[WATCHDOG] mv64x60_wdt: Support the WDIOF_MAGICCLOSE feature

Disallow disabling of the watchdog timer unless a particular
character ('V') was recently written to the watchdog device.

Signed-off-by: Dale Farnsworth <dale@farnsworth.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 24 insertions, 4 deletions

diff --git a/drivers/char/watchdog/mv64x60_wdt.c b/drivers/char/watchdog/mv64x60_wdt.c
index 009b9a2c6efa..e07007543d09 100644
--- a/drivers/char/watchdog/mv64x60_wdt.c
+++ b/drivers/char/watchdog/mv64x60_wdt.c
@@ -44,6 +44,7 @@ static int wdt_status;
 static void __iomem *mv64x60_wdt_regs;
 static int mv64x60_wdt_timeout;
 static unsigned int bus_clk;
+static char expect_close;
 
 static int nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, int, 0);
@@ -115,10 +116,14 @@ static int mv64x60_wdt_open(struct inode *inode, struct file *file)
 
 static int mv64x60_wdt_release(struct inode *inode, struct file *file)
 {
-        mv64x60_wdt_service();
-
-        if (!nowayout)
+        if (expect_close == 42)
                 mv64x60_wdt_handler_disable();
+        else {
+                printk(KERN_CRIT
+                       "mv64x60_wdt: unexpected close, not stopping timer!\n");
+                mv64x60_wdt_service();
+        }
+        expect_close = 0;
 
         clear_bit(MV64x60_WDOG_FLAG_OPENED, &wdt_flags);
 
@@ -128,8 +133,22 @@ static int mv64x60_wdt_release(struct inode *inode, struct file *file)
 static ssize_t mv64x60_wdt_write(struct file *file, const char __user *data,
                                  size_t len, loff_t * ppos)
 {
-        if (len)
+        if (len) {
+                if (!nowayout) {
+                        size_t i;
+
+                        expect_close = 0;
+
+                        for (i = 0; i != len; i++) {
+                                char c;
+                                if(get_user(c, data + i))
+                                        return -EFAULT;
+                                if (c == 'V')
+                                        expect_close = 42;
+                        }
+                }
                 mv64x60_wdt_service();
+        }
 
         return len;
 }
@@ -142,6 +161,7 @@ static int mv64x60_wdt_ioctl(struct inode *inode, struct file *file,
         void __user *argp = (void __user *)arg;
         static struct watchdog_info info = {
                 .options =      WDIOF_SETTIMEOUT        |
+                                WDIOF_MAGICCLOSE        |
                                 WDIOF_KEEPALIVEPING,
                 .firmware_version = 0,
                 .identity = "MV64x60 watchdog",