| What: /sys/bus/usb/devices/.../power/autosuspend |
| 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/autosuspend. This file holds the time (in seconds) |
| the device must be idle before it will be autosuspended. |
| 0 means the device will be autosuspended as soon as |
| possible. Negative values will prevent the device from |
| being autosuspended at all, and writing a negative value |
| will resume the device if it is already suspended. |
| |
| The autosuspend delay for newly-created devices is set to |
| the value of the usbcore.autosuspend module parameter. |
| |
| 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. |
| |
| What: /sys/bus/usb/devices/.../power/persist |
| Date: May 2007 |
| KernelVersion: 2.6.23 |
| Contact: Alan Stern <stern@rowland.harvard.edu> |
| Description: |
| If CONFIG_USB_PERSIST is set, then each USB device directory |
| will contain a file named power/persist. The file holds a |
| boolean value (0 or 1) indicating whether or not the |
| "USB-Persist" facility is enabled for the device. Since the |
| facility is inherently dangerous, it is disabled by default |
| for all devices except hubs. For more information, see |
| Documentation/usb/persist.txt. |
| |
| What: /sys/bus/usb/device/.../power/connected_duration |
| Date: January 2008 |
| KernelVersion: 2.6.25 |
| Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| Description: |
| If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file |
| is present. When read, it returns the total time (in msec) |
| that the USB device has been connected to the machine. This |
| file is read-only. |
| Users: |
| PowerTOP <power@bughost.org> |
| http://www.lesswatts.org/projects/powertop/ |
| |
| What: /sys/bus/usb/device/.../power/active_duration |
| Date: January 2008 |
| KernelVersion: 2.6.25 |
| Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| Description: |
| If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file |
| is present. When read, it returns the total time (in msec) |
| that the USB device has been active, i.e. not in a suspended |
| state. This file is read-only. |
| |
| Tools can use this file and the connected_duration file to |
| compute the percentage of time that a device has been active. |
| For example, |
| echo $((100 * `cat active_duration` / `cat connected_duration`)) |
| will give an integer percentage. Note that this does not |
| account for counter wrap. |
| Users: |
| PowerTOP <power@bughost.org> |
| http://www.lesswatts.org/projects/powertop/ |
| |
| What: /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend |
| Date: January 2008 |
| KernelVersion: 2.6.27 |
| Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| Description: |
| When read, this file returns 1 if the interface driver |
| for this interface supports autosuspend. It also |
| returns 1 if no driver has claimed this interface, as an |
| unclaimed interface will not stop the device from being |
| autosuspended if all other interface drivers are idle. |
| The file returns 0 if autosuspend support has not been |
| added to the driver. |
| Users: |
| USB PM tool |
| git://git.moblin.org/users/sarah/usb-pm-tool/ |
| |
| What: /sys/bus/usb/device/.../authorized |
| Date: July 2008 |
| KernelVersion: 2.6.26 |
| Contact: David Vrabel <david.vrabel@csr.com> |
| Description: |
| Authorized devices are available for use by device |
| drivers, non-authorized one are not. By default, wired |
| USB devices are authorized. |
| |
| Certified Wireless USB devices are not authorized |
| initially and should be (by writing 1) after the |
| device has been authenticated. |
| |
| What: /sys/bus/usb/device/.../wusb_cdid |
| Date: July 2008 |
| KernelVersion: 2.6.27 |
| Contact: David Vrabel <david.vrabel@csr.com> |
| Description: |
| For Certified Wireless USB devices only. |
| |
| A devices's CDID, as 16 space-separated hex octets. |
| |
| What: /sys/bus/usb/device/.../wusb_ck |
| Date: July 2008 |
| KernelVersion: 2.6.27 |
| Contact: David Vrabel <david.vrabel@csr.com> |
| Description: |
| For Certified Wireless USB devices only. |
| |
| Write the device's connection key (CK) to start the |
| authentication of the device. The CK is 16 |
| space-separated hex octets. |
| |
| What: /sys/bus/usb/device/.../wusb_disconnect |
| Date: July 2008 |
| KernelVersion: 2.6.27 |
| Contact: David Vrabel <david.vrabel@csr.com> |
| Description: |
| For Certified Wireless USB devices only. |
| |
| Write a 1 to force the device to disconnect |
| (equivalent to unplugging a wired USB device). |
| |
| What: /sys/bus/usb/drivers/.../remove_id |
| Date: November 2009 |
| Contact: CHENG Renquan <rqcheng@smu.edu.sg> |
| Description: |
| Writing a device ID to this file will remove an ID |
| that was dynamically added via the new_id sysfs entry. |
| The format for the device ID is: |
| idVendor idProduct. After successfully |
| removing an ID, the driver will no longer support the |
| device. This is useful to ensure auto probing won't |
| match the driver to the device. For example: |
| # echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id |
| |
| What: /sys/bus/usb/device/.../avoid_reset |
| Date: December 2009 |
| Contact: Oliver Neukum <oliver@neukum.org> |
| Description: |
| Writing 1 to this file tells the kernel that this |
| device will morph into another mode when it is reset. |
| Drivers will not use reset for error handling for |
| such devices. |
| Users: |
| usb_modeswitch |
