watchdog: pretimeout: add noop pretimeout governor

The change adds noop watchdog pretimeout governor, only an
informational message is printed to the kernel log buffer when a
watchdog triggers a pretimeout event.

While introducing the first pretimeout governor the selected design
assumes that the default pretimeout governor is selected by its name
and it is always built-in, thus the default pretimeout governor can
not be unregistered and the correspondent check can be removed from
the watchdog_unregister_governor() function.

Signed-off-by: Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

4 files changed, 81 insertions, 0 deletions

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 04d535ae497d..4aeb8f95beb4 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -1838,4 +1838,32 @@ config WATCHDOG_PRETIMEOUT_GOV
         help
           The option allows to select watchdog pretimeout governors.
 
+if WATCHDOG_PRETIMEOUT_GOV
+
+choice
+        prompt "Default Watchdog Pretimeout Governor"
+        default WATCHDOG_PRETIMEOUT_DEFAULT_GOV_PANIC
+        help
+          This option selects a default watchdog pretimeout governor.
+          The governor takes its action, if a watchdog is capable
+          to report a pretimeout event.
+
+config WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOOP
+        bool "noop"
+        select WATCHDOG_PRETIMEOUT_GOV_NOOP
+        help
+          Use noop watchdog pretimeout governor by default. If noop
+          governor is selected by a user, write a short message to
+          the kernel log buffer and don't do any system changes.
+
+endchoice
+
+config WATCHDOG_PRETIMEOUT_GOV_NOOP
+        tristate "Noop watchdog pretimeout governor"
+        help
+          Noop watchdog pretimeout governor, only an informational
+          message is added to kernel log buffer.
+
+endif # WATCHDOG_PRETIMEOUT_GOV
+
 endif # WATCHDOG
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 990c36ed4716..0502a21db1db 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -9,6 +9,8 @@ watchdog-objs	+= watchdog_core.o watchdog_dev.o
 
 watchdog-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV)      += watchdog_pretimeout.o
 
+obj-$(CONFIG_WATCHDOG_PRETIMEOUT_GOV_NOOP)      += pretimeout_noop.o
+
 # Only one watchdog can succeed. We probe the ISA/PCI/USB based
 # watchdog-cards first, then the architecture specific watchdog
 # drivers and then the architecture independent "softdog" driver.
diff --git a/drivers/watchdog/pretimeout_noop.c b/drivers/watchdog/pretimeout_noop.c
new file mode 100644
index 000000000000..85f5299d197c
--- /dev/null
+++ b/drivers/watchdog/pretimeout_noop.c
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2015-2016 Mentor Graphics
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/watchdog.h>
+
+#include "watchdog_pretimeout.h"
+
+/**
+ * pretimeout_noop - No operation on watchdog pretimeout event
+ * @wdd - watchdog_device
+ *
+ * This function prints a message about pretimeout to kernel log.
+ */
+static void pretimeout_noop(struct watchdog_device *wdd)
+{
+        pr_alert("watchdog%d: pretimeout event\n", wdd->id);
+}
+
+static struct watchdog_governor watchdog_gov_noop = {
+        .name           = "noop",
+        .pretimeout     = pretimeout_noop,
+};
+
+static int __init watchdog_gov_noop_register(void)
+{
+        return watchdog_register_governor(&watchdog_gov_noop);
+}
+
+static void __exit watchdog_gov_noop_unregister(void)
+{
+        watchdog_unregister_governor(&watchdog_gov_noop);
+}
+module_init(watchdog_gov_noop_register);
+module_exit(watchdog_gov_noop_unregister);
+
+MODULE_AUTHOR("Vladimir Zapolskiy <vladimir_zapolskiy@mentor.com>");
+MODULE_DESCRIPTION("Panic watchdog pretimeout governor");
+MODULE_LICENSE("GPL");
diff --git a/drivers/watchdog/watchdog_pretimeout.h b/drivers/watchdog/watchdog_pretimeout.h
index c6cd9f80adb2..c4b6f88dc9c9 100644
--- a/drivers/watchdog/watchdog_pretimeout.h
+++ b/drivers/watchdog/watchdog_pretimeout.h
@@ -20,6 +20,10 @@ int watchdog_register_pretimeout(struct watchdog_device *wdd);
 void watchdog_unregister_pretimeout(struct watchdog_device *wdd);
 int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf);
 
+#if IS_ENABLED(CONFIG_WATCHDOG_PRETIMEOUT_DEFAULT_GOV_NOOP)
+#define WATCHDOG_PRETIMEOUT_DEFAULT_GOV         "noop"
+#endif
+
 #else
 static inline int watchdog_register_pretimeout(struct watchdog_device *wdd)
 {