// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
/*
 * Copyright (c) 2022 Wesion Technology Co., Ltd.
 *
 * Author: Yan <yan-wyb@foxmail.com> 
 *
 */

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

#define SYSFS_GPIO_DIR  "/sys/class/gpio"
#define MAX_BUF     255

int gpio_export(unsigned int gpio){

    int fd, len;
    char buf[MAX_BUF];

    fd = open(SYSFS_GPIO_DIR "/export", O_WRONLY);

    if (fd < 0) {
        fprintf(stderr, "Can't export GPIO %d pin: %s\n", gpio, strerror(errno));
        return fd;
    }

    len = snprintf(buf, sizeof(buf), "%d", gpio);
    write(fd, buf, len);
    close(fd);

    return 0;
}

int gpio_unexport(unsigned int gpio){

    int fd, len;
    char buf[MAX_BUF];

    fd = open(SYSFS_GPIO_DIR "/unexport", O_WRONLY);

    if (fd < 0) {
        fprintf(stderr, "Can't unexport GPIO %d pin: %s\n", gpio, strerror(errno));
        return fd;
    }

    len = snprintf(buf, sizeof(buf), "%d", gpio);
    write(fd, buf, len);
    close(fd);

    return 0;
}

int gpio_set_edge(unsigned int gpio, char *edge){

    int fd, len;
    char buf[MAX_BUF];

    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/edge", gpio);

    fd = open(buf, O_WRONLY);

    if (fd < 0) {
        fprintf(stderr, "Can't set GPIO %d pin edge: %s\n", gpio, strerror(errno));
        return fd;
    }

    write(fd, edge, strlen(edge)+1);
    close(fd);

    return 0;
}

int gpio_set_pull(unsigned int gpio, char *pull){

    int fd, len;
    char buf[MAX_BUF];

    len = snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/pull", gpio);

    fd = open(buf, O_WRONLY);

    if (fd < 0) {
        fprintf(stderr, "Can't set GPIO %d pin pull: %s\n", gpio, strerror(errno));
        return fd;
    }

    write(fd, pull, strlen(pull)+1);
    close(fd);

    return 0;
}

int main(int argc, char *argv[])
{
    struct pollfd fdset[2];
    int fd, ret, gpio;
    char buf[MAX_BUF];

    if (argc < 3 || argc > 4)   {
        fprintf(stdout, "usage : sudo sysfs_irq_test <gpio> <edge> [pull]\n");
        fflush(stdout);
        return  -1;
    }

    gpio = atoi(argv[1]);
    if (gpio_export(gpio))  {
        fprintf(stdout, "error : export %d\n", gpio);
        fflush(stdout);
        return  -1;
    }

    if (gpio_set_edge(gpio, argv[2])) {
        fprintf(stdout, "error : edge %s\n", argv[2]);
        fflush(stdout);
        return  -1;
    }

    if (argv[3] && gpio_set_pull(gpio, argv[3])) {
        fprintf(stdout, "error : pull %s\n", argv[3]);
        fflush(stdout);
        return  -1;
    }

    snprintf(buf, sizeof(buf), SYSFS_GPIO_DIR "/gpio%d/value", gpio);
    fd = open(buf, O_RDWR);
    if (fd < 0)
        goto out;

    while (1) {
        memset(fdset, 0, sizeof(fdset));
        fdset[0].fd = STDIN_FILENO;
        fdset[0].events = POLLIN;
        fdset[1].fd = fd;
        fdset[1].events = POLLPRI;
        ret = poll(fdset, 2, 3*1000);

        if (ret < 0) {
            perror("poll");
            break;
        }

        fprintf(stderr, ".");

        if (fdset[1].revents & POLLPRI) {
            char c;
            (void)read (fd, &c, 1) ;
            lseek (fd, 0, SEEK_SET) ;
            fprintf(stderr, "\nGPIO %d interrupt occurred!\n", gpio);
        }

        if (fdset[0].revents & POLLIN)
            break;

        fflush(stdout);
    }

    close(fd);
out:
    if (gpio_unexport(gpio))    {
        fprintf(stdout, "error : unexport %d\n", gpio);
        fflush(stdout);
    }

    return 0;
 }