drivers/watchdog/gpio_wdt.c

Source file repositories/reference/linux-study-clean/drivers/watchdog/gpio_wdt.c

File Facts

System
Linux kernel
Corpus path
drivers/watchdog/gpio_wdt.c
Extension
.c
Size
4505 bytes
Lines
195
Domain
Driver Families
Bucket
drivers/watchdog
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

struct gpio_wdt_priv {
	struct gpio_desc	*gpiod;
	bool			state;
	bool			always_running;
	unsigned int		hw_algo;
	struct watchdog_device	wdd;
};

static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
{
	/* Eternal ping */
	gpiod_set_value_cansleep(priv->gpiod, 1);

	/* Put GPIO back to tristate */
	if (priv->hw_algo == HW_ALGO_TOGGLE)
		gpiod_direction_input(priv->gpiod);
}

static int gpio_wdt_ping(struct watchdog_device *wdd)
{
	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);

	switch (priv->hw_algo) {
	case HW_ALGO_TOGGLE:
		/* Toggle output pin */
		priv->state = !priv->state;
		gpiod_set_value_cansleep(priv->gpiod, priv->state);
		break;
	case HW_ALGO_LEVEL:
		/* Pulse */
		gpiod_set_value_cansleep(priv->gpiod, 1);
		udelay(1);
		gpiod_set_value_cansleep(priv->gpiod, 0);
		break;
	}
	return 0;
}

static int gpio_wdt_start(struct watchdog_device *wdd)
{
	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);

	priv->state = 0;
	gpiod_direction_output(priv->gpiod, priv->state);

	set_bit(WDOG_HW_RUNNING, &wdd->status);

	return gpio_wdt_ping(wdd);
}

static int gpio_wdt_stop(struct watchdog_device *wdd)
{
	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);

	if (!priv->always_running) {
		gpio_wdt_disable(priv);
	} else {
		set_bit(WDOG_HW_RUNNING, &wdd->status);
	}

	return 0;
}

static const struct watchdog_info gpio_wdt_ident = {
	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
			  WDIOF_SETTIMEOUT,
	.identity	= "GPIO Watchdog",
};

static const struct watchdog_ops gpio_wdt_ops = {
	.owner		= THIS_MODULE,
	.start		= gpio_wdt_start,
	.stop		= gpio_wdt_stop,
	.ping		= gpio_wdt_ping,
};

static int gpio_wdt_probe(struct platform_device *pdev)
{
	struct device *dev = &pdev->dev;
	struct gpio_wdt_priv *priv;
	enum gpiod_flags gflags;
	unsigned int hw_margin;
	const char *algo;
	int ret;

	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
		return -ENOMEM;

	platform_set_drvdata(pdev, priv);

Annotation

Implementation Notes