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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/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_RUNTIME 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 <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_RUNTIME 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 <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/.../new_id
Date: October 2011
Contact: linux-usb@vger.kernel.org
Description:
Writing a device ID to this file will attempt to
dynamically add a new device ID to a USB device driver.
This may allow the driver to support more hardware than
was included in the driver's static device ID support
table at compile time. The format for the device ID is:
idVendor idProduct bInterfaceClass.
The vendor ID and device ID fields are required, the
interface class is optional.
Upon successfully adding an ID, the driver will probe
for the device and attempt to bind to it. For example:
# echo "8086 10f5" > /sys/bus/usb/drivers/foo/new_id
Reading from this file will list all dynamically added
device IDs in the same format, with one entry per
line. For example:
# cat /sys/bus/usb/drivers/foo/new_id
8086 10f5
dead beef 06
f00d cafe
The list will be truncated at PAGE_SIZE bytes due to
sysfs restrictions.
What: /sys/bus/usb-serial/drivers/.../new_id
Date: October 2011
Contact: linux-usb@vger.kernel.org
Description:
For serial USB drivers, this attribute appears under the
extra bus folder "usb-serial" in sysfs; apart from that
difference, all descriptions from the entry
"/sys/bus/usb/drivers/.../new_id" apply.
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
Reading from this file will list the dynamically added
device IDs, exactly like reading from the entry
"/sys/bus/usb/drivers/.../new_id"
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/.../power/usb2_hardware_lpm
Date: September 2011
Contact: Andiry Xu <andiry.xu@amd.com>
Description:
If CONFIG_PM_RUNTIME is set and a USB 2.0 lpm-capable device
is plugged in to a xHCI host which support link PM, it will
perform a LPM test; if the test is passed and host supports
USB2 hardware LPM (xHCI 1.0 feature), USB2 hardware LPM will
be enabled for the device and the USB device directory will
contain a file named power/usb2_hardware_lpm. The file holds
a string value (enable or disable) indicating whether or not
USB2 hardware LPM is enabled for the device. Developer can
write y/Y/1 or n/N/0 to the file to enable/disable the
feature.
What: /sys/bus/usb/devices/.../removable
Date: February 2012
Contact: Matthew Garrett <mjg@redhat.com>
Description:
Some information about whether a given USB device is
physically fixed to the platform can be inferred from a
combination of hub descriptor bits and platform-specific data
such as ACPI. This file will read either "removable" or
"fixed" if the information is available, and "unknown"
otherwise.
What: /sys/bus/usb/devices/.../ltm_capable
Date: July 2012
Contact: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Description:
USB 3.0 devices may optionally support Latency Tolerance
Messaging (LTM). They indicate their support by setting a bit
in the bmAttributes field of their SuperSpeed BOS descriptors.
If that bit is set for the device, ltm_capable will read "yes".
If the device doesn't support LTM, the file will read "no".
The file will be present for all speeds of USB devices, and will
always read "no" for USB 1.1 and USB 2.0 devices.
What: /sys/bus/usb/devices/.../(hub interface)/portX
Date: August 2012
Contact: Lan Tianyu <tianyu.lan@intel.com>
Description:
The /sys/bus/usb/devices/.../(hub interface)/portX
is usb port device's sysfs directory.
What: /sys/bus/usb/devices/.../(hub interface)/portX/connect_type
Date: January 2013
Contact: Lan Tianyu <tianyu.lan@intel.com>
Description:
Some platforms provide usb port connect types through ACPI.
This attribute is to expose these information to user space.
The file will read "hotplug", "wired" and "not used" if the
information is available, and "unknown" otherwise.
What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
USB 2.0 devices may support hardware link power management (LPM)
L1 sleep state. The usb2_lpm_l1_timeout attribute allows
tuning the timeout for L1 inactivity timer (LPM timer), e.g.
needed inactivity time before host requests the device to go to L1 sleep.
Useful for power management tuning.
Supported values are 0 - 65535 microseconds.
What: /sys/bus/usb/devices/.../power/usb2_lpm_besl
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>
Description:
USB 2.0 devices that support hardware link power management (LPM)
L1 sleep state now use a best effort service latency value (BESL) to
indicate the best effort to resumption of service to the device after the
initiation of the resume event.
If the device does not have a preferred besl value then the host can select
one instead. This usb2_lpm_besl attribute allows to tune the host selected besl
value in order to tune power saving and service latency.
Supported values are 0 - 15.
More information on how besl values map to microseconds can be found in
USB 2.0 ECN Errata for Link Power Management, section 4.10)
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