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31 lines
1.3 KiB
31 lines
1.3 KiB
What: /sys/bus/usb/devices/.../power/level |
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Date: March 2007 |
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KernelVersion: 2.6.21 |
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Contact: Alan Stern <[email protected]> |
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Description: |
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Each USB device directory will contain a file named |
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power/level. This file holds a power-level setting for |
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the device, either "on" or "auto". |
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"on" means that the device is not allowed to autosuspend, |
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although normal suspends for system sleep will still |
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be honored. "auto" means the device will autosuspend |
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and autoresume in the usual manner, according to the |
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capabilities of its driver. |
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During normal use, devices should be left in the "auto" |
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level. The "on" level is meant for administrative uses. |
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If you want to suspend a device immediately but leave it |
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free to wake up in response to I/O requests, you should |
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write "0" to power/autosuspend. |
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Device not capable of proper suspend and resume should be |
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left in the "on" level. Although the USB spec requires |
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devices to support suspend/resume, many of them do not. |
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In fact so many don't that by default, the USB core |
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initializes all non-hub devices in the "on" level. Some |
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drivers may change this setting when they are bound. |
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This file is deprecated and will be removed after 2010. |
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Use the power/control file instead; it does exactly the |
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same thing.
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