#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/select.h>
#include <sys/time.h>
static int led_fd;
static int type = 1;
static void push_leds(void)
{
static unsigned step;
unsigned led_bitmap;
int i;
switch(type) {
case 0:
if (step >= 6) {
step = 0;
}
if (step < 3) {
led_bitmap = 1 << step;
} else {
led_bitmap = 1 << (6 - step);
}
break;
case 1:
if (step > 255) {
step = 0;
}
led_bitmap = step;
break;
default:
led_bitmap = 0;
}
step++;
for (i = 0; i < 4; i++) {
ioctl(led_fd, led_bitmap & 1, i);
led_bitmap >>= 1;
}
}
int main(void)
{
int led_control_pipe;
int null_writer_fd; // for read endpoint not blocking when control process exit
double period = 0.5;
led_fd = open("/dev/leds", 0);
if (led_fd < 0) {
perror("open device leds");
exit(1);
}
unlink("/tmp/led-control");
mkfifo("/tmp/led-control", 0666);
led_control_pipe = open("/tmp/led-control", O_RDONLY | O_NONBLOCK);
if (led_control_pipe < 0) {
perror("open control pipe for read");
exit(1);
}
null_writer_fd = open("/tmp/led-control", O_WRONLY | O_NONBLOCK);
if (null_writer_fd < 0) {
perror("open control pipe for write");
exit(1);
}
for (;;) {
fd_set rds;
struct timeval step;
int ret;
FD_ZERO(&rds);
FD_SET(led_control_pipe, &rds);
step.tv_sec = period;
step.tv_usec = (period - step.tv_sec) * 1000000L;
ret = select(led_control_pipe + 1, &rds, NULL, NULL, &step);
if (ret < 0) {
perror("select");
exit(1);
}
if (ret == 0) {
push_leds();
} else if (FD_ISSET(led_control_pipe, &rds)) {
static char buffer[200];
for (;;) {
char c;
int len = strlen(buffer);
if (len >= sizeof buffer - 1) {
memset(buffer, 0, sizeof buffer);
break;
}
if (read(led_control_pipe, &c, 1) != 1) {
break;
}
if (c == '\r') {
continue;
}
if (c == '\n') {
int tmp_type;
double tmp_period;
if (sscanf(buffer,"%d%lf", &tmp_type, &tmp_period) == 2) {
type = tmp_type;
period = tmp_period;
}
fprintf(stderr, "type is %d, period is %lf\n", type, period);
memset(buffer, 0, sizeof buffer);
break;
}
buffer[len] = c;
}
}
}
close(led_fd);
return 0;
}
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