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: Mon, 7 Mar 2022 11:48:01 +0200 (EET) 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" Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1646646554; x=1678182554; h=date:from:to:cc:subject:in-reply-to:message-id: references:mime-version:content-id; bh=zC3EygN9B67AQNPvzALqT8NwONoTEFy8bHC2L1G4njc=; b=W28BMBpXy598i6KxO4bY4gPGt9zVM5TTEksM0CK9+5j0ciB3OnZJve6t FMRaz+qPkhat8zNr6gakN/43e+5EOXlv25nbnIhzyIHdEL359ipJobi4K WqSqxNcdhtqVu2bi8meJgbr3kN8CDX9ctnuFpvIeOEdEQveWge1Co+DjB CgXKtWBuPaYckQi7PLEbRQ9jIGEMa9M0sIRzXccsckmJHKTqR+DOZJ+Wq aE0FPCmfK8p53EUfrLqjLzGt1BkEc1JAvc4jGghDAuyYhm7+nCQ2FWqps hVlLxCc++MXQo01+pupLlfUh99ByKQqvudFKTgpmmbRNAjVM9TurZizpo A==; In-Reply-To: <20220306194001.GD19394@wunner.de> Content-ID: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linuxppc-dev-bounces+glppe-linuxppc-embedded-2=m.gmane-mx.org@lists.ozlabs.org Sender: "Linuxppc-dev" To: Lukas Wunner 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 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: quoted-printable 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 J=E4rvinen wrote: >=20 > > 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. 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. >=20 > 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=20 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. --=20 i. --8323329-971395012-1646646016=:1677--