kernel_module_learn/03_character_device/test_module.c

#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/uaccess.h>

#define DEVICE_NAME "flodev"
#define CLASS_NAME "chardrv"

static int major_number;
static char msg[256] = { 0 };
static short size_of_msg;
static int device_open(struct inode *, struct file *);
static int device_release(struct inode *, struct file *);
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 struct file_operations fops = {
	.read = device_read,
	.write = device_write,
	.open = device_open,
	.release = device_release,
};

static int __init basic_module_init(void)
{
	pr_info("Bonjour! Le module est chargé.\n");
	major_number = register_chrdev(0, DEVICE_NAME, &fops);
	if (major_number < 0) {
		pr_info("Erreur lors de l'enregistrement du périphérique de caractère\n");
		return major_number;
	}
	pr_info("Périphérique de caractère enregistré avec le numéro de majeur %d\n",
		major_number);
	return 0;
}

static void __exit basic_module_exit(void)
{
	unregister_chrdev(major_number, DEVICE_NAME);
	pr_info("Au revoir! Le module est déchargé.\n");
}

static int device_open(struct inode *inode, struct file *file)
{
	pr_info("flodev - Ouverture du périphérique\n");
	return 0;
}

static int device_release(struct inode *inode, struct file *file)
{
	pr_info("flodev - Fermeture du périphérique\n");
	return 0;
}

static ssize_t device_read(struct file *filp, char *buffer, size_t length,
			   loff_t *offset)
{
	int bytes_read = 0;
	if (*offset >= size_of_msg) {
		return 0;
	}
	if (*offset + length > size_of_msg) {
		length = size_of_msg - *offset;
	}
	if (copy_to_user(buffer, msg + *offset, length)) {
		return -EFAULT;
	}
	*offset += length;
	bytes_read = length;
	pr_info("flodev - Lecture de %d bytes\n", bytes_read);
	return bytes_read;
}

static ssize_t device_write(struct file *filp, const char *buff, size_t len,
			    loff_t *off)
{
	if (copy_from_user(msg, buff, len)) {
		return -EFAULT;
	}
	size_of_msg = len;
	pr_info("flodev - Message reçu: %s\n", msg);
	return len;
}

module_init(basic_module_init);
module_exit(basic_module_exit);

MODULE_LICENSE("MIT License");
MODULE_AUTHOR("Florian RICHER");
MODULE_DESCRIPTION("Un module noyau avec un périphérique de caractère");
MODULE_VERSION("1.0");