could you please provide the working solution for this question ??
Do I want to use major number, minor number and device open function ??
http://www.linuxquestions.org/questi...fs-4175502026/
#include<linux/module.h>
#include<linux/kernel.h>
#include<linux/fs.h>
#include<linux/cdev.h>
#include<asm/uaccess.h>
#include<linux/semaphore.h>
struct cdev *cdev;
struct device {
char array[100];
}chr_arr;
struct file_operations dev_ops = {
.owner = THIS_MODULE,
.read = dev_read,
.write = dev_write,
.open = dev_open,
.release = dev_release
};
ssize_t dev_read(struct file *filp,char *buf,size_t count,loff_t *offset)
{
int i;
i=copy_to_user(buf,chr_arr.array,count);
printk(KERN_ALERT"buff:%s",buf);
return i;
}
ssize_t dev_write(struct file *filp,const char *buf,size_t count,loff_t *offset)
{
//printk(KERN_ALERT"\nsorry,byebye");
int j;
//msg_ptr = kmalloc(count,GFP_KERNEL);
//for(j=0;j<count;j++)
if(count>100)
return -1;
j = copy_from_user(chr_arr.array,buf,count);
//printk(KERN_ALERT"msg_ptr:%s",msg_ptr);
return j;
}
static int dev_release(struct inode *inode,struct file *filp)
{
up(&chr_arr.sem);
return 0;
//module_put(THIS_MODULE);
return 0;
}
static int init_device(void)
{
int result;
dev_t dev_no,dev;
result = alloc_chrdev_region(&dev_no,0,1,"chr_dev");
if(result < 0)
{
printk("sorry no major number left");
return result;
}
major = MAJOR(dev_no);
dev = MKDEV(major,0);
cdev = cdev_alloc();
cdev->ops = &dev_ops;
sema_init(&chr_arr.sem,1);
printk("the major number allocated is %d\n",major);
result = cdev_add(cdev,dev,1);
if(result < 0 )
{
printk(KERN_INFO "Unable to allocate cdev");
return result;
}
/*dev_t dev =0;
dev_major = register_chrdev(dev,"chr_dev",&dev_ops);
printk(KERN_ALERT"MAJOR NUMBER IS:%d and minor is:%d",dev_major,dev_minor);*/
return 0;
}
static void clean_device(void)
{
//dev_t devno = MKDEV(dev_major, dev_minor);
//printk(KERN_ALERT"removing MAJOR NUMBER IS:%d and removing minor is:%d",dev_major,dev_minor);
cdev_del(cdev);
unregister_chrdev_region(major,1);
}
module_init(init_device);
module_exit(clean_device);
if I do only the above code then isnt it good ??
