watchdog: WatchDog Timer Driver Core - Add basic framework
The WatchDog Timer Driver Core is a framework that contains the common code for all watchdog-driver's. It also introduces a watchdog device structure and the operations that go with it. This is the introduction of this framework. This part supports the minimal watchdog userspace API (or with other words: the functionality to use /dev/watchdog's open, release and write functionality as defined in the simplest watchdog API). Extra functionality will follow in the next set of patches. Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Wim Van Sebroeck <wim@iguana.be> Acked-by: Arnd Bergmann <arnd@arndb.de> Acked-by: Wolfram Sang <w.sang@pengutronix.de>
This commit is contained in:
Wim Van Sebroeck
parent
5efc7a6222
commit
43316044d4
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@ -8,6 +8,8 @@ src/
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- directory holding watchdog related example programs.
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watchdog-api.txt
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- description of the Linux Watchdog driver API.
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watchdog-kernel-api.txt
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- description of the Linux WatchDog Timer Driver Core kernel API.
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watchdog-parameters.txt
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- information on driver parameters (for drivers other than
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the ones that have driver-specific files here)
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@ -0,0 +1,119 @@
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The Linux WatchDog Timer Driver Core kernel API.
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===============================================
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Last reviewed: 22-Jul-2011
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Wim Van Sebroeck <wim@iguana.be>
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Introduction
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------------
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This document does not describe what a WatchDog Timer (WDT) Driver or Device is.
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It also does not describe the API which can be used by user space to communicate
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with a WatchDog Timer. If you want to know this then please read the following
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file: Documentation/watchdog/watchdog-api.txt .
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So what does this document describe? It describes the API that can be used by
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WatchDog Timer Drivers that want to use the WatchDog Timer Driver Core
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Framework. This framework provides all interfacing towards user space so that
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the same code does not have to be reproduced each time. This also means that
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a watchdog timer driver then only needs to provide the different routines
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(operations) that control the watchdog timer (WDT).
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The API
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-------
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Each watchdog timer driver that wants to use the WatchDog Timer Driver Core
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must #include <linux/watchdog.h> (you would have to do this anyway when
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writing a watchdog device driver). This include file contains following
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register/unregister routines:
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extern int watchdog_register_device(struct watchdog_device *);
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extern void watchdog_unregister_device(struct watchdog_device *);
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The watchdog_register_device routine registers a watchdog timer device.
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The parameter of this routine is a pointer to a watchdog_device structure.
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This routine returns zero on success and a negative errno code for failure.
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The watchdog_unregister_device routine deregisters a registered watchdog timer
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device. The parameter of this routine is the pointer to the registered
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watchdog_device structure.
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The watchdog device structure looks like this:
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struct watchdog_device {
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const struct watchdog_info *info;
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const struct watchdog_ops *ops;
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void *driver_data;
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unsigned long status;
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};
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It contains following fields:
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* info: a pointer to a watchdog_info structure. This structure gives some
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additional information about the watchdog timer itself. (Like it's unique name)
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* ops: a pointer to the list of watchdog operations that the watchdog supports.
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* driver_data: a pointer to the drivers private data of a watchdog device.
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This data should only be accessed via the watchdog_set_drvadata and
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watchdog_get_drvdata routines.
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* status: this field contains a number of status bits that give extra
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information about the status of the device (Like: is the device opened via
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the /dev/watchdog interface or not, ...).
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The list of watchdog operations is defined as:
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struct watchdog_ops {
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struct module *owner;
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/* mandatory operations */
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int (*start)(struct watchdog_device *);
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int (*stop)(struct watchdog_device *);
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/* optional operations */
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int (*ping)(struct watchdog_device *);
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};
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It is important that you first define the module owner of the watchdog timer
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driver's operations. This module owner will be used to lock the module when
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the watchdog is active. (This to avoid a system crash when you unload the
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module and /dev/watchdog is still open).
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Some operations are mandatory and some are optional. The mandatory operations
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are:
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* start: this is a pointer to the routine that starts the watchdog timer
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device.
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The routine needs a pointer to the watchdog timer device structure as a
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parameter. It returns zero on success or a negative errno code for failure.
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* stop: with this routine the watchdog timer device is being stopped.
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The routine needs a pointer to the watchdog timer device structure as a
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parameter. It returns zero on success or a negative errno code for failure.
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Some watchdog timer hardware can only be started and not be stopped. The
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driver supporting this hardware needs to make sure that a start and stop
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routine is being provided. This can be done by using a timer in the driver
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that regularly sends a keepalive ping to the watchdog timer hardware.
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Not all watchdog timer hardware supports the same functionality. That's why
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all other routines/operations are optional. They only need to be provided if
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they are supported. These optional routines/operations are:
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* ping: this is the routine that sends a keepalive ping to the watchdog timer
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hardware.
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The routine needs a pointer to the watchdog timer device structure as a
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parameter. It returns zero on success or a negative errno code for failure.
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Most hardware that does not support this as a separate function uses the
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start function to restart the watchdog timer hardware. And that's also what
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the watchdog timer driver core does: to send a keepalive ping to the watchdog
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timer hardware it will either use the ping operation (when available) or the
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start operation (when the ping operation is not available).
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The status bits should (preferably) be set with the set_bit and clear_bit alike
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bit-operations. The status bits that are defined are:
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* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
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was opened via /dev/watchdog.
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(This bit should only be used by the WatchDog Timer Driver Core).
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To get or set driver specific data the following two helper functions should be
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used:
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static inline void watchdog_set_drvdata(struct watchdog_device *wdd, void *data)
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static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
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The watchdog_set_drvdata function allows you to add driver specific data. The
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arguments of this function are the watchdog device where you want to add the
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driver specific data to and a pointer to the data itself.
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The watchdog_get_drvdata function allows you to retrieve driver specific data.
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The argument of this function is the watchdog device where you want to retrieve
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data from. The function retruns the pointer to the driver specific data.
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@ -28,6 +28,17 @@ menuconfig WATCHDOG
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if WATCHDOG
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config WATCHDOG_CORE
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bool "WatchDog Timer Driver Core"
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---help---
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Say Y here if you want to use the new watchdog timer driver core.
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This driver provides a framework for all watchdog timer drivers
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and gives them the /dev/watchdog interface (and later also the
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sysfs interface).
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To compile this driver as a module, choose M here: the module will
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be called watchdog.
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config WATCHDOG_NOWAYOUT
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bool "Disable watchdog shutdown on close"
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help
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@ -2,6 +2,10 @@
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# Makefile for the WatchDog device drivers.
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#
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# The WatchDog Timer Driver Core.
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watchdog-objs += watchdog_core.o watchdog_dev.o
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obj-$(CONFIG_WATCHDOG_CORE) += watchdog.o
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# Only one watchdog can succeed. We probe the ISA/PCI/USB based
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# watchdog-cards first, then the architecture specific watchdog
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# drivers and then the architecture independent "softdog" driver.
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@ -0,0 +1,101 @@
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/*
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* watchdog_core.c
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*
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* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
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* All Rights Reserved.
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*
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* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
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*
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* This source code is part of the generic code that can be used
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* by all the watchdog timer drivers.
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*
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* Based on source code of the following authors:
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* Matt Domsch <Matt_Domsch@dell.com>,
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* Rob Radez <rob@osinvestor.com>,
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* Rusty Lynch <rusty@linux.co.intel.com>
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* Satyam Sharma <satyam@infradead.org>
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* Randy Dunlap <randy.dunlap@oracle.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
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* admit liability nor provide warranty for any of this software.
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* This material is provided "AS-IS" and at no charge.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h> /* For EXPORT_SYMBOL/module stuff/... */
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#include <linux/types.h> /* For standard types */
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#include <linux/errno.h> /* For the -ENODEV/... values */
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#include <linux/kernel.h> /* For printk/panic/... */
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#include <linux/watchdog.h> /* For watchdog specific items */
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#include <linux/init.h> /* For __init/__exit/... */
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#include "watchdog_dev.h" /* For watchdog_dev_register/... */
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/**
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* watchdog_register_device() - register a watchdog device
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* @wdd: watchdog device
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*
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* Register a watchdog device with the kernel so that the
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* watchdog timer can be accessed from userspace.
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*
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* A zero is returned on success and a negative errno code for
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* failure.
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*/
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int watchdog_register_device(struct watchdog_device *wdd)
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{
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int ret;
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if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
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return -EINVAL;
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/* Mandatory operations need to be supported */
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if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
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return -EINVAL;
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/*
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* Note: now that all watchdog_device data has been verified, we
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* will not check this anymore in other functions. If data gets
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* corrupted in a later stage then we expect a kernel panic!
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*/
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/* We only support 1 watchdog device via the /dev/watchdog interface */
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ret = watchdog_dev_register(wdd);
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if (ret) {
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pr_err("error registering /dev/watchdog (err=%d).\n", ret);
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(watchdog_register_device);
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/**
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* watchdog_unregister_device() - unregister a watchdog device
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* @wdd: watchdog device to unregister
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*
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* Unregister a watchdog device that was previously successfully
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* registered with watchdog_register_device().
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*/
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void watchdog_unregister_device(struct watchdog_device *wdd)
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{
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int ret;
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if (wdd == NULL)
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return;
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ret = watchdog_dev_unregister(wdd);
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if (ret)
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pr_err("error unregistering /dev/watchdog (err=%d).\n", ret);
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}
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EXPORT_SYMBOL_GPL(watchdog_unregister_device);
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MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
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MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
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MODULE_DESCRIPTION("WatchDog Timer Driver Core");
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MODULE_LICENSE("GPL");
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@ -0,0 +1,235 @@
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/*
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* watchdog_dev.c
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*
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* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
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* All Rights Reserved.
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*
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* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
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*
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*
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* This source code is part of the generic code that can be used
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* by all the watchdog timer drivers.
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*
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* This part of the generic code takes care of the following
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* misc device: /dev/watchdog.
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*
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* Based on source code of the following authors:
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* Matt Domsch <Matt_Domsch@dell.com>,
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* Rob Radez <rob@osinvestor.com>,
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* Rusty Lynch <rusty@linux.co.intel.com>
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* Satyam Sharma <satyam@infradead.org>
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* Randy Dunlap <randy.dunlap@oracle.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
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* admit liability nor provide warranty for any of this software.
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* This material is provided "AS-IS" and at no charge.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h> /* For module stuff/... */
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#include <linux/types.h> /* For standard types (like size_t) */
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#include <linux/errno.h> /* For the -ENODEV/... values */
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#include <linux/kernel.h> /* For printk/panic/... */
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#include <linux/fs.h> /* For file operations */
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#include <linux/watchdog.h> /* For watchdog specific items */
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#include <linux/miscdevice.h> /* For handling misc devices */
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#include <linux/init.h> /* For __init/__exit/... */
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#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
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/* make sure we only register one /dev/watchdog device */
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static unsigned long watchdog_dev_busy;
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/* the watchdog device behind /dev/watchdog */
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static struct watchdog_device *wdd;
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/*
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* watchdog_ping: ping the watchdog.
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* @wddev: the watchdog device to ping
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*
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* If the watchdog has no own ping operation then it needs to be
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* restarted via the start operation. This wrapper function does
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* exactly that.
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*/
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static int watchdog_ping(struct watchdog_device *wddev)
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{
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if (wddev->ops->ping)
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return wddev->ops->ping(wddev); /* ping the watchdog */
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else
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return wddev->ops->start(wddev); /* restart the watchdog */
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}
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/*
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* watchdog_write: writes to the watchdog.
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* @file: file from VFS
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* @data: user address of data
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* @len: length of data
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* @ppos: pointer to the file offset
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*
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* A write to a watchdog device is defined as a keepalive ping.
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*/
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static ssize_t watchdog_write(struct file *file, const char __user *data,
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size_t len, loff_t *ppos)
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{
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size_t i;
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char c;
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if (len == 0)
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return 0;
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for (i = 0; i != len; i++) {
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if (get_user(c, data + i))
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return -EFAULT;
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}
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/* someone wrote to us, so we send the watchdog a keepalive ping */
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watchdog_ping(wdd);
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return len;
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}
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/*
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* watchdog_open: open the /dev/watchdog device.
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* @inode: inode of device
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* @file: file handle to device
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*
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* When the /dev/watchdog device gets opened, we start the watchdog.
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* Watch out: the /dev/watchdog device is single open, so we make sure
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* it can only be opened once.
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*/
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static int watchdog_open(struct inode *inode, struct file *file)
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{
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int err = -EBUSY;
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/* the watchdog is single open! */
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if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
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return -EBUSY;
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/*
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* If the /dev/watchdog device is open, we don't want the module
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* to be unloaded.
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*/
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if (!try_module_get(wdd->ops->owner))
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goto out;
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err = wdd->ops->start(wdd);
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if (err < 0)
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goto out_mod;
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/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
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return nonseekable_open(inode, file);
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out_mod:
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module_put(wdd->ops->owner);
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out:
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clear_bit(WDOG_DEV_OPEN, &wdd->status);
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return err;
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}
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/*
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* watchdog_release: release the /dev/watchdog device.
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* @inode: inode of device
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* @file: file handle to device
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*
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* This is the code for when /dev/watchdog gets closed.
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*/
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static int watchdog_release(struct inode *inode, struct file *file)
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{
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int err;
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err = wdd->ops->stop(wdd);
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if (err != 0) {
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pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
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watchdog_ping(wdd);
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}
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/* Allow the owner module to be unloaded again */
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module_put(wdd->ops->owner);
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/* make sure that /dev/watchdog can be re-opened */
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clear_bit(WDOG_DEV_OPEN, &wdd->status);
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return 0;
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}
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static const struct file_operations watchdog_fops = {
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.owner = THIS_MODULE,
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.write = watchdog_write,
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.open = watchdog_open,
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.release = watchdog_release,
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};
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static struct miscdevice watchdog_miscdev = {
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.minor = WATCHDOG_MINOR,
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.name = "watchdog",
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.fops = &watchdog_fops,
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};
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/*
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* watchdog_dev_register:
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* @watchdog: watchdog device
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*
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* Register a watchdog device as /dev/watchdog. /dev/watchdog
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* is actually a miscdevice and thus we set it up like that.
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*/
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int watchdog_dev_register(struct watchdog_device *watchdog)
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{
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int err;
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/* Only one device can register for /dev/watchdog */
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if (test_and_set_bit(0, &watchdog_dev_busy)) {
|
||||
pr_err("only one watchdog can use /dev/watchdog.\n");
|
||||
return -EBUSY;
|
||||
}
|
||||
|
||||
wdd = watchdog;
|
||||
|
||||
err = misc_register(&watchdog_miscdev);
|
||||
if (err != 0) {
|
||||
pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
|
||||
watchdog->info->identity, WATCHDOG_MINOR, err);
|
||||
goto out;
|
||||
}
|
||||
|
||||
return 0;
|
||||
|
||||
out:
|
||||
wdd = NULL;
|
||||
clear_bit(0, &watchdog_dev_busy);
|
||||
return err;
|
||||
}
|
||||
|
||||
/*
|
||||
* watchdog_dev_unregister:
|
||||
* @watchdog: watchdog device
|
||||
*
|
||||
* Deregister the /dev/watchdog device.
|
||||
*/
|
||||
|
||||
int watchdog_dev_unregister(struct watchdog_device *watchdog)
|
||||
{
|
||||
/* Check that a watchdog device was registered in the past */
|
||||
if (!test_bit(0, &watchdog_dev_busy) || !wdd)
|
||||
return -ENODEV;
|
||||
|
||||
/* We can only unregister the watchdog device that was registered */
|
||||
if (watchdog != wdd) {
|
||||
pr_err("%s: watchdog was not registered as /dev/watchdog.\n",
|
||||
watchdog->info->identity);
|
||||
return -ENODEV;
|
||||
}
|
||||
|
||||
misc_deregister(&watchdog_miscdev);
|
||||
wdd = NULL;
|
||||
clear_bit(0, &watchdog_dev_busy);
|
||||
return 0;
|
||||
}
|
||||
|
|
@ -0,0 +1,33 @@
|
|||
/*
|
||||
* watchdog_core.h
|
||||
*
|
||||
* (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.
|
||||
*/
|
||||
|
||||
/*
|
||||
* Functions/procedures to be called by the core
|
||||
*/
|
||||
int watchdog_dev_register(struct watchdog_device *);
|
||||
int watchdog_dev_unregister(struct watchdog_device *);
|
||||
|
|
@ -59,6 +59,67 @@ struct watchdog_info {
|
|||
#define WATCHDOG_NOWAYOUT 0
|
||||
#endif
|
||||
|
||||
struct watchdog_ops;
|
||||
struct watchdog_device;
|
||||
|
||||
/** struct watchdog_ops - The watchdog-devices operations
|
||||
*
|
||||
* @owner: The module owner.
|
||||
* @start: The routine for starting the watchdog device.
|
||||
* @stop: The routine for stopping the watchdog device.
|
||||
* @ping: The routine that sends a keepalive ping to the watchdog device.
|
||||
*
|
||||
* The watchdog_ops structure contains a list of low-level operations
|
||||
* that control a watchdog device. It also contains the module that owns
|
||||
* these operations. The start and stop function are mandatory, all other
|
||||
* functions are optonal.
|
||||
*/
|
||||
struct watchdog_ops {
|
||||
struct module *owner;
|
||||
/* mandatory operations */
|
||||
int (*start)(struct watchdog_device *);
|
||||
int (*stop)(struct watchdog_device *);
|
||||
/* optional operations */
|
||||
int (*ping)(struct watchdog_device *);
|
||||
};
|
||||
|
||||
/** struct watchdog_device - The structure that defines a watchdog device
|
||||
*
|
||||
* @info: Pointer to a watchdog_info structure.
|
||||
* @ops: Pointer to the list of watchdog operations.
|
||||
* @driver-data:Pointer to the drivers private data.
|
||||
* @status: Field that contains the devices internal status bits.
|
||||
*
|
||||
* The watchdog_device structure contains all information about a
|
||||
* watchdog timer device.
|
||||
*
|
||||
* The driver-data field may not be accessed directly. It must be accessed
|
||||
* via the watchdog_set_drvdata and watchdog_get_drvdata helpers.
|
||||
*/
|
||||
struct watchdog_device {
|
||||
const struct watchdog_info *info;
|
||||
const struct watchdog_ops *ops;
|
||||
void *driver_data;
|
||||
unsigned long status;
|
||||
/* Bit numbers for status flags */
|
||||
#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
|
||||
};
|
||||
|
||||
/* Use the following functions to manipulate watchdog driver specific data */
|
||||
static inline void watchdog_set_drvdata(struct watchdog_device *wdd, void *data)
|
||||
{
|
||||
wdd->driver_data = data;
|
||||
}
|
||||
|
||||
static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
|
||||
{
|
||||
return wdd->driver_data;
|
||||
}
|
||||
|
||||
/* drivers/watchdog/core/watchdog_core.c */
|
||||
extern int watchdog_register_device(struct watchdog_device *);
|
||||
extern void watchdog_unregister_device(struct watchdog_device *);
|
||||
|
||||
#endif /* __KERNEL__ */
|
||||
|
||||
#endif /* ifndef _LINUX_WATCHDOG_H */
|
||||
|
|
|
|||
Reference in New Issue