@@ -244,17 +244,25 @@
#
# Mapping information from a virtual block range to a host file range
#
-# @start: the start byte of the mapped virtual range
+# @start: virtual (guest) offset of the first byte described by this
+# entry
#
# @length: the number of bytes of the mapped virtual range
#
-# @data: whether the mapped range has data
+# @data: reading the image will actually read data from a file (in
+# particular, if @offset is present this means that the sectors
+# are not simply preallocated, but contain actual data in raw
+# format)
#
-# @zero: whether the virtual blocks are zeroed
+# @zero: whether the virtual blocks read as zeroes
#
-# @depth: the depth of the mapping
+# @depth: number of layers (0 = top image, 1 = top image's backing
+# file, ..., n - 1 = bottom image (where n is the number of
+# images in the chain)) before reaching one for which the
+# range is allocated
#
-# @offset: the offset in file that the virtual sectors are mapped to
+# @offset: if present, the image file stores the data for this range
+# in raw format at the given (host) offset
#
# @filename: filename that is referred to by @offset
#