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 92CC8C4332F for ; Mon, 7 Mar 2022 10:21:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241879AbiCGKV3 (ORCPT ); Mon, 7 Mar 2022 05:21:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40592 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240442AbiCGKBC (ORCPT ); Mon, 7 Mar 2022 05:01:02 -0500 Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58372205FE; Mon, 7 Mar 2022 01:48:12 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646646492; x=1678182492; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version:content-id; bh=zC3EygN9B67AQNPvzALqT8NwONoTEFy8bHC2L1G4njc=; b=JstJxVGBbUqE7vEW33wQJkXrLylT4VHJHp2qZByUKOt5Ea7DtujQMZh8 eD4/p7aAvS7znQV2M4cLJCV3289l50yZljmgVJegACGGpfsnYkNK4iwEv 6Rq23GvPRKd9xdGv+/0yFzkXAu32KlTEIdIVlLnEKFwtmE1a8PlsK9Gv9 S5Vy0eNpJ1dwLCb9fVBk5sTsC5VDt96c4+53HwmmVr/stwhCVPE8BChgM H0zS0ozy1z+ffacOSmiAbdAftg5+tnLSBZJ6qerHsv/n+0tvGrKgJ70Fr gtaq25O0hr0Fd+5X5xvgw3//4ynct9C8buIMAbJVhuf23vJHpzDFbVSuv g==; X-IronPort-AV: E=McAfee;i="6200,9189,10278"; a="340782145" X-IronPort-AV: E=Sophos;i="5.90,161,1643702400"; d="scan'208";a="340782145" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Mar 2022 01:48:11 -0800 X-IronPort-AV: E=Sophos;i="5.90,161,1643702400"; d="scan'208";a="553088602" Received: from rabl-mobl2.ger.corp.intel.com ([10.252.54.114]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Mar 2022 01:48:03 -0800 Date: Mon, 7 Mar 2022 11:48:01 +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: <20220306194001.GD19394@wunner.de> Message-ID: References: <20220302095606.14818-1-ilpo.jarvinen@linux.intel.com> <20220302095606.14818-7-ilpo.jarvinen@linux.intel.com> <20220306194001.GD19394@wunner.de> MIME-Version: 1.0 Content-Type: multipart/mixed; BOUNDARY="8323329-971395012-1646646016=:1677" Content-ID: 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. --8323329-971395012-1646646016=:1677 Content-Type: text/plain; CHARSET=ISO-8859-15 Content-Transfer-Encoding: 8BIT Content-ID: <07d5f9f-7fe3-3c54-6566-1873a5191970@linux.intel.com> 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. > > [*] Technically, RS485 is just an electronic spec and does not > > itself specify the 9th bit addressing mode but 9th bit seems > > at least "semi-standard" way to do addressing with RS485. > > Is 9th bit addressing actually used by an Intel customer or was > it implemented just for feature completeness? I think this mode > isn't used often (I've never seen a use case myself), primarily > because it requires disabling parity. On what basis? ...The datasheet I'm looking at has a timing diagram with both D8 (9th bit) and parity so I think your information must be incorrect. I don't have direct contacts with customers but I'm told it's important for other org's customers. -- i. --8323329-971395012-1646646016=:1677--