watchdog: Xen watchdog driver
While the hypervisor change adding SCHEDOP_watchdog support included a
daemon to make use of the new functionality, having a kernel driver
for /dev/watchdog so that user space code doesn't need to distinguish
non-Xen and Xen seems to be preferable.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/drivers/watchdog/xen_wdt.c b/drivers/watchdog/xen_wdt.c
new file mode 100644
index 0000000..49bd9d3
--- /dev/null
+++ b/drivers/watchdog/xen_wdt.c
@@ -0,0 +1,359 @@
+/*
+ * Xen Watchdog Driver
+ *
+ * (c) Copyright 2010 Novell, Inc.
+ *
+ * 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.
+ */
+
+#define DRV_NAME "wdt"
+#define DRV_VERSION "0.01"
+#define PFX DRV_NAME ": "
+
+#include <linux/bug.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/hrtimer.h>
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/init.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/platform_device.h>
+#include <linux/spinlock.h>
+#include <linux/uaccess.h>
+#include <linux/watchdog.h>
+#include <xen/xen.h>
+#include <asm/xen/hypercall.h>
+#include <xen/interface/sched.h>
+
+static struct platform_device *platform_device;
+static DEFINE_SPINLOCK(wdt_lock);
+static struct sched_watchdog wdt;
+static __kernel_time_t wdt_expires;
+static bool is_active, expect_release;
+
+#define WATCHDOG_TIMEOUT 60 /* in seconds */
+static unsigned int timeout = WATCHDOG_TIMEOUT;
+module_param(timeout, uint, S_IRUGO);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds "
+ "(default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, S_IRUGO);
+MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
+ "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+static inline __kernel_time_t set_timeout(void)
+{
+ wdt.timeout = timeout;
+ return ktime_to_timespec(ktime_get()).tv_sec + timeout;
+}
+
+static int xen_wdt_start(void)
+{
+ __kernel_time_t expires;
+ int err;
+
+ spin_lock(&wdt_lock);
+
+ expires = set_timeout();
+ if (!wdt.id)
+ err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+ else
+ err = -EBUSY;
+ if (err > 0) {
+ wdt.id = err;
+ wdt_expires = expires;
+ err = 0;
+ } else
+ BUG_ON(!err);
+
+ spin_unlock(&wdt_lock);
+
+ return err;
+}
+
+static int xen_wdt_stop(void)
+{
+ int err = 0;
+
+ spin_lock(&wdt_lock);
+
+ wdt.timeout = 0;
+ if (wdt.id)
+ err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+ if (!err)
+ wdt.id = 0;
+
+ spin_unlock(&wdt_lock);
+
+ return err;
+}
+
+static int xen_wdt_kick(void)
+{
+ __kernel_time_t expires;
+ int err;
+
+ spin_lock(&wdt_lock);
+
+ expires = set_timeout();
+ if (wdt.id)
+ err = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wdt);
+ else
+ err = -ENXIO;
+ if (!err)
+ wdt_expires = expires;
+
+ spin_unlock(&wdt_lock);
+
+ return err;
+}
+
+static int xen_wdt_open(struct inode *inode, struct file *file)
+{
+ int err;
+
+ /* /dev/watchdog can only be opened once */
+ if (xchg(&is_active, true))
+ return -EBUSY;
+
+ err = xen_wdt_start();
+ if (err == -EBUSY)
+ err = xen_wdt_kick();
+ return err ?: nonseekable_open(inode, file);
+}
+
+static int xen_wdt_release(struct inode *inode, struct file *file)
+{
+ if (expect_release)
+ xen_wdt_stop();
+ else {
+ printk(KERN_CRIT PFX
+ "unexpected close, not stopping watchdog!\n");
+ xen_wdt_kick();
+ }
+ is_active = false;
+ expect_release = false;
+ return 0;
+}
+
+static ssize_t xen_wdt_write(struct file *file, const char __user *data,
+ size_t len, loff_t *ppos)
+{
+ /* See if we got the magic character 'V' and reload the timer */
+ if (len) {
+ if (!nowayout) {
+ size_t i;
+
+ /* in case it was set long ago */
+ expect_release = false;
+
+ /* scan to see whether or not we got the magic
+ character */
+ for (i = 0; i != len; i++) {
+ char c;
+ if (get_user(c, data + i))
+ return -EFAULT;
+ if (c == 'V')
+ expect_release = true;
+ }
+ }
+
+ /* someone wrote to us, we should reload the timer */
+ xen_wdt_kick();
+ }
+ return len;
+}
+
+static long xen_wdt_ioctl(struct file *file, unsigned int cmd,
+ unsigned long arg)
+{
+ int new_options, retval = -EINVAL;
+ int new_timeout;
+ int __user *argp = (void __user *)arg;
+ static const struct watchdog_info ident = {
+ .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
+ .firmware_version = 0,
+ .identity = DRV_NAME,
+ };
+
+ switch (cmd) {
+ case WDIOC_GETSUPPORT:
+ return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
+
+ case WDIOC_GETSTATUS:
+ case WDIOC_GETBOOTSTATUS:
+ return put_user(0, argp);
+
+ case WDIOC_SETOPTIONS:
+ if (get_user(new_options, argp))
+ return -EFAULT;
+
+ if (new_options & WDIOS_DISABLECARD)
+ retval = xen_wdt_stop();
+ if (new_options & WDIOS_ENABLECARD) {
+ retval = xen_wdt_start();
+ if (retval == -EBUSY)
+ retval = xen_wdt_kick();
+ }
+ return retval;
+
+ case WDIOC_KEEPALIVE:
+ xen_wdt_kick();
+ return 0;
+
+ case WDIOC_SETTIMEOUT:
+ if (get_user(new_timeout, argp))
+ return -EFAULT;
+ if (!new_timeout)
+ return -EINVAL;
+ timeout = new_timeout;
+ xen_wdt_kick();
+ /* fall through */
+ case WDIOC_GETTIMEOUT:
+ return put_user(timeout, argp);
+
+ case WDIOC_GETTIMELEFT:
+ retval = wdt_expires - ktime_to_timespec(ktime_get()).tv_sec;
+ return put_user(retval, argp);
+ }
+
+ return -ENOTTY;
+}
+
+static const struct file_operations xen_wdt_fops = {
+ .owner = THIS_MODULE,
+ .llseek = no_llseek,
+ .write = xen_wdt_write,
+ .unlocked_ioctl = xen_wdt_ioctl,
+ .open = xen_wdt_open,
+ .release = xen_wdt_release,
+};
+
+static struct miscdevice xen_wdt_miscdev = {
+ .minor = WATCHDOG_MINOR,
+ .name = "watchdog",
+ .fops = &xen_wdt_fops,
+};
+
+static int __devinit xen_wdt_probe(struct platform_device *dev)
+{
+ struct sched_watchdog wd = { .id = ~0 };
+ int ret = HYPERVISOR_sched_op(SCHEDOP_watchdog, &wd);
+
+ switch (ret) {
+ case -EINVAL:
+ if (!timeout) {
+ timeout = WATCHDOG_TIMEOUT;
+ printk(KERN_INFO PFX
+ "timeout value invalid, using %d\n", timeout);
+ }
+
+ ret = misc_register(&xen_wdt_miscdev);
+ if (ret) {
+ printk(KERN_ERR PFX
+ "cannot register miscdev on minor=%d (%d)\n",
+ WATCHDOG_MINOR, ret);
+ break;
+ }
+
+ printk(KERN_INFO PFX
+ "initialized (timeout=%ds, nowayout=%d)\n",
+ timeout, nowayout);
+ break;
+
+ case -ENOSYS:
+ printk(KERN_INFO PFX "not supported\n");
+ ret = -ENODEV;
+ break;
+
+ default:
+ printk(KERN_INFO PFX "bogus return value %d\n", ret);
+ break;
+ }
+
+ return ret;
+}
+
+static int __devexit xen_wdt_remove(struct platform_device *dev)
+{
+ /* Stop the timer before we leave */
+ if (!nowayout)
+ xen_wdt_stop();
+
+ misc_deregister(&xen_wdt_miscdev);
+
+ return 0;
+}
+
+static void xen_wdt_shutdown(struct platform_device *dev)
+{
+ xen_wdt_stop();
+}
+
+static int xen_wdt_suspend(struct platform_device *dev, pm_message_t state)
+{
+ return xen_wdt_stop();
+}
+
+static int xen_wdt_resume(struct platform_device *dev)
+{
+ return xen_wdt_start();
+}
+
+static struct platform_driver xen_wdt_driver = {
+ .probe = xen_wdt_probe,
+ .remove = __devexit_p(xen_wdt_remove),
+ .shutdown = xen_wdt_shutdown,
+ .suspend = xen_wdt_suspend,
+ .resume = xen_wdt_resume,
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = DRV_NAME,
+ },
+};
+
+static int __init xen_wdt_init_module(void)
+{
+ int err;
+
+ if (!xen_domain())
+ return -ENODEV;
+
+ printk(KERN_INFO PFX "Xen WatchDog Timer Driver v%s\n", DRV_VERSION);
+
+ err = platform_driver_register(&xen_wdt_driver);
+ if (err)
+ return err;
+
+ platform_device = platform_device_register_simple(DRV_NAME,
+ -1, NULL, 0);
+ if (IS_ERR(platform_device)) {
+ err = PTR_ERR(platform_device);
+ platform_driver_unregister(&xen_wdt_driver);
+ }
+
+ return err;
+}
+
+static void __exit xen_wdt_cleanup_module(void)
+{
+ platform_device_unregister(platform_device);
+ platform_driver_unregister(&xen_wdt_driver);
+ printk(KERN_INFO PFX "module unloaded\n");
+}
+
+module_init(xen_wdt_init_module);
+module_exit(xen_wdt_cleanup_module);
+
+MODULE_AUTHOR("Jan Beulich <jbeulich@novell.com>");
+MODULE_DESCRIPTION("Xen WatchDog Timer Driver");
+MODULE_VERSION(DRV_VERSION);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);