linux/drivers/watchdog/watchdog_dev.c
Wim Van Sebroeck 8b9468d496 watchdog: core: fix WDIOC_GETSTATUS return value
In commit 7a87982420 we added
a wrapper for the WDIOC_GETSTATUS ioctl call. The code results
however in a different behaviour: it returns an error if the
driver doesn't support the status operation. This is not
according to the API that says that when we don't support
the status operation, that we just should return a 0 value.
Only when the device isn't there anymore, we should return an
error.

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2012-06-28 20:40:56 +02:00

602 lines
14 KiB
C

/*
* 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/... */
#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 ((wddev->max_timeout != 0) &&
(timeout < wddev->min_timeout || timeout > wddev->max_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) {
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);
return err;
}
old_wdd = watchdog;
}
/* 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);
}