static MAJOR number allocation in character device driver in linux

static MAJOR number allocation in character device driver in linux

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/major.h>
#include <linux/capability.h>
#include <asm/uaccess.h>
#include <linux/cdev.h>


static ssize_t sample_char_read(struct file * file, char __user * buf,
 size_t count, loff_t *ppos)
{
 printk("sample_char_read size(%ld) ", count);
 return 0;
}

static ssize_t sample_char_write(struct file *filp, const char *buf,
 size_t size, loff_t *offp)
{
 printk("sample_char_write size(%ld) ", size);
 return size;

}

int sample_char_open(struct inode *inode, struct file *filp)
{
 printk("sample_char_open ");
 return 0;
}

int sample_char_release(struct inode *inode, struct file *filp)
{

 printk("sample_char_release ");
 return 0;
}

static struct file_operations sample_char_fops = {
       read: sample_char_read,
       write: sample_char_write,
       open: sample_char_open,
       release: sample_char_release,
};

#define sample_major_number 249
#define max_minors 1

static struct cdev char_cdev;
static dev_t dev;
int init_module(void)
{
 int ret = 0;

 dev = MKDEV(sample_major_number, 0);
 printk(" Loading the sample char device driver ");

 ret = register_chrdev_region(dev, max_minors, "sample_char");
 if (ret)
 {
 printk("register_chrdev_region Error ");
 goto error;
 }
 cdev_init(&char_cdev, &sample_char_fops);
 ret = cdev_add(&char_cdev, dev, max_minors);
 if (ret) {
 printk("cdev_add Error ");
 goto error_region;
 }
 return 0;

error_region:
 unregister_chrdev_region(dev, max_minors);
error:
 return ret;
}

void cleanup_module(void)
{
 cdev_del(&char_cdev);
 unregister_chrdev_region(dev, max_minors);
 printk(" Unloading the sample char device driver ");

}

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