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sysfs-bus-usb

sysfs-bus-usb 2.3 KB
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  1. What:		/sys/bus/usb/devices/.../power/autosuspend
    2. 

  2. Date:		March 2007
    3. 

  3. KernelVersion:	2.6.21
    4. 

  4. Contact:	Alan Stern <stern@rowland.harvard.edu>
    5. 

  5. Description:
    6. 

  6. 		Each USB device directory will contain a file named
    7. 

  7. 		power/autosuspend.  This file holds the time (in seconds)
    8. 

  8. 		the device must be idle before it will be autosuspended.
    9. 

  9. 		0 means the device will be autosuspended as soon as
    10. 

  10. 		possible.  Negative values will prevent the device from
    11. 

  11. 		being autosuspended at all, and writing a negative value
    12. 

  12. 		will resume the device if it is already suspended.
    13. 

  13. 

  14. 		The autosuspend delay for newly-created devices is set to
    15. 

  15. 		the value of the usbcore.autosuspend module parameter.
    16. 

  16. 

  17. What:		/sys/bus/usb/devices/.../power/level
    18. 

  18. Date:		March 2007
    19. 

  19. KernelVersion:	2.6.21
    20. 

  20. Contact:	Alan Stern <stern@rowland.harvard.edu>
    21. 

  21. Description:
    22. 

  22. 		Each USB device directory will contain a file named
    23. 

  23. 		power/level.  This file holds a power-level setting for
    24. 

  24. 		the device, one of "on", "auto", or "suspend".
    25. 

  25. 

  26. 		"on" means that the device is not allowed to autosuspend,
    27. 

  27. 		although normal suspends for system sleep will still
    28. 

  28. 		be honored.  "auto" means the device will autosuspend
    29. 

  29. 		and autoresume in the usual manner, according to the
    30. 

  30. 		capabilities of its driver.  "suspend" means the device
    31. 

  31. 		is forced into a suspended state and it will not autoresume
    32. 

  32. 		in response to I/O requests.  However remote-wakeup requests
    33. 

  33. 		from the device may still be enabled (the remote-wakeup
    34. 

  34. 		setting is controlled separately by the power/wakeup
    35. 

  35. 		attribute).
    36. 

  36. 

  37. 		During normal use, devices should be left in the "auto"
    38. 

  38. 		level.  The other levels are meant for administrative uses.
    39. 

  39. 		If you want to suspend a device immediately but leave it
    40. 

  40. 		free to wake up in response to I/O requests, you should
    41. 

  41. 		write "0" to power/autosuspend.
    42. 

  42. 

  43. What:		/sys/bus/usb/devices/.../power/persist
    44. 

  44. Date:		May 2007
    45. 

  45. KernelVersion:	2.6.23
    46. 

  46. Contact:	Alan Stern <stern@rowland.harvard.edu>
    47. 

  47. Description:
    48. 

  48. 		If CONFIG_USB_PERSIST is set, then each USB device directory
    49. 

  49. 		will contain a file named power/persist.  The file holds a
    50. 

  50. 		boolean value (0 or 1) indicating whether or not the
    51. 

  51. 		"USB-Persist" facility is enabled for the device.  Since the
    52. 

  52. 		facility is inherently dangerous, it is disabled by default
    53. 

  53. 		for all devices except hubs.  For more information, see
    54. 

  54. 		Documentation/usb/persist.txt.
    55.