watchdog: WatchDog Timer Driver Core - Add Magic Close feature
Add support for the Magic Close feature to the
WatchDog Timer Driver Core framework.
Signed-off-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Wolfram Sang <w.sang@pengutronix.de>
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 2c0289d..db40c6c 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -122,6 +122,8 @@
* @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,
@@ -133,9 +135,18 @@
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 */
@@ -259,14 +270,24 @@
* @inode: inode of device
* @file: file handle to device
*
- * This is the code for when /dev/watchdog gets closed.
+ * This is the code for when /dev/watchdog gets 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)
{
- int err;
+ int err = -EBUSY;
- err = watchdog_stop(wdd);
+ /*
+ * We only stop the watchdog if we received the magic character
+ * or if WDIOF_MAGICCLOSE is not set
+ */
+ 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) {
pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
watchdog_ping(wdd);