From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-15?Q?Ilpo_J=E4rvinen?= Subject: Re: [RFC PATCH 6/7] serial: General support for multipoint addresses Date: Thu, 10 Mar 2022 14:29:21 +0200 (EET) 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" Return-path: 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==; In-Reply-To: <20220309190521.GA9832@wunner.de> List-ID: 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 , Pau 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: quoted-printable On Wed, 9 Mar 2022, Lukas Wunner wrote: > On Mon, Mar 07, 2022 at 11:48:01AM +0200, Ilpo J=E4rvinen wrote: > > On Sun, 6 Mar 2022, Lukas Wunner wrote: > > > On Wed, Mar 02, 2022 at 11:56:05AM +0200, Ilpo J=E4rvinen wrote: > > > > This change is necessary for supporting devices with RS485 > > > > multipoint addressing [*]. > > >=20 > > > 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. > >=20 > > 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. >=20 > 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. >=20 > 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=20 RS232-to-RS485 converter, it could make some sense. If I put them back to serial_rs485 / rs485 config, it's basically just=20 where I initially started from with this patchset (offlist). --=20 i. --8323329-24784813-1646915371=:1973--