greybus: define BUNDLE_ID_NONE

Define a bundle ID that means "no bundle".  This will be used for
tracing connection events during the portion of a connection's
lifetime when it has no bundle associated with it.  Don't allow
any bundle to be created using that ID.
Signed-off-by: Alex Elder <elder@linaro.org>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/bundle.c

@@ -102,6 +102,11 @@ struct gb_bundle *gb_bundle_create(struct gb_interface *intf, u8 bundle_id,
 {
 	struct gb_bundle *bundle;
 
+	if (bundle_id == BUNDLE_ID_NONE) {
+		dev_err(&intf->dev, "can't use bundle id %u\n", bundle_id);
+		return NULL;
+	}
+
 	/*
 	 * Reject any attempt to reuse a bundle id.  We initialize
 	 * these serially, so there's no need to worry about keeping

drivers/staging/greybus/bundle.h

@@ -12,6 +12,8 @@
 
 #include <linux/list.h>
 
+#define	BUNDLE_ID_NONE	U8_MAX
+
 /* Greybus "public" definitions" */
 struct gb_bundle {
 	struct device		dev;