lib.h: Add missing documentation of FILE argument to `device_size'.

diff --git a/lib.h b/lib.h
index e9abbaa..553a5fe 100644 (file)
--- a/lib.h
+++ b/lib.h
@@ -235,7 +235,7 @@ extern off_t device_size(int fd, const char *file, int *blksz_out);
         * device only, store the block size in *BLKSZ_OUT.  (Hence,
         * *BLKSZ_OUT will be left unchanged if FD is open on a regular
         * file.)  If FD refers to any other kind of object then report a
-        * fatal error.
+        * fatal error quoting FILE as the name of the device.
         */
 
 /*----- Progress utilities ------------------------------------------------*/