| What: /sys/bus/usb/devices/.../power/persist |
| Date: May 2007 |
| KernelVersion: 2.6.23 |
| Contact: Alan Stern <stern@rowland.harvard.edu> |
| Description: |
| USB device directories can 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. For |
| hubs this facility is always enabled and their device |
| directories will not contain this file. |
| |
| For more information, see Documentation/driver-api/usb/persist.rst. |
| |
| 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/device/.../power/connected_duration |
| Date: January 2008 |
| KernelVersion: 2.6.25 |
| Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| Description: |
| If CONFIG_PM is 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 <powertop@lists.01.org> |
| https://01.org/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 is 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 <powertop@lists.01.org> |
| https://01.org/powertop/ |
| |
| What: /sys/bus/usb/devices/<busnum>-<port[.port]>...:<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/.../avoid_reset_quirk |
| 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 |
| |
| What: /sys/bus/usb/devices/.../devnum |
| KernelVersion: since at least 2.6.18 |
| Description: |
| Device address on the USB bus. |
| Users: |
| libusb |
| |
| What: /sys/bus/usb/devices/.../bConfigurationValue |
| KernelVersion: since at least 2.6.18 |
| Description: |
| bConfigurationValue of the *active* configuration for the |
| device. Writing 0 or -1 to bConfigurationValue will reset the |
| active configuration (unconfigure the device). Writing |
| another value will change the active configuration. |
| |
| Note that some devices, in violation of the USB spec, have a |
| configuration with a value equal to 0. Writing 0 to |
| bConfigurationValue for these devices will install that |
| configuration, rather then unconfigure the device. |
| |
| Writing -1 will always unconfigure the device. |
| Users: |
| libusb |
| |
| What: /sys/bus/usb/devices/.../busnum |
| KernelVersion: 2.6.22 |
| Description: |
| Bus-number of the USB-bus the device is connected to. |
| Users: |
| libusb |
| |
| What: /sys/bus/usb/devices/.../descriptors |
| KernelVersion: 2.6.26 |
| Description: |
| Binary file containing cached descriptors of the device. The |
| binary data consists of the device descriptor followed by the |
| descriptors for each configuration of the device. |
| Note that the wTotalLength of the config descriptors can not |
| be trusted, as the device may have a smaller config descriptor |
| than it advertises. The bLength field of each (sub) descriptor |
| can be trusted, and can be used to seek forward one (sub) |
| descriptor at a time until the next config descriptor is found. |
| All descriptors read from this file are in bus-endian format |
| Users: |
| libusb |
| |
| What: /sys/bus/usb/devices/.../speed |
| KernelVersion: since at least 2.6.18 |
| Description: |
| Speed the device is connected with to the usb-host in |
| Mbit / second. IE one of 1.5 / 12 / 480 / 5000. |
| Users: |
| libusb |
