[WATCHDOG] sbc60xxwdt.c patch

general cleanup of trailing spaces and comments
fix possible wdt_is_open race
add KERN_* to printk's
changed watchdog_info to correctly reflect what the driver offers
added WDIOC_GETSTATUS, WDIOC_GETBOOTSTATUS, WDIOC_SETTIMEOUT, WDIOC_GETTIMEOUT, and WDIOC_SETOPTIONS ioctls
made timeout (the emulated heartbeat) a module_param
made the keepalive ping an internal subroutine
added MODULE_AUTHOR and MODULE_DESCRIPTION info

drivers/char/watchdog/sbc60xxwdt.c

@@ -7,51 +7,38 @@
  *	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.
- *	
- *	The author does NOT admit liability nor provide warranty for 
- *	any of this software. This material is provided "AS-IS" in 
- *      the hope that it may be useful for others.
  *
- *	(c) Copyright 2000    Jakob Oestergaard <jakob@ostenfeld.dk>
+ *	The author does NOT admit liability nor provide warranty for
+ *	any of this software. This material is provided "AS-IS" in
+ *	the hope that it may be useful for others.
+ *
+ *	(c) Copyright 2000    Jakob Oestergaard <jakob@unthought.net>
  *
  *           12/4 - 2000      [Initial revision]
  *           25/4 - 2000      Added /dev/watchdog support
  *           09/5 - 2001      [smj@oro.net] fixed fop_write to "return 1" on success
+ *           12/4 - 2002      [rob@osinvestor.com] eliminate fop_read
+ *                            fix possible wdt_is_open race
+ *                            add CONFIG_WATCHDOG_NOWAYOUT support
+ *                            remove lock_kernel/unlock_kernel pairs
+ *                            added KERN_* to printk's
+ *                            got rid of extraneous comments
+ *                            changed watchdog_info to correctly reflect what the driver offers
+ *                            added WDIOC_GETSTATUS, WDIOC_GETBOOTSTATUS, WDIOC_SETTIMEOUT,
+ *                            WDIOC_GETTIMEOUT, and WDIOC_SETOPTIONS ioctls
+ *           09/8 - 2003      [wim@iguana.be] cleanup of trailing spaces
+ *                            use module_param
+ *                            made timeout (the emulated heartbeat) a module_param
+ *                            made the keepalive ping an internal subroutine
+ *                            added MODULE_AUTHOR and MODULE_DESCRIPTION info
  *
  *
- *  Theory of operation:
- *  A Watchdog Timer (WDT) is a hardware circuit that can 
- *  reset the computer system in case of a software fault.
- *  You probably knew that already.
- *
- *  Usually a userspace daemon will notify the kernel WDT driver
- *  via the /proc/watchdog special device file that userspace is
- *  still alive, at regular intervals.  When such a notification
- *  occurs, the driver will usually tell the hardware watchdog
- *  that everything is in order, and that the watchdog should wait
- *  for yet another little while to reset the system.
- *  If userspace fails (RAM error, kernel bug, whatever), the
- *  notifications cease to occur, and the hardware watchdog will
- *  reset the system (causing a reboot) after the timeout occurs.
- *
- *  This WDT driver is different from the other Linux WDT 
- *  drivers in several ways:
+ *  This WDT driver is different from the other Linux WDT
+ *  drivers in the following ways:
  *  *)  The driver will ping the watchdog by itself, because this
  *      particular WDT has a very short timeout (one second) and it
  *      would be insane to count on any userspace daemon always
  *      getting scheduled within that time frame.
- *  *)  This driver expects the userspace daemon to send a specific
- *      character code ('V') to /dev/watchdog before closing the
- *      /dev/watchdog file.  If the userspace daemon closes the file
- *      without sending this special character, the driver will assume
- *      that the daemon (and userspace in general) died, and will
- *      stop pinging the WDT without disabling it first.  This will
- *      cause a reboot.
- *
- *  Why `V' ?  Well, `V' is the character in ASCII for the value 86,
- *  and we all know that 86 is _the_ most random number in the universe.
- *  Therefore it is the letter that has the slightest chance of occurring
- *  by chance, when the system becomes corrupted.
  *
  */
 
@@ -73,11 +60,12 @@
 #include <asm/system.h>
 
 #define OUR_NAME "sbc60xxwdt"
+#define PFX OUR_NAME ": "
 
 /*
  * You must set these - The driver cannot probe for the settings
  */
- 
+
 #define WDT_STOP 0x45
 #define WDT_START 0x443
 
@@ -92,19 +80,16 @@
 /*
  * We must not require too good response from the userspace daemon.
  * Here we require the userspace daemon to send us a heartbeat
- * char to /dev/watchdog every 10 seconds.
- * If the daemon pulses us every 5 seconds, we can still afford
+ * char to /dev/watchdog every 30 seconds.
+ * If the daemon pulses us every 25 seconds, we can still afford
  * a 5 second scheduling delay on the (high priority) daemon. That
  * should be sufficient for a box under any load.
  */
 
-#define WDT_HEARTBEAT (HZ * 10)
-
-static void wdt_timer_ping(unsigned long);
-static struct timer_list timer;
-static unsigned long next_heartbeat;
-static int wdt_is_open;
-static int wdt_expect_close;
+#define WATCHDOG_TIMEOUT 30		/* 30 sec default timeout */
+static int timeout = WATCHDOG_TIMEOUT;	/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
+module_param(timeout, int, 0);
+MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<=3600, default=WATCHDOG_TIMEOUT)");
 
 #ifdef CONFIG_WATCHDOG_NOWAYOUT
 static int nowayout = 1;
@@ -115,6 +100,12 @@ static int nowayout = 0;
 module_param(nowayout, int, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
 
+static void wdt_timer_ping(unsigned long);
+static struct timer_list timer;
+static unsigned long next_heartbeat;
+static unsigned long wdt_is_open;
+static char wdt_expect_close;
+
 /*
  *	Whack the dog
  */
@@ -122,9 +113,9 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CON
 static void wdt_timer_ping(unsigned long data)
 {
 	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
-	 * we agree to ping the WDT 
+	 * we agree to ping the WDT
 	 */
-	if(time_before(jiffies, next_heartbeat)) 
+	if(time_before(jiffies, next_heartbeat))
 	{
 		/* Ping the WDT by reading from WDT_START */
 		inb_p(WDT_START);
@@ -132,22 +123,22 @@ static void wdt_timer_ping(unsigned long data)
 		timer.expires = jiffies + WDT_INTERVAL;
 		add_timer(&timer);
 	} else {
-		printk(OUR_NAME ": Heartbeat lost! Will not ping the watchdog\n");
+		printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
 	}
 }
 
-/* 
+/*
  * Utility routines
  */
 
 static void wdt_startup(void)
 {
-	next_heartbeat = jiffies + WDT_HEARTBEAT;
+	next_heartbeat = jiffies + (timeout * HZ);
 
 	/* Start the timer */
-	timer.expires = jiffies + WDT_INTERVAL;	
+	timer.expires = jiffies + WDT_INTERVAL;
 	add_timer(&timer);
-	printk(OUR_NAME ": Watchdog timer is now enabled.\n");  
+	printk(KERN_INFO PFX "Watchdog timer is now enabled.\n");
 }
 
 static void wdt_turnoff(void)
@@ -155,9 +146,14 @@ static void wdt_turnoff(void)
 	/* Stop the timer */
 	del_timer(&timer);
 	inb_p(WDT_STOP);
-	printk(OUR_NAME ": Watchdog timer is now disabled...\n");
+	printk(KERN_INFO PFX "Watchdog timer is now disabled...\n");
 }
 
+static void wdt_keepalive(void)
+{
+	/* user land ping */
+	next_heartbeat = jiffies + (timeout * HZ);
+}
 
 /*
  * /dev/watchdog handling
@@ -169,63 +165,58 @@ static ssize_t fop_write(struct file * file, const char * buf, size_t count, lof
 	if(ppos != &file->f_pos)
 		return -ESPIPE;
 
-	/* See if we got the magic character */
-	if(count) 
+	/* See if we got the magic character 'V' and reload the timer */
+	if(count)
 	{
-		size_t ofs;
-
-		/* note: just in case someone wrote the magic character
-		 * five months ago... */
-		wdt_expect_close = 0;
-
-		/* now scan */
-		for(ofs = 0; ofs != count; ofs++) 
+		if (!nowayout)
 		{
-			char c;
-			if(get_user(c, buf+ofs))
-				return -EFAULT;
-			if(c == 'V')
-				wdt_expect_close = 1;
+			size_t ofs;
+
+			/* note: just in case someone wrote the magic character
+			 * five months ago... */
+			wdt_expect_close = 0;
+
+			/* scan to see wether or not we got the magic character */
+			for(ofs = 0; ofs != count; ofs++)
+			{
+				char c;
+				if(get_user(c, buf+ofs))
+					return -EFAULT;
+				if(c == 'V')
+					wdt_expect_close = 42;
+			}
 		}
+
 		/* Well, anyhow someone wrote to us, we should return that favour */
-		next_heartbeat = jiffies + WDT_HEARTBEAT;
-		return 1;
+		wdt_keepalive();
 	}
-	return 0;
+	return count;
 }
 
 static int fop_open(struct inode * inode, struct file * file)
 {
-	switch(minor(inode->i_rdev)) 
-	{
-		case WATCHDOG_MINOR:
-			/* Just in case we're already talking to someone... */
-			if(wdt_is_open)
-				return -EBUSY;
-			if (nowayout) 
-				__module_get(THIS_MODULE);
-			/* Good, fire up the show */
-			wdt_is_open = 1;
-			wdt_startup();
-			return 0;
+	/* Just in case we're already talking to someone... */
+	if(test_and_set_bit(0, &wdt_is_open))
+		return -EBUSY;
 
-		default:
-			return -ENODEV;
-	}
+	if (nowayout)
+		__module_get(THIS_MODULE);
+
+	/* Good, fire up the show */
+	wdt_startup();
+	return 0;
 }
 
 static int fop_close(struct inode * inode, struct file * file)
 {
-	if(minor(inode->i_rdev) == WATCHDOG_MINOR) 
-	{
-		if(wdt_expect_close && !nowayout)
-			wdt_turnoff();
-		else {
-			del_timer(&timer);
-			printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n");
-		}
+	if(wdt_expect_close == 42)
+		wdt_turnoff();
+	else {
+		del_timer(&timer);
+		printk(KERN_CRIT PFX "device file closed unexpectedly. Will not stop the WDT!\n");
 	}
-	wdt_is_open = 0;
+	clear_bit(0, &wdt_is_open);
+	wdt_expect_close = 0;
 	return 0;
 }
 
@@ -234,20 +225,58 @@ static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 {
 	static struct watchdog_info ident=
 	{
-		.options = WDIOF_MAGICCLOSE,
+		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 		.firmware_version = 1,
-		.identity = "SB60xx"
+		.identity = "SBC60xx",
 	};
-	
+
 	switch(cmd)
 	{
 		default:
 			return -ENOTTY;
 		case WDIOC_GETSUPPORT:
 			return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident))?-EFAULT:0;
+		case WDIOC_GETSTATUS:
+		case WDIOC_GETBOOTSTATUS:
+			return put_user(0, (int *)arg);
 		case WDIOC_KEEPALIVE:
-			next_heartbeat = jiffies + WDT_HEARTBEAT;
+			wdt_keepalive();
 			return 0;
+		case WDIOC_SETOPTIONS:
+		{
+			int new_options, retval = -EINVAL;
+
+			if(get_user(new_options, (int *)arg))
+				return -EFAULT;
+
+			if(new_options & WDIOS_DISABLECARD) {
+				wdt_turnoff();
+				retval = 0;
+			}
+
+			if(new_options & WDIOS_ENABLECARD) {
+				wdt_startup();
+				retval = 0;
+			}
+
+			return retval;
+		}
+		case WDIOC_SETTIMEOUT:
+		{
+			int new_timeout;
+
+			if(get_user(new_timeout, (int *)arg))
+				return -EFAULT;
+
+			if(new_timeout < 1 || new_timeout > 3600) /* arbitrary upper limit */
+				return -EINVAL;
+
+			timeout = new_timeout;
+			wdt_keepalive();
+			/* Fall through */
+		}
+		case WDIOC_GETTIMEOUT:
+			return put_user(timeout, (int *)arg);
 	}
 }
 
@@ -257,13 +286,13 @@ static struct file_operations wdt_fops = {
 	.write		= fop_write,
 	.open		= fop_open,
 	.release	= fop_close,
-	.ioctl		= fop_ioctl
+	.ioctl		= fop_ioctl,
 };
 
 static struct miscdevice wdt_miscdev = {
 	.minor = WATCHDOG_MINOR,
 	.name = "watchdog",
-	.fops = &wdt_fops
+	.fops = &wdt_fops,
 };
 
 /*
@@ -273,21 +302,21 @@ static struct miscdevice wdt_miscdev = {
 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 	void *unused)
 {
-	if(code==SYS_DOWN || code==SYS_HALT) 
+	if(code==SYS_DOWN || code==SYS_HALT)
 		wdt_turnoff();
 	return NOTIFY_DONE;
 }
- 
+
 /*
  *	The WDT needs to learn about soft shutdowns in order to
- *	turn the timebomb registers off. 
+ *	turn the timebomb registers off.
  */
- 
+
 static struct notifier_block wdt_notifier=
 {
 	.notifier_call = wdt_notify_sys,
 	.next = NULL,
-	.priority = 0
+	.priority = 0,
 };
 
 static void __exit sbc60xxwdt_unload(void)
@@ -312,6 +341,13 @@ static int __init sbc60xxwdt_init(void)
 	if (!request_region(WDT_START, 1, "SBC 60XX WDT"))
 		goto err_out_region1;
 
+	if(timeout < 1 || timeout > 3600) /* arbitrary upper limit */
+	{
+		timeout = WATCHDOG_TIMEOUT;
+		printk (KERN_INFO PFX "timeout value must be 1<=x<=3600, using %d\n",
+			timeout);
+ 	}
+
 	init_timer(&timer);
 	timer.function = wdt_timer_ping;
 	timer.data = 0;
@@ -324,8 +360,8 @@ static int __init sbc60xxwdt_init(void)
 	if (rc)
 		goto err_out_miscdev;
 
-	printk(KERN_INFO OUR_NAME ": WDT driver for 60XX single board computer initialised.\n");
-	
+	printk(KERN_INFO PFX "WDT driver for 60XX single board computer initialised.\n");
+
 	return 0;
 
 err_out_miscdev:
@@ -341,4 +377,6 @@ static int __init sbc60xxwdt_init(void)
 module_init(sbc60xxwdt_init);
 module_exit(sbc60xxwdt_unload);
 
+MODULE_AUTHOR("Jakob Oestergaard <jakob@unthought.net>");
+MODULE_DESCRIPTION("60xx Single Board Computer Watchdog Timer driver");
 MODULE_LICENSE("GPL");