tty: Define ASYNC_ replacement bits

Prepare for relocating kernel private state bits out of tty_port::flags
field; tty_port::flags field is not atomic and can become corrupted
by concurrent updates. It also suffers from the complication of sharing
in a userspace-visible field which must be masked.

Define new tty_port::iflags field and new, substitute bit definitions
for the former ASYNC_* flags.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 89f9c91..4e0dbda0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -228,7 +228,8 @@
 	int			count;		/* Usage count */
 	wait_queue_head_t	open_wait;	/* Open waiters */
 	wait_queue_head_t	delta_msr_wait;	/* Modem status change */
-	unsigned long		flags;		/* TTY flags ASY_*/
+	unsigned long		flags;		/* User TTY flags ASYNC_ */
+	unsigned long		iflags;		/* Internal flags TTY_PORT_ */
 	unsigned char		console:1,	/* port is a console */
 				low_latency:1;	/* optional: tune for latency */
 	struct mutex		mutex;		/* Locking */
@@ -242,6 +243,19 @@
 	struct kref		kref;		/* Ref counter */
 };
 
+/* tty_port::iflags bits -- use atomic bit ops */
+#define TTY_PORT_INITIALIZED	0	/* device is initialized */
+#define TTY_PORT_SUSPENDED	1	/* device is suspended */
+#define TTY_PORT_ACTIVE		2	/* device is open */
+
+/*
+ * uart drivers: use the uart_port::status field and the UPSTAT_* defines
+ * for s/w-based flow control steering and carrier detection status
+ */
+#define TTY_PORT_CTS_FLOW	3	/* h/w flow control enabled */
+#define TTY_PORT_CHECK_CD	4	/* carrier detect enabled */
+
+
 /*
  * Where all of the state associated with a tty is kept while the tty
  * is open.  Since the termios state should be kept even if the tty