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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DCAAFC433F5 for ; Thu, 10 Mar 2022 12:31:13 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4KDpMN4QHvz3088 for ; Thu, 10 Mar 2022 23:31:12 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=KdptwUPf; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=linux.intel.com (client-ip=192.55.52.88; helo=mga01.intel.com; envelope-from=ilpo.jarvinen@linux.intel.com; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.a=rsa-sha256 header.s=Intel header.b=KdptwUPf; dkim-atps=neutral Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4KDpLg2gPWz30RT for ; Thu, 10 Mar 2022 23:30:34 +1100 (AEDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646915435; x=1678451435; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version; bh=KpU7qHsFQttScVYV4Sy+C7cKf/dHAGOyV91juLQL6gk=; b=KdptwUPf5/tvnjZpAFms6t1JBthFZUSwXzkro8AQm07L+kpZDnLgUz4U LfQD+FchUBifWcfvpA8jB5ncHVhea8fSNKRKDhXlPusPn3jr9tktvZOj3 dsPXpMEBCmFnOaIqCp1HehwRvj5STN7Z+CIy+ktLKd3yTB3CuO0XdQUsD V2avj3WX965Rs/SawMnj/0hXmkAcipcm3yr2SO3e0AgYz/sbXyiin6BC+ SuLvGm7xkMug70r0YeCOsBSoQi4B7nbXLRLWbbJ8P7J3ZsyNyOJKNCcp2 pjmN4t7NihMx+O5Np+6Q2t0vxISCG/ySPPID/YctpxgDKsQ+AqDcRN34U g==; X-IronPort-AV: E=McAfee;i="6200,9189,10281"; a="279974514" X-IronPort-AV: E=Sophos;i="5.90,170,1643702400"; d="scan'208";a="279974514" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by fmsmga101.fm.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 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" X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Heikki Krogerus , linux-sh@vger.kernel.org, LKML , "James E.J. Bottomley" , Max Filippov , Rich Felker , Paul Mackerras , sparclinux@vger.kernel.org, linux-api@vger.kernel.org, Jiri Slaby , linux-arch@vger.kernel.org, Yoshinori Sato , Helge Deller , linux-doc@vger.kernel.org, linux-serial , Matt Turner , linux-xtensa@linux-xtensa.org, Arnd Bergmann , Johan Hovold , Ivan Kokshaysky , Andy Shevchenko , Richard Henderson , Chris Zankel , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, Greg Kroah-Hartman , linux-mips@vger.kernel.org, linux-alpha@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, "David S. Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" 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--