[POWERPC] Add of_device_is_available function

IEEE 1275 defined a standard "status" property to indicate the operational
status of a device.  The property has four possible values: okay, disabled,
fail, fail-xxx.  The absence of this property means the operational status
of the device is unknown or okay.

This adds a function called of_device_is_available that checks the state
of the status property of a device.  If the property is absent or set to
either "okay" or "ok", it returns 1.  Otherwise it returns 0.
Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

drivers/of/base.c

@@ -116,6 +116,32 @@ int of_device_is_compatible(const struct device_node *device,
 }
 EXPORT_SYMBOL(of_device_is_compatible);
 
+/**
+ *  of_device_is_available - check if a device is available for use
+ *
+ *  @device: Node to check for availability
+ *
+ *  Returns 1 if the status property is absent or set to "okay" or "ok",
+ *  0 otherwise
+ */
+int of_device_is_available(const struct device_node *device)
+{
+	const char *status;
+	int statlen;
+
+	status = of_get_property(device, "status", &statlen);
+	if (status == NULL)
+		return 1;
+
+	if (statlen > 0) {
+		if (!strcmp(status, "okay") || !strcmp(status, "ok"))
+			return 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(of_device_is_available);
+
 /**
  *	of_get_parent - Get a node's parent if any
  *	@node:	Node to get parent

include/linux/of.h

@@ -62,6 +62,7 @@ extern struct property *of_find_property(const struct device_node *np,
 					 int *lenp);
 extern int of_device_is_compatible(const struct device_node *device,
 				   const char *);
+extern int of_device_is_available(const struct device_node *device);
 extern const void *of_get_property(const struct device_node *node,
 				const char *name,
 				int *lenp);