diff options
Diffstat (limited to 'drivers/watchdog/watchdog_dev.c')
| -rw-r--r-- | drivers/watchdog/watchdog_dev.c | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c new file mode 100644 index 000000000000..366f49ce69b8 --- /dev/null +++ b/drivers/watchdog/watchdog_dev.c @@ -0,0 +1,235 @@ +/* + * 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 <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/... */ + +/* 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; + +/* + * 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; + + 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; + + 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; +} + +static const struct file_operations watchdog_fops = { + .owner = THIS_MODULE, + .write = watchdog_write, + .open = watchdog_open, + .release = watchdog_release, +}; + +static struct miscdevice watchdog_miscdev = { + .minor = WATCHDOG_MINOR, + .name = "watchdog", + .fops = &watchdog_fops, +}; + +/* + * 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; + + 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; +} |
