1、概述

通过在openwrt源码目录下（或者SDK包的openwrt的目录下）编写gpio的字符驱动生成ipk包，发送到开发板上insmod加载驱动，然后通过编写APP来进行测试。

2、在源码目录的 ./package/kernel下创建gpio_control_driver文件夹

mkdir gpio_control_driver

3、在gpio_control_driver文件夹下创建Makefile和src文件夹

mkdir src
touch Makefile

4、编写Makefile

include $(TOPDIR)/rules.mk
include $(INCLUDE_DIR)/kernel.mk
 
PKG_NAME:=gpio_control_driver
PKG_RELEASE:=1

include $(INCLUDE_DIR)/package.mk
 
define KernelPackage/$(PKG_NAME)
  SUBMENU:=Other modules
  DEPENDS:=@GPIO_SUPPORT
  TITLE:=Driver for FA156 gpios control
  FILES:=$(PKG_BUILD_DIR)/gpio_control_driver.ko
  AUTOLOAD:=$(call AutoLoad,30,gpio_control_driver)
endef
 
define KernelPackage/$(PKG_NAME)/description
 Kernel module to control gpios for  FA156
endef
 
 
define Build/Prepare
	mkdir -p $(PKG_BUILD_DIR)
	cp -rf  ./src/* $(PKG_BUILD_DIR)/
endef
 
define Build/Compile
	$(MAKE) -C "$(LINUX_DIR)" \
		CROSS_COMPILE="$(TARGET_CROSS)" \
		ARCH="$(LINUX_KARCH)" \
		SUBDIRS="$(PKG_BUILD_DIR)" \
		EXTRA_CFLAGS="$(BUILDFLAGS)" \
		$(EXTRA_KCONFIG) \
		modules
endef

$(eval $(call KernelPackage,$(PKG_NAME)))

makefile注释在https://editor.csdn.net/md/?articleId=109803571这篇文章里，我详细注释了。

5、进入src目录下创建gpio_control_driver.c 、 Makefile

touch gpio_control_driver.c 
touch Makefile

6、编写gpio_control_driver.c 、Makefile

Makefile：

obj-m := gpio_control_driver.o

gpio_control_driver.c:

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/cdev.h>
#include <linux/device.h>
#include <asm/uaccess.h>
#include <asm/io.h>

#define NEWCHRLED_CNT			1		  	
#define NEWCHRLED_NAME			"gpio_control"	
#define GPIO_CONTROL_SET_OUT			0x01
#define GPIO_CONTROL_SET_IN			    0x02
//#define GPIO_CONTROL_GET_DIRECTION	0x03
#define GPIO_CONTROL_SET_VALUE			0x04
#define GPIO_CONTROL_GET_VALUE			0x05
#define GPIO_CONTROL_REQUEST_GPIO		0x06
#define GPIO_CONTROL_FREE_GPIO			0x07
#define GET_GPIO_NUM(arg1)	        (unsigned char)((arg1 >> 24) & 0xff)
#define GET_GPIO_VALUE(arg1)	    (unsigned char)((arg1 >> 16) & 0xff)



struct  gpio_control_dev{
    
	dev_t devid;			
	struct cdev cdev;		
	struct class *class;		
	struct device *device;	
	int major;				
	int minor;				
};
struct  gpio_control_dev  gpio_control;

static int gpio_control_open(struct inode *pinode, struct file *pfile)
{
    
        printk("***%s***\n",__func__);

        return 0;
}

static int gpio_control_release(struct inode *pinode, struct file *pfile)
{
    
        printk("***%s***\n",__func__);

        return 0;
}
static long gpio_control_ioctl(struct file *pfile, unsigned int cmd, unsigned long arg)
{
    
	int ret;
	unsigned char gpio_number;
	unsigned char gpio_value;
 
 
	gpio_number = GET_GPIO_NUM(arg);
	gpio_value  = GET_GPIO_VALUE(arg);
 
	switch (cmd){
    
	case GPIO_CONTROL_SET_OUT:
		ret = gpio_direction_output(gpio_number, gpio_value);
		if (ret < 0){
    
			return -1;
		}
		break;
 
	case GPIO_CONTROL_SET_IN:
		ret = gpio_direction_input(gpio_number);
		if (ret < 0){
    
			return -1;
		}
		break;
	case GPIO_CONTROL_SET_VALUE:
		gpio_set_value(gpio_number, gpio_value);
		break;
 
	case GPIO_CONTROL_GET_VALUE:
		ret = gpio_get_value(gpio_number);
		if (ret < 0){
    
			return -1;
		}
		break;
 
	case GPIO_CONTROL_REQUEST_GPIO:
		if (0 > gpio_request(gpio_number, "gpio_ctrl")){
    
			return -1;
		}
		break;
 
	case GPIO_CONTROL_FREE_GPIO:
		gpio_free(gpio_number);
		break;
 
	default:
		printk("***Unknown command:0x%02X\n***\n", cmd);
		break;
 
	}
 
	return 0;
}

static const struct file_operations gpio_control_ops = {
    
                .owner                  = THIS_MODULE,
                .open                   = gpio_control_open,
                .release                = gpio_control_release,
                .unlocked_ioctl         = gpio_control_ioctl,
};

static int __init led_init(void)
{
    
    unsigned int ret = 0;

    /*1. register chrdev*/
    if (gpio_control.major) {
    		
		gpio_control.devid = MKDEV(gpio_control.major, 0);
		ret =register_chrdev_region(gpio_control.devid, NEWCHRLED_CNT, NEWCHRLED_NAME);
	} else {
    						
		ret = alloc_chrdev_region(&gpio_control.devid, 0, NEWCHRLED_CNT, NEWCHRLED_NAME);	
	}
    if(ret < 0 )
    {
    
        goto faial_alloc_chrdeev;
    }

    /* 2. init chrdev*/
    gpio_control.cdev.owner = THIS_MODULE;
	cdev_init(&gpio_control.cdev, &gpio_control_ops);
    
    /* 3. add chrdev */
    ret = cdev_add(&gpio_control.cdev, gpio_control.devid, NEWCHRLED_CNT);
    if (ret < 0)
    {
    
        goto faial_add_chrdeev;
    }
    /* 4. create class */
    gpio_control.class = class_create(THIS_MODULE, NEWCHRLED_NAME);
	if (IS_ERR(gpio_control.class)) {
    
        goto  faial_create_class;
	}
    
    /* 5. create device */
    gpio_control.device = device_create(gpio_control.class, NULL, gpio_control.devid, NULL, NEWCHRLED_NAME);
	if (IS_ERR(gpio_control.device)) {
    
		goto faial_create_device;
	}

    return 0;

faial_create_device:
    device_destroy(gpio_control.class, gpio_control.devid);
faial_create_class:
    class_destroy(gpio_control.class);
faial_add_chrdeev:
    cdev_del(&gpio_control.cdev);
faial_alloc_chrdeev:
    unregister_chrdev_region(gpio_control.devid, NEWCHRLED_CNT);

}

static void __exit led_exit(void)
{
    
    cdev_del(&gpio_control.cdev);
    unregister_chrdev_region(gpio_control.devid, NEWCHRLED_CNT);
    
    device_destroy(gpio_control.class, gpio_control.devid);
    class_destroy(gpio_control.class);
}

module_init(led_init);
module_exit(led_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("qingmu");

7、配置menuconfig

make  menuconfig

8、编译

回到openwrt的根目录下

make ./package/kernel/gpio_control_driver/compile V=s

9、把生成的ipk包发送到板子上去

找到生成的ipk包

发送到板子上去

scp ./bin/ipq/packages/base/kmod-gpio_control_driver_4.4.60-1_ipq.ipk [email protected]:/root

10、安装ipk包

opkg install kmod-gpio_control_driver_4.4.60-1_ipq.ipk

11、加载驱动

在/lib/modules/4.19.57/下可以找到gpio_control_driver.ko,执行

insmod gpio_control_driver.ko

这样驱动就加载完成了，如果想卸载，可以执行

rmmod gpio_control_driver.ko

12、驱动测试

12.1、同样的方式把测试文件也打包成ipk包发送到板子上运行

• 1、在openwrt的源码目录下（SDK包的openwrt的目录下）的./package目录下创建gpio_test目录，

mkdir gpio_test

• 2、在gpio_test的目录下创建Makefile和src目录

touch Makefile
mkdir src

• 3、编写Makefile
  makefile:

obj-m := gpio_control_driver.o

• 4、在src的目录下创建gpiotest.c、gpio_test.h、Makefile

touch gpiotest.c
touch gpiotest.h
touch Makefile

gpio_test.c :

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/time.h>
#include <sys/types.h>
#include "gpio_test.h"
 
static unsigned char gpio_pin;//define GPIOs to be use
static int gpio_dev_fd;
 
void demo1_release(int signal_no)
{
    
	ioctl(gpio_dev_fd, GPIO_CONTROL_SET_IN, GPIO_IOCTL_PRAM(gpio_pin, 0));
	ioctl(gpio_dev_fd, GPIO_CONTROL_FREE_GPIO, GPIO_IOCTL_PRAM(gpio_pin, 0));
	exit(0);
}
 
 
//指定管脚拉高, 拉低
int set_gpio(unsigned char pin, int state)
{
       
 
    if(state == 1)
    {
    
        ioctl(gpio_dev_fd, GPIO_CONTROL_SET_VALUE, GPIO_IOCTL_PRAM(pin, 1));
    }
    else if(state == 0)
    {
    
        ioctl(gpio_dev_fd, GPIO_CONTROL_SET_VALUE, GPIO_IOCTL_PRAM(pin, 0));
    }
    else
    {
    
        printf("No such set\n");
        goto ERROR;
    }
 
    return 0;
 
    ERROR:
        return -1; 
}
 
int gpio_init(int pin)
{
    
    int ret;
 
    gpio_pin = pin;
 
    gpio_dev_fd = open(GPIO_CONTROL_DEVICE_PATH, O_RDWR);//open gpio device
    if (gpio_dev_fd < 0){
    
        printf("###open %s ERROR###\n", GPIO_CONTROL_DEVICE_PATH);
        goto ERROR;
    }else{
    
        printf("***open %s success***\n", GPIO_CONTROL_DEVICE_PATH);
    }
    
    ret = ioctl(gpio_dev_fd, GPIO_CONTROL_REQUEST_GPIO, GPIO_IOCTL_PRAM(pin, 0));
	if (ret < 0){
    
		printf("###request GPIO %d error###", pin);
		goto ERROR;
	}
	ret = ioctl(gpio_dev_fd, GPIO_CONTROL_SET_OUT, GPIO_IOCTL_PRAM(pin, 0));
	if (ret < 0){
    
		printf("###set GPIO %d output error###", pin);
		goto ERROR;
	}
 
	signal(SIGINT, demo1_release);//register terminal signal
 
    return 0;
 
    ERROR:
        return -1; 
}
 
 
int main()
{
    
    gpio_init(30);
    gpio_init(29);
   
    while(1)
    {
    
        set_gpio(30, 0);
        usleep(200000);
        set_gpio(30, 1);
        usleep(200000);
        set_gpio(29, 0);
        usleep(200000);
        set_gpio(29, 1);
        usleep(200000);
    }
	return 0;
}

注意：我这里的LED的灯的gpio口是GPIO30和GPIO29，大家个根据自己的GPIO口进行更改

gpio_test.h :

#ifndef GPIO_CONTROL_TEST_H_
#define GPIO_CONTROL_TEST_H_
 
#define GPIO_CONTROL_DEVICE_PATH		"/dev/gpio_control"
 
#define GPIO_IOCTL_PRAM(gpio_num, arg1) (((unsigned long)gpio_num << 24) + ((unsigned long)arg1 << 16))
#define GET_GPIO_NUM(arg1) (unsigned char)((arg1 >> 24) & 0xff)
#define GET_GPIO_VALUE(arg1) (unsigned char)((arg1 >> 16) & 0xff)
 
//IOCTRL CMDs
#define GPIO_CONTROL_SET_OUT			0x01
#define GPIO_CONTROL_SET_IN			0x02
//#define GPIO_CONTROL_GET_DIRECTION		0x03
#define GPIO_CONTROL_SET_VALUE			0x04
#define GPIO_CONTROL_GET_VALUE			0x05
#define GPIO_CONTROL_REQUEST_GPIO		0x06
#define GPIO_CONTROL_FREE_GPIO			0x07
 
int set_gpio(unsigned char pin, int state);
int gpio_init(int pin);
void delay_ms(int ms);
 
 
 
#endif

• 5、回到openwrt根目录下编译

make ./package/gpio_test/compile V=s

• 6、找到对应的ipk包并发送到板子上

find ./ -name gpio_te*.ipk

发送到对应的开发板，这里大家根据自己的实际情况来：

scp ./bin/ipq/packages/base/gpio_test_1-1.0_ipq.ipk [email protected]:/root

• 6、安装goio_test的ipk包

opkg install gpio_test_1-1.0_ipq.ipk

• 7、运行gpio_test应用程序

gpio_test

此时LED灯开始闪烁，大功告成