Character driver finished

LKM/hello_func.c

@@ -0,0 +1,41 @@
+#include <linux/module.h>   // included for all kernel module
+#include <linux/kernel.h>   // included for KERN_INFO
+#include <linux/init.h>     // included for __init and __exit macros
+
+
+void func(void);
+EXPORT_SYMBOL_GPL(func);
+
+/**
+ *  EXPORT_SYMBOL_GPL:
+ *  Since, in user space to use variable/function of one
+ *  file to another file we use extern or header file. But
+ *  for kernel space such thing is not allowed. But to use
+ *  variable or function in another module/file we use
+ *  EXPORT_SYMBOL_GPL(<fun or var name>) to export the 
+ *  function or variable to global scope for all the modules.
+ */
+
+int val = 300;
+
+void func(){
+
+    printk(KERN_INFO"func invoked\n ");
+    printk(KERN_INFO" val = %d \n", val);
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Junet Hossain");
+MODULE_DESCRIPTION("A Simple Hello World module");
+
+static int __init hello_init(void){
+    printk(KERN_INFO "Init Hello func module\n");
+    return 0; // Non-zero return means that the module couldn't be loaded.
+}
+
+static void  __exit hello_cleanup(void){
+    printk(KERN_INFO "Cleaning up hello func module.\n");
+}
+
+module_init(hello_init);
+module_exit(hello_cleanup);