Linux内核学习－字符设备驱动学习（二）
在Linux内核学习－字符设备驱动学习（一）中编写字符设备驱动的一种方法，但是需要手动创建设备节点。
有没有能够自动的创建设备节点的呢？
有！使用class_create()和device_create()函数可以自动创建节点。
class_create : 创建class
class_destroy : 销毁class
class_device_create : 创建device
class_device_destroy : 销毁device
class_create()
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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/下创建类目录
class_device_create()
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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
在驱动模块初始化函数中实现设备节点的自动创建
设备驱动文件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); /////////////////////////////////////////////////
测试文件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 $@ $^