关键字：字符驱动、动态生成设备节点、helloworld
linux驱动编程，个人觉得第一件事就是配置好平台文件，这里以字符设备，也就是传说中的helloworld为例~
此驱动程序基于linux3.0的内核，exynos4412开发板。
首先，打开平台文件，此开发板的平台文件是arch\arm\mach-exynos\mach-itop4412.c，不同平台位置是不一样的。
申明一下设备信息，这里以编译进kernel为例
#ifdef CONFIG_HELLO_CHAR_CTL
struct platform_device s3c_device_hello_char_ctl = {
.name = "Hello_Jni_Char",
.id = -,
};
#endif
然后在struct platform_device *smdk4x12_devices[]数组里注册设备信息
#ifdef CONFIG_HELLO_CHAR_CTL
&s3c_device_hello_char_ctl,
#endif
至此，平台文件配置完毕。
接下来，开始大餐，驱动程序的编写！
注意：在linux的每一个驱动程序里面都需要加上如下信息，表明开源
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("pngcui");
每一个驱动程序都是从init函数开始的，同时也需要编写exit函数，在初始化函数中需要生成主设备号与从设备号，因为linux是根据主从设备号来寻找相应的硬件的
#define DEV_MAJOR 0
#define DEV_MINOR 0 int numdev_major = DEV_MAJOR;
int numdev_minor = DEV_MINOR; /*输入主设备号*/
module_param(numdev_major,int,S_IRUSR);
/*输入次设备号*/
module_param(numdev_minor,int,S_IRUSR);
进入驱动程序中的init函数中,进行注册设备号，生成设备节点DEVICE_NAME
#define DEVICE_NAME "chardevnode"
注意：此驱动由于控制了两个gpio引脚所以出现了gpio_init()，在这里可以忽略，对于gpio的控制，在下一篇博客中会写到。
static int scdev_init(void)
{
int ret = ,i;
dev_t num_dev; printk(KERN_EMERG "numdev_major is %d!\n",numdev_major);
printk(KERN_EMERG "numdev_minor is %d!\n",numdev_minor); if(numdev_major){
num_dev = MKDEV(numdev_major,numdev_minor);
ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);
}
else{
/*动态注册设备号*/
ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);
/*获得主设备号*/
numdev_major = MAJOR(num_dev);
printk(KERN_EMERG "adev_region req %d !\n",numdev_major);
}
if(ret<){
printk(KERN_EMERG "register_chrdev_region req %d is failed!\n",numdev_major);
}
myclass = class_create(THIS_MODULE,DEVICE_NAME); my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);
if(!my_devices){
ret = -ENOMEM;
goto fail;
}
memset(my_devices,,DEVICE_MINOR_NUM * sizeof(struct reg_dev)); /*设备初始化*/
for(i=;i<DEVICE_MINOR_NUM;i++){
my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL);
memset(my_devices[i].data,,REGDEV_SIZE);
/*设备注册到系统*/
reg_init_cdev(&my_devices[i],i); /*创建设备节点*/
device_create(myclass,NULL,MKDEV(numdev_major,numdev_minor+i),NULL,DEVICE_NAME"%d",i);
} ret = gpio_init();
if(ret){
printk(KERN_EMERG "gpio_init failed!\n");
} printk(KERN_EMERG "scdev_init!\n");
return ; fail:
/*注销设备号*/
unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
printk(KERN_EMERG "kmalloc is fail!\n"); return ret;
} static void scdev_exit(void)
{
int i;
printk(KERN_EMERG "scdev_exit!\n"); /*除去字符设备*/
for(i=;i<DEVICE_MINOR_NUM;i++){
cdev_del(&(my_devices[i].cdev));
/*摧毁设备节点函数*/
device_destroy(myclass,MKDEV(numdev_major,numdev_minor+i));
}
/*释放设备class*/
class_destroy(myclass);
/*释放内存*/
kfree(my_devices); /*释放GPIO*/
for(i=;i<LED_NUM;i++){
gpio_free(led_gpios[i]);
} unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
} module_init(scdev_init);
/*初始化函数*/
module_exit(scdev_exit);
/*卸载函数*/
然后把设备注册到系统
static void reg_init_cdev(struct reg_dev *dev,int index){
int err;
int devno = MKDEV(numdev_major,numdev_minor+index);
/*数据初始化*/
cdev_init(&dev->cdev,&my_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &my_fops;
/*注册到系统*/
err = cdev_add(&dev->cdev,devno,);
if(err){
printk(KERN_EMERG "cdev_add %d is fail! %d\n",index,err);
}
else{
printk(KERN_EMERG "cdev_add %d is success!\n",numdev_minor+index);
}
}
dev->cdev.ops = &my_fops;这一句就指明了此驱动程序的函数接口
struct file_operations my_fops = {
.owner = THIS_MODULE,
.open = chardevnode_open,
.release = chardevnode_release,
.unlocked_ioctl = chardevnode_ioctl,
.read = chardevnode_read,
.write = chardevnode_write,
.llseek = chardevnode_llseek,
};
在这里的所有函数接口必须都实现，否则会编译报错。
其中最重要的两个函数是open、ioctl这两个函数，open函数用来打开设备节点，然后才可以对设备进行驱动。
然后是ioctl函数，一般上层应用都是通过调用此函数来对设备进行操作的。
/*打开操作*/
static int chardevnode_open(struct inode *inode, struct file *file){
printk(KERN_EMERG "chardevnode_open is success!\n"); return ;
}
/*关闭操作*/
static int chardevnode_release(struct inode *inode, struct file *file){
printk(KERN_EMERG "chardevnode_release is success!\n"); return ;
}
/*IO操作*/
static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){ switch(cmd)
{
case :
case :
if (arg > LED_NUM) {
return -EINVAL;
} gpio_set_value(led_gpios[arg], cmd);
break; default:
return -EINVAL;
} printk(KERN_EMERG "chardevnode_ioctl is success! cmd is %d,arg is %d \n",cmd,arg); return ;
} ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){
return ;
} ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){
return ;
} loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){
return ;
}
到这里一个完整的字符驱动就编写完毕了。
最后附上完整的驱动程序
/*包含初始化宏定义的头文件,代码中的module_init和module_exit在此文件中*/
#include <linux/init.h>
/*包含初始化加载模块的头文件,代码中的MODULE_LICENSE在此头文件中*/
#include <linux/module.h>
/*定义module_param module_param_array的头文件*/
#include <linux/moduleparam.h>
/*定义module_param module_param_array中perm的头文件*/
#include <linux/stat.h>
/*三个字符设备函数*/
#include <linux/fs.h>
/*MKDEV转换设备号数据类型的宏定义*/
#include <linux/kdev_t.h>
/*定义字符设备的结构体*/
#include <linux/cdev.h>
/*分配内存空间函数头文件*/
#include <linux/slab.h>
/*包含函数device_create 结构体class等头文件*/
#include <linux/device.h> /*自定义头文件*/
#include "char_driver_leds.h" /*Linux中申请GPIO的头文件*/
#include <linux/gpio.h>
/*三星平台的GPIO配置函数头文件*/
/*三星平台EXYNOS系列平台，GPIO配置参数宏定义头文件*/
#include <plat/gpio-cfg.h>
/*三星平台4412平台，GPIO宏定义头文件*/
#include <mach/gpio-exynos4.h> MODULE_LICENSE("Dual BSD/GPL");
/*声明是开源的，没有内核版本限制*/
MODULE_AUTHOR("iTOPEET_dz");
/*声明作者*/ static int led_gpios[] = {
EXYNOS4_GPL2(),EXYNOS4_GPK1(),
};
#define LED_NUM ARRAY_SIZE(led_gpios) #define DEVICE_NAME "chardevnode" #define DEVICE_MINOR_NUM 1 #define DEV_MAJOR 0
#define DEV_MINOR 0
#define REGDEV_SIZE 3000 struct reg_dev
{
char *data;
unsigned long size; struct cdev cdev;
}; int numdev_major = DEV_MAJOR;
int numdev_minor = DEV_MINOR; /*输入主设备号*/
module_param(numdev_major,int,S_IRUSR);
/*输入次设备号*/
module_param(numdev_minor,int,S_IRUSR); static struct class *myclass;
struct reg_dev *my_devices; /*打开操作*/
static int chardevnode_open(struct inode *inode, struct file *file){
printk(KERN_EMERG "chardevnode_open is success!\n"); return ;
}
/*关闭操作*/
static int chardevnode_release(struct inode *inode, struct file *file){
printk(KERN_EMERG "chardevnode_release is success!\n"); return ;
}
/*IO操作*/
static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){ switch(cmd)
{
case :
case :
if (arg > LED_NUM) {
return -EINVAL;
} gpio_set_value(led_gpios[arg], cmd);
break; default:
return -EINVAL;
} printk(KERN_EMERG "chardevnode_ioctl is success! cmd is %d,arg is %d \n",cmd,arg); return ;
} ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){
return ;
} ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){
return ;
} loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){
return ;
}
struct file_operations my_fops = {
.owner = THIS_MODULE,
.open = chardevnode_open,
.release = chardevnode_release,
.unlocked_ioctl = chardevnode_ioctl,
.read = chardevnode_read,
.write = chardevnode_write,
.llseek = chardevnode_llseek,
}; /*设备注册到系统*/
static void reg_init_cdev(struct reg_dev *dev,int index){
int err;
int devno = MKDEV(numdev_major,numdev_minor+index); /*数据初始化*/
cdev_init(&dev->cdev,&my_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &my_fops; /*注册到系统*/
err = cdev_add(&dev->cdev,devno,);
if(err){
printk(KERN_EMERG "cdev_add %d is fail! %d\n",index,err);
}
else{
printk(KERN_EMERG "cdev_add %d is success!\n",numdev_minor+index);
}
} static int gpio_init(void){
int i=,ret; for(i=;i<LED_NUM;i++){
ret = gpio_request(led_gpios[i], "LED");
if (ret) {
printk("%s: request GPIO %d for LED failed, ret = %d\n", DEVICE_NAME,i,ret);
return -;
}
else{
s3c_gpio_cfgpin(led_gpios[i], S3C_GPIO_OUTPUT);
gpio_set_value(led_gpios[i], );
}
} return ;
} static int scdev_init(void)
{
int ret = ,i;
dev_t num_dev; printk(KERN_EMERG "numdev_major is %d!\n",numdev_major);
printk(KERN_EMERG "numdev_minor is %d!\n",numdev_minor); if(numdev_major){
num_dev = MKDEV(numdev_major,numdev_minor);
ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);
}
else{
/*动态注册设备号*/
ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);
/*获得主设备号*/
numdev_major = MAJOR(num_dev);
printk(KERN_EMERG "adev_region req %d !\n",numdev_major);
}
if(ret<){
printk(KERN_EMERG "register_chrdev_region req %d is failed!\n",numdev_major);
}
myclass = class_create(THIS_MODULE,DEVICE_NAME); my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);
if(!my_devices){
ret = -ENOMEM;
goto fail;
}
memset(my_devices,,DEVICE_MINOR_NUM * sizeof(struct reg_dev)); /*设备初始化*/
for(i=;i<DEVICE_MINOR_NUM;i++){
my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL);
memset(my_devices[i].data,,REGDEV_SIZE);
/*设备注册到系统*/
reg_init_cdev(&my_devices[i],i); /*创建设备节点*/
device_create(myclass,NULL,MKDEV(numdev_major,numdev_minor+i),NULL,DEVICE_NAME"%d",i);
} return ; fail:
/*注销设备号*/
unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
printk(KERN_EMERG "kmalloc is fail!\n"); return ret;
} static void scdev_exit(void)
{
int i;
printk(KERN_EMERG "scdev_exit!\n"); /*除去字符设备*/
for(i=;i<DEVICE_MINOR_NUM;i++){
cdev_del(&(my_devices[i].cdev));
/*摧毁设备节点函数d*/
device_destroy(myclass,MKDEV(numdev_major,numdev_minor+i));
}
/*释放设备class*/
class_destroy(myclass);
/*释放内存*/
kfree(my_devices); /*释放GPIO*/
for(i=;i<LED_NUM;i++){
gpio_free(led_gpios[i]);
} unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
} module_init(scdev_init);
/*初始化函数*/
module_exit(scdev_exit);
/*卸载函数*/
以及完整的测试程序
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <stdio.h> int main(){ int fd; if((fd = open("/dev/chardevnode0",O_RDWR|O_NDELAY)) < )
printf("Hello_Jni open failed!\n"); ioctl(fd,,);
ioctl(fd,,); close(fd); return ;
}