From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yegor Yefremov Subject: [PATCH] RS485 documentation: add 16C950 UART description Date: Mon, 22 Nov 2010 11:06:32 +0100 Message-ID: <4CEA40A8.5090401@visionsystems.de> Reply-To: yegor_sub1@visionsystems.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: Received: from hhlx01.visionsystems.de ([62.145.30.242]:42653 "EHLO mail.visionsystems.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752830Ab0KVKGn (ORCPT ); Mon, 22 Nov 2010 05:06:43 -0500 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org Cc: gregkh@suse.de, claudio@evidence.eu.com Add a notion about 16C950 UART, that is using DTR signal for RS485 mode. Signed-off-by: Yegor Yefremov Index: b/Documentation/serial/serial-rs485.txt =================================================================== --- a/Documentation/serial/serial-rs485.txt 2010-11-19 03:48:08.000000000 +0100 +++ b/Documentation/serial/serial-rs485.txt 2010-11-19 10:42:22.000000000 +0100 @@ -11,10 +11,11 @@ 2. HARDWARE-RELATED CONSIDERATIONS - Some CPUs (e.g., Atmel AT91) contain a built-in half-duplex mode capable of - automatically controlling line direction by toggling RTS. That can used to - control external half-duplex hardware like an RS485 transceiver or any - RS232-connected half-duplex device like some modems. + Some CPUs/UARTs (e.g., Atmel AT91 or 16C950 UART) contain a built-in + half-duplex mode capable of automatically controlling line direction by + toggling RTS or DTR signals. That can be used to control external + half-duplex hardware like an RS485 transceiver or any RS232-connected + half-duplex devices like some modems. For these microcontrollers, the Linux driver should be made capable of working in both modes, and proper ioctls (see later) should be made