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USB 3.0 devices can optionally support Latency Tolerance Messaging (LTM). Add a new sysfs file in the device directory to show whether a device is LTM capable. This file will be present for both USB 2.0 and USB 3.0 devices. Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
223 lines
8.1 KiB
Plaintext
223 lines
8.1 KiB
Plaintext
What: /sys/bus/usb/devices/.../power/autosuspend
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Date: March 2007
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KernelVersion: 2.6.21
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Contact: Alan Stern <stern@rowland.harvard.edu>
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Description:
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Each USB device directory will contain a file named
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power/autosuspend. This file holds the time (in seconds)
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the device must be idle before it will be autosuspended.
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0 means the device will be autosuspended as soon as
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possible. Negative values will prevent the device from
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being autosuspended at all, and writing a negative value
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will resume the device if it is already suspended.
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The autosuspend delay for newly-created devices is set to
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the value of the usbcore.autosuspend module parameter.
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What: /sys/bus/usb/devices/.../power/persist
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Date: May 2007
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KernelVersion: 2.6.23
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Contact: Alan Stern <stern@rowland.harvard.edu>
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Description:
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If CONFIG_USB_PERSIST is set, then each USB device directory
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will contain a file named power/persist. The file holds a
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boolean value (0 or 1) indicating whether or not the
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"USB-Persist" facility is enabled for the device. Since the
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facility is inherently dangerous, it is disabled by default
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for all devices except hubs. For more information, see
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Documentation/usb/persist.txt.
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What: /sys/bus/usb/device/.../power/connected_duration
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Date: January 2008
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KernelVersion: 2.6.25
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Contact: Sarah Sharp <sarah.a.sharp@intel.com>
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Description:
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If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
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is present. When read, it returns the total time (in msec)
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that the USB device has been connected to the machine. This
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file is read-only.
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Users:
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PowerTOP <power@bughost.org>
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http://www.lesswatts.org/projects/powertop/
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What: /sys/bus/usb/device/.../power/active_duration
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Date: January 2008
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KernelVersion: 2.6.25
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Contact: Sarah Sharp <sarah.a.sharp@intel.com>
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Description:
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If CONFIG_PM and CONFIG_USB_SUSPEND are enabled, then this file
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is present. When read, it returns the total time (in msec)
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that the USB device has been active, i.e. not in a suspended
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state. This file is read-only.
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Tools can use this file and the connected_duration file to
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compute the percentage of time that a device has been active.
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For example,
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echo $((100 * `cat active_duration` / `cat connected_duration`))
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will give an integer percentage. Note that this does not
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account for counter wrap.
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Users:
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PowerTOP <power@bughost.org>
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http://www.lesswatts.org/projects/powertop/
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What: /sys/bus/usb/device/<busnum>-<devnum>...:<config num>-<interface num>/supports_autosuspend
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Date: January 2008
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KernelVersion: 2.6.27
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Contact: Sarah Sharp <sarah.a.sharp@intel.com>
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Description:
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When read, this file returns 1 if the interface driver
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for this interface supports autosuspend. It also
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returns 1 if no driver has claimed this interface, as an
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unclaimed interface will not stop the device from being
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autosuspended if all other interface drivers are idle.
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The file returns 0 if autosuspend support has not been
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added to the driver.
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Users:
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USB PM tool
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git://git.moblin.org/users/sarah/usb-pm-tool/
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What: /sys/bus/usb/device/.../authorized
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Date: July 2008
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KernelVersion: 2.6.26
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Contact: David Vrabel <david.vrabel@csr.com>
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Description:
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Authorized devices are available for use by device
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drivers, non-authorized one are not. By default, wired
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USB devices are authorized.
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Certified Wireless USB devices are not authorized
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initially and should be (by writing 1) after the
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device has been authenticated.
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What: /sys/bus/usb/device/.../wusb_cdid
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Date: July 2008
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KernelVersion: 2.6.27
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Contact: David Vrabel <david.vrabel@csr.com>
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Description:
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For Certified Wireless USB devices only.
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A devices's CDID, as 16 space-separated hex octets.
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What: /sys/bus/usb/device/.../wusb_ck
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Date: July 2008
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KernelVersion: 2.6.27
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Contact: David Vrabel <david.vrabel@csr.com>
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Description:
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For Certified Wireless USB devices only.
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Write the device's connection key (CK) to start the
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authentication of the device. The CK is 16
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space-separated hex octets.
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What: /sys/bus/usb/device/.../wusb_disconnect
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Date: July 2008
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KernelVersion: 2.6.27
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Contact: David Vrabel <david.vrabel@csr.com>
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Description:
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For Certified Wireless USB devices only.
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Write a 1 to force the device to disconnect
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(equivalent to unplugging a wired USB device).
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What: /sys/bus/usb/drivers/.../new_id
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Date: October 2011
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Contact: linux-usb@vger.kernel.org
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Description:
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Writing a device ID to this file will attempt to
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dynamically add a new device ID to a USB device driver.
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This may allow the driver to support more hardware than
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was included in the driver's static device ID support
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table at compile time. The format for the device ID is:
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idVendor idProduct bInterfaceClass.
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The vendor ID and device ID fields are required, the
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interface class is optional.
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Upon successfully adding an ID, the driver will probe
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for the device and attempt to bind to it. For example:
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# echo "8086 10f5" > /sys/bus/usb/drivers/foo/new_id
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Reading from this file will list all dynamically added
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device IDs in the same format, with one entry per
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line. For example:
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# cat /sys/bus/usb/drivers/foo/new_id
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8086 10f5
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dead beef 06
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f00d cafe
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The list will be truncated at PAGE_SIZE bytes due to
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sysfs restrictions.
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What: /sys/bus/usb-serial/drivers/.../new_id
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Date: October 2011
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Contact: linux-usb@vger.kernel.org
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Description:
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For serial USB drivers, this attribute appears under the
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extra bus folder "usb-serial" in sysfs; apart from that
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difference, all descriptions from the entry
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"/sys/bus/usb/drivers/.../new_id" apply.
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What: /sys/bus/usb/drivers/.../remove_id
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Date: November 2009
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Contact: CHENG Renquan <rqcheng@smu.edu.sg>
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Description:
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Writing a device ID to this file will remove an ID
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that was dynamically added via the new_id sysfs entry.
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The format for the device ID is:
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idVendor idProduct. After successfully
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removing an ID, the driver will no longer support the
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device. This is useful to ensure auto probing won't
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match the driver to the device. For example:
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# echo "046d c315" > /sys/bus/usb/drivers/foo/remove_id
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Reading from this file will list the dynamically added
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device IDs, exactly like reading from the entry
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"/sys/bus/usb/drivers/.../new_id"
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What: /sys/bus/usb/device/.../avoid_reset_quirk
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Date: December 2009
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Contact: Oliver Neukum <oliver@neukum.org>
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Description:
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Writing 1 to this file tells the kernel that this
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device will morph into another mode when it is reset.
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Drivers will not use reset for error handling for
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such devices.
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Users:
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usb_modeswitch
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What: /sys/bus/usb/devices/.../power/usb2_hardware_lpm
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Date: September 2011
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Contact: Andiry Xu <andiry.xu@amd.com>
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Description:
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If CONFIG_USB_SUSPEND is set and a USB 2.0 lpm-capable device
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is plugged in to a xHCI host which support link PM, it will
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perform a LPM test; if the test is passed and host supports
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USB2 hardware LPM (xHCI 1.0 feature), USB2 hardware LPM will
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be enabled for the device and the USB device directory will
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contain a file named power/usb2_hardware_lpm. The file holds
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a string value (enable or disable) indicating whether or not
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USB2 hardware LPM is enabled for the device. Developer can
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write y/Y/1 or n/N/0 to the file to enable/disable the
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feature.
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What: /sys/bus/usb/devices/.../removable
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Date: February 2012
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Contact: Matthew Garrett <mjg@redhat.com>
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Description:
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Some information about whether a given USB device is
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physically fixed to the platform can be inferred from a
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combination of hub descriptor bits and platform-specific data
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such as ACPI. This file will read either "removable" or
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"fixed" if the information is available, and "unknown"
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otherwise.
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What: /sys/bus/usb/devices/.../ltm_capable
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Date: July 2012
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Contact: Sarah Sharp <sarah.a.sharp@linux.intel.com>
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Description:
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USB 3.0 devices may optionally support Latency Tolerance
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Messaging (LTM). They indicate their support by setting a bit
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in the bmAttributes field of their SuperSpeed BOS descriptors.
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If that bit is set for the device, ltm_capable will read "yes".
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If the device doesn't support LTM, the file will read "no".
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The file will be present for all speeds of USB devices, and will
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always read "no" for USB 1.1 and USB 2.0 devices.
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