字符设备驱动【misc设备】

misc主设备号是10，MISC_MAJOR，初始化和注册在drivers/char/misc.c中进行，实际上是通过register_chrdev完成的，可见misc实际上也是一个cdev字符设备。

static int __init misc_init(void)
{
        int err;

#ifdef CONFIG_PROC_FS
        proc_create("misc", 0, NULL, &misc_proc_fops);
#endif
        misc_class = class_create(THIS_MODULE, "misc");
        err = PTR_ERR(misc_class);
        if (IS_ERR(misc_class))
                goto fail_remove;

        err = -EIO;
        if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
                goto fail_printk;
        misc_class->devnode = misc_devnode;
        return 0;

fail_printk:
        printk("unable to get major %d for misc devices\n", MISC_MAJOR);
        class_destroy(misc_class);
fail_remove:
        remove_proc_entry("misc", NULL);
        return err;
}
subsys_initcall(misc_init);

miscdevice，混杂设备，由device结构派生而来。

使用misc子系统注册的字符驱动。

#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>

#define DEVICE_NAME     "charmisc"

static int char_misc_open(struct inode *inode, struct file *file )
{
    try_module_get(THIS_MODULE);
    printk(KERN_INFO DEVICE_NAME "opened!\n");

    return 0;
}

static int char_misc_release(struct inode *inode, struct file *file )
{
    printk(KERN_INFO DEVICE_NAME "closed!\n");

    module_put(THIS_MODULE);
    return 0;
}


static ssize_t char_misc_read(struct file *file, char *buf,size_t count, loff_t *f_pos)
{
    printk(KERN_INFO DEVICE_NAME "read method!\n");

    return count;
}

static ssize_t char_misc_write(struct file *file, const char *buf, size_t count, loff_t *f_pos)
{
    printk(KERN_INFO DEVICE_NAME "write method!\n");

    return count;
}

static int char_misc_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
{
    printk(KERN_INFO DEVICE_NAME "ioctl method!\n");

    return 0;
}

struct file_operations char_misc_fops = {
    .owner        = THIS_MODULE,
    .read        = char_misc_read,
    .write        = char_misc_write,
    .open        = char_misc_open,
    .release    = char_misc_release,
    .ioctl        = char_misc_ioctl
};

/*  misc结构体 */
static struct miscdevice char_misc = {
    .minor     = MISC_DYNAMIC_MINOR,
    .name    = DEVICE_NAME,
    .fops    = &char_misc_fops,
};

static int __init char_misc_init(void)
{
    int ret;

    ret = misc_register(&char_misc); //注册misc设备
    if (ret < 0) {
        printk(KERN_ERR "misc_register error!\n");
        return -1;
    }

    return 0;
}

static void __exit char_misc_exit(void)
{
     misc_deregister(&char_misc); //卸载misc设备
}

module_init(char_misc_init);
module_exit(char_misc_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Chenxibing,[e-mail]");

使用方法：

#insmod char_misc.ko

#ls /dev/charmisc -l

crw------- 1 root root 10, 53 2011-01-16 21:19 /dev/charmisc

主设备号是misc的主设备号10，53是新注册设备的次设备号。

在/sys/class/misc/目录下创建了charmisc目录：

#ls /sys/class/misc/charmisc/

dev  power  subsystem  uevent

#rmmod char_misc

/dev/charmisc设备消失

/sys/class/misc/charmisc/目录消失