commit 440061eca5e843406368a4b9e39b9fdb84cdc691
Author: Wim Van Sebroeck <wim@xxxxxxxxx>
Date: Sun Jul 18 10:44:44 2010 +0000
watchdog: WatchDog Timer Driver Core - Part 7
Add support for the Magic Close feature to the
WatchDog Timer Driver Core framework.
Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Wim Van Sebroeck <wim@xxxxxxxxx>
diff --git a/Documentation/watchdog/src/watchdog-with-timer-example.c b/Documentation/watchdog/src/watchdog-with-timer-example.c
index 604fd91..158c61d 100644
--- a/Documentation/watchdog/src/watchdog-with-timer-example.c
+++ b/Documentation/watchdog/src/watchdog-with-timer-example.c
@@ -123,6 +123,7 @@ static int wdt_set_timeout(struct watchdog_device *wdd, int new_timeout)
static const struct watchdog_info wdt_info = {
.identity = DRV_NAME,
.options = WDIOF_SETTIMEOUT |
+ WDIOF_MAGICCLOSE |
WDIOF_KEEPALIVEPING,
};
diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index 472bfea..036c30f 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -131,3 +131,10 @@ bit-operations. The status bit's that are defined are:
When re-opening /dev/watchdog before a reboot occurs, you can then still use
and ping the watchdog timer device.
(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 feauture. To use
+the magic close feauture you must set the WDIOF_MAGICCLOSE bit in the options
+field of the watchdog's info structure.
diff --git a/drivers/watchdog/core/watchdog_dev.c b/drivers/watchdog/core/watchdog_dev.c
index d3dfac2..4a99aeb 100644
--- a/drivers/watchdog/core/watchdog_dev.c
+++ b/drivers/watchdog/core/watchdog_dev.c
@@ -148,6 +148,8 @@ static int watchdog_stop(struct watchdog_device *wddev)
* @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,
@@ -161,9 +163,18 @@ static ssize_t watchdog_write(struct file *file, const char __user *data,
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 */
@@ -297,7 +308,9 @@ out:
* @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)
@@ -305,9 +318,14 @@ static int watchdog_release(struct inode *inode, struct file *file)
int err = -1;
trace("%p, %p", inode, file);
-
- /* stop the watchdog */
- err = watchdog_stop(wdd);
+ 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);
+ else watchdog_ping(wdd);
/* If the watchdog stopped correctly we let the module unload again */
if (err == 0)
diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
index ba08f38..7dbb135 100644
--- a/include/linux/watchdog.h
+++ b/include/linux/watchdog.h
@@ -87,6 +87,7 @@ struct watchdog_device {
* /dev/watchdog */
#define WDOG_ORPHAN 2 /* is the device module still loaded
* after closing /dev/watchdog */
+#define WDOG_EXPECT_RELEASE 3 /* did we receive the magic char ? */
};
/* drivers/watchdog/core/watchdog_core.c */
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