linux/Documentation/device-mapper/dm-uevent.txt
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   1The device-mapper uevent code adds the capability to device-mapper to create
   2and send kobject uevents (uevents).  Previously device-mapper events were only
   3available through the ioctl interface.  The advantage of the uevents interface
   4is the event contains environment attributes providing increased context for
   5the event avoiding the need to query the state of the device-mapper device after
   6the event is received.
   7
   8There are two functions currently for device-mapper events.  The first function
   9listed creates the event and the second function sends the event(s).
  10
  11void dm_path_uevent(enum dm_uevent_type event_type, struct dm_target *ti,
  12                    const char *path, unsigned nr_valid_paths)
  13
  14void dm_send_uevents(struct list_head *events, struct kobject *kobj)
  15
  16
  17The variables added to the uevent environment are:
  18
  19Variable Name: DM_TARGET
  20Uevent Action(s): KOBJ_CHANGE
  21Type: string
  22Description:
  23Value: Name of device-mapper target that generated the event.
  24
  25Variable Name: DM_ACTION
  26Uevent Action(s): KOBJ_CHANGE
  27Type: string
  28Description:
  29Value: Device-mapper specific action that caused the uevent action.
  30        PATH_FAILED - A path has failed.
  31        PATH_REINSTATED - A path has been reinstated.
  32
  33Variable Name: DM_SEQNUM
  34Uevent Action(s): KOBJ_CHANGE
  35Type: unsigned integer
  36Description: A sequence number for this specific device-mapper device.
  37Value: Valid unsigned integer range.
  38
  39Variable Name: DM_PATH
  40Uevent Action(s): KOBJ_CHANGE
  41Type: string
  42Description: Major and minor number of the path device pertaining to this
  43event.
  44Value: Path name in the form of "Major:Minor"
  45
  46Variable Name: DM_NR_VALID_PATHS
  47Uevent Action(s): KOBJ_CHANGE
  48Type: unsigned integer
  49Description:
  50Value: Valid unsigned integer range.
  51
  52Variable Name: DM_NAME
  53Uevent Action(s): KOBJ_CHANGE
  54Type: string
  55Description: Name of the device-mapper device.
  56Value: Name
  57
  58Variable Name: DM_UUID
  59Uevent Action(s): KOBJ_CHANGE
  60Type: string
  61Description: UUID of the device-mapper device.
  62Value: UUID. (Empty string if there isn't one.)
  63
  64An example of the uevents generated as captured by udevmonitor is shown
  65below.
  66
  671.) Path failure.
  68UEVENT[1192521009.711215] change@/block/dm-3
  69ACTION=change
  70DEVPATH=/block/dm-3
  71SUBSYSTEM=block
  72DM_TARGET=multipath
  73DM_ACTION=PATH_FAILED
  74DM_SEQNUM=1
  75DM_PATH=8:32
  76DM_NR_VALID_PATHS=0
  77DM_NAME=mpath2
  78DM_UUID=mpath-35333333000002328
  79MINOR=3
  80MAJOR=253
  81SEQNUM=1130
  82
  832.) Path reinstate.
  84UEVENT[1192521132.989927] change@/block/dm-3
  85ACTION=change
  86DEVPATH=/block/dm-3
  87SUBSYSTEM=block
  88DM_TARGET=multipath
  89DM_ACTION=PATH_REINSTATED
  90DM_SEQNUM=2
  91DM_PATH=8:32
  92DM_NR_VALID_PATHS=1
  93DM_NAME=mpath2
  94DM_UUID=mpath-35333333000002328
  95MINOR=3
  96MAJOR=253
  97SEQNUM=1131
  98
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