Linux內核學習－字符設備驅動學習（二）

在Linux內核學習－字符設備驅動學習（一）中編寫字符設備驅動的一種方法，但是需要手動創建設備節點。

有沒有能夠自動的創建設備節點的呢？

有！使用class_create()和device_create()函數可以自動創建節點。

 

    class_create                 :    創建class
    class_destroy               :    銷燬class
    class_device_create     :    創建device
    class_device_destroy   :    銷燬device

class_create()
-------------------------------------------------
linux-2.6.22/include/linux/device.h
struct class *class_create(struct module *owner, const char *name)
    class_create - create a struct class structure
    @owner: pointer to the module that is to "own" this struct class
    @name: pointer to a string for the name of this class.
在/sys/class/下創建類目錄

 

class_device_create()
-------------------------------------------------
linux-2.6.22/include/linux/device.h
struct class_device *class_device_create(struct class        *cls,
                                         struct class_device *parent,
                                         dev_t               devt,
                                         struct device       *device,
                                         const char          *fmt, ...)

    class_device_create - creates a class device and registers it with sysfs
    @cls: pointer to the struct class that this device should be registered to.
    @parent: pointer to the parent struct class_device of this new device, if any.
    @devt: the dev_t for the char device to be added.
    @device: a pointer to a struct device that is assiociated with this class device.
    @fmt: string for the class device's name
在驅動模塊初始化函數中實現設備節點的自動創建

設備驅動文件char01.c

#include <linux/init.h> #include <linux/module.h> #include <linux/cdev.h> #include <linux/device.h> #include <linux/kdev_t.h> #include <linux/fs.h> ///////////////////////////////////////////////// int char01_open(struct inode *inode, struct file *filp) { printk("char01 open!/n"); return 0; } int char01_release(struct inode *inode, struct file *filp) { printk("char01 release!/n"); return 0; } ssize_t char01_read(struct file *filp, char *buf, size_t count, loff_t *fpos) { printk("char01 read!/n"); return 0; } ssize_t char01_write(struct file *filp, const char *buf, size_t count, loff_t *fpos) { printk("char01 write!/n"); return 0; } int char01_ioctl(struct inode *inode, struct file *filp, unsigned int cmd, unsigned long param) { printk("char01 ioctl!/n"); printk("cmd:%d param:%ld/n", cmd, param); return 0; } ///////////////////////////////////////////////// struct file_operations fops = { .owner = THIS_MODULE, .open = char01_open, .release = char01_release, .read = char01_read, .write = char01_write, .ioctl = char01_ioctl }; dev_t devno; struct class *pclass; struct cdev dev; int char01_dev_init(void) { int result; result = alloc_chrdev_region(&devno, 0, 1, "char01"); if (result != 0) { printk("alloc_chrdev_region failed!/n"); goto ERR1; } cdev_init(&dev, &fops); dev.owner = THIS_MODULE; dev.ops = &fops; result = cdev_add(&dev, devno, 1); if (result != 0) { printk("cdev_add failed!/n"); goto ERR2; } pclass = class_create(THIS_MODULE, "char01"); if (IS_ERR(pclass)) { printk("class_create failed!/n"); goto ERR3; } device_create(pclass, NULL, devno, NULL, "char01"); return 0; ERR3: cdev_del(&dev); ERR2: unregister_chrdev_region(devno, 1); ERR1: return -1; } ///////////////////////////////////////////////// ///////////////////////////////////////////////// ///////////////////////////////////////////////// static int __init char01_init(void) { printk("module char01 init!/n"); return char01_dev_init(); } static void __exit char01_exit(void) { printk("module char01 exit!/n"); class_destroy(pclass); device_destroy(pclass,devno); cdev_del(&dev); unregister_chrdev_region(devno, 1); } ///////////////////////////////////////////////// MODULE_LICENSE("Dual BSD/GPL"); MODULE_AUTHOR("Yao.GUET"); module_init(char01_init); module_exit(char01_exit); /////////////////////////////////////////////////

測試文件char01_test.c

#include <stdio.h> #include <fcntl.h> #include <errno.h> #include <sys/stat.h> ///////////////////////////////////////////////// int main(int argc, char *argv) { int fd; fd = open("/dev/char01", O_RDWR); if (fd<0) { printf("open /dev/char01 failed!/n"); printf("%s/n", strerror(errno)); return -1; } printf("open /dev/char01 ok!/n"); ioctl(fd, 0); close(fd); }

Makefile文件：

obj-m := char01.o PWD := $(shell pwd) K_DIR := /lib/modules/$(shell uname -r)/build all: $(MAKE) -C $(K_DIR) M=$(PWD) modules clean: $(MAKE) -C $(K_DIR) M=$(PWD) clean test:char01_test.o gcc -o $@ $^