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Date: Sat, 18 Jun 2011 19:24:47 +0200
From: Wim Van Sebroeck <wim@...ana.be>
To: LKML <linux-kernel@...r.kernel.org>,
Linux Watchdog Mailing List <linux-watchdog@...r.kernel.org>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: [PATCH 6/10 v2] Generic Watchdog Timer Driver
watchdog: WatchDog Timer Driver Core - Part 6
Add support for the Magic Close feature to the
WatchDog Timer Driver Core framework.
Signed-off-by: Alan Cox <alan@...rguk.ukuu.org.uk>
Signed-off-by: Wim Van Sebroeck <wim@...ana.be>
diff -urN linux-2.6.38-generic-part5/Documentation/watchdog/src/watchdog-with-timer-example.c linux-2.6.38-generic-part6/Documentation/watchdog/src/watchdog-with-timer-example.c
--- linux-2.6.38-generic-part5/Documentation/watchdog/src/watchdog-with-timer-example.c 2011-06-16 20:13:58.331178125 +0200
+++ linux-2.6.38-generic-part6/Documentation/watchdog/src/watchdog-with-timer-example.c 2011-06-16 21:04:06.283940741 +0200
@@ -123,6 +123,7 @@
static const struct watchdog_info wdt_info = {
.identity = DRV_NAME,
.options = WDIOF_SETTIMEOUT |
+ WDIOF_MAGICCLOSE |
WDIOF_KEEPALIVEPING,
};
diff -urN linux-2.6.38-generic-part5/Documentation/watchdog/watchdog-kernel-api.txt linux-2.6.38-generic-part6/Documentation/watchdog/watchdog-kernel-api.txt
--- linux-2.6.38-generic-part5/Documentation/watchdog/watchdog-kernel-api.txt 2011-06-16 20:09:01.759178229 +0200
+++ linux-2.6.38-generic-part6/Documentation/watchdog/watchdog-kernel-api.txt 2011-06-16 21:04:06.287940722 +0200
@@ -126,3 +126,10 @@
* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
was opened via /dev/watchdog.
(This bit should only be used by the WatchDog Timer Driver Core).
+* WDOG_EXPECT_RELEASE: this bit stores whether or not the magic close character
+ has been sent (so that we can support the magic close feature).
+ (This bit should only be used by the WatchDog Timer Driver Core).
+
+Note: The WatchDog Timer Driver Core supports the magic close feature. To use
+the magic close feature you must set the WDIOF_MAGICCLOSE bit in the options
+field of the watchdog's info structure.
diff -urN linux-2.6.38-generic-part5/drivers/watchdog/core/watchdog_dev.c linux-2.6.38-generic-part6/drivers/watchdog/core/watchdog_dev.c
--- linux-2.6.38-generic-part5/drivers/watchdog/core/watchdog_dev.c 2011-06-16 20:09:01.759178229 +0200
+++ linux-2.6.38-generic-part6/drivers/watchdog/core/watchdog_dev.c 2011-06-16 22:52:56.763937624 +0200
@@ -150,6 +150,8 @@
* @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.
*/
static ssize_t watchdog_write(struct file *file, const char __user *data,
@@ -163,9 +165,18 @@
if (len == 0) /* Can we see this even ? */
return 0;
+ /* note: just in case someone wrote the magic character
+ * five months ago... */
+ clear_bit(WDOG_EXPECT_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_EXPECT_RELEASE, &wdd->status);
+ dbg("received the magic character");
+ }
}
/* someone wrote to us, so we sent the watchdog a keepalive ping */
@@ -294,7 +305,9 @@
* @inode: inode of device
* @file: file handle to device
*
- * This is the code for when /dev/watchdog get's closed.
+ * This is the code for when /dev/watchdog get's closed. We will only
+ * stop the watchdog when we have received the magic char, else the
+ * watchdog will keep running.
*/
static int watchdog_release(struct inode *inode, struct file *file)
@@ -302,9 +315,15 @@
int err = -1;
trace("%p, %p", inode, file);
+ dbg("expect_release=%d", test_bit(WDOG_EXPECT_RELEASE, &wdd->status));
+
+ /* We only stop the watchdog if we received the magic character
+ * or if WDIOF_MAGICCLOSE is not set */
+ if (test_and_clear_bit(WDOG_EXPECT_RELEASE, &wdd->status) ||
+ !(wdd->info->options & WDIOF_MAGICCLOSE))
+ err = watchdog_stop(wdd);
- /* stop the watchdog */
- err = watchdog_stop(wdd);
+ /* If the watchdog was not stopped, sent a keepalive ping */
if (err < 0) {
pr_crit("%s: not stopping watchdog!\n", wdd->name);
watchdog_ping(wdd);
diff -urN linux-2.6.38-generic-part5/include/linux/watchdog.h linux-2.6.38-generic-part6/include/linux/watchdog.h
--- linux-2.6.38-generic-part5/include/linux/watchdog.h 2011-06-16 20:09:01.759178229 +0200
+++ linux-2.6.38-generic-part6/include/linux/watchdog.h 2011-06-17 12:17:15.285063678 +0200
@@ -85,6 +85,7 @@
#define WDOG_ACTIVE 0 /* is the watchdog running/active */
#define WDOG_DEV_OPEN 1 /* is the watchdog opened via
* /dev/watchdog */
+#define WDOG_EXPECT_RELEASE 2 /* did we receive the magic char ? */
};
/* drivers/watchdog/core/watchdog_core.c */
--
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