UM0851 datasheet(214/245 Pages) STMICROELECTRONICS

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Miscellaneous device drivers

UM0851

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Doc ID 16604 Rev 2

fd = open(wdt_dev, O_RDWR);

if (fd < 0) {

printf("Error in opening device\n");

}

Configuring WDT

IOCTL calls can be used to program and configure watchdog timer. The following code

snippet demonstrates the use of these ioctls.

int ret = 0;

int timeleft=0;

struct watchdog_info ident;

int timeout = 45;

/* in seconds */

/* to find out supported options in watchdog */

ret = ioctl(fd, WDIOC_GETSUPPORT, &ident);

/* to set time out */

ioctl(fd, WDIOC_SETTIMEOUT, &timeout);

/* to find out how much time is left before reset */

ret = ioctl(fd, WDIOC_GETTIMEOUT, &timeleft);

/* Refresh watchdog timer at every 10 secs to prevent reset */

while (1) {

ioctl(fd, WDIOC,KEEPALIVE, 0);

sleep(10);

}

The following table lists the standard ioctl calls supported by the SPEAr watchdog driver.

Watchdog deamon

The watchdog is a daemon. It opens /dev/watchdog, and keeps writing to it often enough to

keep the kernel from resetting, at least once per minute. Each write delays the reboot time

another minute. After a minute the watchdog hardware generates a reset. The watchdog

can be stopped without causing a reboot if the device /dev/watchdog is closed correctly,

unless your kernel is compiled with the CONFIG_WATCHDOG_NOWAYOUT option

enabled.

Table 56.

Watchdog IOCTLs

IOCTLs

Purpose

WDIOC_GETSUPPORT

The fields returned in the ident structure are:

identity: A string identifying the watchdog driver firmware_version: the

firmware version of the card if available.

options: A flags describing what the device supports.

WDIOC_KEEPALIVE

This ioctl does exactly the same thing as a write to the watchdog device

and hence refreshes the timer

WDIOC_SETTIMEOUT

Set time out in seconds, after which reset would be generated (if wdt is

not refreshed)

WDIOC_GETTIMEOUT

Query the current timeout

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