diff --git a/rootdir/ueventd.rc b/rootdir/ueventd.rc
index b735dc3..6ef491c 100644
--- a/rootdir/ueventd.rc
+++ b/rootdir/ueventd.rc
@@ -1,6 +1,13 @@
 subsystem adf
 	devname uevent_devname
 
+# ueventd can only set permissions on device nodes and their associated
+# sysfs attributes, not on arbitrary paths.
+#
+# format for /dev rules: devname mode uid gid
+# format for /sys rules: nodename attr mode uid gid
+# shortcut: "mtd@NN" expands to "/dev/mtd/mtdNN"
+
 /dev/null                 0666   root       root
 /dev/zero                 0666   root       root
 /dev/full                 0666   root       root