#include <linux/init.h>
#include <linux/module.h> /** needed by all modules **/
#include <linux/kernel.h>  /** This is for KERN_ALERT **/
#include <linux/fs.h>
#include <linux/cdev.h>

/** for putuser **/
 #include <asm/uaccess.h>

MODULE_LICENSE("SJ BSD/GPL");


static struct cdev SimpleDevs[2];

static int simple_major = 0;


static ssize_t sj_read(struct file *filp,
   char *buffer,    /* The buffer to fill with data */
   size_t length,   /* The length of the buffer     */
   loff_t *offset);

static int sj_open(struct inode *inode, struct file *file);


static struct file_operations fops = {
  .read = sj_read,
  //.write = sj_write,
  .open = sj_open,
  //.release = sj_release
};

static ssize_t sj_read(struct file *filp,
   char *buffer,    /* The buffer to fill with data */
   size_t length,   /* The length of the buffer     */
   loff_t *offset)  /* Our offset in the file       */
{

     char msg[1024] = "Hello SJ_read";
     copy_to_user( buffer, msg, sizeof(msg) );

      return sizeof(msg);

}

static void simple_setup_cdev(struct cdev *dev, int minor,
                 struct file_operations *fops)
{
        int err, devno = MKDEV(simple_major, minor);

         dev = cdev_alloc();

         cdev_init(dev, fops);
         dev->owner = THIS_MODULE;
         dev->ops = fops;
         err = cdev_add (dev, devno, 1);
         /* Fail gracefully if need be */
         if (err)
                 printk (KERN_NOTICE "Error %d adding simple%d", err, minor);
 }

static int sjDevInit(void)
{

    int result;
    dev_t dev;

    printk("Device Init now..");


    /** int alloc_chrdev_region(dev_t *dev, unsigned int firstminor,unsigned int count, char *name);  **/
    /** dev -> The dev_t variable type,which will get the major number that the kernel allocates.  **/
    /**The same name will appear in /proc/devices.  **/
    result = alloc_chrdev_region(&dev, 0, 1, "simple");
    if( result < 0 )
    {
      printk("Error in allocating device");
      return -1;
    }
    // printk("simple_major ..");
     simple_major = MAJOR(dev);
     printk("simple_major number is %d ..rn",simple_major );

    /* Now set up two cdevs. */

    simple_setup_cdev(SimpleDevs, 0, &fops);
    simple_setup_cdev(SimpleDevs + 1, 1, &fops);

    return 0;

}


static void sjDevRel(void)
{
    printk("Releasing Simple Devsrn");
    cdev_del(SimpleDevs);

}

static int sj_open(struct inode *inode, struct file *file)
{

   printk("Kernel..Sj_open ..I am openedrn");

   return 0;
}

module_init(sjDevInit);
module_exit(sjDevRel);

err = cdev_add (dev, devno, 1);
/* Fail gracefully if need be */
if (err)
    printk (KERN_NOTICE "Error %d adding simple%d", err, minor);
kobject_uevent(&dev->kobj, KOBJ_ADD);

kobject_uevent(&SimpleDevs[0]->kobj, KOBJ_REMOVE);
printk("Releasing Simple Devsrn");
cdev_del(SimpleDevs[0]);

char event[] = "DISK_RO=1";
char *envp[] = { event, NULL };

if (!ro)
    event[8] = '0';
kobject_uevent_env(&disk_to_dev(gd)->kobj, KOBJ_CHANGE, envp);