text: #
  # Copyright (c) 2005 XenSource Ltd.
  #
  # This library is free software; you can redistribute it and/or
  # modify it under the terms of version 2.1 of the GNU Lesser General Public
  # License as published by the Free Software Foundation.
  #
  # This library is distributed in the hope that it will be useful,
  # but WITHOUT ANY WARRANTY; without even the implied warranty of
  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  # Lesser General Public License for more details.
  #
  # You should have received a copy of the GNU Lesser General Public
  # License along with this library; If not, see <http://www.gnu.org/licenses/>.
  #
  
  
  dir=$(dirname "$0")
  . "$dir/xen-hotplug-common.sh"
  
  findCommand "$@"
  
  if [ "$command" != "add" ] &&
     [ "$command" != "remove" ]
  then
    log err "Invalid command: $command"
    exit 1
  fi
  
  
  XENBUS_PATH="${XENBUS_PATH:?}"
  
  
  ebusy()
  {
    xenstore_write "$XENBUS_PATH/hotplug-error" "$*" \
                   "$XENBUS_PATH/hotplug-status" busy
    log err "$@"
    exit 1
  }
  
  
  ##
  # Print the given device's major and minor numbers, written in hex and
  # separated by a colon.
  device_major_minor()
  {
    stat -L -c %t:%T "$1"
  }
  
  
  ##
  # Write physical-device = MM,mm to the store, where MM and mm are the major 
  # and minor numbers of device respectively.
  #
  # @param device The device from which major and minor numbers are read, which
  #               will be written into the store.
  #
  write_dev() {
    local mm
    
    mm=$(device_major_minor "$1")
   
    if [ -z $mm ]
    then
      fatal "Backend device does not exist"
    fi
   
    xenstore_write "$XENBUS_PATH/physical-device" "$mm"
    xenstore_write "$XENBUS_PATH/physical-device-path" "$1"
    
    success
  }
  
  
  ##
  # canonicalise_mode mode
  #
  # Takes the given mode, which may be r, w, ro, rw, w!, or rw!, or variations
  # thereof, and canonicalises them to one of
  #
  #   'r': perform checks for a new read-only mount;
  #   'w': perform checks for a read-write mount; or
  #   '!': perform no checks at all.
  #
  canonicalise_mode()
  {
    local mode="$1"
  
    if ! expr index "$mode" 'w' >/dev/null
    then
      echo 'r'
    elif ! expr index "$mode" '!' >/dev/null
    then
      echo 'w'
    else
      echo '!'
    fi
  }
  
  
  same_vm()
  {
    local otherdom="$1"
    # Note that othervm can be MISSING here, because Xend will be racing with
    # the hotplug scripts -- the entries in /local/domain can be removed by
    # Xend before the hotplug scripts have removed the entry in
    # /local/domain/0/backend/.  In this case, we want to pretend that the
    # VM is the same as FRONTEND_UUID, because that way the 'sharing' will be
    # allowed.
    local othervm=$(xenstore_read_default "/local/domain/$otherdom/vm"         \
                    "$FRONTEND_UUID")
    local target=$(xenstore_read_default  "/local/domain/$FRONTEND_ID/target"   \
                   "-1")
    local targetvm=$(xenstore_read_default "/local/domain/$target/vm" "-1")
    local otarget=$(xenstore_read_default  "/local/domain/$otherdom/target"   \
                   "-1")
    local otvm=$(xenstore_read_default  "/local/domain/$otarget/vm"   \
                   "-1")
    otvm=${otvm%-1}
    othervm=${othervm%-1}
    targetvm=${targetvm%-1}
    local frontend_uuid=${FRONTEND_UUID%-1}
    
    [ "$frontend_uuid" = "$othervm" -o "$targetvm" = "$othervm" -o \
      "$frontend_uuid" = "$otvm" -o "$targetvm" = "$otvm" ]
  }
  
  