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| 1 | +What: /sys/bus/usb/devices/.../power/persist |
| 2 | +Date: May 2007 |
| 3 | +KernelVersion: 2.6.23 |
| 4 | +Contact: Alan Stern <stern@rowland.harvard.edu> |
| 5 | +Description: |
| 6 | + If CONFIG_USB_PERSIST is set, then each USB device directory |
| 7 | + will contain a file named power/persist. The file holds a |
| 8 | + boolean value (0 or 1) indicating whether or not the |
| 9 | + "USB-Persist" facility is enabled for the device. Since the |
| 10 | + facility is inherently dangerous, it is disabled by default |
| 11 | + for all devices except hubs. For more information, see |
| 12 | + Documentation/usb/persist.txt. |
| 13 | + |
| 14 | +What: /sys/bus/usb/devices/.../power/autosuspend |
| 15 | +Date: March 2007 |
| 16 | +KernelVersion: 2.6.21 |
| 17 | +Contact: Alan Stern <stern@rowland.harvard.edu> |
| 18 | +Description: |
| 19 | + Each USB device directory will contain a file named |
| 20 | + power/autosuspend. This file holds the time (in seconds) |
| 21 | + the device must be idle before it will be autosuspended. |
| 22 | + 0 means the device will be autosuspended as soon as |
| 23 | + possible. Negative values will prevent the device from |
| 24 | + being autosuspended at all, and writing a negative value |
| 25 | + will resume the device if it is already suspended. |
| 26 | + |
| 27 | + The autosuspend delay for newly-created devices is set to |
| 28 | + the value of the usbcore.autosuspend module parameter. |
| 29 | + |
| 30 | +What: /sys/bus/usb/device/.../power/connected_duration |
| 31 | +Date: January 2008 |
| 32 | +KernelVersion: 2.6.25 |
| 33 | +Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| 34 | +Description: |
| 35 | + If CONFIG_PM_RUNTIME is enabled then this file |
| 36 | + is present. When read, it returns the total time (in msec) |
| 37 | + that the USB device has been connected to the machine. This |
| 38 | + file is read-only. |
| 39 | +Users: |
| 40 | + PowerTOP <power@bughost.org> |
| 41 | + http://www.lesswatts.org/projects/powertop/ |
| 42 | + |
| 43 | +What: /sys/bus/usb/device/.../power/active_duration |
| 44 | +Date: January 2008 |
| 45 | +KernelVersion: 2.6.25 |
| 46 | +Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| 47 | +Description: |
| 48 | + If CONFIG_PM_RUNTIME is enabled then this file |
| 49 | + is present. When read, it returns the total time (in msec) |
| 50 | + that the USB device has been active, i.e. not in a suspended |
| 51 | + state. This file is read-only. |
| 52 | + |
| 53 | + Tools can use this file and the connected_duration file to |
| 54 | + compute the percentage of time that a device has been active. |
| 55 | + For example, |
| 56 | + echo $((100 * `cat active_duration` / `cat connected_duration`)) |
| 57 | + will give an integer percentage. Note that this does not |
| 58 | + account for counter wrap. |
| 59 | +Users: |
| 60 | + PowerTOP <power@bughost.org> |
| 61 | + http://www.lesswatts.org/projects/powertop/ |
| 62 | + |
| 63 | +What: /sys/bus/usb/devices/<busnum>-<port[.port]>...:<config num>-<interface num>/supports_autosuspend |
| 64 | +Date: January 2008 |
| 65 | +KernelVersion: 2.6.27 |
| 66 | +Contact: Sarah Sharp <sarah.a.sharp@intel.com> |
| 67 | +Description: |
| 68 | + When read, this file returns 1 if the interface driver |
| 69 | + for this interface supports autosuspend. It also |
| 70 | + returns 1 if no driver has claimed this interface, as an |
| 71 | + unclaimed interface will not stop the device from being |
| 72 | + autosuspended if all other interface drivers are idle. |
| 73 | + The file returns 0 if autosuspend support has not been |
| 74 | + added to the driver. |
| 75 | +Users: |
| 76 | + USB PM tool |
| 77 | + git://git.moblin.org/users/sarah/usb-pm-tool/ |
| 78 | + |
| 79 | +What: /sys/bus/usb/device/.../avoid_reset_quirk |
| 80 | +Date: December 2009 |
| 81 | +Contact: Oliver Neukum <oliver@neukum.org> |
| 82 | +Description: |
| 83 | + Writing 1 to this file tells the kernel that this |
| 84 | + device will morph into another mode when it is reset. |
| 85 | + Drivers will not use reset for error handling for |
| 86 | + such devices. |
| 87 | +Users: |
| 88 | + usb_modeswitch |
| 89 | + |
| 90 | +What: /sys/bus/usb/devices/.../devnum |
| 91 | +KernelVersion: since at least 2.6.18 |
| 92 | +Description: |
| 93 | + Device address on the USB bus. |
| 94 | +Users: |
| 95 | + libusb |
| 96 | + |
| 97 | +What: /sys/bus/usb/devices/.../bConfigurationValue |
| 98 | +KernelVersion: since at least 2.6.18 |
| 99 | +Description: |
| 100 | + bConfigurationValue of the *active* configuration for the |
| 101 | + device. Writing 0 or -1 to bConfigurationValue will reset the |
| 102 | + active configuration (unconfigure the device). Writing |
| 103 | + another value will change the active configuration. |
| 104 | + |
| 105 | + Note that some devices, in violation of the USB spec, have a |
| 106 | + configuration with a value equal to 0. Writing 0 to |
| 107 | + bConfigurationValue for these devices will install that |
| 108 | + configuration, rather then unconfigure the device. |
| 109 | + |
| 110 | + Writing -1 will always unconfigure the device. |
| 111 | +Users: |
| 112 | + libusb |
| 113 | + |
| 114 | +What: /sys/bus/usb/devices/.../busnum |
| 115 | +KernelVersion: 2.6.22 |
| 116 | +Description: |
| 117 | + Bus-number of the USB-bus the device is connected to. |
| 118 | +Users: |
| 119 | + libusb |
| 120 | + |
| 121 | +What: /sys/bus/usb/devices/.../descriptors |
| 122 | +KernelVersion: 2.6.26 |
| 123 | +Description: |
| 124 | + Binary file containing cached descriptors of the device. The |
| 125 | + binary data consists of the device descriptor followed by the |
| 126 | + descriptors for each configuration of the device. |
| 127 | + Note that the wTotalLength of the config descriptors can not |
| 128 | + be trusted, as the device may have a smaller config descriptor |
| 129 | + than it advertises. The bLength field of each (sub) descriptor |
| 130 | + can be trusted, and can be used to seek forward one (sub) |
| 131 | + descriptor at a time until the next config descriptor is found. |
| 132 | + All descriptors read from this file are in bus-endian format |
| 133 | +Users: |
| 134 | + libusb |
| 135 | + |
| 136 | +What: /sys/bus/usb/devices/.../speed |
| 137 | +KernelVersion: since at least 2.6.18 |
| 138 | +Description: |
| 139 | + Speed the device is connected with to the usb-host in |
| 140 | + Mbit / second. IE one of 1.5 / 12 / 480 / 5000. |
| 141 | +Users: |
| 142 | + libusb |
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