watchdog: Add support for WDIOC_GETTIMELEFT IOCTL in watchdog core

This patch adds support for WDIOC_GETTIMELEFT IOCTL in watchdog core. So, there
is another function pointer added to struct watchdog_ops, which can be passed by
drivers to support this IOCTL.

Related documentation is updated too.
Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/convert_drivers_to_kernel_api.txt

@@ -59,6 +59,10 @@ Here is a overview of the functions and probably needed actions:
 	WDIOC_GETTIMEOUT:
 		No preparations needed
 
+	WDIOC_GETTIMELEFT:
+		It needs get_timeleft() callback to be defined. Otherwise it
+		will return EOPNOTSUPP
+
   Other IOCTLs can be served using the ioctl-callback. Note that this is mainly
   intended for porting old drivers; new drivers should not invent private IOCTLs.
   Private IOCTLs are processed first. When the callback returns with

Documentation/watchdog/watchdog-kernel-api.txt

 The Linux WatchDog Timer Driver Core kernel API.
 ===============================================
-Last reviewed: 29-Nov-2011
+Last reviewed: 16-Mar-2012
 
 Wim Van Sebroeck <wim@iguana.be>
 
@@ -77,6 +77,7 @@ struct watchdog_ops {
 	int (*ping)(struct watchdog_device *);
 	unsigned int (*status)(struct watchdog_device *);
 	int (*set_timeout)(struct watchdog_device *, unsigned int);
+	unsigned int (*get_timeleft)(struct watchdog_device *);
 	long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
 };
 
@@ -123,6 +124,7 @@ they are supported. These optional routines/operations are:
   because the watchdog does not necessarily has a 1 second resolution).
   (Note: the WDIOF_SETTIMEOUT needs to be set in the options field of the
   watchdog's info structure).
+* get_timeleft: this routines returns the time that's left before a reset.
 * ioctl: if this routine is present then it will be called first before we do
   our own internal ioctl call handling. This routine should return -ENOIOCTLCMD
   if a command is not supported. The parameters that are passed to the ioctl

drivers/watchdog/watchdog_dev.c

@@ -236,6 +236,11 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 		if (wdd->timeout == 0)
 			return -EOPNOTSUPP;
 		return put_user(wdd->timeout, p);
+	case WDIOC_GETTIMELEFT:
+		if (!wdd->ops->get_timeleft)
+			return -EOPNOTSUPP;
+
+		return put_user(wdd->ops->get_timeleft(wdd), p);
 	default:
 		return -ENOTTY;
 	}

include/linux/watchdog.h

@@ -66,6 +66,7 @@ struct watchdog_device;
  * @ping:	The routine that sends a keepalive ping to the watchdog device.
  * @status:	The routine that shows the status of the watchdog device.
  * @set_timeout:The routine for setting the watchdog devices timeout value.
+ * @get_timeleft:The routine that get's the time that's left before a reset.
  * @ioctl:	The routines that handles extra ioctl calls.
  *
  * The watchdog_ops structure contains a list of low-level operations
@@ -82,6 +83,7 @@ struct watchdog_ops {
 	int (*ping)(struct watchdog_device *);
 	unsigned int (*status)(struct watchdog_device *);
 	int (*set_timeout)(struct watchdog_device *, unsigned int);
+	unsigned int (*get_timeleft)(struct watchdog_device *);
 	long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
 };