Currently, watchdog subsystem require the misc subsystem to
register a watchdog. This may not be the case in case of an
early registration of a watchdog, which can be required when
the watchdog cannot be disabled.
This patch use deferral mechanism to remove this requirement.
Signed-off-by: Jean-Baptiste Theou <jtheou@xxxxxxxxxxxxxxxxxx>
---
drivers/watchdog/watchdog_core.c | 92 ++++++++++++++++++++++++++++++++++++++--
include/linux/watchdog.h | 3 ++
2 files changed, 91 insertions(+), 4 deletions(-)
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index cec9b55..edf6294 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -43,6 +43,41 @@
static DEFINE_IDA(watchdog_ida);
static struct class *watchdog_class;
+/*
+ * Deferred Registration infrastructure.
+ *
+ * Sometimes watchdog drivers need to be loaded as soon as possible,
+ * for example when it's impossible to disable it. To do so,
+ * raising the initcall level of the watchdog driver is a solution.
+ * But in such case, the miscdev is maybe not ready (subsys_initcall), and
+ * watchdog core need miscdev to be populate.
+ *
+ * The deferred registration infrastructure offer a way for the watchdog
+ * subsystem to register a watchdog properly, even before miscdev is ready
+ *
+ * This is based on driver probe deferral mechanism.
+ */
+
+static DEFINE_MUTEX(watchdog_deferred_registration_mutex);
+static LIST_HEAD(watchdog_deferred_registration_pending_list);
+static bool watchdog_deferred_registration_done;
+
+static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
+{
+ dev_dbg(wdd->dev, "Added to deferred list\n");
+ list_add(&wdd->deferred_registration,
+ &watchdog_deferred_registration_pending_list);
+ return 0;
+}
+
+static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
+{
+ if (!list_empty(&wdd->deferred_registration)) {
+ dev_dbg(wdd->dev, "Removed from deferred list\n");
+ list_del_init(&wdd->deferred_registration);
+ }
+}
+
static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
{
/*
@@ -99,7 +134,7 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
EXPORT_SYMBOL_GPL(watchdog_init_timeout);
/**
- * watchdog_register_device() - register a watchdog device
+ * __watchdog_register_device() - register a watchdog device
* @wdd: watchdog device
*
* Register a watchdog device with the kernel so that the
@@ -108,7 +143,7 @@ EXPORT_SYMBOL_GPL(watchdog_init_timeout);
* A zero is returned on success and a negative errno code for
* failure.
*/
-int watchdog_register_device(struct watchdog_device *wdd)
+int __watchdog_register_device(struct watchdog_device *wdd)
{
int ret, id, devno;
@@ -164,16 +199,35 @@ int watchdog_register_device(struct watchdog_device *wdd)
return 0;
}
+
+/*
+ * watchdog_register_device use either the deferred approach,
+ * or directly register the watchdog, depending on the current
+ * initcall level.
+ */
+
+int watchdog_register_device(struct watchdog_device *wdd)
+{
+ int ret;
+
+ mutex_lock(&watchdog_deferred_registration_mutex);
+ if (watchdog_deferred_registration_done)
+ ret = __watchdog_register_device(wdd);
+ else
+ ret = watchdog_deferred_registration_add(wdd);
+ mutex_unlock(&watchdog_deferred_registration_mutex);
+ return ret;
+}
EXPORT_SYMBOL_GPL(watchdog_register_device);
/**
- * watchdog_unregister_device() - unregister a watchdog device
+ * __watchdog_unregister_device() - unregister a watchdog device
* @wdd: watchdog device to unregister
*
* Unregister a watchdog device that was previously successfully
* registered with watchdog_register_device().
*/
-void watchdog_unregister_device(struct watchdog_device *wdd)
+void __watchdog_unregister_device(struct watchdog_device *wdd)
{
int ret;
int devno;
@@ -189,8 +243,37 @@ void watchdog_unregister_device(struct watchdog_device *wdd)
ida_simple_remove(&watchdog_ida, wdd->id);
wdd->dev = NULL;
}
+
+void watchdog_unregister_device(struct watchdog_device *wdd)
+{
+ mutex_lock(&watchdog_deferred_registration_mutex);
+ if (watchdog_deferred_registration_done)
+ __watchdog_unregister_device(wdd);
+ else
+ watchdog_deferred_registration_del(wdd);
+ mutex_unlock(&watchdog_deferred_registration_mutex);
+}
+
EXPORT_SYMBOL_GPL(watchdog_unregister_device);
+/**
+ * watchdog_deferred_registration_initcall() - Register queued watchdog
+ */
+static int watchdog_deferred_registration_initcall(void)
+{
+ mutex_lock(&watchdog_deferred_registration_mutex);
+ watchdog_deferred_registration_done = true;
+ while (!list_empty(&watchdog_deferred_registration_pending_list)) {
+ struct watchdog_device *wdd = list_first_entry(&watchdog_deferred_registration_pending_list,
+ struct watchdog_device, deferred_registration);
+ list_del_init(&wdd->deferred_registration);
+ __watchdog_register_device(wdd);
+ }
+ mutex_unlock(&watchdog_deferred_registration_mutex);
+ return 0;
+}
+late_initcall(watchdog_deferred_registration_initcall);
+
static int __init watchdog_init(void)
{
int err;
@@ -222,5 +305,6 @@ module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>");
MODULE_AUTHOR("Wim Van Sebroeck <wim@xxxxxxxxx>");
+MODULE_AUTHOR("Jean-Baptiste Theou <jbtheou@xxxxxxxxx>");
MODULE_DESCRIPTION("WatchDog Timer Driver Core");
MODULE_LICENSE("GPL");
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index a746bf5..fcc190e 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -65,6 +65,8 @@ struct watchdog_ops {
* @driver-data:Pointer to the drivers private data.
* @lock: Lock for watchdog core internal use only.
* @status: Field that contains the devices internal status bits.
+ * @deferred_registration: entry in deferred_registration_list which is used to
+ * register early initialized watchdog.
*
* The watchdog_device structure contains all information about a
* watchdog timer device.
@@ -95,6 +97,7 @@ struct watchdog_device {
#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
#define WDOG_NO_WAY_OUT 3 /* Is 'nowayout' feature set ? */
#define WDOG_UNREGISTERED 4 /* Has the device been unregistered */
+ struct list_head deferred_registration;
};
#define WATCHDOG_NOWAYOUT IS_BUILTIN(CONFIG_WATCHDOG_NOWAYOUT)
--
2.4.2
--
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