/* * watchdog_dev.c * * (c) Copyright 2008-2011 Alan Cox , * All Rights Reserved. * * (c) Copyright 2008-2011 Wim Van Sebroeck . * * * 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 , * Rob Radez , * Rusty Lynch * Satyam Sharma * Randy Dunlap * * 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 /* For module stuff/... */ #include /* For standard types (like size_t) */ #include /* For the -ENODEV/... values */ #include /* For printk/panic/... */ #include /* For file operations */ #include /* For watchdog specific items */ #include /* For handling misc devices */ #include /* For __init/__exit/... */ #include /* For copy_to_user/put_user/... */ #include "watchdog_core.h" /* the dev_t structure to store the dynamically allocated watchdog devices */ static dev_t watchdog_devt; /* the watchdog device behind /dev/watchdog */ static struct watchdog_device *old_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. * We only ping when the watchdog device is running. */ static int watchdog_ping(struct watchdog_device *wddev) { int err = 0; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_ping; } if (!watchdog_active(wddev)) goto out_ping; if (wddev->ops->ping) err = wddev->ops->ping(wddev); /* ping the watchdog */ else err = wddev->ops->start(wddev); /* restart watchdog */ out_ping: mutex_unlock(&wddev->lock); return err; } /* * watchdog_start: wrapper to start the watchdog. * @wddev: the watchdog device to start * * Start the watchdog if it is not active and mark it active. * This function returns zero on success or a negative errno code for * failure. */ static int watchdog_start(struct watchdog_device *wddev) { int err = 0; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_start; } if (watchdog_active(wddev)) goto out_start; err = wddev->ops->start(wddev); if (err == 0) set_bit(WDOG_ACTIVE, &wddev->status); out_start: mutex_unlock(&wddev->lock); return err; } /* * watchdog_stop: wrapper to stop the watchdog. * @wddev: the watchdog device to stop * * Stop the watchdog if it is still active and unmark it active. * This function returns zero on success or a negative errno code for * failure. * If the 'nowayout' feature was set, the watchdog cannot be stopped. */ static int watchdog_stop(struct watchdog_device *wddev) { int err = 0; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_stop; } if (!watchdog_active(wddev)) goto out_stop; if (test_bit(WDOG_NO_WAY_OUT, &wddev->status)) { dev_info(wddev->dev, "nowayout prevents watchdog being stopped!\n"); err = -EBUSY; goto out_stop; } err = wddev->ops->stop(wddev); if (err == 0) clear_bit(WDOG_ACTIVE, &wddev->status); out_stop: mutex_unlock(&wddev->lock); return err; } /* * watchdog_get_status: wrapper to get the watchdog status * @wddev: the watchdog device to get the status from * @status: the status of the watchdog device * * Get the watchdog's status flags. */ static int watchdog_get_status(struct watchdog_device *wddev, unsigned int *status) { int err = 0; *status = 0; if (!wddev->ops->status) return -EOPNOTSUPP; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_status; } *status = wddev->ops->status(wddev); out_status: mutex_unlock(&wddev->lock); return err; } /* * watchdog_set_timeout: set the watchdog timer timeout * @wddev: the watchdog device to set the timeout for * @timeout: timeout to set in seconds */ static int watchdog_set_timeout(struct watchdog_device *wddev, unsigned int timeout) { int err; if ((wddev->ops->set_timeout == NULL) || !(wddev->info->options & WDIOF_SETTIMEOUT)) return -EOPNOTSUPP; if (watchdog_timeout_invalid(wddev, timeout)) return -EINVAL; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_timeout; } err = wddev->ops->set_timeout(wddev, timeout); out_timeout: mutex_unlock(&wddev->lock); return err; } /* * watchdog_get_timeleft: wrapper to get the time left before a reboot * @wddev: the watchdog device to get the remaining time from * @timeleft: the time that's left * * Get the time before a watchdog will reboot (if not pinged). */ static int watchdog_get_timeleft(struct watchdog_device *wddev, unsigned int *timeleft) { int err = 0; *timeleft = 0; if (!wddev->ops->get_timeleft) return -EOPNOTSUPP; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_timeleft; } *timeleft = wddev->ops->get_timeleft(wddev); out_timeleft: mutex_unlock(&wddev->lock); return err; } /* * watchdog_ioctl_op: call the watchdog drivers ioctl op if defined * @wddev: the watchdog device to do the ioctl on * @cmd: watchdog command * @arg: argument pointer */ static int watchdog_ioctl_op(struct watchdog_device *wddev, unsigned int cmd, unsigned long arg) { int err; if (!wddev->ops->ioctl) return -ENOIOCTLCMD; mutex_lock(&wddev->lock); if (test_bit(WDOG_UNREGISTERED, &wddev->status)) { err = -ENODEV; goto out_ioctl; } err = wddev->ops->ioctl(wddev, cmd, arg); out_ioctl: mutex_unlock(&wddev->lock); return err; } /* * 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. * Writing the magic 'V' sequence allows the next close to turn * off the watchdog (if 'nowayout' is not set). */ static ssize_t watchdog_write(struct file *file, const char __user *data, size_t len, loff_t *ppos) { struct watchdog_device *wdd = file->private_data; size_t i; char c; if (len == 0) return 0; /* * Note: just in case someone wrote the magic character * five months ago... */ clear_bit(WDOG_ALLOW_RELEASE, &wdd->status); /* scan to see whether or not we got the magic character */ for (i = 0; i != len; i++) { if (get_user(c, data + i)) return -EFAULT; if (c == 'V') set_bit(WDOG_ALLOW_RELEASE, &wdd->status); } /* someone wrote to us, so we send the watchdog a keepalive ping */ watchdog_ping(wdd); return len; } /* * watchdog_ioctl: handle the different ioctl's for the watchdog device. * @file: file handle to the device * @cmd: watchdog command * @arg: argument pointer * * The watchdog API defines a common set of functions for all watchdogs * according to their available features. */ static long watchdog_ioctl(struct file *file, unsigned int cmd, unsigned long arg) { struct watchdog_device *wdd = file->private_data; void __user *argp = (void __user *)arg; int __user *p = argp; unsigned int val; int err; err = watchdog_ioctl_op(wdd, cmd, arg); if (err != -ENOIOCTLCMD) return err; switch (cmd) { case WDIOC_GETSUPPORT: return copy_to_user(argp, wdd->info, sizeof(struct watchdog_info)) ? -EFAULT : 0; case WDIOC_GETSTATUS: err = watchdog_get_status(wdd, &val); if (err == -ENODEV) return err; return put_user(val, p); case WDIOC_GETBOOTSTATUS: return put_user(wdd->bootstatus, p); case WDIOC_SETOPTIONS: if (get_user(val, p)) return -EFAULT; if (val & WDIOS_DISABLECARD) { err = watchdog_stop(wdd); if (err < 0) return err; } if (val & WDIOS_ENABLECARD) { err = watchdog_start(wdd); if (err < 0) return err; } return 0; case WDIOC_KEEPALIVE: if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) return -EOPNOTSUPP; watchdog_ping(wdd); return 0; case WDIOC_SETTIMEOUT: if (get_user(val, p)) return -EFAULT; err = watchdog_set_timeout(wdd, val); if (err < 0) return err; /* If the watchdog is active then we send a keepalive ping * to make sure that the watchdog keep's running (and if * possible that it takes the new timeout) */ watchdog_ping(wdd); /* Fall */ case WDIOC_GETTIMEOUT: /* timeout == 0 means that we don't know the timeout */ if (wdd->timeout == 0) return -EOPNOTSUPP; return put_user(wdd->timeout, p); case WDIOC_GETTIMELEFT: err = watchdog_get_timeleft(wdd, &val); if (err) return err; return put_user(val, p); default: return -ENOTTY; } } /* * watchdog_open: open the /dev/watchdog* devices. * @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; struct watchdog_device *wdd; /* Get the corresponding watchdog device */ if (imajor(inode) == MISC_MAJOR) wdd = old_wdd; else wdd = container_of(inode->i_cdev, struct watchdog_device, cdev); /* 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 = watchdog_start(wdd); if (err < 0) goto out_mod; file->private_data = wdd; if (wdd->ops->ref) wdd->ops->ref(wdd); /* 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 watchdog device. * @inode: inode of device * @file: file handle to device * * This is the code for when /dev/watchdog gets closed. We will only * stop the watchdog when we have received the magic char (and nowayout * was not set), else the watchdog will keep running. */ static int watchdog_release(struct inode *inode, struct file *file) { struct watchdog_device *wdd = file->private_data; int err = -EBUSY; /* * We only stop the watchdog if we received the magic character * or if WDIOF_MAGICCLOSE is not set. If nowayout was set then * watchdog_stop will fail. */ if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) || !(wdd->info->options & WDIOF_MAGICCLOSE)) err = watchdog_stop(wdd); /* If the watchdog was not stopped, send a keepalive ping */ if (err < 0) { mutex_lock(&wdd->lock); if (!test_bit(WDOG_UNREGISTERED, &wdd->status)) dev_crit(wdd->dev, "watchdog did not stop!\n"); mutex_unlock(&wdd->lock); 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); /* Note wdd may be gone after this, do not use after this! */ if (wdd->ops->unref) wdd->ops->unref(wdd); return 0; } static const struct file_operations watchdog_fops = { .owner = THIS_MODULE, .write = watchdog_write, .unlocked_ioctl = watchdog_ioctl, .open = watchdog_open, .release = watchdog_release, }; static struct miscdevice watchdog_miscdev = { .minor = WATCHDOG_MINOR, .name = "watchdog", .fops = &watchdog_fops, }; /* * watchdog_dev_register: register a watchdog device * @watchdog: watchdog device * * Register a watchdog device including handling the legacy * /dev/watchdog node. /dev/watchdog is actually a miscdevice and * thus we set it up like that. */ int watchdog_dev_register(struct watchdog_device *watchdog) { int err, devno; if (watchdog->id == 0) { old_wdd = watchdog; watchdog_miscdev.parent = watchdog->parent; 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); if (err == -EBUSY) pr_err("%s: a legacy watchdog module is probably present.\n", watchdog->info->identity); old_wdd = NULL; return err; } } /* Fill in the data structures */ devno = MKDEV(MAJOR(watchdog_devt), watchdog->id); cdev_init(&watchdog->cdev, &watchdog_fops); watchdog->cdev.owner = watchdog->ops->owner; /* Add the device */ err = cdev_add(&watchdog->cdev, devno, 1); if (err) { pr_err("watchdog%d unable to add device %d:%d\n", watchdog->id, MAJOR(watchdog_devt), watchdog->id); if (watchdog->id == 0) { misc_deregister(&watchdog_miscdev); old_wdd = NULL; } } return err; } /* * watchdog_dev_unregister: unregister a watchdog device * @watchdog: watchdog device * * Unregister the watchdog and if needed the legacy /dev/watchdog device. */ int watchdog_dev_unregister(struct watchdog_device *watchdog) { mutex_lock(&watchdog->lock); set_bit(WDOG_UNREGISTERED, &watchdog->status); mutex_unlock(&watchdog->lock); cdev_del(&watchdog->cdev); if (watchdog->id == 0) { misc_deregister(&watchdog_miscdev); old_wdd = NULL; } return 0; } /* * watchdog_dev_init: init dev part of watchdog core * * Allocate a range of chardev nodes to use for watchdog devices */ int __init watchdog_dev_init(void) { int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog"); if (err < 0) pr_err("watchdog: unable to allocate char dev region\n"); return err; } /* * watchdog_dev_exit: exit dev part of watchdog core * * Release the range of chardev nodes used for watchdog devices */ void __exit watchdog_dev_exit(void) { unregister_chrdev_region(watchdog_devt, MAX_DOGS); }