#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;}