/**********************************************************************
* linux watchdog demo hacking
* 说明：
* 本文主要解析linux watchdog大概应该如何操作。
*
* 2016-3-28 深圳 南山平山村 曾剑锋
*********************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/watchdog.h>
int fd;
/*
* This function simply sends an IOCTL to the driver, which in turn ticks
* the PC Watchdog card to reset its internal timer so it doesn't trigger
* a computer reset.
* 这个函数仅仅是发送一个IOCTL命令给驱动，重新启动Watchdog的内部时钟计数器，
* 这样就不会导致系统重启。
*/
static void keep_alive(void)
{
int dummy;
ioctl(fd, WDIOC_KEEPALIVE, &dummy);
}
/*
* The main program. Run the program with "-d" to disable the card,
* or "-e" to enable the card.
* 主程序，通过传递参数-d来关闭watchdog，-e来打开watchdog。
*/
int main(int argc, char *argv[])
{
int flags;
// 打开设备节点
fd = open("/dev/watchdog", O_WRONLY);
if (fd == -) {
fprintf(stderr, "Watchdog device not enabled.\n");
fflush(stderr);
exit(-);
}
if (argc > ) {
// 关闭watchdog
if (!strncasecmp(argv[], "-d", )) {
flags = WDIOS_DISABLECARD;
ioctl(fd, WDIOC_SETOPTIONS, &flags);
fprintf(stderr, "Watchdog card disabled.\n");
fflush(stderr);
exit();
// 使能watchdog
} else if (!strncasecmp(argv[], "-e", )) {
flags = WDIOS_ENABLECARD;
ioctl(fd, WDIOC_SETOPTIONS, &flags);
fprintf(stderr, "Watchdog card enabled.\n");
fflush(stderr);
exit();
} else {
fprintf(stderr, "-d to disable, -e to enable.\n");
fprintf(stderr, "run by itself to tick the card.\n");
fflush(stderr);
exit();
}
} else {
fprintf(stderr, "Watchdog Ticking Away!\n");
fflush(stderr);
}
while() {
// 每一秒喂狗一次
keep_alive();
sleep();
}
}