linux/drivers/watchdog/watchdog_core.c
Jean-Baptiste Theou ef90174f82 watchdog: watchdog_core: Add watchdog registration deferral mechanism
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 <jtheou@adeneo-embedded.us>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2015-06-29 11:51:06 +02:00

309 lines
8.3 KiB
C

/*
* watchdog_core.c
*
* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
* All Rights Reserved.
*
* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
*
* This source code is part of the generic code that can be used
* by all the watchdog timer drivers.
*
* Based on source code of the following authors:
* Matt Domsch <Matt_Domsch@dell.com>,
* Rob Radez <rob@osinvestor.com>,
* Rusty Lynch <rusty@linux.co.intel.com>
* Satyam Sharma <satyam@infradead.org>
* Randy Dunlap <randy.dunlap@oracle.com>
*
* 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.
*
* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
* admit liability nor provide warranty for any of this software.
* This material is provided "AS-IS" and at no charge.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */
#include <linux/types.h> /* For standard types */
#include <linux/errno.h> /* For the -ENODEV/... values */
#include <linux/kernel.h> /* For printk/panic/... */
#include <linux/watchdog.h> /* For watchdog specific items */
#include <linux/init.h> /* For __init/__exit/... */
#include <linux/idr.h> /* For ida_* macros */
#include <linux/err.h> /* For IS_ERR macros */
#include <linux/of.h> /* For of_get_timeout_sec */
#include "watchdog_core.h" /* For watchdog_dev_register/... */
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)
{
/*
* Check that we have valid min and max timeout values, if
* not reset them both to 0 (=not used or unknown)
*/
if (wdd->min_timeout > wdd->max_timeout) {
pr_info("Invalid min and max timeout values, resetting to 0!\n");
wdd->min_timeout = 0;
wdd->max_timeout = 0;
}
}
/**
* watchdog_init_timeout() - initialize the timeout field
* @timeout_parm: timeout module parameter
* @dev: Device that stores the timeout-sec property
*
* Initialize the timeout field of the watchdog_device struct with either the
* timeout module parameter (if it is valid value) or the timeout-sec property
* (only if it is a valid value and the timeout_parm is out of bounds).
* If none of them are valid then we keep the old value (which should normally
* be the default timeout value.
*
* A zero is returned on success and -EINVAL for failure.
*/
int watchdog_init_timeout(struct watchdog_device *wdd,
unsigned int timeout_parm, struct device *dev)
{
unsigned int t = 0;
int ret = 0;
watchdog_check_min_max_timeout(wdd);
/* try to get the timeout module parameter first */
if (!watchdog_timeout_invalid(wdd, timeout_parm) && timeout_parm) {
wdd->timeout = timeout_parm;
return ret;
}
if (timeout_parm)
ret = -EINVAL;
/* try to get the timeout_sec property */
if (dev == NULL || dev->of_node == NULL)
return ret;
of_property_read_u32(dev->of_node, "timeout-sec", &t);
if (!watchdog_timeout_invalid(wdd, t) && t)
wdd->timeout = t;
else
ret = -EINVAL;
return ret;
}
EXPORT_SYMBOL_GPL(watchdog_init_timeout);
static int __watchdog_register_device(struct watchdog_device *wdd)
{
int ret, id, devno;
if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
return -EINVAL;
/* Mandatory operations need to be supported */
if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
return -EINVAL;
watchdog_check_min_max_timeout(wdd);
/*
* Note: now that all watchdog_device data has been verified, we
* will not check this anymore in other functions. If data gets
* corrupted in a later stage then we expect a kernel panic!
*/
mutex_init(&wdd->lock);
id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
if (id < 0)
return id;
wdd->id = id;
ret = watchdog_dev_register(wdd);
if (ret) {
ida_simple_remove(&watchdog_ida, id);
if (!(id == 0 && ret == -EBUSY))
return ret;
/* Retry in case a legacy watchdog module exists */
id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
if (id < 0)
return id;
wdd->id = id;
ret = watchdog_dev_register(wdd);
if (ret) {
ida_simple_remove(&watchdog_ida, id);
return ret;
}
}
devno = wdd->cdev.dev;
wdd->dev = device_create(watchdog_class, wdd->parent, devno,
NULL, "watchdog%d", wdd->id);
if (IS_ERR(wdd->dev)) {
watchdog_dev_unregister(wdd);
ida_simple_remove(&watchdog_ida, id);
ret = PTR_ERR(wdd->dev);
return ret;
}
return 0;
}
/**
* 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)
{
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;
if (wdd == NULL)
return;
devno = wdd->cdev.dev;
ret = watchdog_dev_unregister(wdd);
if (ret)
pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
device_destroy(watchdog_class, devno);
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;
watchdog_class = class_create(THIS_MODULE, "watchdog");
if (IS_ERR(watchdog_class)) {
pr_err("couldn't create class\n");
return PTR_ERR(watchdog_class);
}
err = watchdog_dev_init();
if (err < 0) {
class_destroy(watchdog_class);
return err;
}
watchdog_deferred_registration();
return 0;
}
static void __exit watchdog_exit(void)
{
watchdog_dev_exit();
class_destroy(watchdog_class);
ida_destroy(&watchdog_ida);
}
subsys_initcall_sync(watchdog_init);
module_exit(watchdog_exit);
MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
MODULE_DESCRIPTION("WatchDog Timer Driver Core");
MODULE_LICENSE("GPL");