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 X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D81AC2D0DC for ; Thu, 2 Jan 2020 21:13:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2806021582 for ; Thu, 2 Jan 2020 21:13:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725790AbgABVNa (ORCPT ); Thu, 2 Jan 2020 16:13:30 -0500 Received: from sauhun.de ([88.99.104.3]:50000 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725783AbgABVNa (ORCPT ); Thu, 2 Jan 2020 16:13:30 -0500 Received: from localhost (x4dbfb270.dyn.telefonica.de [77.191.178.112]) by pokefinder.org (Postfix) with ESMTPSA id 0694E2C0162; Thu, 2 Jan 2020 22:13:27 +0100 (CET) Date: Thu, 2 Jan 2020 22:13:27 +0100 From: Wolfram Sang To: Luca Ceresoli Cc: Laurent Pinchart , Wolfram Sang , linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Kieran Bingham , Jacopo Mondi , Vladimir Zapolskiy Subject: Re: [RFC PATCH 3/5] i2c: core: add function to request an alias Message-ID: <20200102211327.GB1030@kunai> References: <20191231161400.1688-1-wsa+renesas@sang-engineering.com> <20191231161400.1688-4-wsa+renesas@sang-engineering.com> <20200101165515.GC6226@pendragon.ideasonboard.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="dTy3Mrz/UPE2dbVg" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-renesas-soc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-renesas-soc@vger.kernel.org --dTy3Mrz/UPE2dbVg Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Luca, > > This looks quite inefficient, especially if the beginning of the range > > is populated with devices. Furthermore, I think there's a high risk of > > false negatives, as acquiring a free address and reprogramming the > > client to make use of it are separate operations. >=20 > Right. Applying the alias could raise other errors, thus one would need > i2c_new_alias_device() to keep the alias locked until programming it has > either failed or has been successfully programmed. Please see my reply to Laurent, I don't think it is racy. But please elaborate if you think I am wrong. > > What happened to the idea of reporting busy address ranges in the > > firmware (DT, ACPI, ...) ? >=20 > Indeed that's how I remember it as well, and I'm a bit suspicious about > sending out probe messages that might have side effects (even if the > false negative issue mentioned by Laurent were solved). You know, I've > been taught to "expect the worse" :) so I'd like to better understand > what are the strong reasons in favor of probing, as well as the > potential side effects. As I said to Laurent, too, I think the risk that a bus is not fully described is higher than a device which does not respond to a read_byte. In both cases, we would wrongly use an address in use. Also, all the best for you in 2020! Wolfram --dTy3Mrz/UPE2dbVg Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAl4OXPcACgkQFA3kzBSg KbZxRw//YHEcEWbTuhwt3Cq3XI305L3vMkgMBmKl6YIPwJkASlA+JsKFJeskatPx 4vzx3BemXe29Mt+GcQ6J8Isi3d8dqB5u+gsZlR8/2jL08hFmB++bnGqWHYzzyFye ppXYuX9xhXNzEnK2Bd24SoguRATKifW++ZySwTPFoqKy4rJ4hE2tijBkJ8uPlKsP nudkVwDxuFEH4DcIh9n/XeRYy95dFuqpM70FYWSqSYEyjMeT4OpNHb7hb6pusTqZ qklOxZc8wLf35I4GrBDMs9OUtFzobPRRDmOzBYmkAN7MGkPLSfohpvYvWKhlUi3T X1RIb7+m3Jp1lPgo4ZIbAWzYFzZdHv9EWNZNKkwioNRFKJQ/D4tnKwBKxGRSXqhQ Fbf9mdBj+XO5ZwsN3Mz8vzHwwYUFerGKpe07u2GJ4hegoA36ZfC6AAg890W6oVQA SUHq/Z8HwDyEd8MKOu7B49PrywEJVu+bg9tgDgAMOsLxsaKo+OcOkAavaT2ITCAO sT/cb978WChsE7aE3cn6tLL4BLgOIWYyuK73y8WPFZdO9t4jCURhsPFKpJQdcwOb Xs8peXBcTp0npcN9YX7tjdTwpJ2UjIGNsgcMARzfyGfCfSBIU4nWB8TTA4maAqF0 AWNyts+QzOXOewoTX1CRTDrH/kVAI4LYPw66NIqIZ8ExDbtNy74= =Cy7J -----END PGP SIGNATURE----- --dTy3Mrz/UPE2dbVg--