- toggles whether @dfn{discard} (also known as @dfn{trim} or @dfn{unmap})
- requests are ignored or passed to the filesystem. The default is no
- (@samp{--discard=ignore}).
+Control whether @dfn{discard} (also known as @dfn{trim} or @dfn{unmap})
+requests are ignored or passed to the filesystem. @var{discard} is one of
+@samp{ignore} (or @samp{off}), @samp{unmap} (or @samp{on}). The default is
+@samp{ignore}.
+@item --detect-zeroes=@var{detect-zeroes}
+Control the automatic conversion of plain zero writes by the OS to
+driver-specific optimized zero write commands. @var{detect-zeroes} is one of
+@samp{off}, @samp{on} or @samp{unmap}. @samp{unmap}
+converts a zero write to an unmap operation and can only be used if
+@var{discard} is set to @samp{unmap}. The default is @samp{off}.