tty: warn on deprecated serial flags

When somebody calls TIOCSSERIAL ioctl with serial flags to set one of
* ASYNC_SESSION_LOCKOUT
* ASYNC_PGRP_LOCKOUT
* ASYNC_CALLOUT_NOHUP
* ASYNC_AUTOPROBE
nothing happens. We actually ignore the flags for over a decade at
least (I checked 2.6.0).

So start yelling at users who use those flags, that they shouldn't.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/include/uapi/linux/tty_flags.h b/include/uapi/linux/tty_flags.h
index d2bc4ff..fae4864 100644
--- a/include/uapi/linux/tty_flags.h
+++ b/include/uapi/linux/tty_flags.h
@@ -64,6 +64,8 @@
 #define ASYNC_MAGIC_MULTIPLIER	(1U << ASYNCB_MAGIC_MULTIPLIER)
 
 #define ASYNC_FLAGS		((1U << (ASYNCB_LAST_USER + 1)) - 1)
+#define ASYNC_DEPRECATED	(ASYNC_SESSION_LOCKOUT | ASYNC_PGRP_LOCKOUT | \
+		ASYNC_CALLOUT_NOHUP | ASYNC_AUTOPROBE)
 #define ASYNC_USR_MASK		(ASYNC_SPD_MASK|ASYNC_CALLOUT_NOHUP| \
 		ASYNC_LOW_LATENCY)
 #define ASYNC_SPD_CUST		(ASYNC_SPD_HI|ASYNC_SPD_VHI)