【NanoPi M2试用体验】字符类GPIO的驱动源码

论坛

作为初学者，笔者尝试了“hello world”——点灯。然而鉴于论坛和百度中许多大神用了杂项设备的方法，笔者自己尝试了下字符型设备，编译方法就略过了，以下是源码：
char_driver_leds.h

#ifndef _CHAR_DRIVER_LEDS_H_
#define _CHAR_DRIVER_LEDS_H_
#ifndef DEVICE_NAME
#define DEVICE_NAME "charGPIO"
#endif
#ifndef DEVICE_MINOR_NUM
#define DEVICE_MINOR_NUM 2
#endif
#ifndef DEV_MAJOR
#define DEV_MAJOR 0
#endif
#ifndef DEV_MINOR
#define DEV_MINOR 0
#endif
#ifndef REGDEV_SIZE
#define REGDEV_SIZE 3000
#endif
struct reg_dev
{
char *data;
struct cdev cdev;
};
#endif

复制代码

char_driver_leds.c

/*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
/*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
/*定义module_param module_param_array的头文件*/
#include
/*定义module_param module_param_array中perm的头文件*/
#include
/*三个字符设备函数*/
#include
/*MKDEV转换设备号数据类型的宏定义*/
#include
/*定义字符设备的结构体*/
#include
/*分配内存空间函数头文件*/
#include
/*包含函数device_create 结构体class等头文件*/
#include
#include
#include //包含prink等函数
#include //与c++相关的东西
#include //Linux中申请GPIO的头文件
/*自定义头文件*/
#include "char_driver_leds.h"
#include //不同平台使用的文件
#include
MODULE_LICENSE("Dual BSD/GPL");
/*声明是开源的，没有内核版本限制*/
MODULE_AUTHOR("XIE_dz");
/*声明作者*/
static int led_gpios[] = {
PAD_GPIO_C + 11,PAD_GPIO_C + 10,
};
#define LED_NUM ARRAY_SIZE(led_gpios)
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 0;
}
/*关闭操作*/
static int chardevnode_release(struct inode *inode, struct file *file){
printk(KERN_EMERG "chardevnode_release is success!n");
return 0;
}
/*IO操作*/
static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){
switch(cmd)
{
case 0:
case 1:
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 0;
}
ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){
return 0;
}
ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){
return 0;
}
loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){
return 0;
}
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;
/*注册到系统*/
err = cdev_add(&dev->cdev,devno,1);
if(err){
printk(KERN_EMERG "cdev_add %d is fail! %dn",index,err);
}
else{
printk(KERN_EMERG "cdev_add %d is success!n",numdev_minor+index);
}
}
static int gpio_init(void){
int i=0,ret;
for(i=0;i
ret = gpio_request(led_gpios[i], "LED");
if (ret) {
printk("%s: request GPIO %d for LED failed, ret = %dn", DEVICE_NAME,i,ret);
return -1;
}
else{
gpio_direction_output(led_gpios[i], 1);
//gpio_set_value(led_gpios[i], 1);
}
}
return 0;
}
static int scdev_init(void)
{
int ret = 0,i;
dev_t num_dev;
printk(KERN_EMERG "numdev_major is %d!n",numdev_major);//主设备号
printk(KERN_EMERG "numdev_minor is %d!n",numdev_minor);//次设备号
if(numdev_major){
num_dev = MKDEV(numdev_major,numdev_minor);//生成设备号
ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);//向系统申请设备号（已知设备号）
}
else{
/*动态注册设备号*/
ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);//向系统申请设备号（动态申请）
/*获得主设备号*/
numdev_major = MAJOR(num_dev);
printk(KERN_EMERG "adev_region req %d !n",numdev_major);
}
if(ret<0){
printk(KERN_EMERG "register_chrdev_region req %d is failed!n",numdev_major);
}
myclass = class_create(THIS_MODULE,DEVICE_NAME);//创建设备类别文件
my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);//分配内存
if(!my_devices){
ret = -ENOMEM;
goto fail;
}
memset(my_devices,0,DEVICE_MINOR_NUM * sizeof(struct reg_dev));//将s中前n个字节用 ch 替换并返回 s 。
/*设备初始化*/
for(i=0;i
my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL);//GFP_KERNEL是一个宏，分配内核空间
memset(my_devices[i].data,0,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");
/*打印信息，KERN_EMERG表示紧急信息*/
return 0;
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=0;i
cdev_del(&(my_devices[i].cdev));//这个函数会干掉cdev_map 散列表及dev本身
/*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=0;i
gpio_free(led_gpios[i]);
}
//释放设备号
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*/