From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jean Delvare Subject: Re: [PATCH 03/14 v3] Input: atmel_mxt_ts - refactor mxt_read/write_reg to take a length Date: Wed, 9 May 2012 09:05:00 +0200 Message-ID: <20120509090500.1dc9143e@endymion.delvare> References: <1334755319-21365-1-git-send-email-djkurtz@chromium.org> <1334755319-21365-4-git-send-email-djkurtz@chromium.org> <20120509055411.GG10514@core.coreip.homeip.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from zoneX.GCU-Squad.org ([194.213.125.0]:38186 "EHLO services.gcu-squad.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754131Ab2EIHFO (ORCPT ); Wed, 9 May 2012 03:05:14 -0400 In-Reply-To: <20120509055411.GG10514@core.coreip.homeip.net> Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Dmitry Torokhov Cc: Daniel Kurtz , Henrik Rydberg , Joonyoung Shim , Nick Dyer , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, Benson Leung , Yufeng Shen Hi Dmirty, On Tue, 8 May 2012 22:54:11 -0700, Dmitry Torokhov wrote: > Hi Daniel, > > On Wed, Apr 18, 2012 at 09:21:48PM +0800, Daniel Kurtz wrote: > > + ret = i2c_transfer(client->adapter, xfer, 2); > > + if (ret != 2) { > > + dev_err(&client->dev, "i2c read reg failed (%d)\n", ret); > > + if (ret >= 0) > > + ret = -EIO; > > } > > > > - return 0; > > + return (ret == 2) ? 0 : ret; > > } > > Would prefer: > > ret = i2c_transfer(client->adapter, xfer, ARRAY_SIZE(xfer)); > if (ret != ARRAY_SIZE(xfer)) { > if (ret >= 0) > ret = -EIO; > dev_err(&client->dev, "i2c read reg failed (%d)\n", ret); > return ret; > } > > return 0; > > > Or maybe we need i2c_transfer_exact() wrapper? Jean? What would this function do? Return 0 on success instead of the number of transferred messages? And -EIO on partial transfers? That would make sense. Partial success is a rare case anyway, and recovery possibilities are even rarer. I think most drivers don't bother and either retry the whole transaction or fail right away. In fact the number of messages successfully transferred is more useful to diagnose problems during driver development or debugging. Feel free to write and send a patch introducing i2c_transfer_exact(). It would make sense to have it log a debug message on partial success, as it is a rare case. Bonus points if you also sent one or more patches converting (some of) the existing callers to make use of the new function. -- Jean Delvare