From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0952DC433F5 for ; Thu, 10 Mar 2022 12:29:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242020AbiCJMah (ORCPT ); Thu, 10 Mar 2022 07:30:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47790 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233734AbiCJMae (ORCPT ); Thu, 10 Mar 2022 07:30:34 -0500 Received: from mga07.intel.com (mga07.intel.com [134.134.136.100]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7266A818A5; Thu, 10 Mar 2022 04:29:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646915373; x=1678451373; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=KpU7qHsFQttScVYV4Sy+C7cKf/dHAGOyV91juLQL6gk=; b=NgFY8eRdD81ohSejE1d5DO20LjYbv3RY7ET76nPkYeMlSHg+aTstckek S8/ctGS3G1ijTVnjn2V2MsmQBDECfd/WZvpxEVm2IgscOkJs+vKOoW2R1 Tg5/RbkIrbMIVpdK/CSoAwz4XaaVqm/BSVs7q72b21hpCQNN2lU//vuSh KrvPemzpbYV7jvLCigfVO/dNhbya2kQUeWEN3/Dclbug8ZNYwZd4FyuZW fQTUUJSUa5eBvBFgNovM0f5gwecjeXRZKDkfFUsU6KY5xe+PUvF7W7awO v+fMUYdLsZ5fp5+4hzDD/MyQsKaGsAhe6tFIDP6zC3mCuyqEtSCIUS5B/ g==; X-IronPort-AV: E=McAfee;i="6200,9189,10281"; a="318459313" X-IronPort-AV: E=Sophos;i="5.90,170,1643702400"; d="scan'208";a="318459313" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 04:29:31 -0800 X-IronPort-AV: E=Sophos;i="5.90,170,1643702400"; d="scan'208";a="554624288" Received: from mborg-mobl.ger.corp.intel.com ([10.252.33.144]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Mar 2022 04:29:23 -0800 Date: Thu, 10 Mar 2022 14:29:21 +0200 (EET) From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= To: Lukas Wunner cc: linux-serial , Jiri Slaby , Greg Kroah-Hartman , LKML , Johan Hovold , Andy Shevchenko , Heikki Krogerus , linux-api@vger.kernel.org, Richard Henderson , Ivan Kokshaysky , Matt Turner , linux-alpha@vger.kernel.org, Thomas Bogendoerfer , linux-mips@vger.kernel.org, "James E.J. Bottomley" , Helge Deller , linux-parisc@vger.kernel.org, Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, Yoshinori Sato , Rich Felker , linux-sh@vger.kernel.org, "David S. Miller" , sparclinux@vger.kernel.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Arnd Bergmann , linux-arch@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [RFC PATCH 6/7] serial: General support for multipoint addresses In-Reply-To: <20220309190521.GA9832@wunner.de> Message-ID: <6feb796a-ea58-9a6-f2f9-a11ca72acfd@linux.intel.com> References: <20220302095606.14818-1-ilpo.jarvinen@linux.intel.com> <20220302095606.14818-7-ilpo.jarvinen@linux.intel.com> <20220306194001.GD19394@wunner.de> <20220309190521.GA9832@wunner.de> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="8323329-24784813-1646915371=:1973" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. --8323329-24784813-1646915371=:1973 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT On Wed, 9 Mar 2022, Lukas Wunner wrote: > On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo Järvinen wrote: > > On Sun, 6 Mar 2022, Lukas Wunner wrote: > > > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo Järvinen wrote: > > > > This change is necessary for supporting devices with RS485 > > > > multipoint addressing [*]. > > > > > > If this is only used with RS485, why can't we just store the > > > addresses in struct serial_rs485 and use the existing TIOCSRS485 > > > and TIOCGRS485 ioctls? There's 20 bytes of padding left in > > > struct serial_rs485 which you could use. No need to add more > > > user-space ABI. > > > > It could if it is agreed that serial multipoint addressing is just > > a thing in RS-485 and nowhere else? In that case, there is no point > > in adding more generic support for it. > > It's just that the above-quoted sentence in the commit message > specifically mentions RS485. That sentence is just to justify why addressing mode is needed, not to take a stance on whether it is only used with RS485 or not. > If you intend to use it with RS232 > as well, that should be made explicit, otherwise one wonders why > it wasn't integrated into struct serial_rs485. > > I have no idea how common 9th bit addressing mode is with RS232. > Goggle turns up links saying it's mainly used with RS485, "but also > RS232". Since RS232 isn't a bus but a point-to-point link, > 9th bit addressing doesn't seem to make as much sense. While I don't know any better, I can image though that with an RS232-to-RS485 converter, it could make some sense. If I put them back to serial_rs485 / rs485 config, it's basically just where I initially started from with this patchset (offlist). -- i. --8323329-24784813-1646915371=:1973--