tools/gpio/lsgpio.c

   1 /*
   2  * lsgpio - example on how to list the GPIO lines on a system
   3  *
   4  * Copyright (C) 2015 Linus Walleij
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published by
   8  * the Free Software Foundation.
   9  *
  10  * Usage:
  11  *      lsgpio <-n device-name>
  12  */
  13
  14 #include <unistd.h>
  15 #include <stdlib.h>
  16 #include <stdbool.h>
  17 #include <stdio.h>
  18 #include <dirent.h>
  19 #include <errno.h>
  20 #include <string.h>
  21 #include <poll.h>
  22 #include <fcntl.h>
  23 #include <getopt.h>
  24 #include <sys/ioctl.h>
  25 #include <linux/gpio.h>
  26
  27 #include "gpio-utils.h"
  28
  29 int list_device(const char *device_name)
  30 {
  31         struct gpiochip_info cinfo;
  32         char *chrdev_name;
  33         int fd;
  34         int ret;
  35
  36         ret = asprintf(&chrdev_name, "/dev/%s", device_name);
  37         if (ret < 0)
  38                 return -ENOMEM;
  39
  40         fd = open(chrdev_name, 0);
  41         if (fd == -1) {
  42                 ret = -errno;
  43                 fprintf(stderr, "Failed to open %s\n", chrdev_name);
  44                 goto free_chrdev_name;
  45         }
  46
  47         /* Inspect this GPIO chip */
  48         ret = ioctl(fd, GPIO_GET_CHIPINFO_IOCTL, &cinfo);
  49         if (ret == -1) {
  50                 ret = -errno;
  51                 fprintf(stderr, "Failed to retrieve GPIO fd\n");
  52                 if (close(fd) == -1)
  53                         perror("Failed to close GPIO character device file");
  54
  55                 goto free_chrdev_name;
  56         }
  57         fprintf(stdout, "GPIO chip: %s, \"%s\", %u GPIO lines\n",
  58                 cinfo.name, cinfo.label, cinfo.lines);
  59
  60         if (close(fd) == -1)  {
  61                 ret = -errno;
  62                 goto free_chrdev_name;
  63         }
  64
  65 free_chrdev_name:
  66         free(chrdev_name);
  67
  68         return ret;
  69
  70 }
  71
  72 void print_usage(void)
  73 {
  74         fprintf(stderr, "Usage: lsgpio [options]...\n"
  75                 "List GPIO chips, lines and states\n"
  76                 "  -n <name>  List GPIOs on a named device\n"
  77                 "  -?         This helptext\n"
  78         );
  79 }
  80
  81 int main(int argc, char **argv)
  82 {
  83         const char *device_name;
  84         int ret;
  85         int c;
  86
  87         while ((c = getopt(argc, argv, "n:")) != -1) {
  88                 switch (c) {
  89                 case 'n':
  90                         device_name = optarg;
  91                         break;
  92                 case '?':
  93                         print_usage();
  94                         return -1;
  95                 }
  96         }
  97
  98         if (device_name)
  99                 ret = list_device(device_name);
 100         else {
 101                 const struct dirent *ent;
 102                 DIR *dp;
 103
 104                 /* List all GPIO devices one at a time */
 105                 dp = opendir("/dev");
 106                 if (!dp) {
 107                         ret = -errno;
 108                         goto error_out;
 109                 }
 110
 111                 ret = -ENOENT;
 112                 while (ent = readdir(dp), ent) {
 113                         if (check_prefix(ent->d_name, "gpiochip")) {
 114                                 ret = list_device(ent->d_name);
 115                                 if (ret)
 116                                         break;
 117                         }
 118                 }
 119
 120                 ret = 0;
 121                 if (closedir(dp) == -1) {
 122                         perror("scanning devices: Failed to close directory");
 123                         ret = -errno;
 124                 }
 125         }
 126 error_out:
 127         return ret;
 128 }