watchdog: WatchDog Timer Driver Core - Add nowayout feature
Add support for the nowayout feature to the WatchDog Timer Driver Core framework. This feature prevents the watchdog timer from being stopped. 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>
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@ -59,8 +59,8 @@ It contains following fields:
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watchdog_get_drvdata routines.
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watchdog_get_drvdata routines.
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* status: this field contains a number of status bits that give extra
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* status: this field contains a number of status bits that give extra
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information about the status of the device (Like: is the watchdog timer
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information about the status of the device (Like: is the watchdog timer
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running/active, is the device opened via the /dev/watchdog interface or not,
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running/active, is the nowayout bit set, is the device opened via
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...).
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the /dev/watchdog interface or not, ...).
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The list of watchdog operations is defined as:
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The list of watchdog operations is defined as:
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@ -130,10 +130,13 @@ bit-operations. The status bits that are defined are:
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* WDOG_ALLOW_RELEASE: this bit stores whether or not the magic close character
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* WDOG_ALLOW_RELEASE: this bit stores whether or not the magic close character
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has been sent (so that we can support the magic close feature).
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has been sent (so that we can support the magic close feature).
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(This bit should only be used by the WatchDog Timer Driver Core).
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(This bit should only be used by the WatchDog Timer Driver Core).
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* WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
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If this bit is set then the watchdog timer will not be able to stop.
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Note: The WatchDog Timer Driver Core supports the magic close feature. To use
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Note: The WatchDog Timer Driver Core supports the magic close feature and
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the magic close feature you must set the WDIOF_MAGICCLOSE bit in the options
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the nowayout feature. To use the magic close feature you must set the
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field of the watchdog's info structure.
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WDIOF_MAGICCLOSE bit in the options field of the watchdog's info structure.
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The nowayout feature will overrule the magic close feature.
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To get or set driver specific data the following two helper functions should be
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To get or set driver specific data the following two helper functions should be
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used:
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used:
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@ -98,11 +98,18 @@ static int watchdog_start(struct watchdog_device *wddev)
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* Stop the watchdog if it is still active and unmark it active.
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* Stop the watchdog if it is still active and unmark it active.
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* This function returns zero on success or a negative errno code for
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* This function returns zero on success or a negative errno code for
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* failure.
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* failure.
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* If the 'nowayout' feature was set, the watchdog cannot be stopped.
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*/
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*/
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static int watchdog_stop(struct watchdog_device *wddev)
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static int watchdog_stop(struct watchdog_device *wddev)
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{
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{
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int err;
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int err = -EBUSY;
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if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
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pr_info("%s: nowayout prevents watchdog to be stopped!\n",
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wdd->info->identity);
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return err;
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}
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if (test_bit(WDOG_ACTIVE, &wdd->status)) {
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if (test_bit(WDOG_ACTIVE, &wdd->status)) {
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err = wddev->ops->stop(wddev);
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err = wddev->ops->stop(wddev);
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@ -123,7 +130,7 @@ static int watchdog_stop(struct watchdog_device *wddev)
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*
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*
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* A write to a watchdog device is defined as a keepalive ping.
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* A write to a watchdog device is defined as a keepalive ping.
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* Writing the magic 'V' sequence allows the next close to turn
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* Writing the magic 'V' sequence allows the next close to turn
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* off the watchdog.
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* off the watchdog (if 'nowayout' is not set).
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*/
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*/
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static ssize_t watchdog_write(struct file *file, const char __user *data,
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static ssize_t watchdog_write(struct file *file, const char __user *data,
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@ -271,8 +278,8 @@ out:
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* @file: file handle to device
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* @file: file handle to device
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*
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*
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* This is the code for when /dev/watchdog gets closed. We will only
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* This is the code for when /dev/watchdog gets closed. We will only
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* stop the watchdog when we have received the magic char, else the
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* stop the watchdog when we have received the magic char (and nowayout
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* watchdog will keep running.
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* was not set), else the watchdog will keep running.
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*/
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*/
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static int watchdog_release(struct inode *inode, struct file *file)
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static int watchdog_release(struct inode *inode, struct file *file)
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@ -281,7 +288,8 @@ static int watchdog_release(struct inode *inode, struct file *file)
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/*
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/*
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* We only stop the watchdog if we received the magic character
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* We only stop the watchdog if we received the magic character
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* or if WDIOF_MAGICCLOSE is not set
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* or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
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* watchdog_stop will fail.
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*/
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*/
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if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
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if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
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!(wdd->info->options & WDIOF_MAGICCLOSE))
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!(wdd->info->options & WDIOF_MAGICCLOSE))
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@ -113,6 +113,7 @@ struct watchdog_device {
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#define WDOG_ACTIVE 0 /* Is the watchdog running/active */
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#define WDOG_ACTIVE 0 /* Is the watchdog running/active */
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#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
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#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
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#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
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#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
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#define WDOG_NO_WAY_OUT 3 /* Is 'nowayout' feature set ? */
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};
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};
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/* Use the following functions to manipulate watchdog driver specific data */
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/* Use the following functions to manipulate watchdog driver specific data */
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