From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Tosoni" Subject: RE: should RTS init in serial core be tied to CRTSCTS Date: Thu, 8 Mar 2007 19:43:15 +0100 Message-ID: <000201c761b1$a281cdf0$2e01a8c0@acksys.local> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from smtp22.msg.oleane.net ([62.161.4.22]:34695 "EHLO smtp22.msg.oleane.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933079AbXCHTNS (ORCPT ); Thu, 8 Mar 2007 14:13:18 -0500 In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: 'Krzysztof Halasa' , 'Carl-Daniel Hailfinger' Cc: 'Robin Getz' , 'Oleksiy Kebkal' , 'Mike Frysinger' , 'Linux Kernel Mailing List' , linux-serial@vger.kernel.org Krzysztof Halasa wrote: > OTOH I wonder what does the device in question require WRT the > serial port and WRT RTS line in particular. > I know there are some half-duplex converters which drive RTS only > while sending and which require CTS to send. As far as I know in the old times this was the *standard* way to use a modem (per CCITT V24), and even nowadays many modems can handle this method for transmit, to stay compatible with the standard. Think of radio modems. Some are inherently half duplex. > They are perhaps a bit broken No, no, they apply an old standard. Probably they are old as well. > > I don't know if one can expect RTS to stay low all the time. Even > a simple /sbin/setserial from /etc/rc.* would drive it high for > a moment. I'm afraid the only way which makes sense may be using > a customized plug. It's a pity that Linux (or Unixes) never handled RTS this way. I feel that the /proc or sysfs solutions are the best to alter this well established default in this driver. It would not break existing installed hardware.