From mboxrd@z Thu Jan 1 00:00:00 1970 From: Grant Edwards Subject: Re: New serial card development Date: Tue, 23 Oct 2012 19:48:01 +0000 (UTC) Message-ID: References: <5074703E.408@commtech-fastcom.com> <20121014093704.GA6207@thunk.org> <20121016002608.64b33de5@pyramind.ukuu.org.uk> <20121016023226.GA17446@thunk.org> <20121019212158.GB4721@thunk.org> <20121023192633.18849645@pyramind.ukuu.org.uk> <20121023202404.7e916cca@pyramind.ukuu.org.uk> Return-path: Received: from plane.gmane.org ([80.91.229.3]:52869 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932223Ab2JWTsT (ORCPT ); Tue, 23 Oct 2012 15:48:19 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1TQkSc-00084k-MG for linux-serial@vger.kernel.org; Tue, 23 Oct 2012 21:48:22 +0200 Received: from dsl.comtrol.com ([64.122.56.22]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 23 Oct 2012 21:48:22 +0200 Received: from grant.b.edwards by dsl.comtrol.com with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 23 Oct 2012 21:48:22 +0200 Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org On 2012-10-23, Alan Cox wrote: >> FWIW, in some products we're planning that will require support for >> various industrial serial protocols, I'm leaning towards abandoning >> the tty driver approach and writing a stand-alone character device >> driver. The byte-stream oriented tty/line-discipline layer just >> doesn't fit well when dealing with frame-oriented industrial protocols >> that depend on things like 9th bit addressing and detecting >> sub-millisecond inter-byte timeouts. When I add in the lack of >> long-term stability in the tty API it seems like it might not be such >> a bad idea to give up trying to make the tty abstraction fit a use >> case that's just nothing like a teletype. > > Not unreasonable but we do need to cover it to some extent because there > are a lot of 'multi-use' port types where you need to share the hardware > or switch modes. Agreed. Providing support for things like 9 bit mode, inter-byte timeouts, arbitrary baud rates, half-duplex mode, and user-selectable electrical interfaces (232/422/485/etc.) in the standard tty API would be a good thing. Half-duplex mode (sometimes called RS485 mode) and arbitrary baud rate are great recent additions. > Although we don't use it that way its not entirely accidental that the > tty buffer code supports chains of buffers with lengths 8) Thanks, that's good to know. -- Grant Edwards grant.b.edwards Yow! I can't decide which at WRONG TURN to make first!! gmail.com I wonder if BOB GUCCIONE has these problems!