testing/sysfs-bus-usb | |
| parent | f42ecb2808db5386f983d593a7c08d3ea3b94a27 (diff) | |
USB: power management documentation update
This patch (as1313) updates the documentation concerning USB power
management.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'Documentation/ABI/testing/sysfs-bus-usb')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-bus-usb | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb index deb6b489e4e5..a07c0f366f91 100644 --- a/Documentation/ABI/testing/sysfs-bus-usb +++ b/Documentation/ABI/testing/sysfs-bus-usb @@ -21,25 +21,27 @@ Contact: Alan Stern <stern@rowland.harvard.edu> Description: 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". + the device, either "on" or "auto". "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). + capabilities of its driver. During normal use, devices should be left in the "auto" - level. The other levels are meant for administrative uses. + level. The "on" level is 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. + Device not capable of proper suspend and resume should be + left in the "on" level. Although the USB spec requires + devices to support suspend/resume, many of them do not. + In fact so many don't that by default, the USB core + initializes all non-hub devices in the "on" level. Some + drivers may change this setting when they are bound. + What: /sys/bus/usb/devices/.../power/persist Date: May 2007 KernelVersion: 2.6.23 |