linux下使用文件IO监听GPIO中断

完整的程序如下：

#include<stdlib.h>
#include<stdio.h>
#include<string.h>
#include<unistd.h>
#include<fcntl.h>
#include<poll.h>

#define MSG(args...) printf(args) 

//函数声明
static int gpio_export(int pin);
static int gpio_unexport(int pin);
static int gpio_direction(int pin, int dir);
static int gpio_write(int pin, int value);
static int gpio_read(int pin);
static int gpio_edge(int pin, int edge);

static int gpio_export(int pin)
{
    char buffer[64];
    int len;
    int fd;  

    fd = open("/sys/class/gpio/export", O_WRONLY);
    if (fd < 0)
    {
        MSG("Failed to open export for writing!\n");
        return(-1);
    }  

    len = snprintf(buffer, sizeof(buffer), "%d", pin);
    printf("%s,%d,%d\n",buffer,sizeof(buffer),len);
    if (write(fd, buffer, len) < 0)
    {
        MSG("Failed to export gpio!");
        return -1;
    }  

    close(fd);
    return 0;
}
static int gpio_unexport(int pin)
{
    char buffer[64];
    int len;
    int fd;  

    fd = open("/sys/class/gpio/unexport", O_WRONLY);
    if (fd < 0)
    {
        MSG("Failed to open unexport for writing!\n");
        return -1;
    }  

    len = snprintf(buffer, sizeof(buffer), "%d", pin);
    if (write(fd, buffer, len) < 0)
    {
        MSG("Failed to unexport gpio!");
        return -1;
    }  

    close(fd);
    return 0;
}
//dir: 0-->IN, 1-->OUT
static int gpio_direction(int pin, int dir)
{
    static const char dir_str[] = "in\0out";
    char path[64];
    int fd;  

    snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/direction", pin);
    fd = open(path, O_WRONLY);
    if (fd < 0)
    {
        MSG("Failed to open gpio direction for writing!\n");
        return -1;
    }  

    if (write(fd, &dir_str[dir == 0 ? 0 : 3], dir == 0 ? 2 : 3) < 0)
    {
        MSG("Failed to set direction!\n");
        return -1;
    }  

    close(fd);
    return 0;
}
//value: 0-->LOW, 1-->HIGH
static int gpio_write(int pin, int value)
{
    static const char values_str[] = "01";
    char path[64];
    int fd;  

    snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/value", pin);
    fd = open(path, O_WRONLY);
    if (fd < 0)
    {
        MSG("Failed to open gpio value for writing!\n");
        return -1;
    }  

    if (write(fd, &values_str[value == 0 ? 0 : 1], 1) < 0)
    {
        MSG("Failed to write value!\n");
        return -1;
    }  

    close(fd);
    return 0;
}
static int gpio_read(int pin)
{
    char path[64];
    char value_str[3];
    int fd;  

    snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/value", pin);
    fd = open(path, O_RDONLY);
    if (fd < 0)
    {
        MSG("Failed to open gpio value for reading!\n");
        return -1;
    }  

    if (read(fd, value_str, 3) < 0)
    {
        MSG("Failed to read value!\n");
        return -1;
    }  

    close(fd);
    return (atoi(value_str));
}
// none表示引脚为输入，不是中断引脚
// rising表示引脚为中断输入，上升沿触发
// falling表示引脚为中断输入，下降沿触发
// both表示引脚为中断输入，边沿触发
// 0-->none, 1-->rising, 2-->falling, 3-->both
static int gpio_edge(int pin, int edge)
{
const char dir_str[] = "none\0rising\0falling\0both";
char ptr;
char path[64];
    int fd;
switch(edge)
{
    case 0:
        ptr = 0;
        break;
    case 1:
        ptr = 5;
        break;
    case 2:
        ptr = 12;
        break;
    case 3:
        ptr = 20;
        break;
    default:
        ptr = 0;
} 

    snprintf(path, sizeof(path), "/sys/class/gpio/gpio%d/edge", pin);
    fd = open(path, O_WRONLY);
    if (fd < 0)
    {
        MSG("Failed to open gpio edge for writing!\n");
        return -1;
    }  

    if (write(fd, &dir_str[ptr], strlen(&dir_str[ptr])) < 0)
    {
        MSG("Failed to set edge!\n");
        return -1;
    }  

    close(fd);
    return 0;
}
//GPIO1_17
int main()
{
    int gpio_fd, ret;
    struct pollfd fds[1];
    char buff[10];
    unsigned char cnt = 0;

    gpio_unexport(44);
    gpio_unexport(45);

    //p8_12 init
    gpio_export(44);
    gpio_direction(44, 1);//output out
    gpio_write(44, 1);

    //p8_11 init
    gpio_export(45);
    gpio_direction(45, 0);//input in
    gpio_edge(45,2);
    gpio_fd = open("/sys/class/gpio/gpio45/value",O_RDONLY);
    if(gpio_fd < 0)
    {
        MSG("Failed to open value!\n");
        return -1;
    }
    fds[0].fd = gpio_fd;
    fds[0].events  = POLLPRI;

    while(1)
    {
        ret = read(gpio_fd,buff,10);
        if( ret == -1 )
        MSG("read\n");

        ret = poll(fds,1,0);
        if( ret == -1 )
        MSG("poll\n");
        if( fds[0].revents & POLLPRI)
        {
            ret = lseek(gpio_fd,0,SEEK_SET);
            if( ret == -1 )
            MSG("lseek\n");

            //gpio_write(44, cnt++%2);
            printf("**********************************\n");
        }
        usleep(5);
    }
    return 0;
}