openwrt 编写驱动控制led

一、编写GPIO驱动

1. 查找 GPIO 寄存器配置（gpio0为例）
   查手册获取 GPIO0 设置相关的寄存器
   GPIO#11 引脚，GPIO1_MODE[1:0] (01)来设置其为GPIO功能
   通过设置 GPIO_CTRL_0 [11号引脚]为1将 GPIO11 设置为输出模式
   通过设置 GPIO_DATA_0 [11号引脚]为0或1 将 GPIO11 输出设置为0或1

二、创建模块文件目录：

1、在源码目录下的/package/kernel/目录下创建chardrv目录
2、在chardrv目录下创建Makefile文件和src目录
3、在src目录下创建Makefile文件和chardrv.c文件

三、编写驱动文件

1、chardrv目录下的Makefile文件内容：

#
# Copyright (C) 2008 OpenWrt.org
#
# This is free software, licensed under the GNU General Public License v2.
# See /LICENSE for more information.
#

include $(TOPDIR)/rules.mk
include $(INCLUDE_DIR)/kernel.mk

PKG_NAME:=chardrv  #字符设备驱动模块名称
PKG_RELEASE:=2   #版本号

include $(INCLUDE_DIR)/package.mk

define KernelPackage/chardrv #内核模块
  SUBMENU:=Other modules #进行归类
  TITLE:=chardrv  #标题
  FILES:=$(PKG_BUILD_DIR)/chardrv.ko #模块文件
  AUTOLOAD:=$(call AutoLoad,61,chardrv,1) #开启自动装载
  KCONFIG:=
endef

define KernelPackage/chardrv/description
 Kernel module for register chardrv. #描述
endef

EXTRA_KCONFIG:= \
    CONFIG_CHARDRV=m

EXTRA_CFLAGS:= \
    $(patsubst CONFIG_%, -DCONFIG_%=1, $(patsubst %=m,%,$(filter %=m,$(EXTRA_KCONFIG)))) \
    $(patsubst CONFIG_%, -DCONFIG_%=1, $(patsubst %=y,%,$(filter %=y,$(EXTRA_KCONFIG)))) \

MAKE_OPTS:= \
    ARCH="$(LINUX_KARCH)" \
    CROSS_COMPILE="$(TARGET_CROSS)" \
    SUBDIRS="$(PKG_BUILD_DIR)" \
    EXTRA_CFLAGS="$(EXTRA_CFLAGS)" \
    $(EXTRA_KCONFIG)

define Build/Prepare
    mkdir -p $(PKG_BUILD_DIR)
    $(CP) ./src/* $(PKG_BUILD_DIR)/
endef

define Build/Compile
    $(MAKE) -C "$(LINUX_DIR)" \
        $(MAKE_OPTS) \
        modules
endef

$(eval $(call KernelPackage,chardrv))

2、src目录下的Makefile文件内容：

obj-${CONFIG_CHARDRV} += chardrv.o

3、src目录下的chardrv.c文件内容：

/***************************** 
*
*   字符设备驱动程序模板
*
*******************************/ 
#include  
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/****************  基本定义 **********************/ 

#define LED_ON 0
#define LED_OFF 1

//define registers 
volatile unsigned long *GPIO_CTRL_0;// GPIO0-GPIO31 direction control register 
volatile unsigned long *GPIO_DATA_0;// GPIO0-GPIO31 data register 
volatile unsigned long *GPIO1_MODE;// GPIO1 purpose selection register 
volatile unsigned long *AGPIO_CFG;// Analog GPIO configuartion, GPIO14-17 purpose

//加密函数参数内容： _IOW(IOW_CHAR , IOW_NUMn , IOW_TYPE) 
//加密函数用于chardrv_ioctl函数中 
//使用举例：ioctl(fd , _IOW('L',0x80,long) , 0x1); 

//#define NUMn chardrv 
#define IOW_CHAR 'L' 
#define IOW_TYPE  long 
#define IOW_NUM1  0x80 

//初始化函数必要资源定义 
//用于初始化函数当中 
//device number; 
    //设备号 
    dev_t dev_num; 
//struct dev 

//字符设备 
    struct cdev chardrv_cdev; 
//auto "mknode /dev/chardrv c dev_num minor_num" 

//自动创建设备对象 
struct class *chardrv_class = NULL; 
struct device *chardrv_device = NULL; 

/**************** 结构体 file_operations 成员函数 *****************/ 

//open 
static int chardrv_open(struct inode *inode, struct file *file) 
{ 
    printk("chardrv drive open...\n"); 
      *GPIO_DATA_0&=~(1<<11);
    return 0; 
} 
//close 
static int chardrv_close(struct inode *inode , struct file *file) 
{ 
    printk("chardrv drive close...\n"); 
    return 0; 
} 

//read 
static ssize_t chardrv_read(struct file *file, char __user *buffer, size_t len, loff_t *pos) 
{ 
    int ret_v = 0; 
    printk("chardrv drive read...\n"); 
    return ret_v; 
} 


//write 
static ssize_t chardrv_write( struct file *file , const char __user *buffer, size_t len , loff_t *offset ) 
{ 
    int ret_v = 0; 
    printk("chardrv drive write...\n"); 
    return ret_v; 
} 

//unlocked_ioctl 
static int chardrv_ioctl (struct file *filp , unsigned int cmd , unsigned long arg) 
{ 
    int ret_v = 0; 
    printk("chardrv drive ioctl...\n"); 
    switch(cmd) { 
        //常规： 
        //cmd值自行进行修改 
    case LED_ON: 
        { 
            *GPIO_DATA_0 |= (1<<11);
           printk("set gpio 0 on\n"); 
    } 
    break; 

    case LED_OFF:
        {
            *GPIO_DATA_0 &= ~(1<<11);
            printk("set gpio 0 off\n"); 
        }
    break; 
    //带密码保护： 
    //请在"基本定义"进行必要的定义 
    case _IOW(IOW_CHAR,IOW_NUM1,IOW_TYPE): 
    { 
        if(arg == 0x1) //第二条件 
        {

        } 
    } 
    break;  

    default: 
    break; 
    } 
    return ret_v;

} /***************** 结构体： file_operations ，该结构体将驱动中的函数和应用层函数关联（例如当调用应用层调用open函数时就会调用驱动中的open函数）************************/ 
static const struct file_operations chardrv_fops = { 
    .owner = THIS_MODULE, 
    .open = chardrv_open, 
    .release = chardrv_close, 
    .read = chardrv_read, 
    .write = chardrv_write, 
    .unlocked_ioctl = chardrv_ioctl, 
}; 

unsigned char init_flag = 0;
unsigned char add_code_flag = 0;

//使用insmod挂载驱动时回调 
static __init int chardrv_init(void) 
{ 
    int ret_v = 0; 
    printk("mydrv drive init...\n"); 
    /*
    函数alloc_chrdev_region主要参数说明：
    参数1： 自动分配的设备号
    参数2： 次设备号
    参数3： 创建多少个设备
    */ 
    if( ( ret_v = alloc_chrdev_region(&dev_num,0,1,"chardrv") ) < 0 ) //为chardrv动态分配设备号 
    { 
        goto dev_reg_error; 
    } 

    init_flag = 1; //标示设备创建成功   

    //打印主设备号和次设备号 
    printk("The drive info of chardrv:\nmajor: %d\nminor: %d\n", MAJOR(dev_num),MINOR(dev_num)); 

    //关联设备和操作函数 
    cdev_init(&chardrv_cdev,&chardrv_fops); 
    //注册设备 
    if( (ret_v = cdev_add(&chardrv_cdev,dev_num,1)) != 0 ) 
    { 
        goto cdev_add_error; 
    } 

    //创建设备类，用于自动创建设备 
    chardrv_class = class_create(THIS_MODULE,"chardrv"); 
    if( IS_ERR(chardrv_class) ) 
    { 
        goto class_c_error; 
    } 

    //通过设备类创建设备 
    chardrv_device = device_create(chardrv_class,NULL,dev_num,NULL,"chardrv"); 
    if( IS_ERR(chardrv_device) ) 
    { 
        goto device_c_error; 
    } 
    printk("auto mknod success!\n"); 
    //------------   请在此添加您的初始化程序  --------------// 
    //AGPIO_CFG = (volatile unsigned long *)ioremap(0x1000003c,4); //init register address 
    GPIO1_MODE = (volatile unsigned long *)ioremap(0x10000060,4); 
    GPIO_CTRL_0 = (volatile unsigned long *)ioremap(0x10000600,4); 
    GPIO_DATA_0 = (volatile unsigned long *)ioremap(0x10000620,4); 

    *GPIO1_MODE&=~(1<<1); //set SPIS purpose as GPIO11
    *GPIO1_MODE|=1; 

    *GPIO_CTRL_0|=(1<<11); //set GPIO17 as output pin

    //如果需要做错误处理，请：goto mydrv_error; 
    add_code_flag = 1;  
    //----------------------  END  ---------------------------// 
    goto init_success; 
    
dev_reg_error: 
    printk("alloc_chrdev_region failed\n"); 
    return ret_v; 

cdev_add_error: 
    printk("cdev_add failed\n"); 
    unregister_chrdev_region(dev_num, 1); 

    init_flag = 0;
    return ret_v; 
class_c_error: 
    printk("class_create failed\n"); 
    cdev_del(&chardrv_cdev); 
    unregister_chrdev_region(dev_num, 1); 
    init_flag = 0;
    return PTR_ERR(chardrv_class); 
device_c_error: 
    printk("device_create failed\n"); 
    cdev_del(&chardrv_cdev); 
    unregister_chrdev_region(dev_num, 1); 
    class_destroy(chardrv_class); 
    init_flag = 0;

    return PTR_ERR(chardrv_device); 
//------------------ 请在此添加您的错误处理内容 ----------------// 
chardrv_error: 
   add_code_flag = 0; 
    return -1; 
//--------------------          END         -------------------// 
init_success: 
    printk("chardrv init success!\n"); 
    return 0; 
} 
//使用rmmod卸载驱动是回调该函数 
static __exit void chardrv_exit(void) 
{ 
  printk("chardrv drive exit...\n"); 
    if (add_code_flag == 1)
    {
        printk("free your resources...\n"); 
        iounmap(GPIO1_MODE); 
        iounmap(GPIO_CTRL_0); 
        iounmap(GPIO_DATA_0); 
        printk("free finish\n");
    }

    //释放初始化使用到的资源; 
    if (init_flag == 1) {
        cdev_del(&chardrv_cdev); 
        unregister_chrdev_region(dev_num, 1); 
        device_unregister(chardrv_device); 
        class_destroy(chardrv_class); 
    }
}

/**************** module operations**********************/
 //声明加载函数和卸载函数 
 module_init(chardrv_init); 
 module_exit(chardrv_exit); 
 //some infomation 

 MODULE_LICENSE("GPL v2"); 
 MODULE_AUTHOR("LFJ"); 
 /*********************  The End ***************************/

四、编译驱动

1、切换到源码目录的根目录：如openwrt目录
2、make menconfig
3、选择Kernel modules -->other modules-->kmod-chardrv，保存退出
4、sudo make package/kernel/chardrv/compile V=99
5、编译成功后的文件在openwrt/bin/ramips/packages/kernel/ 目录下的kmod-chardrv_4.4.7-2_ramips_24kec.ipk文件

五、装载驱动模块到内核和卸载模块

1、可以通过scp将kmod-chardrv_4.4.7-2_ramips_24kec.ipk文件拷贝到板子上
2、在板子上执行opkg install kmod-chardrv_4.4.7-2_ramips_24kec.ipk 执行成功后在/lib/modules/4.4.7/目录下可以找到chardrv.ko文件
3、insmod chardrv.ko #将装载到内核中
4、rmmod chardrv.ko #将chardrv.ko模块从内核中卸载

六、应用程序测试

1、编写应用程序测试代码my_led.c

/*************************************************************************
    > File Name: led_app.c
    > Author: 
    > Mail: LFJ
    > Created Time: 2019年01月17日 星期四 17时56分19秒
 ************************************************************************/
#include  
#include  
#include  
#include  
#include  
#include  
#include  
#define LED_ON 0 
#define LED_OFF 1 

char str_dev[]="/dev/leddrv";
int main(int argc,char* argv[]) 
{ 
    int fd;

    if(argc!=2) { 
        printf(" %s  to turn on or off LED on GPIO11\n",argv[0]); 
        return -1; 
    }
    fd=open(str_dev,O_RDWR|O_NONBLOCK); 
    if(fd<0) { 
        printf("can't open %s \n",str_dev); 
        return -1; 
    } if(!strcmp("on",argv[1])) {
        while(1) { 
            ioctl(fd,LED_ON); 
            sleep(1);
            ioctl(fd,LED_OFF); 
            sleep(1);
        } 
    } else if(!strcmp("off",argv[1])) {
        ioctl(fd,LED_OFF);
    } else { 
        printf(" %s  to turn on or off LED on GPIO11\n",argv[0]); 
        return -1; 
    }

 return 0; 
}

2、编译程序
执行mipsel-openwrt-linux-gcc my_led.c -o my_led
3、通过scp将my_led可执行文件拷贝到openwrt板子上./ my_led on执行，执行成功GPIO0将会循环亮、灭