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watchdog: watchdog_core: Add watchdog registration deferral mechanism

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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 introduces a deferral mechanism to remove this requirement.

Signed-off-by: Jean-Baptiste Theou <[email protected]>
Reviewed-by: Guenter Roeck <[email protected]>
Signed-off-by: Wim Van Sebroeck <[email protected]>
This commit is contained in:
Jean-Baptiste Theou 2015-06-09 09:55:02 -07:00 • committed by Wim Van Sebroeck
commit ef90174f82
3 changed files with 110 additions and 18 deletions
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118
drivers/watchdog/watchdog_core.c
View file

@ -43,6 +43,45 @@
static DEFINE_IDA(watchdog_ida);
static struct class *watchdog_class;
/*
* Deferred Registration infrastructure.
*
* Sometimes watchdog drivers needs 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 register the watchdog as a char device.
*
* The deferred registration infrastructure offer a way for the watchdog
* subsystem to register a watchdog properly, even before miscdev is ready.
*/
static DEFINE_MUTEX(wtd_deferred_reg_mutex);
static LIST_HEAD(wtd_deferred_reg_list);
static bool wtd_deferred_reg_done;
static int watchdog_deferred_registration_add(struct watchdog_device *wdd)
{
list_add_tail(&wdd->deferred,
&wtd_deferred_reg_list);
return 0;
}
static void watchdog_deferred_registration_del(struct watchdog_device *wdd)
{
struct list_head *p, *n;
struct watchdog_device *wdd_tmp;
list_for_each_safe(p, n, &wtd_deferred_reg_list) {
wdd_tmp = list_entry(p, struct watchdog_device,
deferred);
if (wdd_tmp == wdd) {
list_del(&wdd_tmp->deferred);
break;
}
}
}
static void watchdog_check_min_max_timeout(struct watchdog_device *wdd)
{
/*
@ -98,17 +137,7 @@ int watchdog_init_timeout(struct watchdog_device *wdd,
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);
/**
* watchdog_register_device() - register a watchdog device
* @wdd: watchdog device
*
* Register a watchdog device with the kernel so that the
* watchdog timer can be accessed from userspace.
*
* A zero is returned on success and a negative errno code for
* failure.
*/
int watchdog_register_device(struct watchdog_device *wdd)
static int __watchdog_register_device(struct watchdog_device *wdd)
{
int ret, id, devno;
@ -164,16 +193,33 @@ int watchdog_register_device(struct watchdog_device *wdd)
return 0;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);
/**
* watchdog_unregister_device() - unregister a watchdog device
* @wdd: watchdog device to unregister
* watchdog_register_device() - register a watchdog device
* @wdd: watchdog device
*
* Unregister a watchdog device that was previously successfully
* registered with watchdog_register_device().
* Register a watchdog device with the kernel so that the
* watchdog timer can be accessed from userspace.
*
* A zero is returned on success and a negative errno code for
* failure.
*/
void watchdog_unregister_device(struct watchdog_device *wdd)
int watchdog_register_device(struct watchdog_device *wdd)
{
int ret;
mutex_lock(&wtd_deferred_reg_mutex);
if (wtd_deferred_reg_done)
ret = __watchdog_register_device(wdd);
else
ret = watchdog_deferred_registration_add(wdd);
mutex_unlock(&wtd_deferred_reg_mutex);
return ret;
}
EXPORT_SYMBOL_GPL(watchdog_register_device);
static void __watchdog_unregister_device(struct watchdog_device *wdd)
{
int ret;
int devno;
@ -189,8 +235,43 @@ void watchdog_unregister_device(struct watchdog_device *wdd)
ida_simple_remove(&watchdog_ida, wdd->id);
wdd->dev = NULL;
}
/**
* 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)
{
mutex_lock(&wtd_deferred_reg_mutex);
if (wtd_deferred_reg_done)
__watchdog_unregister_device(wdd);
else
watchdog_deferred_registration_del(wdd);
mutex_unlock(&wtd_deferred_reg_mutex);
}
EXPORT_SYMBOL_GPL(watchdog_unregister_device);
static int __init watchdog_deferred_registration(void)
{
mutex_lock(&wtd_deferred_reg_mutex);
wtd_deferred_reg_done = true;
while (!list_empty(&wtd_deferred_reg_list)) {
struct watchdog_device *wdd;
wdd = list_first_entry(&wtd_deferred_reg_list,
struct watchdog_device, deferred);
list_del(&wdd->deferred);
__watchdog_register_device(wdd);
}
mutex_unlock(&wtd_deferred_reg_mutex);
return 0;
}
static int __init watchdog_init(void)
{
int err;
@ -207,6 +288,7 @@ static int __init watchdog_init(void)
return err;
}
watchdog_deferred_registration();
return 0;
}
@ -217,7 +299,7 @@ static void __exit watchdog_exit(void)
ida_destroy(&watchdog_ida);
}
subsys_initcall(watchdog_init);
subsys_initcall_sync(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox <[email protected]>");