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Diffstat (limited to 'Documentation/ABI/obsolete/sysfs-bus-usb')
| -rw-r--r-- | Documentation/ABI/obsolete/sysfs-bus-usb | 31 |
1 files changed, 31 insertions, 0 deletions
diff --git a/Documentation/ABI/obsolete/sysfs-bus-usb b/Documentation/ABI/obsolete/sysfs-bus-usb new file mode 100644 index 00000000..bd096d33 --- /dev/null +++ b/Documentation/ABI/obsolete/sysfs-bus-usb @@ -0,0 +1,31 @@ +What: /sys/bus/usb/devices/.../power/level +Date: March 2007 +KernelVersion: 2.6.21 +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, 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. + + During normal use, devices should be left in the "auto" + 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. + + This file is deprecated and will be removed after 2010. + Use the power/control file instead; it does exactly the + same thing. |