7 GPIO 子系统/内核GPIO 的使用

demo.c

/* head file */
#include <linux/init.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
#include <linux/wait.h>
#include <linux/poll.h>
#include <linux/miscdevice.h>
#include <linux/sched.h>
#include <linux/io.h>
#include <linux/gpio.h>

#include "ioctl.h"

#define DEVNAME "gpioleds"

static int gpioleds[4] = { //定义引脚数组
    EXYNOS4X12_GPM4(0),
    EXYNOS4X12_GPM4(1),
    EXYNOS4X12_GPM4(2),
    EXYNOS4X12_GPM4(3),
};

enum {ON, OFF};//0 1

void mill_ctl_led(int cmd, int num)
{
    gpio_set_value(gpioleds[num-1], cmd);//设置相应gpio口值
}

int mill_ctl_stat (unsigned long arg)
{
    char kbuf[4];//定义4个灯的状态数组
    int i;

    for (i = 0; i < 4; i++) {
        kbuf[i] = !gpio_get_value(gpioleds[i]);//读取4个gpio口的状态值
    }

    if (copy_to_user((void *)arg, kbuf, 4))     {//将内核读取到的gpio状态值返回给应用层
        return -EINVAL;
    } 

    return 0;
}

static long 
mill_unlocked_ioctl (struct file *filp, unsigned int request, unsigned long arg)
{
    if (_IOC_TYPE(request) != LEDTYPE) {
        return -EINVAL;
    }

    switch (_IOC_NR(request)) {
        default:
            return -EINVAL;
        case 1:
            if (arg < 1 || arg > 4) {
                return -EINVAL;
            }

            mill_ctl_led(ON, arg);
            break;
        case 2:
            if (arg < 1 || arg > 4) {
                return -EINVAL;
            }
            mill_ctl_led(OFF, arg);
            break;
        case 3:
            if (mill_ctl_stat(arg) < 0) {
                return -EINVAL;
            }
            break;
    }

    return 0;
}

static struct file_operations fops = {
    .owner         = THIS_MODULE,    
    .unlocked_ioctl = mill_unlocked_ioctl,
};


/*一个杂项设备对应如下一个结构体对象*/
static struct miscdevice misc = {
    .minor    = MISC_DYNAMIC_MINOR,
    .name    = DEVNAME,
    .fops    = &fops,    
};

static int __init demo_init(void)
{
    int i;
    int ret;

    for (i = 0; i < ARRAY_SIZE(gpioleds); ++i) {
        ret = gpio_request(gpioleds[i], "led");//申请要用的4个gpio口
        if (ret < 0) {
            goto error0;//申请失败则去一一释放
        }
        ret = gpio_direction_output(gpioleds[i], OFF);//设置gpio口为输出功能
        if (ret < 0) {
            gpio_free(gpioleds[i]);//不要忘了应该释放完全
            goto error0;//设置失败则去一一释放
        }
    }
    
    if((ret = misc_register(&misc)) < 0) {    //注册杂项设备
        goto error0;
    }

    return 0;
error0:
    while (i--) {
        gpio_free(gpioleds[i]);//一一释放
    }

    return ret;//返回错误负值
}

module_init(demo_init);

/* driver module exit */
static void __exit demo_exit(void)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(gpioleds); ++i) {
        gpio_set_value(gpioleds[i], OFF);//设置4个gpio口数据为1，即为默认状态下关灯
        gpio_free(gpioleds[i]);//释放所有gpio口
    }

    misc_deregister(&misc);//移除该杂项设备
}
module_exit(demo_exit);

/* driver module description */
MODULE_LICENSE("GPL");

MODULE_AUTHOR("millet9527");
MODULE_VERSION("millet plus 18");
MODULE_DESCRIPTION("example for driver module arch");

makefile

obj-m    := demo.o

KERNEL    := /linux-3.5

all:
    make -C $(KERNEL) M=`pwd`
clean:
    make -C $(KERNEL) M=`pwd` clean
    

ioctl.h

#ifndef _MILLET_LED_H_
#define _MILLET_LED_H_

#include <linux/ioctl.h>

#define  LEDTYPE 'l'

#define  LED_CTL_ON   _IOW(LEDTYPE, 1, int)
#define  LED_CTL_OFF  _IOW(LEDTYPE, 2, int)
#define  LED_CTL_STAT _IOR(LEDTYPE, 3, int)

#endif

ledapp.c

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <assert.h>

#include "ioctl.h"

void usage(char *str)
{
    printf("Usage:\n");
    printf("      %s on/off 1/2/3/4\n", str);
    printf("      %s state\n", str);
    
    exit(1);
}

int main(int argc, char **argv)
{
    int i;
    int fd;
    int ret;
    int request, arg;
    char buf[4] = { 0 };

    if((argc !=2) && (argc != 3)) {
        usage(argv[0]);
    }

    fd = open("/dev/gpioleds", O_RDWR | O_NDELAY);
    assert(fd > 0);

    if (argc == 3) {
        if (!strncmp("on", argv[1], 2)) {
            request = LED_CTL_ON;            
        } else if (!strncmp("off", argv[1], 3)) {
            request = LED_CTL_OFF;            
        } else {
            usage(argv[0]);
        }
        
        arg = atoi(argv[2]);
        
        if (arg < 1 || arg > 4) {
            usage(argv[0]);
        }

        ret = ioctl(fd, request, arg);
        assert(ret == 0);
    } else if (argc == 2) {
        if (!strncmp("state", argv[1], 5)) {
            request = LED_CTL_STAT;
        }
        ret = ioctl(fd, request, buf);
        assert(ret == 0);

        for (i = 0; i < 4; i++) {
            printf("led %d is %s!\n", i+1, \
                buf[i]?"on":"off");
        }
    }


    return 0;
}

ioctl.h

#ifndef _MILLET_LED_H_
#define _MILLET_LED_H_

#include <linux/ioctl.h>

#define  LEDTYPE 'l'

#define  LED_CTL_ON   _IOW(LEDTYPE, 1, int)
#define  LED_CTL_OFF  _IOW(LEDTYPE, 2, int)
#define  LED_CTL_STAT _IOR(LEDTYPE, 3, int)

#endif

makefile

 CC=arm-linux-gcc 

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