Commit bc44fa73 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Wim Van Sebroeck
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watchdog: make nowayout sysfs file writable 



It can be useful to delay setting the nowayout feature for a watchdog
device. Moreover, not every driver (notably gpio_wdt) implements a
nowayout module parameter/otherwise respects CONFIG_WATCHDOG_NOWAYOUT,
and modifying those drivers carries a risk of causing a regression for
someone who has two watchdog devices, sets CONFIG_WATCHDOG_NOWAYOUT
and somehow relies on the gpio_wdt driver being ignorant of
that (i.e., allowing one to gracefully close a gpio_wdt but not the
other watchdog in the system).

So instead, simply make the nowayout sysfs file writable. Obviously,
setting nowayout is a one-way street.

Signed-off-by: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191105205118.11359-1-linux@rasmusvillemoes.dk


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@linux-watchdog.org>
parent a19f8933

Documentation/ABI/testing/sysfs-class-watchdog

+7 −2
Original line number Original line Diff line number Diff line
@@ -17,8 +17,13 @@ What: /sys/class/watchdog/watchdogn/nowayout 
Date:		August 2015

Date:		August 2015

Contact:	Wim Van Sebroeck <wim@iguana.be>

Contact:	Wim Van Sebroeck <wim@iguana.be>

Description:

Description:

		It is a read only file. While reading, it gives '1' if that

		It is a read/write file. While reading, it gives '1'

		device supports nowayout feature else, it gives '0'.

		if the device has the nowayout feature set, otherwise

		it gives '0'. Writing a '1' to the file enables the

		nowayout feature. Once set, the nowayout feature

		cannot be disabled, so writing a '0' either has no

		effect (if the feature was already disabled) or

		results in a permission error.





What:		/sys/class/watchdog/watchdogn/state

What:		/sys/class/watchdog/watchdogn/state

Date:		August 2015

Date:		August 2015

drivers/watchdog/watchdog_dev.c

+20 −1
Original line number Original line Diff line number Diff line
@@ -452,7 +452,26 @@ static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr, 




	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));

	return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));

}

}

static DEVICE_ATTR_RO(nowayout);



static ssize_t nowayout_store(struct device *dev, struct device_attribute *attr,

				const char *buf, size_t len)

{

	struct watchdog_device *wdd = dev_get_drvdata(dev);

	unsigned int value;

	int ret;



	ret = kstrtouint(buf, 0, &value);

	if (ret)

		return ret;

	if (value > 1)

		return -EINVAL;

	/* nowayout cannot be disabled once set */

	if (test_bit(WDOG_NO_WAY_OUT, &wdd->status) && !value)

		return -EPERM;

	watchdog_set_nowayout(wdd, value);

	return len;

}

static DEVICE_ATTR_RW(nowayout);





static ssize_t status_show(struct device *dev, struct device_attribute *attr,

static ssize_t status_show(struct device *dev, struct device_attribute *attr,

				char *buf)

				char *buf)

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