UM0851 datasheet(213/245 Pages) STMICROELECTRONICS

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UM0851

Miscellaneous device drivers

Doc ID 16604 Rev 2

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Figure 60.

WDT software architecture

In the Linux source tree, the watchdog driver is present in drivers/watchdog/spr_wdt_st.c

9.2.3

Watchdog device driver interface with misc device layer

As mentioned, the watchdog driver behaves as a character device, so you use normal file

operations (open, close, ioctl, write) to access its features. For this the driver uses the misc

device layer and registers.

static const struct file_operations spear_wdt_fops = {

.owner = THIS_MODULE,

.write = spear_wdt_write,

.unlocked_ioctl = spear_wdt_ioctl,

.open = spear_wdt_open,

.release = spear_wdt_release,

};

/* minor no. is standard, defined in miscdevice.h */

spear_wdt_miscdev.minor = WATCHDOG_MINOR;

spear_wdt_miscdev.name = "watchdog";

spear_wdt_miscdev.fops = &spear_wdt_fops;

/* register watchdog driver */

ret = misc_register(&spear_wdt_miscdev);

9.2.4

Watchdog driver usage

The watchdog device driver provides a char device interface (/dev/watchdog) to the user.

You can use standard file operations to open and configure watchdog device. The following

sections explain how the watchdog device can be used.

Opening WDT

The watchdog timer is enabled as soon as it is opened by the user. The usual open call can

be used to open the watchdog device.

char wdt_dev[] = "/dev/watchdog"

int fd;

Watchdog daemon

/dev/watchdog

misc dev layer

Watchdog driver

Watchdog timer

Hardware

Kernel space

User space

application

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