linux-kernel - [PATCH v10 2/3] watchdog: introduce CONFIG_WATCHDOG_OPEN

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Message-ID: <20190605140628.618-3-rasmus.villemoes@prevas.dk>
Date:   Wed, 5 Jun 2019 14:06:43 +0000
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     "linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Jonathan Corbet <corbet@....net>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        Esben Haabendal <esben@...bendal.dk>,
        Jerry Hoemann <jerry.hoemann@....com>,
        Rasmus Villemoes <Rasmus.Villemoes@...vas.se>
Subject: [PATCH v10 2/3] watchdog: introduce CONFIG_WATCHDOG_OPEN_TIMEOUT

This allows setting a default value for the watchdog.open_timeout
commandline parameter via Kconfig.

Some BSPs allow remote updating of the kernel image and root file
system, but updating the bootloader requires physical access. Hence, if
one has a firmware update that requires relaxing the
watchdog.open_timeout a little, the value used must be baked into the
kernel image itself and cannot come from the u-boot environment via the
kernel command line.

Being able to set the initial value in .config doesn't change the fact
that the value on the command line, if present, takes precedence, and is
of course immensely useful for development purposes while one has
console acccess, as well as usable in the cases where one can make a
permanent update of the kernel command line.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@...vas.dk>
---
 Documentation/watchdog/watchdog-parameters.txt | 8 ++++----
 drivers/watchdog/Kconfig                       | 9 +++++++++
 drivers/watchdog/watchdog_dev.c                | 5 +++--
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/Documentation/watchdog/watchdog-parameters.txt b/Documentation/watchdog/watchdog-parameters.txt
index 32d3606caa65..ec919dc895ff 100644
--- a/Documentation/watchdog/watchdog-parameters.txt
+++ b/Documentation/watchdog/watchdog-parameters.txt
@@ -11,10 +11,10 @@ modules.
 The watchdog core parameter watchdog.open_timeout is the maximum time,
 in seconds, for which the watchdog framework will take care of pinging
 a running hardware watchdog until userspace opens the corresponding
-/dev/watchdogN device. A value of 0 (the default) means an infinite
-timeout. Setting this to a non-zero value can be useful to ensure that
-either userspace comes up properly, or the board gets reset and allows
-fallback logic in the bootloader to try something else.
+/dev/watchdogN device. A value of 0 means an infinite timeout. Setting
+this to a non-zero value can be useful to ensure that either userspace
+comes up properly, or the board gets reset and allows fallback logic
+in the bootloader to try something else.
 
 
 -------------------------------------------------
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index ffe754539f5a..a8bd621e12f8 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -58,6 +58,15 @@ config WATCHDOG_HANDLE_BOOT_ENABLED
 	  the watchdog on its own. Thus if your userspace does not start fast
 	  enough your device will reboot.
 
+config WATCHDOG_OPEN_TIMEOUT
+	int "Timeout value for opening watchdog device"
+	default 0
+	help
+	  The maximum time, in seconds, for which the watchdog framework takes
+	  care of pinging a hardware watchdog.  A value of 0 means infinite. The
+	  value set here can be overridden by the commandline parameter
+	  "watchdog.open_timeout".
+
 config WATCHDOG_SYSFS
 	bool "Read different watchdog information through sysfs"
 	help
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index e4b51db48f0e..334b810db2cf 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -88,7 +88,7 @@ static struct kthread_worker *watchdog_kworker;
 static bool handle_boot_enabled =
 	IS_ENABLED(CONFIG_WATCHDOG_HANDLE_BOOT_ENABLED);
 
-static unsigned open_timeout;
+static unsigned open_timeout = CONFIG_WATCHDOG_OPEN_TIMEOUT;
 
 static bool watchdog_past_open_deadline(struct watchdog_core_data *data)
 {
@@ -1214,4 +1214,5 @@ MODULE_PARM_DESC(handle_boot_enabled,
 
 module_param(open_timeout, uint, 0644);
 MODULE_PARM_DESC(open_timeout,
-	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default=0)");
+	"Maximum time (in seconds, 0 means infinity) for userspace to take over a running watchdog (default="
+	__MODULE_STRING(CONFIG_WATCHDOG_OPEN_TIMEOUT) ")");
-- 
2.20.1