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#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <asm/uaccess.h>
#include "chardev.h"
#define SUCCESS 0
#define DEVICE_NAME "chardev"
#define BUF_LEN 80
static int Major;
static int opened = 0;
static char chardev_buffer[BUF_LEN];
static char* msg_ptr;
void dumb(void)
{
printk(KERN_INFO "DUMB EXECUTED\n");
}
EXPORT_SYMBOL(dumb);
static struct file_operations fops = {
.read = device_read,
.write = device_write,
.open = device_open,
.release = device_release
};
int init_module(void)
{
Major = register_chrdev(0, DEVICE_NAME, &fops);
if (Major < 0) {
printk(KERN_ALERT "Registering char device failed with %d\n", Major);
return Major;
}
printk(KERN_INFO "I was assigned major number %d. To talk to\n", Major);
printk(KERN_INFO "the driver, create a dev file with\n");
printk(KERN_INFO "'mknod /dev/%s c %d 0'.\n", DEVICE_NAME, Major);
printk(KERN_INFO "Try to cat and echo to the device file.\n");
printk(KERN_INFO "Remove the device file and module when done.\n");
return SUCCESS;
}
void cleanup_module(void)
{
unregister_chrdev(Major, DEVICE_NAME);
}
static int device_open(struct inode* inode, struct file* filp)
{
static int counter = 0;
if (opened)
return -EBUSY;
opened++;
if (counter++ == 0)
sprintf(chardev_buffer, "Come on, write something here :D\n");
msg_ptr = chardev_buffer;
try_module_get(THIS_MODULE);
return SUCCESS;
}
static int device_release(struct inode* inode, struct file* filp)
{
opened--;
module_put(THIS_MODULE);
return 0;
}
static ssize_t device_read(struct file* filp, char* buff, size_t len, loff_t* off)
{
int bytes = 0;
char strpid[14];
snprintf(strpid, 14, "PID: %d", (current->pid));
if (*msg_ptr == 0)
return 0;
while (len-- && *msg_ptr) {
put_user(*msg_ptr++, buff++);
bytes++;
}
copy_to_user(buff, strpid, 14);
bytes += 14;
buff += 14;
put_user('\n', buff++);
bytes++;
return bytes;
}
static ssize_t device_write(struct file* filp, const char* buff, size_t len, loff_t* off)
{
int bytes = 0;
if (len > BUF_LEN) {
printk(KERN_ALERT "Error: dude you tried to overflow my buffer!\n");
return -ENOBUFS;
}
while (len--) {
get_user(chardev_buffer[bytes], buff++);
bytes++;
}
chardev_buffer[bytes] = '\0';
msg_ptr = chardev_buffer;
return bytes;
}
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Guillermo Ramos");
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