Hello linux driver(勉強会配布用)

hello_driver.c

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

#define DEVICE_NAME "hello"

static int major_num;

static ssize_t hello_read(struct file *file, char __user *buf, size_t count, loff_t * ppos)
{
	static const char *val = "Hello!!!";
	ssize_t size;

	if (*ppos)
		return 0;

	size = strlen(val);
	if (copy_to_user(buf, val, size))
		return -EFAULT;

	*ppos = size;
	return size;
}

static const struct file_operations device_ops = {
	.owner = THIS_MODULE,
	.read = hello_read,
};

static int __devinit hello_probe(struct platform_device *dev)
{
	major_num = register_chrdev(0, DEVICE_NAME, &device_ops);
	if (major_num < 0) {
		printk(KERN_ERR"hello driver: Unable to register char device\n");
		return major_num;
	}

	return 0;
}

static int __devexit hello_remove(struct platform_device *dev)
{
	unregister_chrdev(major_num, DEVICE_NAME);
	return 0;
}

static struct platform_device *hello_device;

static struct platform_driver hello_driver = {
	.driver		= {
		.name	= "hello",
		.owner	= THIS_MODULE,
	},
	.probe		= hello_probe,
	.remove		= __devexit_p(hello_remove),
};

static int __init hello_driver_init(void)
{
	int ret;

	printk(KERN_INFO"Initialize hello driver\n");
	hello_device = platform_device_alloc("hello", -1);
	if (!hello_device) {
		ret = -ENOMEM;
		goto err_device_alloc;
	}

	ret = platform_device_add(hello_device);
	if (ret) {
		printk(KERN_ERR"hello driver: Unable to add device\n");
		goto err_device_add;
	}

	ret = platform_driver_register(&hello_driver);
	if (ret) {
		printk(KERN_ERR"hello driver: Unable to register driver\n");
		goto err_driver_register;
	}

	return 0;

err_driver_register:
	platform_device_unregister(hello_device);
err_device_add:
	platform_device_put(hello_device);
err_device_alloc:
	return ret;
}

static void __exit hello_driver_exit(void)
{
	printk(KERN_INFO"Cleanup hello driver\n");
	platform_driver_unregister(&hello_driver);
	platform_device_unregister(hello_device);
}

MODULE_LICENSE("GPL");

module_init(hello_driver_init);
module_exit(hello_driver_exit);

Makefile

KERNEL ?= /usr/src/linux
PWD := $(shell pwd)

obj-m := hello_driver.o

all:
	make -C $(KERNEL) M=$(PWD) modules
clean:
	rm -f *.o *.ko *.mod.c

勉強会配布用

シンプルなキャラクタデバイスドライバです。insmod後
$ cat /proc/devices
でメジャー番号を確認し、
$ mknod /dev/hello c {メジャー番号} 0
でデバイスファイルを作成して下さい。
$ cat /dev/hello
とすると"Helllo!!!"と表示されるはずです。