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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,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 89834C3815B for ; Wed, 15 Apr 2020 08:38:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5EF932078A for ; Wed, 15 Apr 2020 08:38:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="YJHXYax3" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2894705AbgDOIif (ORCPT ); Wed, 15 Apr 2020 04:38:35 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S2894680AbgDOIiJ (ORCPT ); Wed, 15 Apr 2020 04:38:09 -0400 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B9696C061A0C; Wed, 15 Apr 2020 01:38:08 -0700 (PDT) Received: from [192.168.0.20] (cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 81BBB2D1; Wed, 15 Apr 2020 10:38:06 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1586939887; bh=m17M/qxOXVGsFQJ698T1Ff8MtF5x26XIRLZsnobAhNg=; h=Reply-To:Subject:To:Cc:References:From:Date:In-Reply-To:From; b=YJHXYax3vn++WTEV3ZgsaAvu0Np/2TLyVoFAzk/SXaOkJgHeaTy+3qpw2qOZurZqX 6IVPyXrZX9N8VJqLF0Mc5OTr6mZORtiKu6Q4+vFNM2DQJECPvFLsBVNmlTJrv7BPPL 8UlYHHVmPO7J16i7Sm3gN5xiQO6qWFL3jtZ8+DsE= Reply-To: kieran.bingham+renesas@ideasonboard.com Subject: Re: [RFC PATCH v2 2/6] i2c: allow DT nodes without 'compatible' To: Wolfram Sang Cc: Luca Ceresoli , Wolfram Sang , linux-i2c@vger.kernel.org, linux-renesas-soc@vger.kernel.org, linux-i3c@lists.infradead.org, =?UTF-8?Q?Niklas_S=c3=b6derlund?= , Jacopo Mondi , Laurent Pinchart , Vladimir Zapolskiy , linux-kernel@vger.kernel.org, Geert Uytterhoeven , Rob Herring References: <20200318150059.21714-1-wsa+renesas@sang-engineering.com> <20200318150059.21714-3-wsa+renesas@sang-engineering.com> <11ca7487-ac07-f714-8573-20d1a0040212@lucaceresoli.net> <20200415075911.GA1141@ninjato> <8937e466-fe3f-3686-98a9-8013990bc3f9@ideasonboard.com> <20200415081654.GC1141@ninjato> From: Kieran Bingham Organization: Ideas on Board Message-ID: Date: Wed, 15 Apr 2020 09:38:03 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1 MIME-Version: 1.0 In-Reply-To: <20200415081654.GC1141@ninjato> Content-Type: text/plain; charset=windows-1252 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Wolfram, On 15/04/2020 09:16, Wolfram Sang wrote: > >> Aha, is it easy enough to distinguish that difference in user-space so >> that we can present a specific character to indicate this in i2cdetect? >> Or is that not so easy? > > I thought about it shortly but have not come up with a way of doing > that. This is the code in i2cdetect: > > /* Set slave address */ > if (ioctl(file, I2C_SLAVE, i+j) < 0) { > if (errno == EBUSY) { > printf("UU "); > continue; > } else { > fprintf(stderr, "Error: Could not set " > "address to 0x%02x: %s\n", i+j, > strerror(errno)); > return -1; > } > } > > So, if we chose to use another errno to indicate 'reserved' and update > i2cdetect, all old versions of i2cdetect will have ugly error messages. > And adding another IOCTL just for printing reserved addresses neither > sounds great. Indeed, a different errno would be about all we could do - and it would seemingly leave old i2cdetects with complete failures, if it goes through that non-EBUSY code path. Ayeeeee :-S -- Kieran