From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Subject: Re: [PATCH/RFC] 8250: Auto RS485 direction control Date: Thu, 7 Aug 2008 13:50:28 +0000 (UTC) Message-ID: References: <002101c8f6fa$9273ab10$2e01a8c0@acksys.local> <1218033008.6275.86.camel@thetriton.toftronix.com.au> <200808071050.35380.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]:38606 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752231AbYHGNui (ORCPT ); Thu, 7 Aug 2008 09:50:38 -0400 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1KR5sx-0005ME-V6 for linux-serial@vger.kernel.org; Thu, 07 Aug 2008 13:50:35 +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 ; Thu, 07 Aug 2008 13:50:35 +0000 Received: from grante by 65.111.170.175 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 07 Aug 2008 13:50:35 +0000 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org On 2008-08-07, Laurent Pinchart wrote: >> From what I can gather through the man pages it seems inappropriate to >> add this to termios cflag, though the CRTSCTS flag does set a precedent. >> I'm an advocate of the idea of introducing a new IOCTL for setting up >> non standard hand-shaking settings. I would suggest that things that >> should be considered in the interface are settings for lead-in and >> lead-out timing on the direction line (for the use of radio modems for >> example) and means to specify if it's appropriate to have the CPU spin >> on the shift register empty flag on the last byte of a block, if RTS >> timing really is that critical. > > I don't think we want to introduce software emulation, but > feel free to prove me wrong. I think that should be left up to the author of the driver. It seems to me that it would be pretty difficult to do a decent job of it at the line-discipline layer. If the author of the driver for a particular UART wants to do SW emulation of auto-RTS, then I think that's where it belongs. Only the UART driver knows whether there's a shift-register empty interrupt (and whether that interrupt happens before or after that final stop bit has been transmitted). -- Grant Edwards grante Yow! I KAISER ROLL?! at What good is a Kaiser Roll visi.com without a little COLE SLAW on the SIDE?