driver-tutorial finished

kernel_timer/demo_timer_driver.c

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+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kdev_t.h>
+#include <linux/fs.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/timer.h>
+#include <linux/jiffies.h>
+
+//Timer Variable
+#define TIMEOUT 5000 //milliseconds
+static struct timer_list demo_timer;
+static unsigned int count = 0;
+
+dev_t dev = 0;
+static struct class *dev_class;
+static struct cdev demo_timer_cdev;
+static int __init demo_timer_driver_init(void);
+static void __exit demo_timer_driver_exit(void);
+
+/***************Driver fucntions******************/
+static int demo_timer_open(struct inode *inode, struct file *file);
+static int demo_timer_release(struct inode *inode , struct file *file);
+static ssize_t demo_timer_read(struct file *filp, char __user *buf, size_t len, loff_t *off);
+static ssize_t demo_timer_write(struct file *filp, const char __user *buf, size_t len, loff_t *off);
+/*************************************************/
+
+//File operation structure
+static struct file_operations fops = {
+    .owner          = THIS_MODULE,
+    .read           = demo_timer_read,
+    .write          = demo_timer_write,
+    .open           = demo_timer_open,
+    .release        = demo_timer_release
+};
+
+//Timer Callback function. This will be called when timer expires
+void timer_callback(struct timer_list *timer){
+    /* do your timer stuff here */
+    pr_info("Timer Callback function Called [%d]\n", count++);
+
+    /**
+     * Re-enable timer. Because this function will be called only first time.
+     * If we re-enable this will work like periodic timer.
+     */
+
+    mod_timer(&demo_timer, jiffies + msecs_to_jiffies(TIMEOUT));
+}
+
+/**
+ * This function will be called when we open the device file
+ */
+static int demo_timer_open(struct inode *inode, struct file *file){
+    pr_info("Device File Opened...!!!\n");
+    return 0;
+}
+
+/**
+ * This function will be called when we close the Device file
+ */
+static int demo_timer_release(struct inode *inode , struct file *file){
+    pr_info("Read Function\n");
+    return 0;    
+}
+
+/**
+ * This function will be called when we read the Device file
+ */
+static ssize_t demo_timer_read(struct file *filp, char __user *buf, size_t len, loff_t *off){
+    pr_info("Read function\n");
+    return 0;
+}
+
+/**
+ * This function will be called when we write the Device file
+ */
+static ssize_t demo_timer_write(struct file *filp, const char __user *buf, size_t len, loff_t *off){
+    pr_info("Write function\n");
+    return len;
+}
+
+/**
+ * Module Init function
+ */
+static int __init demo_timer_driver_init(void){
+    /*Allocating Major number*/
+    if(alloc_chrdev_region(&dev, 0, 1, "demo_timer_Dev") < 0 ){
+        pr_err("Cannot allocate major number\n");
+        return -1;
+    }
+
+    pr_info("Major = %d Minor = %d \n", MAJOR(dev), MINOR(dev));
+
+    /*Creating cdev structure*/
+    cdev_init(&demo_timer_cdev, &fops);
+
+    /*Adding character device to the system*/
+    if((cdev_add(&demo_timer_cdev, dev, 1)) < 0){
+        pr_err("Cannot add the device to the system\n");
+    }
+
+    /* setup your timer to call my_timer_callback */
+    timer_setup(&demo_timer, timer_callback, 0);
+
+    //We can also use add_timer.
+    /* setup timer interval to based on TIMEOUT Macro */
+    /* kernel timer should be in ticks or jiffs*/
+    mod_timer(&demo_timer, jiffies + msecs_to_jiffies(TIMEOUT));
+
+    pr_info("Device Driver Insert...Done!!!\n");
+    return 0;
+}
+
+/**
+ * 
+ * Module exit function
+ */
+
+static void __exit demo_timer_driver_exit(void){
+    /* remove kernel when unloading module */
+    del_timer(&demo_timer);
+    cdev_del(&demo_timer_cdev);
+    unregister_chrdev_region(dev, 1);
+    pr_info("Device Driver Remove...Done!!!\n");
+}
+
+module_init(demo_timer_driver_init);
+module_exit(demo_timer_driver_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Junet Hossain");
+MODULE_DESCRIPTION("A Simple kernel timer module");