From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Subject: Re: Suggested patch for linux Date: Fri, 18 Jul 2008 13:55:38 +0000 (UTC) Message-ID: References: <487546D5.8050908@freesurf.ch> <20080710095904.16dfdb08@the-village.bc.nu> <487619C8.7080509@commtech-fastcom.com> <200807181219.54170.laurentp@cse-semaphore.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from main.gmane.org ([80.91.229.2]:37518 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753706AbYGRNzx (ORCPT ); Fri, 18 Jul 2008 09:55:53 -0400 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1KJqR1-0007R7-UJ for linux-serial@vger.kernel.org; Fri, 18 Jul 2008 13:55:48 +0000 Received: from 65.111.170.175 ([65.111.170.175]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 18 Jul 2008 13:55:47 +0000 Received: from grante by 65.111.170.175 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 18 Jul 2008 13:55:47 +0000 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org Cc: linux-usb@vger.kernel.org On 2008-07-18, Laurent Pinchart wrote: >> I believe that he is referring to something much simpler than >> you are thinking. He is talking about 2-wire RS485 >> transmissions in which the RTS signal is used to enable the >> driver chips just before transmitting data and disabling >> (tri-stating) them just after transmitting data. There are >> some UARTs that have this behavior built into them. > > And that feature is currently not supported by Linux, even > with UARTs that have hardware support for "Auto RS485" mode, > such as the 8250-compatible XR16C2850. > > The issue is that no flag is defined for the c_cflag field of > the termios structure to enable that feature. The following > patch is an example of what would be required. I'd definitely be in favor of such a flag. It sucks having to resort to various hacks to control support of that feature in Linux serial drivers. -- Grant Edwards grante Yow! In Newark the at laundromats are open 24 visi.com hours a day!