ARM上LED控制程序

ID:201115 · 发表于 2017-5-15 21:09

/********************************************************************
Header File Inclusion
*******************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <errno.h>

/********************************************************************
Macros
SH_USR_LED_CNT  : shell commnad for counting user led devices
SH_USR_LED_DEV  : shell command for retrieving user led devices' name
********************************************************************/
#define SH_USR_LED_CNT "find /sys/class/leds/*/ | grep trigger | \
                     xargs grep \'\\[default-on\\]\' | wc -l"
#define SH_USR_LED_DEV "find /sys/class/leds/*/ | grep trigger | \
                     xargs grep \'\\[default-on\\]\' |          \
                     awk -F \'/\' '{printf $5\"\\n\" }\'"
#define LEN_NAME 48
#define LEN_CMD 128
#define MAX_COUNT 10

/* quit signal tag */
volatile bool quit = false;

/*=====================restore_devices==================*/
/* set all led devices as [default on] state          */
static int restore_devices(char names[][LEN_NAME], int count) {
int i;
char cmd[MAX_COUNT][LEN_CMD];

for (i = 0; i < count; i++) {
      snprintf(cmd[i], LEN_CMD,
            "echo default-on > /sys/class/leds/%s/trigger", names[i]);
      if (system(cmd[i]) != 0) {
         fprintf(stderr, "fail to restore devices\n");
         return -1;
      }
}

return 0;
}

/*=====================turn_off==========================*/
/* turn off all led devices                            */
static int turn_off(char names[][LEN_NAME], int count) {
int i;
char cmd[MAX_COUNT][LEN_CMD];

for (i = 0; i < count; i++) {
      snprintf(cmd[i], LEN_CMD,
            "echo 0 > /sys/class/leds/%s/brightness", names[i]);
      if (system(cmd[i]) != 0) {
         fprintf(stderr, "fail to turn off %s\n", names[i]);
         return -1;
      }
}

return 0;
}

/*=====================turn_on===========================*/
/* turn on all led devices                            */
static int turn_on(char names[][LEN_NAME], int count) {
int i;
char cmd[MAX_COUNT][LEN_CMD];

for (i = 0; i < count; i++) {
      snprintf(cmd[i], LEN_CMD,
            "echo 1 > /sys/class/leds/%s/brightness", names[i]);
      if (system(cmd[i]) != 0) {
         fprintf(stderr, "fail to turn on %s\n", names[i]);
         return -1;
      }
}

return 0;
}

/*=====================show_devices======================*/
/* show all led devices                               */
static void show_devices(char names[][LEN_NAME], int count) {
int i;

printf("twinkle %d leds\n", count);
for (i = 0; i < count; i++)
      printf("%d. /sys/class/leds/%s\n", i + 1, names[i]);
}

/*=====================get_devices_names======================*/
/* retrieve user led devices' name                         */
static int get_devices_names(char names[][LEN_NAME], int count) {
int i;
FILE *f;

/* the popen() function opens a process by creating
   * a pipe, forking, and invoking the shell */
f = popen(SH_USR_LED_DEV, "r");
if (! f)
      goto err;

for (i = 0; i < count; i++)
      if (fscanf(f, "%s", names[i]) == EOF)
         goto err;

pclose(f);
return 0;

err:
fprintf(stderr, "something error, maybe there's no led device\n");
if (f)
      pclose(f);
return -1;
}

/*=================get_devices_count==================*/
/* retrieve the amount of user led devices          */
static int get_devices_count(int *count) {
FILE *f;

/* the popen() function opens a process by creating
   * a pipe, forking, and invoking the shell */
f = popen(SH_USR_LED_CNT, "r");
if (! f)
      goto err;

if(fscanf(f, "%d", count) == EOF)
      goto err;

if (*count == 0) {
      printf("warning: there's no led device\n");
      return -2;
}

if (*count > MAX_COUNT) {
      *count = MAX_COUNT;
      printf("warning: max numbuer of leds is %d, dope tail\n", MAX_COUNT);
}

pclose(f);
return 0;

err:
fprintf(stderr, "something error, maybe there's no led device\n");
if (f)
      pclose(f);
return -1;
}

/*=====================sig_handle======================*/
/* response to ctrl+c                               */
static void sig_handle(int signo) {
quit = true;
}

/*==============================main===============================*/
/* this program twinkle the leds which set as [defualt on] during  */
/* the time of kernel booting. you can check it by bellow command: */
/* $ cat /sys/class/leds/${device_name}/trigger                   */
int main(int argc, char **argv) {
int i;
int count;
char names[MAX_COUNT][LEN_NAME];

/* ctrl+c handler */
signal(SIGINT, sig_handle);

if (get_devices_count(&count) < 0)
      return -1;

if (get_devices_names(names, count) < 0)
      return -1;

show_devices(names, count);

/* twinkle
   * 1. turn on all leds
   * 2. sleep 0.5 s
   * 3. tunn off all leds
   * 4. goto 1
   * */
for (i = 0; i < 10; i++) {
      /* set as true while ctrl+c */
      if (quit)
         break;

      if (turn_on(names, count) < 0)
         break;

      usleep(500 * 1000);

      if (turn_off(names, count) < 0)
         break;
}

restore_devices(names, count);

return 0;
}

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