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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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