commit 7cd528626db3006de498feb0ac936f2c246d66a1
Author: KoroLion <korolion31@yandex.ru>
Date:   Fri Jan 8 15:18:01 2021 +0300

    Initial commit

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8536d48
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,22 @@
+BINARY := kl_char_driver
+KERNEL := /lib/modules/$(shell uname -r)/build
+KMOD_DIR := $(shell pwd)
+
+ccflags-y += -Wall
+obj-m += $(BINARY).o
+$(BINARY)-y := main.o
+
+$(BINARY).ko: main.c
+	make -C $(KERNEL) M=$(KMOD_DIR) modules
+
+showlog:
+	tail -n10 /var/log/messages
+enable: $(BINARY).ko
+	-insmod $(BINARY).ko
+disable:
+	-rmmod $(BINARY)
+check: disable enable
+	echo wolf228 > /dev/kl_char_dev-0 && head -1 /dev/kl_char_dev-0 && make showlog
+
+clean:
+	make -C $(KERNEL) M=$(KMOD_DIR) clean
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..1e86a64
--- /dev/null
+++ b/README.md
@@ -0,0 +1,3 @@
+This driver creates devices in /dev. You could save anything to these devices and then read.
+
+Compile and check driver using **sudo make check**
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..d365d9a
--- /dev/null
+++ b/main.c
@@ -0,0 +1,143 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/cdev.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+
+#define DEVICES_AMOUNT 3
+#define MAX_DATA_LEN 64
+const char DEVICE_NAME[] = "kl_char_dev";
+
+static char user_data[DEVICES_AMOUNT][MAX_DATA_LEN];
+
+static int char_dev_open(struct inode *inode, struct file *file);
+static int char_dev_release(struct inode *inode, struct file *file);
+static ssize_t char_dev_read(struct file *file, char __user *buf, size_t count, loff_t *offset);
+static ssize_t char_dev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset);
+
+static const struct file_operations char_dev_fops = {
+    .owner      = THIS_MODULE,
+
+    .open       = char_dev_open,
+    .release    = char_dev_release,
+    .read       = char_dev_read,
+    .write      = char_dev_write
+};
+
+struct CHAR_DEV_DATA {
+    struct cdev cdev;
+};
+
+static int dev_major = 0;
+static struct class *char_dev_class = NULL;
+static struct CHAR_DEV_DATA char_dev_data[DEVICES_AMOUNT];
+
+static int char_dev_uevent(struct device *dev, struct kobj_uevent_env *env) {
+    // permissions for device file
+    add_uevent_var(env, "DEVMODE=%#o", 0666);
+    return 0;
+}
+
+static int char_dev_init(void) {
+    int err, i;
+    dev_t dev;
+    size_t dev_num;
+
+    err = alloc_chrdev_region(&dev, 0, DEVICES_AMOUNT, DEVICE_NAME);
+
+    dev_major = MAJOR(dev);
+
+    char_dev_class = class_create(THIS_MODULE, DEVICE_NAME);
+    char_dev_class->dev_uevent = char_dev_uevent;
+
+    for (i = 0; i < DEVICES_AMOUNT; i++) {
+        cdev_init(&char_dev_data[i].cdev, &char_dev_fops);
+        char_dev_data[i].cdev.owner = THIS_MODULE;
+
+        dev_num = MKDEV(dev_major, i);
+        cdev_add(&char_dev_data[i].cdev, dev_num, 1);
+        device_create(char_dev_class, NULL, dev_num, NULL, "%s-%d", DEVICE_NAME, i);
+
+        if (i % 2 == 0) {
+            strncpy(user_data[i], "WOLF\n", MAX_DATA_LEN);
+        } else {
+            strncpy(user_data[i], "LION\n", MAX_DATA_LEN);
+        }
+    }
+
+    return 0;
+}
+
+static void char_dev_exit(void) {
+    int i;
+
+    for (i = 0; i < DEVICES_AMOUNT; i++) {
+        device_destroy(char_dev_class, MKDEV(dev_major, i));
+    }
+
+    class_unregister(char_dev_class);
+    class_destroy(char_dev_class);
+
+    unregister_chrdev_region(MKDEV(dev_major, 0), MINORMASK);
+}
+
+static int char_dev_open(struct inode *inode, struct file *file) {
+    int minor = MINOR(file->f_path.dentry->d_inode->i_rdev);
+    printk(KERN_INFO "#%s: minor %d opened\n", DEVICE_NAME, minor);
+    return 0;
+}
+
+static int char_dev_release(struct inode *inode, struct file *file) {
+    int minor = MINOR(file->f_path.dentry->d_inode->i_rdev);
+    printk(KERN_INFO "#%s: minor %d closed\n", DEVICE_NAME, minor);
+    return 0;
+}
+
+static ssize_t char_dev_read(struct file *file, char __user *buf, size_t count, loff_t *offset) {
+    size_t datalen;
+
+    int minor = MINOR(file->f_path.dentry->d_inode->i_rdev);
+    printk(KERN_INFO "#%s: reading from minor %d\n", DEVICE_NAME, minor);
+
+    datalen = strlen(user_data[minor]);
+
+    if (count > datalen) {
+        count = datalen;
+    }
+
+    if (copy_to_user(buf, user_data[minor], count)) {
+        return -EFAULT;
+    }
+
+    return count;
+}
+
+static ssize_t char_dev_write(struct file *file, const char __user *buf, size_t count, loff_t *offset) {
+    size_t not_copied;
+
+    int minor = MINOR(file->f_path.dentry->d_inode->i_rdev);
+    printk(KERN_INFO "#%s: writing to minor %d\n", DEVICE_NAME, minor);
+
+    if (count > MAX_DATA_LEN) {
+        count = MAX_DATA_LEN;
+    }
+
+    not_copied = copy_from_user(user_data[minor], buf, count);
+    if (not_copied != 0) {
+        printk(KERN_WARNING "#%s: unable to copy %zd bytes from the user\n", DEVICE_NAME, not_copied);
+    }
+
+    user_data[minor][count] = 0;
+
+    printk(KERN_INFO "#%s: received from user: %s", DEVICE_NAME, user_data[minor]);
+
+    return count;
+}
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("KoroLion <github.com/KoroLion>");
+
+module_init(char_dev_init);
+module_exit(char_dev_exit);