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>
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@ -127,6 +127,13 @@ bit-operations. The status bits that are defined are:
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* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
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was opened via /dev/watchdog.
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(This bit should only be used by the WatchDog Timer Driver Core).
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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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(This bit should only be used by the WatchDog Timer Driver Core).
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Note: The WatchDog Timer Driver Core supports the magic close feature. To use
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the magic close feature you must set the WDIOF_MAGICCLOSE bit in the options
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field of the watchdog's info structure.
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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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@ -122,6 +122,8 @@ static int watchdog_stop(struct watchdog_device *wddev)
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* @ppos: pointer to the file offset
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*
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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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* off the watchdog.
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*/
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static ssize_t watchdog_write(struct file *file, const char __user *data,
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@ -133,9 +135,18 @@ static ssize_t watchdog_write(struct file *file, const char __user *data,
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if (len == 0)
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return 0;
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/*
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* Note: just in case someone wrote the magic character
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* five months ago...
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*/
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clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
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/* scan to see whether or not we got the magic character */
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for (i = 0; i != len; i++) {
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if (get_user(c, data + i))
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return -EFAULT;
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if (c == 'V')
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set_bit(WDOG_ALLOW_RELEASE, &wdd->status);
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}
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/* someone wrote to us, so we send the watchdog a keepalive ping */
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@ -259,14 +270,24 @@ out:
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* @inode: inode of device
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* @file: file handle to device
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*
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* This is the code for when /dev/watchdog gets closed.
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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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* watchdog will keep running.
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*/
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static int watchdog_release(struct inode *inode, struct file *file)
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{
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int err;
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int err = -EBUSY;
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/*
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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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*/
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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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err = watchdog_stop(wdd);
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/* If the watchdog was not stopped, send a keepalive ping */
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if (err < 0) {
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pr_crit("%s: watchdog did not stop!\n", wdd->info->identity);
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watchdog_ping(wdd);
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@ -112,6 +112,7 @@ struct watchdog_device {
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/* Bit numbers for status flags */
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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_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
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};
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/* Use the following functions to manipulate watchdog driver specific data */
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