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    Subject[PATCH 01/11] 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>
    ---
    Documentation/watchdog/watchdog-kernel-api.txt | 103 ++++++++++
    drivers/watchdog/Kconfig | 11 +
    drivers/watchdog/Makefile | 4 +
    drivers/watchdog/watchdog_core.c | 108 ++++++++++
    drivers/watchdog/watchdog_dev.c | 261 ++++++++++++++++++++++++
    drivers/watchdog/watchdog_dev.h | 33 +++
    include/linux/watchdog.h | 27 +++
    7 files changed, 547 insertions(+), 0 deletions(-)
    create mode 100644 Documentation/watchdog/watchdog-kernel-api.txt
    create mode 100644 drivers/watchdog/watchdog_core.c
    create mode 100644 drivers/watchdog/watchdog_dev.c
    create mode 100644 drivers/watchdog/watchdog_dev.h

    diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
    new file mode 100644
    index 0000000..03c1066
    --- /dev/null
    +++ b/Documentation/watchdog/watchdog-kernel-api.txt
    @@ -0,0 +1,103 @@
    +The Linux WatchDog Timer Driver Core kernel API.
    +===============================================
    +Last reviewed: 09-Jul-2011
    +
    +Wim Van Sebroeck <wim@iguana.be>
    +
    +Introduction
    +------------
    +This document does not describe what a WatchDog Timer (WDT) Driver or Device is.
    +It also does not describe the API which can be used by user space to communicate
    +with a WatchDog Timer. If you want to know this then please read the following
    +file: Documentation/watchdog/watchdog-api.txt .
    +
    +So what does this document describe? It describes the API that can be used by
    +WatchDog Timer Drivers that want to use the WatchDog Timer Driver Core
    +Framework. This framework provides all interfacing towards user space so that
    +the same code does not have to be reproduced each time. This also means that
    +a watchdog timer driver then only needs to provide the different routines
    +(operations) that control the watchdog timer (WDT).
    +
    +The API
    +-------
    +Each watchdog timer driver that wants to use the WatchDog Timer Driver Core
    +must #include <linux/watchdog.h> (you would have to do this anyway when
    +writing a watchdog device driver). This include file contains following
    +register/unregister routines:
    +
    +extern int watchdog_register_device(struct watchdog_device *);
    +extern void watchdog_unregister_device(struct watchdog_device *);
    +
    +The watchdog_register_device routine registers a watchdog timer device.
    +The parameter of this routine is a pointer to a watchdog_device structure.
    +This routine returns zero on success and a negative errno code for failure.
    +
    +The watchdog_unregister_device routine deregisters a registered watchdog timer
    +device. The parameter of this routine is the pointer to the registered
    +watchdog_device structure.
    +
    +The watchdog device structure looks like this:
    +
    +struct watchdog_device {
    + const struct watchdog_info *info;
    + const struct watchdog_ops *ops;
    + void *priv;
    + unsigned long status;
    +};
    +
    +It contains following fields:
    +* info: a pointer to a watchdog_info structure. This structure gives some
    + additional information about the watchdog timer itself. (Like it's unique name)
    +* ops: a pointer to the list of watchdog operations that the watchdog supports.
    +* priv: a pointer to the private data of a watchdog device
    +* status: this field contains a number of status bits that give extra
    + information about the status of the device (Like: is the device opened via
    + the /dev/watchdog interface or not, ...)
    +
    +The list of watchdog operations is defined as:
    +
    +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 *);
    +};
    +
    +It is important that you first define the module owner of the watchdog timer
    +driver's operations. This module owner will be used to lock the module when
    +the watchdog is active. (This to avoid a system crash when you unload the
    +module and /dev/watchdog is still open).
    +Some operations are mandatory and some are optional. The mandatory operations
    +are:
    +* start: this is a pointer to the routine that starts the watchdog timer
    + device.
    + The routine needs a pointer to the watchdog timer device structure as a
    + parameter. It returns zero on success or a negative errno code for failure.
    +* stop: with this routine the watchdog timer device is being stopped.
    + The routine needs a pointer to the watchdog timer device structure as a
    + parameter. It returns zero on success or a negative errno code for failure.
    + Some watchdog timer hardware can only be started and not be stopped. The
    + driver supporting this hardware needs to make sure that a start and stop
    + routine is being provided. This can be done by using a timer in the driver
    + that regularly sends a keepalive ping to the watchdog timer hardware.
    +
    +Not all watchdog timer hardware supports the same functionality. That's why
    +all other routines/operations are optional. They only need to be provided if
    +they are supported. These optional routines/operations are:
    +* ping: this is the routine that sends a keepalive ping to the watchdog timer
    + hardware.
    + The routine needs a pointer to the watchdog timer device structure as a
    + parameter. It returns zero on success or a negative errno code for failure.
    + Most hardware that does not support this as a separate function uses the
    + start function to restart the watchdog timer hardware. And that's also what
    + the watchdog timer driver core does: to send a keepalive ping to the watchdog
    + timer hardware it will either use the ping operation (when available) or the
    + start operation (when the ping operation is not available).
    +
    +The status bits should (preferably) be set with the set_bit and clear_bit alike
    +bit-operations. The status bits that are defined are:
    +* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
    + was opened via /dev/watchdog.
    + (This bit should only be used by the WatchDog Timer Driver Core).
    diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
    index 372bc64..edb0f1b 100644
    --- a/drivers/watchdog/Kconfig
    +++ b/drivers/watchdog/Kconfig
    @@ -28,6 +28,17 @@ menuconfig WATCHDOG

    if WATCHDOG

    +config WATCHDOG_CORE
    + tristate "WatchDog Timer Driver Core"
    + ---help---
    + Say Y here if you want to use the new watchdog timer driver core.
    + This driver provides a framework for all watchdog timer drivers
    + and gives them the /dev/watchdog interface (and later also the
    + sysfs interface).
    +
    + To compile this driver as a module, choose M here: the module will
    + be called watchdog.
    +
    config WATCHDOG_NOWAYOUT
    bool "Disable watchdog shutdown on close"
    help
    diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
    index b2ddff7..7b26484 100644
    --- a/drivers/watchdog/Makefile
    +++ b/drivers/watchdog/Makefile
    @@ -2,6 +2,10 @@
    # Makefile for the WatchDog device drivers.
    #

    +# The WatchDog Timer Driver Core.
    +watchdog-objs += watchdog_core.o watchdog_dev.o
    +obj-$(CONFIG_WATCHDOG_CORE) += watchdog.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/watchdog_core.c b/drivers/watchdog/watchdog_core.c
    new file mode 100644
    index 0000000..79684ad
    --- /dev/null
    +++ b/drivers/watchdog/watchdog_core.c
    @@ -0,0 +1,108 @@
    +/*
    + * 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 files
    + */
    +#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 "watchdog_dev.h" /* For watchdog_dev_register/... */
    +
    +/**
    + * 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;
    +
    + /* Make sure we have a valid watchdog_device structure */
    + if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
    + return -EINVAL;
    +
    + /* Make sure that the mandatory operations are supported */
    + if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
    + return -EINVAL;
    +
    + /*
    + * 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!
    + */
    +
    + /* We only support 1 watchdog device via the /dev/watchdog interface */
    + ret = watchdog_dev_register(wdd);
    + if (ret) {
    + pr_err("error registering /dev/watchdog (err=%d).\n", ret);
    + return ret;
    + }
    +
    + return 0;
    +}
    +EXPORT_SYMBOL_GPL(watchdog_register_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)
    +{
    + int ret;
    +
    + /* Make sure we have a valid watchdog_device structure */
    + if (wdd == NULL)
    + return;
    +
    + /* remove the /dev/watchdog interface */
    + ret = watchdog_dev_unregister(wdd);
    + if (ret)
    + pr_err("error unregistering /dev/watchdog (err=%d).\n", ret);
    +}
    +EXPORT_SYMBOL_GPL(watchdog_unregister_device);
    +
    +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");
    +MODULE_SUPPORTED_DEVICE("watchdog");
    diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
    new file mode 100644
    index 0000000..c47154c
    --- /dev/null
    +++ b/drivers/watchdog/watchdog_dev.c
    @@ -0,0 +1,261 @@
    +/*
    + * watchdog_dev.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.
    + *
    + * This part of the generic code takes care of the following
    + * misc device: /dev/watchdog.
    + *
    + * 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 files
    + */
    +#include <linux/module.h> /* For module stuff/... */
    +#include <linux/types.h> /* For standard types (like size_t) */
    +#include <linux/errno.h> /* For the -ENODEV/... values */
    +#include <linux/kernel.h> /* For printk/panic/... */
    +#include <linux/fs.h> /* For file operations */
    +#include <linux/watchdog.h> /* For watchdog specific items */
    +#include <linux/miscdevice.h> /* For handling misc devices */
    +#include <linux/init.h> /* For __init/__exit/... */
    +#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
    +
    +/*
    + * Locally used variables
    + */
    +
    +/* make sure we only register one /dev/watchdog device */
    +static unsigned long watchdog_dev_busy;
    +/* the watchdog device behind /dev/watchdog */
    +static struct watchdog_device *wdd;
    +
    +/*
    + * /dev/watchdog operations
    + */
    +
    +/*
    + * watchdog_ping: ping the watchdog.
    + * @wddev: the watchdog device to ping
    + *
    + * If the watchdog has no own ping operation then it needs to be
    + * restarted via the start operation. This wrapper function does
    + * exactly that.
    + */
    +
    +static int watchdog_ping(struct watchdog_device *wddev)
    +{
    + if (wddev->ops->ping)
    + return wddev->ops->ping(wddev); /* ping the watchdog */
    + else
    + return wddev->ops->start(wddev); /* restart the watchdog */
    +}
    +
    +/*
    + * watchdog_write: writes to the watchdog.
    + * @file: file from VFS
    + * @data: user address of data
    + * @len: length of data
    + * @ppos: pointer to the file offset
    + *
    + * A write to a watchdog device is defined as a keepalive ping.
    + */
    +
    +static ssize_t watchdog_write(struct file *file, const char __user *data,
    + size_t len, loff_t *ppos)
    +{
    + size_t i;
    + char c;
    +
    + if (len == 0)
    + return 0;
    +
    + for (i = 0; i != len; i++) {
    + if (get_user(c, data + i))
    + return -EFAULT;
    + }
    +
    + /* someone wrote to us, so we send the watchdog a keepalive ping */
    + watchdog_ping(wdd);
    +
    + return len;
    +}
    +
    +/*
    + * watchdog_open: open the /dev/watchdog device.
    + * @inode: inode of device
    + * @file: file handle to device
    + *
    + * When the /dev/watchdog device gets opened, we start the watchdog.
    + * Watch out: the /dev/watchdog device is single open, so we make sure
    + * it can only be opened once.
    + */
    +
    +static int watchdog_open(struct inode *inode, struct file *file)
    +{
    + int err = -EBUSY;
    +
    + /* the watchdog is single open! */
    + if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
    + return -EBUSY;
    +
    + /*
    + * If the /dev/watchdog device is open, we don't want the module
    + * to be unloaded.
    + */
    + if (!try_module_get(wdd->ops->owner))
    + goto out;
    +
    + /* start the watchdog */
    + err = wdd->ops->start(wdd);
    + if (err < 0)
    + goto out_mod;
    +
    + /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
    + return nonseekable_open(inode, file);
    +
    +out_mod:
    + module_put(wdd->ops->owner);
    +out:
    + clear_bit(WDOG_DEV_OPEN, &wdd->status);
    + return err;
    +}
    +
    +/*
    + * watchdog_release: release the /dev/watchdog device.
    + * @inode: inode of device
    + * @file: file handle to device
    + *
    + * This is the code for when /dev/watchdog gets closed.
    + */
    +
    +static int watchdog_release(struct inode *inode, struct file *file)
    +{
    + int err;
    +
    + /* stop the watchdog */
    + err = wdd->ops->stop(wdd);
    + if (err != 0) {
    + pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
    + watchdog_ping(wdd);
    + }
    +
    + /* Allow the owner module to be unloaded again */
    + module_put(wdd->ops->owner);
    +
    + /* make sure that /dev/watchdog can be re-opened */
    + clear_bit(WDOG_DEV_OPEN, &wdd->status);
    +
    + return 0;
    +}
    +
    +/*
    + * /dev/watchdog kernel interfaces
    + */
    +
    +static const struct file_operations watchdog_fops = {
    + .owner = THIS_MODULE,
    + .llseek = no_llseek,
    + .write = watchdog_write,
    + .open = watchdog_open,
    + .release = watchdog_release,
    +};
    +
    +static struct miscdevice watchdog_miscdev = {
    + .minor = WATCHDOG_MINOR,
    + .name = "watchdog",
    + .fops = &watchdog_fops,
    +};
    +
    +/*
    + * /dev/watchdog register and unregister functions
    + */
    +
    +/*
    + * watchdog_dev_register:
    + * @watchdog: watchdog device
    + *
    + * Register a watchdog device as /dev/watchdog. /dev/watchdog
    + * is actually a miscdevice and thus we set it up like that.
    + */
    +
    +int watchdog_dev_register(struct watchdog_device *watchdog)
    +{
    + int err;
    +
    + /* Only one device can register for /dev/watchdog */
    + if (test_and_set_bit(0, &watchdog_dev_busy)) {
    + pr_err("only one watchdog can use /dev/watchdog.\n");
    + return -EBUSY;
    + }
    +
    + wdd = watchdog;
    +
    + /* Register the miscdevice */
    + 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;
    + }
    +
    + /* Unregister the miscdevice */
    + misc_deregister(&watchdog_miscdev);
    + wdd = NULL;
    + clear_bit(0, &watchdog_dev_busy);
    + return 0;
    +}
    +
    +MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
    diff --git a/drivers/watchdog/watchdog_dev.h b/drivers/watchdog/watchdog_dev.h
    new file mode 100644
    index 0000000..bc7612b
    --- /dev/null
    +++ b/drivers/watchdog/watchdog_dev.h
    @@ -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 *);
    diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
    index 011bcfe..40333ff 100644
    --- a/include/linux/watchdog.h
    +++ b/include/linux/watchdog.h
    @@ -59,6 +59,33 @@ struct watchdog_info {
    #define WATCHDOG_NOWAYOUT 0
    #endif

    +struct watchdog_ops;
    +struct watchdog_device;
    +
    +/* The watchdog-devices operations */
    +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 *);
    +};
    +
    +/* The structure that defines a watchdog device */
    +struct watchdog_device {
    + const struct watchdog_info *info;
    + const struct watchdog_ops *ops;
    + void *priv;
    + unsigned long status;
    +/* Bit numbers for status flags */
    +#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
    +};
    +
    +/* 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 */
    --
    1.7.6


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