linux-kernel - [PATCH 6/5] watchdog: Document reboot API

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Message-ID: <20140510162329.GA19884@roeck-us.net>
Date:	Sat, 10 May 2014 09:23:29 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Randy Dunlap <rdunlap@...radead.org>
Cc:	linux-watchdog@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Wim Van Sebroeck <wim@...ana.be>,
	Catalin Marinas <catalin.marinas@....com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Will Deacon <will.deacon@....com>,
	Arnd Bergmann <arnd@...db.de>,
	Heiko Stuebner <heiko@...ech.de>,
	Russell King <linux@....linux.org.uk>,
	Jonas Jensen <jonas.jensen@...il.com>,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: [PATCH 6/5] watchdog: Document reboot API

Document the new reboot API functionality.

Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 Documentation/watchdog/watchdog-kernel-api.txt | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index a0438f3..f8f0f18 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -90,6 +90,8 @@ struct watchdog_ops {
 	int (*stop)(struct watchdog_device *);
 	/* optional operations */
 	int (*ping)(struct watchdog_device *);
+	void (*reboot)(struct watchdog_device *, enum reboot_mode,
+		       const char *);
 	unsigned int (*status)(struct watchdog_device *);
 	int (*set_timeout)(struct watchdog_device *, unsigned int);
 	unsigned int (*get_timeleft)(struct watchdog_device *);
@@ -148,6 +150,10 @@ they are supported. These optional routines/operations are:
   info structure).
 * status: this routine checks the status of the watchdog timer device. The
   status of the device is reported with watchdog WDIOF_* status flags/bits.
+* reboot: if this routine is present, it may be called to reboot the system.
+  Parameters are the pointer to the watchdog device, the reboot mode, and a
+  command string. The latter two parameters are the system reboot mode
+  and the cmd parameter passed to machine_restart().
 * set_timeout: this routine checks and changes the timeout of the watchdog
   timer device. It returns 0 on success, -EINVAL for "parameter out of range"
   and -EIO for "could not write value to the watchdog". On success this
@@ -224,3 +230,11 @@ the device tree (if the module timeout parameter is invalid). Best practice is
 to set the default timeout value as timeout value in the watchdog_device and
 then use this function to set the user "preferred" timeout value.
 This routine returns zero on success and a negative errno code for failure.
+
+The watchdog_do_reboot function can be used reboot the system. This is intended
+to be used in systems which do not have an explicit reboot capability, but
+implement reboot by programming the watchdog to expire immediately. If the
+function is called, and a watchdog driver with reboot functionality was
+previously registered, the reboot function of that driver will be called.
+Architecture code should call watchdog_do_reboot from its machine_reboot
+function after other means to reboot the system failed.
-- 
1.9.1

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