get rid of lkmc package, move userland and kernel-modules to top

Rationale: we already had a non buildroot build system,
maintaining both will be hard, and having short paths is more awesome.

kernel_modules/debugfs.c

@@ -0,0 +1,67 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#debugfs */
+
+#include <linux/debugfs.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <uapi/linux/stat.h> /* S_IRUSR */
+
+static struct dentry *dir, *toplevel_file;
+static u32 value = 42;
+
+/* This basically re-implents the write operation of debugfs_create_u32,
+ * it is just an excuse to illustrate a fop. */
+static ssize_t write(struct file *filp, const char __user *buf, size_t len, loff_t *off)
+{
+	int ret;
+	unsigned long long res;
+	/* https://stackoverflow.com/questions/6139493/how-convert-char-to-int-in-linux-kernel */
+	ret = kstrtoull_from_user(buf, len, 10, &res);
+	if (ret) {
+		/* Negative error code. */
+		return ret;
+	} else {
+		value = res;
+		*off= len;
+		return len;
+	}
+}
+
+static const struct file_operations fops = {
+	.owner = THIS_MODULE,
+	.write = write,
+};
+
+static int myinit(void)
+{
+	struct dentry *file;
+	dir = debugfs_create_dir("lkmc_debugfs", 0);
+	if (!dir) {
+		pr_alert("debugfs_create_dir failed");
+		return -1;
+	}
+	file = debugfs_create_u32("myfile", S_IRUSR | S_IWUSR, dir, &value);
+	if (!file) {
+		pr_alert("debugfs_create_u32 failed");
+		return -1;
+	}
+
+	/* Created on the toplevel of the debugfs mount,
+	 * and with explicit fops instead of a fixed integer value.
+	 */
+	toplevel_file = debugfs_create_file(
+		"lkmc_debugfs_file", S_IWUSR, NULL, NULL, &fops);
+	if (!toplevel_file) {
+		return -1;
+	}
+	return 0;
+}
+
+static void myexit(void)
+{
+	debugfs_remove_recursive(dir);
+	debugfs_remove(toplevel_file);
+}
+
+module_init(myinit)
+module_exit(myexit)
+MODULE_LICENSE("GPL");