projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| eaafbc3a AS |
1 | What: /sys/bus/usb/devices/.../power/autosuspend |
| 2 | Date: March 2007 | |
| 3 | KernelVersion: 2.6.21 | |
| 4 | Contact: Alan Stern <stern@rowland.harvard.edu> | |
| 5 | Description: | |
| 6 | Each USB device directory will contain a file named | |
| 7 | power/autosuspend. This file holds the time (in seconds) | |
| 8 | the device must be idle before it will be autosuspended. | |
| 9 | 0 means the device will be autosuspended as soon as | |
| 10 | possible. Negative values will prevent the device from | |
| 11 | being autosuspended at all, and writing a negative value | |
| 12 | will resume the device if it is already suspended. | |
| 13 | ||
| 14 | The autosuspend delay for newly-created devices is set to | |
| 15 | the value of the usbcore.autosuspend module parameter. | |
| 2add5229 AS |
16 | |
| 17 | What: /sys/bus/usb/devices/.../power/level | |
| 18 | Date: March 2007 | |
| 19 | KernelVersion: 2.6.21 | |
| 20 | Contact: Alan Stern <stern@rowland.harvard.edu> | |
| 21 | Description: | |
| 22 | Each USB device directory will contain a file named | |
| 23 | power/level. This file holds a power-level setting for | |
| 24 | the device, one of "on", "auto", or "suspend". | |
| 25 | ||
| 26 | "on" means that the device is not allowed to autosuspend, | |
| 27 | although normal suspends for system sleep will still | |
| 28 | be honored. "auto" means the device will autosuspend | |
| 29 | and autoresume in the usual manner, according to the | |
| 30 | capabilities of its driver. "suspend" means the device | |
| 31 | is forced into a suspended state and it will not autoresume | |
| 32 | in response to I/O requests. However remote-wakeup requests | |
| 33 | from the device may still be enabled (the remote-wakeup | |
| 34 | setting is controlled separately by the power/wakeup | |
| 35 | attribute). | |
| 36 | ||
| 37 | During normal use, devices should be left in the "auto" | |
| 38 | level. The other levels are meant for administrative uses. | |
| 39 | If you want to suspend a device immediately but leave it | |
| 40 | free to wake up in response to I/O requests, you should | |
| 41 | write "0" to power/autosuspend. | |
| b41a60ec AS |
42 | |
| 43 | What: /sys/bus/usb/devices/.../power/persist | |
| 44 | Date: May 2007 | |
| 45 | KernelVersion: 2.6.23 | |
| 46 | Contact: Alan Stern <stern@rowland.harvard.edu> | |
| 47 | Description: | |
| 48 | If CONFIG_USB_PERSIST is set, then each USB device directory | |
| 49 | will contain a file named power/persist. The file holds a | |
| 50 | boolean value (0 or 1) indicating whether or not the | |
| 51 | "USB-Persist" facility is enabled for the device. Since the | |
| 52 | facility is inherently dangerous, it is disabled by default | |
| 53 | for all devices except hubs. For more information, see | |
| 54 | Documentation/usb/persist.txt. | |
| 979e524a SS |
55 | |
| 56 | What: /sys/bus/usb/device/.../power/connected_duration | |
| 57 | Date: January 2008 | |
| 58 | KernelVersion: 2.6.25 | |
| 59 | Contact: Sarah Sharp <sarah.a.sharp@intel.com> | |
| 60 | Description: | |
| 61 | If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file | |
| 62 | is present. When read, it returns the total time (in msec) | |
| 63 | that the USB device has been connected to the machine. This | |
| 64 | file is read-only. | |
| 65 | Users: | |
| 66 | PowerTOP <power@bughost.org> | |
| 67 | http://www.lesswatts.org/projects/powertop/ | |
| 68 | ||
| 69 | What: /sys/bus/usb/device/.../power/active_duration | |
| 70 | Date: January 2008 | |
| 71 | KernelVersion: 2.6.25 | |
| 72 | Contact: Sarah Sharp <sarah.a.sharp@intel.com> | |
| 73 | Description: | |
| 74 | If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file | |
| 75 | is present. When read, it returns the total time (in msec) | |
| 76 | that the USB device has been active, i.e. not in a suspended | |
| 77 | state. This file is read-only. | |
| 78 | ||
| 79 | Tools can use this file and the connected_duration file to | |
| 80 | compute the percentage of time that a device has been active. | |
| 81 | For example, | |
| 82 | echo $((100 * `cat active_duration` / `cat connected_duration`)) | |
| 83 | will give an integer percentage. Note that this does not | |
| 84 | account for counter wrap. | |
| 85 | Users: | |
| 86 | PowerTOP <power@bughost.org> | |
| 87 | http://www.lesswatts.org/projects/powertop/ |