#include <linux/module.h> /* Needed by all modules */
#include <linux/kernel.h> /* Needed for KERN_INFO */
#include <linux/init.h> /* Needed for the macros */
#include <linux/moduleparam.h>
#include <linux/fs.h>
#include <asm/uaccess.h> /* for put_user */
#define DRIVER_AUTHOR "Vurguuzko <vurguuz@gmail.com>"
#define DRIVER_DESC "A simple driver"
#define DEVICE_NAME "vurguuz"
#define BUF_LEN 80 /* Max length of the message from the device */
static ssize_t device_read(struct file *, char *, size_t, loff_t *);
static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
static int __init module_start(void);
static void __exit module_stop(void);
static int myint = 5;
static int maj_num; /* Major number assigned to our device driver */
static char msg[BUF_LEN]; /* The msg the device will give when asked */
static char *msg_Ptr;
static struct file_operations fops = {
.read = device_read,
.write = device_write,
};
static int __init module_start(void)
{
maj_num = register_chrdev(0, DEVICE_NAME, &fops);
if (maj_num < 0)
{
printk(KERN_ALERT "Registering char device failed with %d\n", maj_num);
return maj_num;
}
printk(KERN_INFO "Hello world. ");
printk(KERN_INFO "myint = %d\n", myint);
printk(KERN_INFO "I was assigned major number %d. To talk to\n", maj_num);
printk(KERN_INFO "the driver, create a dev file with\n");
printk(KERN_INFO "'mknod /dev/%s c %d 0'.\n", DEVICE_NAME, maj_num);
return 0;
}
static void __exit module_stop(void)
{
printk(KERN_INFO "Goodbye world.\n");
}
static ssize_t device_read(struct file *filp, /* see include/linux/fs.h */
char *buffer, /* buffer to fill with data */
size_t length, /* length of the buffer */
loff_t * offset)
{
int bytes_read = 0;
sprintf(msg, "Random\n");
msg_Ptr = msg;
/*
* If we're at the end of the message,
* return 0 signifying end of file
*/
if (*msg_Ptr == 0)
return 0;
/*
* Actually put the data into the buffer
*/
while (length && *msg_Ptr) {
/*
* The buffer is in the user data segment, not the kernel
* segment so "*" assignment won't work. We have to use
* put_user which copies data from the kernel data segment to
* the user data segment.
*/
put_user(*(msg_Ptr++), buffer++);
length--;
bytes_read++;
}
/*
* Most read functions return the number of bytes put into the buffer
*/
return bytes_read;
}
/*
* Called when a process writes to dev file: echo "hi" > /dev/hello
*/
static ssize_t
device_write(struct file *filp, const char *buff, size_t len, loff_t * off)
{
printk(KERN_ALERT "written \"%s\".\n", buff);
return len;
}
module_param(myint, int, 0);
module_init(module_start);
module_exit(module_stop);
MODULE_LICENSE("GPL");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);