From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.8 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=unavailable autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 000487D08A for ; Wed, 17 Oct 2018 13:19:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726974AbeJQVOW (ORCPT ); Wed, 17 Oct 2018 17:14:22 -0400 Received: from mail.bootlin.com ([62.4.15.54]:52871 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727255AbeJQVOW (ORCPT ); Wed, 17 Oct 2018 17:14:22 -0400 Received: by mail.bootlin.com (Postfix, from userid 110) id AD9A4207C4; Wed, 17 Oct 2018 15:18:39 +0200 (CEST) Received: from bbrezillon (AAubervilliers-681-1-7-245.w90-88.abo.wanadoo.fr [90.88.129.245]) by mail.bootlin.com (Postfix) with ESMTPSA id E3D9520712; Wed, 17 Oct 2018 15:18:28 +0200 (CEST) Date: Wed, 17 Oct 2018 15:18:29 +0200 From: Boris Brezillon To: gregkh Cc: Arnd Bergmann , Wolfram Sang , Linux I2C , Jonathan Corbet , "open list:DOCUMENTATION" , Przemyslaw Sroka , Arkadiusz Golec , Alan Douglas , Bartosz Folta , Damian Kos , Alicja Jurasik-Urbaniak , Cyprian Wronka , Suresh Punnoose , Rafal Ciepiela , Thomas Petazzoni , Nishanth Menon , Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , DTML , Linux Kernel Mailing List , Vitor Soares , Geert Uytterhoeven , Linus Walleij , Xiang Lin , "open list:GPIO SUBSYSTEM" , Sekhar Nori , Przemyslaw Gaj , Peter Rosin , mshettel@codeaurora.org, swboyd@chromium.org Subject: Re: [PATCH v8 00/10] Add the I3C subsystem Message-ID: <20181017151829.470930a7@bbrezillon> In-Reply-To: References: <20181003132212.12619-1-boris.brezillon@bootlin.com> X-Mailer: Claws Mail 3.15.0-dirty (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi Greg, On Mon, 8 Oct 2018 12:47:21 +0200 Arnd Bergmann wrote: > On Wed, Oct 3, 2018 at 3:22 PM Boris Brezillon > wrote: > > > > Sorry for the huge delay between v7 and v8 despite the small amount of > > things I was asked to fix/rework. > > > > This patch series is adding a new subsystem to support I3C devices. > > > > This is just adding support for basic features. Extra features will > > be added afterwards. > > > > There are a few design choices that are worth mentioning because they > > impact the way I3C device drivers can interact with their devices: > > > > - all functions used to send I3C/I2C frames must be called in > > non-atomic context. Mainly done this way to ease implementation, but > > this is still open to discussion. Please let me know if you think it's > > worth considering an asynchronous model here > > - the I3C bus and I3C master controller are now tightly coupled even > > though they're still allocated separately. There's now a 1:1 > > relationship between these objects, and the I3C master is no longer > > represented under the I3C bus object. > > Arnd, let me know if you had something different in mind, and I'll > > rework the implementation accordingly. > > I looked at the entire series again and I'm rather happy with how > it turned out. I've commented on a tiny issue about the readsl() > that should be easy to resolve one way or another, with that > you can add my > > Reviewed-by: Arnd Bergmann > > There is one additional issue that we've talked about previously > and that I'd like to hear about from GregKH or maybe other > subsystem maintainers: In the current version, you have a single > 'bus_type' object, and this is used to represent both a 'host' and > a 'device'. I think we concluded that this is done in other > subsystems as well, and that this is fitting here because a > host (master device) can hand over being a master to another > device (slave), which then becomes the host and sees this > one as a slave. Also a lot of the sysfs attributes are the same > because of this relationship. > > It also means that you get a mix of things in sysfs: > > /sys/devices/i3c/ > /sys/devices/i3c/ > /sys/devices/i3c// > > which is a bit like what we have on USB where we can have hub > devices that are again parents of other USB devices, but I don't > think we can have i3c hubs or multiplexers in the same way, so > it's only a single level. > > I'm ok with this model after our previous discussion and couldn't > come up with a better one. If anyone else still sees it as > problematic and has a better idea, please let us know now. I know you're quite busy with the 4.19 release, but if you find a bit of time, that'd be great to have your feedback on this. Thanks, Boris