127 lines
4.8 KiB
Plaintext
127 lines
4.8 KiB
Plaintext
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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/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/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_RUNTIME is 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_RUNTIME is 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/devices/<busnum>-<port[.port]>...:<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/.../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/.../devnum
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KernelVersion: since at least 2.6.18
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Description:
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Device address on the USB bus.
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What: /sys/bus/usb/devices/.../bConfigurationValue
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KernelVersion: since at least 2.6.18
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Description:
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bConfigurationValue of the *active* configuration for the
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device. Writing 0 or -1 to bConfigurationValue will reset the
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active configuration (unconfigure the device). Writing
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another value will change the active configuration.
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Note that some devices, in violation of the USB spec, have a
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configuration with a value equal to 0. Writing 0 to
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bConfigurationValue for these devices will install that
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configuration, rather then unconfigure the device.
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Writing -1 will always unconfigure the device.
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What: /sys/bus/usb/devices/.../busnum
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KernelVersion: 2.6.22
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Description:
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Bus-number of the USB-bus the device is connected to.
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What: /sys/bus/usb/devices/.../descriptors
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KernelVersion: 2.6.26
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Description:
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Binary file containing cached descriptors of the device. The
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binary data consists of the device descriptor followed by the
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descriptors for each configuration of the device.
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Note that the wTotalLength of the config descriptors can not
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be trusted, as the device may have a smaller config descriptor
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than it advertises. The bLength field of each (sub) descriptor
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can be trusted, and can be used to seek forward one (sub)
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descriptor at a time until the next config descriptor is found.
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All descriptors read from this file are in bus-endian format
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