split kernel module api docs to README

rootfs_overlay/dep.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+set -e
+f=/sys/kernel/debug/lkmc_dep
+f2=/sys/kernel/debug/lkmc_dep2
+
+insmod /dep.ko
+insmod /dep2.ko
+
+# Initial value.
+[ "$(cat "$f")" = 0 ]
+
+# Changhing dep2 also changes dep.
+printf 1 > "$f2"
+[ "$(cat "$f")" = 1 ]
+
+# Changhing dep also changes dep2.
+printf 2 > "$f"
+[ "$(cat "$f2")" = 2 ]
+
+# sysfs shows us that the module has dependants.
+[ "$(cat /sys/module/dep/refcnt)" = 1 ]
+[ "$(ls /sys/module/dep/holders)" = dep2 ]
+rmmod /dep2.ko
+[ "$(cat /sys/module/dep/refcnt)" = 0 ]
+[ -z "$(ls /sys/module/dep/holders)" ]
+
+rmmod /dep.ko