| Alan Stern | eaafbc3 | 2007-03-13 16:39:15 -0400 | [diff] [blame] | 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. |
| Alan Stern | 2add522 | 2007-03-20 14:59:39 -0400 | [diff] [blame] | 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. |
| Alan Stern | b41a60e | 2007-05-30 15:39:33 -0400 | [diff] [blame] | 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. |
| Sarah Sharp | 979e524 | 2008-01-17 10:24:38 -0800 | [diff] [blame] | 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/ |