9. Watchdog Operation Guide¶

This documentDescriptionin CV184x on the platformThrough Linux Watchdog Operation ， DriverConfiguration、Common ioctl andExampleCode。

9.1. Preparation¶

1. Kernel Requirements

Use SDK kernel，andEnsurefollowingConfigurationalready （Driver KernelBuild，No need to insmod）：

CONFIG_WATCHDOG=y
CONFIG_WATCHDOG_CORE=y
CONFIG_DW_WATCHDOG=y

2. UseMethod

in ThroughCommand LineOperation /dev/watchdog Device，orinKernel space/User spacePrograminThrough open、ioctl、write、close etc.InterfaceOperation can。

9.2. Operation Flow¶

UseFlowas follows：

EnableDevice ：Enable /dev/watchdog，Enable ，。
（Optional）SettingsTimeout ：Through WDIOC_SETTIMEOUT Set the timeout（seconds）；notSettings UseDriverDefaultValue（42 seconds）。
：Enableafter WDIOC_KEEPALIVE ， inDefault/SettingsTimeout 。
Period ：in Run ，inTimeout to before WDIOC_KEEPALIVE ； must beforeTimeout 。
DisableDevice ：not Need to ， Execute： WDIOC_SETOPTIONS WDIOS_DISABLECARD Disable ， write(fd, "V", 1) Write ， after close(fd)； DisableFileDescription after ，Timeoutwill 。

Need to beforeTimeoutor ，caninon Flowin Use WDIOC_GETTIMEOUT、WDIOC_GETTIMELEFT。

9.3. Operation Example¶

Overview

Watchdog Linux ，Provide 。UserThroughEnableDevice、Set the timeout、（keepalive）orDisableDevice canUse。
Timeout ，Systemwill 。
DefaultStatus ： DefaultDisable， User 。
canSettingsofTimeout （Unit：seconds）：1、2、5、10、21、42、85。IfSettingsofValuenotinon Table，Driver etc. Valueof ；for exampleSettings 8 seconds ，Actual 10 seconds。If SettingsTimeout，DriverDefaultUse 42 seconds。

followingExampleneedInclude File <linux/watchdog.h>，ioctl Macro（If WDIOC_SETTIMEOUT、WDIOC_KEEPALIVE） FileProvide，No need to Definition。

9.3.1. Enable Watchdog and feed it immediately¶

Enable /dev/watchdog ，。Enableafter ， inTimeout System 。

/* needInclude File：stdio.h, stdlib.h, unistd.h, fcntl.h, string.h, errno.h, sys/ioctl.h, linux/watchdog.h */
int wdt_fd;
int ret;

wdt_fd = open("/dev/watchdog", O_WRONLY);
if (wdt_fd < 0) {
    printf("Enable /dev/watchdog Failure: %s\n", strerror(errno));
    return -1;
}
printf("[Steps 1] Enable /dev/watchdog Success, fd=%d\n", wdt_fd);

ret = ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);
if (ret != 0)
    printf("Warning: Enableafter  ioctl Return %d: %s\n", ret, strerror(errno));
else
    printf("      EnableafteralreadyExecute  (WDIOC_KEEPALIVE)\n\n");

9.3.2. Set the timeout¶

Through ioctl WDIOC_SETTIMEOUT Set the timeout，Unitisseconds。canSettingsValueis：1、2、5、10、21、42、85； Value ，Driver etc. Valueof SupportValue。

int timeout = 10;   /* Unit：seconds，Support 1/2/5/10/21/42/85 */
int ret = ioctl(wdt_fd, WDIOC_SETTIMEOUT, &timeout);
if (ret != 0) {
    printf("[Steps 2] SettingsTimeoutFailure: %s\n", strerror(errno));
} else {
    printf("[Steps 2] SettingsTimeout %d secondsSuccess，DriverActual : %d seconds\n\n", 10, timeout);
}

9.3.3. Feed the Dog (Keepalive)¶

inTimeout to before，need WDIOC_KEEPALIVE ， Timeoutwill System 。 beforeSettingsofTimeout 。

const int keepalive_loops = 5;   /*  ，can is while(running) etc. */
int i;

printf("[Steps 3]  Period （  %d  ，  1 seconds）\n", keepalive_loops);
for (i = 0; i < keepalive_loops; i++) {
    ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);
    printf("        %d  \n", i + 1);
    sleep(1);
}
printf("\n");

9.3.4. Get the current timeout¶

Through WDIOC_GETTIMEOUT can Driver before ofTimeout （seconds）。

int timeout_sec = 0;
if (ioctl(wdt_fd, WDIOC_GETTIMEOUT, &timeout_sec) == 0) {
    printf("[Steps 4]  beforeTimeout : %d seconds\n", timeout_sec);
} else {
    printf("[Steps 4] GetTimeout Failure（Optional）\n");
}

9.3.5. Get the remaining time¶

IfDriverSupport，canThrough WDIOC_GETTIMELEFT under Timeout seconds， or 。

int timeleft_sec = 0;
if (ioctl(wdt_fd, WDIOC_GETTIMELEFT, &timeleft_sec) == 0) {
    printf("[Steps 5]  under Timeout : %d seconds\n\n", timeleft_sec);
} else {
    printf("[Steps 5] Get the remaining timenotSupportorFailure（Optional）\n\n");
}

9.3.6. Disable Watchdog（Magic Close）¶

DriverSupport Magic Close ：inDisableDevicebefore， must Disable ， DeviceWrite 'V'， after close。 Disable FileDescription ，，Timeout will System 。

：WDIOS_DISABLECARD → write(..., "V", 1) → close。

int option = WDIOS_DISABLECARD;
int ret;

printf("[Steps 6] Disable Watchdog (Magic Close)\n");
ret = ioctl(wdt_fd, WDIOC_SETOPTIONS, &option);
if (ret != 0)
    printf("      Warning: WDIOC_SETOPTIONS WDIOS_DISABLECARD Return %d: %s\n", ret, strerror(errno));

if (wdt_fd >= 0) {
    if (write(wdt_fd, "V", 1) != 1)
        printf("      Warning: Write  'V' Failure: %s\n", strerror(errno));
    else
        printf("      alreadyWrite  'V'\n");
    close(wdt_fd);
    wdt_fd = -1;
    printf("      already close Device\n");
}
printf("\nProgram \n");

9.3.7. CompleteUser-Space Program Example¶

followingiswillon Steps ofComplete C Program，can BuildRun。needInclude File <linux/watchdog.h>，ioctl Macro FileProvide。

/*
 * Watchdog Operation Example（  Linux  ）
 * needInclude File <linux/watchdog.h>，ioctl Macro FileProvide。
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <linux/watchdog.h>

int main(void)
{
    int wdt_fd;
    int timeout;
    int timeout_sec;
    int timeleft_sec;
    int option;
    int ret;
    int i;
    const int keepalive_loops = 5;  /*  ，can is while(running) etc. */

    printf("=== Watchdog Operation Example ===\n\n");

    /* Steps 1：Enable Watchdog and feed it immediately */
    wdt_fd = open("/dev/watchdog", O_WRONLY);
    if (wdt_fd < 0) {
        printf("Enable /dev/watchdog Failure: %s\n", strerror(errno));
        return -1;
    }
    printf("[Steps 1] Enable /dev/watchdog Success, fd=%d\n", wdt_fd);

    ret = ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);
    if (ret != 0)
        printf("Warning: Enableafter  ioctl Return %d: %s\n", ret, strerror(errno));
    else
        printf("      EnableafteralreadyExecute  (WDIOC_KEEPALIVE)\n\n");

    /* Steps 2：Set the timeout（Unit：seconds，Support 1/2/5/10/21/42/85） */
    timeout = 10;
    ret = ioctl(wdt_fd, WDIOC_SETTIMEOUT, &timeout);
    if (ret != 0) {
        printf("[Steps 2] SettingsTimeoutFailure: %s\n", strerror(errno));
    } else {
        printf("[Steps 2] SettingsTimeout %d secondsSuccess，DriverActual : %d seconds\n\n", 10, timeout);
    }

   /* Steps 3：SettingsTimeoutafter ，and Period  */
   ret = ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);
   if (ret != 0) {
       printf("[Steps 3] SettingsTimeoutafter Failure: %s\n", strerror(errno));
   } else {
       printf("[Steps 3] SettingsTimeoutafteralready \n");
   }

   printf("[Steps 3]  Period （  %d  ，  1 seconds）\n", keepalive_loops);
   for (i = 0; i < keepalive_loops; i++) {
       ret = ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);
       if (ret != 0) {
           printf("        %d  Failure: %s\n", i + 1, strerror(errno));
           break;
       }
       printf("        %d  Success\n", i + 1);
       sleep(1);
   }
   printf("\n");

   /* Steps 4：Get the current timeout */
   timeout_sec = 0;
   if (ioctl(wdt_fd, WDIOC_GETTIMEOUT, &timeout_sec) == 0) {
       printf("[Steps 4]  beforeTimeout : %d seconds\n", timeout_sec);
   } else {
       printf("[Steps 4] GetTimeout Failure（Optional）\n");
   }

   /* Steps 5：Get the remaining time（Optional， DriverSupport） */
   timeleft_sec = 0;
   if (ioctl(wdt_fd, WDIOC_GETTIMELEFT, &timeleft_sec) == 0) {
       printf("[Steps 5]  under Timeout : %d seconds\n\n", timeleft_sec);
   } else {
       printf("[Steps 5] Get the remaining timenotSupportorFailure（Optional）\n\n");
   }

    /* Steps 6：Disable Watchdog（Magic Close）*/
    /*  : WDIOS_DISABLECARD -> write("V", 1) -> close */
    printf("[Steps 6] Disable Watchdog (Magic Close)\n");
    option = WDIOS_DISABLECARD;
    ret = ioctl(wdt_fd, WDIOC_SETOPTIONS, &option);
    if (ret != 0)
        printf("      Warning: WDIOC_SETOPTIONS WDIOS_DISABLECARD Return %d: %s\n", ret, strerror(errno));

    if (wdt_fd >= 0) {
        if (write(wdt_fd, "V", 1) != 1)
            printf("      Warning: Write  'V' Failure: %s\n", strerror(errno));
        else
            printf("      alreadyWrite  'V'\n");
        close(wdt_fd);
        wdt_fd = -1;
        printf("      already close Device\n");
    }
    printf("\nProgram \n");
    return 0;
}

9.3.8. Quick Command-Line Example¶

followingDescriptionIf inCommand LineunderImplementationandon 「CompleteUser-Space Program Example」 ofFunction。Note ：Enable /dev/watchdog afterIfnot ，System inTimeoutafter ，Please inTests Use。SettingsTimeout（WDIOC_SETTIMEOUT）、 Timeout/ （WDIOC_GETTIMEOUT / WDIOC_GETTIMELEFT）needThrough C Programoretc. ToolsComplete； BuildandRunon ofCompleteUser spaceProgramwith Complete Steps。

： Complete Function

BuildandRunon 「CompleteUser-Space Program Example」inofComplete C Program，can Complete：Enableand 、SettingsTimeout、Get beforeTimeoutand 、Period 、Magic Close Disable。

# Build（Example： Fileis watchdog_demo.c ，BuildToolsis arm-none-linux-uclibcgnueabihf-gcc）
arm-none-linux-uclibcgnueabihf-gcc -o watchdog_demo watchdog_demo.c -static
# willRunFileCopyto ，andRun
./watchdog_demo

Steps 1：（）

in or ofbefore under，， andinTimeoutbefore 。

# Method 1：  watchdog Tools（10 secondsTimeout，after Run）
watchdog -t 10 /dev/watchdog &

# Method 2： Tools  Shell  
( while true; do echo -n '.' > /dev/watchdog; sleep 1; done ) &

Steps 2：Disable Watchdog（Magic Close）

killall watchdog   #   magic close Function， ExecuteDisable Operation