xref: /openbmc/linux/Documentation/ABI/testing/sysfs-bus-usb (revision 2add5229d77a3de08015feef437653e02372162f)
1eaafbc3aSAlan SternWhat:		/sys/bus/usb/devices/.../power/autosuspend
2eaafbc3aSAlan SternDate:		March 2007
3eaafbc3aSAlan SternKernelVersion:	2.6.21
4eaafbc3aSAlan SternContact:	Alan Stern <stern@rowland.harvard.edu>
5eaafbc3aSAlan SternDescription:
6eaafbc3aSAlan Stern		Each USB device directory will contain a file named
7eaafbc3aSAlan Stern		power/autosuspend.  This file holds the time (in seconds)
8eaafbc3aSAlan Stern		the device must be idle before it will be autosuspended.
9eaafbc3aSAlan Stern		0 means the device will be autosuspended as soon as
10eaafbc3aSAlan Stern		possible.  Negative values will prevent the device from
11eaafbc3aSAlan Stern		being autosuspended at all, and writing a negative value
12eaafbc3aSAlan Stern		will resume the device if it is already suspended.
13eaafbc3aSAlan Stern
14eaafbc3aSAlan Stern		The autosuspend delay for newly-created devices is set to
15eaafbc3aSAlan Stern		the value of the usbcore.autosuspend module parameter.
16*2add5229SAlan Stern
17*2add5229SAlan SternWhat:		/sys/bus/usb/devices/.../power/level
18*2add5229SAlan SternDate:		March 2007
19*2add5229SAlan SternKernelVersion:	2.6.21
20*2add5229SAlan SternContact:	Alan Stern <stern@rowland.harvard.edu>
21*2add5229SAlan SternDescription:
22*2add5229SAlan Stern		Each USB device directory will contain a file named
23*2add5229SAlan Stern		power/level.  This file holds a power-level setting for
24*2add5229SAlan Stern		the device, one of "on", "auto", or "suspend".
25*2add5229SAlan Stern
26*2add5229SAlan Stern		"on" means that the device is not allowed to autosuspend,
27*2add5229SAlan Stern		although normal suspends for system sleep will still
28*2add5229SAlan Stern		be honored.  "auto" means the device will autosuspend
29*2add5229SAlan Stern		and autoresume in the usual manner, according to the
30*2add5229SAlan Stern		capabilities of its driver.  "suspend" means the device
31*2add5229SAlan Stern		is forced into a suspended state and it will not autoresume
32*2add5229SAlan Stern		in response to I/O requests.  However remote-wakeup requests
33*2add5229SAlan Stern		from the device may still be enabled (the remote-wakeup
34*2add5229SAlan Stern		setting is controlled separately by the power/wakeup
35*2add5229SAlan Stern		attribute).
36*2add5229SAlan Stern
37*2add5229SAlan Stern		During normal use, devices should be left in the "auto"
38*2add5229SAlan Stern		level.  The other levels are meant for administrative uses.
39*2add5229SAlan Stern		If you want to suspend a device immediately but leave it
40*2add5229SAlan Stern		free to wake up in response to I/O requests, you should
41*2add5229SAlan Stern		write "0" to power/autosuspend.
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