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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 630667D87A for ; Thu, 6 Sep 2018 13:50:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730012AbeIFS0B (ORCPT ); Thu, 6 Sep 2018 14:26:01 -0400 Received: from us01smtprelay-2.synopsys.com ([198.182.60.111]:47782 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726926AbeIFS0A (ORCPT ); Thu, 6 Sep 2018 14:26:00 -0400 Received: from mailhost.synopsys.com (mailhost1.synopsys.com [10.12.238.239]) by smtprelay.synopsys.com (Postfix) with ESMTP id A8E7D10C1317; Thu, 6 Sep 2018 06:50:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=synopsys.com; s=mail; t=1536241821; bh=5RAP9nqSKQ926+vpff6dok6KZ88dtvepvkeIiCG3YWs=; h=Subject:To:CC:References:From:Date:In-Reply-To:From; b=RjDymW4Fu80i0kr/Pnjb0wbNUNsP1EnplgGWxTQaxHejdxmbxDGy0cEnZzgUKB6Tr y6+a5RMY3bkCn21mkjhbc+ZEHybSO3dhDZqlu8KB79B61u4CsbCKxy2B5flTNwXyeb 7ZN7uV7uW5YBTYoMR/zwuUDja3GZv3qoeylF6kDqHDfJZuyhrdZVJlClkXGecXdFo4 LyJ7lhUCDPWQx1yOnJ6ts49HGtH9YMErAp34w2UfpooQzw9omMHYKXiPxLZ+Pl4ttA M0yGbJBi7A2kHs+gMxxaipdTGA11DWCQfoA6xUY2p4qpKHJIa50/nlmRHZXskLaOY/ 7mYrckTk1geMA== Received: from US01WEHTC3.internal.synopsys.com (us01wehtc3.internal.synopsys.com [10.15.84.232]) by mailhost.synopsys.com (Postfix) with ESMTP id 90CE45465; Thu, 6 Sep 2018 06:50:18 -0700 (PDT) Received: from DE02WEHTCB.internal.synopsys.com (10.225.19.94) by US01WEHTC3.internal.synopsys.com (10.15.84.232) with Microsoft SMTP Server (TLS) id 14.3.361.1; Thu, 6 Sep 2018 06:50:18 -0700 Received: from DE02WEHTCA.internal.synopsys.com (10.225.19.92) by DE02WEHTCB.internal.synopsys.com (10.225.19.94) with Microsoft SMTP Server (TLS) id 14.3.361.1; Thu, 6 Sep 2018 15:50:12 +0200 Received: from [10.0.2.15] (10.107.25.90) by DE02WEHTCA.internal.synopsys.com (10.225.19.80) with Microsoft SMTP Server (TLS) id 14.3.361.1; Thu, 6 Sep 2018 15:50:11 +0200 Subject: Re: [PATCH v6 01/10] i3c: Add core I3C infrastructure To: Boris Brezillon , Arnd Bergmann CC: Przemyslaw Gaj , Vitor Soares , "open list:GPIO SUBSYSTEM" , Sekhar Nori , Wolfram Sang , Linux I2C , Jonathan Corbet , "open list:DOCUMENTATION" , gregkh , 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 , Geert Uytterhoeven , Linus Walleij , Xiang Lin , Peter Rosin References: <20180719152930.3715-1-boris.brezillon@bootlin.com> <20180719152930.3715-2-boris.brezillon@bootlin.com> <20180824143934.6d6b6487@bbrezillon> <20180824201600.7d80bca9@bbrezillon> <20180828140209.29155d00@bbrezillon> <4DBE768F-3CDC-41BE-9CC8-E294E7277CB1@cadence.com> <8abfb007-d755-36a4-5960-fddd61d04aa2@synopsys.com> <3D2681D9-1ACC-42FF-9FAB-D86B3C689003@cadence.com> <9584757a-e7e2-5bfe-fc2c-e9bc14ad65a8@synopsys.com> <25862F03-9823-42B0-87AC-AE36D7E9C780@cadence.com> <20180906151437.4259d6fc@bbrezillon> <20180906152055.5618d235@bbrezillon> From: vitor Message-ID: Date: Thu, 6 Sep 2018 14:50:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180906152055.5618d235@bbrezillon> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.107.25.90] Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Hi, On 06-09-2018 14:20, Boris Brezillon wrote: > On Thu, 6 Sep 2018 15:14:37 +0200 > Boris Brezillon wrote: > >> On Thu, 6 Sep 2018 14:59:46 +0200 >> Arnd Bergmann wrote: >> >>> On Thu, Sep 6, 2018 at 2:43 PM Przemyslaw Gaj wrote: >>>> Hi Boris, Vitor, >>>> >>>> This repository does not contain full kernel sources, but it should be enough to discuss mastership request feature. >>>> https://urldefense.proofpoint.com/v2/url?u=https-3A__github.com_przemekgaj_i3c-2Dlinux_commit_d54fe68a9d3e573c0c454a2c6f1afafc20142ec5&d=DwICAg&c=DPL6_X_6JkXFx7AXWqB0tg&r=qVuU64u9x77Y0Kd0PhDK_lpxFgg6PK9PateHwjb_DY0&m=Q9DWw3KGmshGw0f5QTiffbpbESyUlPx6KmASuDBtX9Y&s=HHE_y1kyMszJvP_tSP9JkDlPYxDywBeHwkMGgCR11uI&e= >>>> >>>> Please keep in mind that this is initial version, but mastership works correctly. I added one property to DT to reflect relationship between masters. >>>> It is possible to request mastership on demand (using sysfs. Useful in case when Linux machine is equipped only with secondary master controller) or automatically change operation mode when device driver wants to read/write something from/to device. >>>> >>>> I'm sure I will have to rework something because this was implemented on sources from PATCH v4. I saw that Boris released v7 yesterday :) >>> >>> Can you explain the reason for having a user space interface and DT property? >>> I thought we had concluded earlier that we wouldn't need that, but it's possible >>> that I missed something in the discussion since then. >> I don't think the sysfs knob is needed, this being said, after thinking >> a bit more about mastership handover and the secondary master case, I >> think we have something important to solve. >> >> When a master is not in control of the bus, it gets informed of devices >> present on the bus by monitoring DAA or DEFSLVS broadcast events. That >> means the secondary master should populate the bus with I3C/I2C devices >> on such events, but that's not enough, because DEFSLVS/DAA do not >> provide all device info.Some of them (like read/write/ibi limitations) >> require extra CCC commands, and, to send those CCC commands, the >> secondary master must claim the bus. We could add a case where we >> declare devices as partially discovered until the master acquires >> ownership of the bus, but that means part of the data returned by >> i3c_device_get_info() will be inaccurate, which might have an impact on >> some i3c driver ->probe() functions. > Hm, one possible solution would be to register partially discovered > devices to the device model and let i3c_device_get_info() claim the bus > and request missing data when needed. This way, if the driver needs to > call i3c_device_get_info() in its probe path, it should work just fine. Why don't use the i3c_master_add_i3c_dev_locked that job? It create, attach and retrieve the device info. This can be triggered after the secondary master receive ENEC MR until them is keep in the driver memory. Best regards, Vitor Soares