From patchwork Fri Dec 16 23:23:56 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Russell King (Oracle)" X-Patchwork-Id: 9478703 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id ADCFC601C2 for ; Fri, 16 Dec 2016 23:26:10 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 9D4F228658 for ; Fri, 16 Dec 2016 23:26:10 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8E75228681; Fri, 16 Dec 2016 23:26:10 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 746BE28658 for ; Fri, 16 Dec 2016 23:26:09 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.85_2 #1 (Red Hat Linux)) id 1cI1rk-0003LO-7x; Fri, 16 Dec 2016 23:24:40 +0000 Received: from pandora.armlinux.org.uk ([2001:4d48:ad52:3201:214:fdff:fe10:1be6]) by bombadil.infradead.org with esmtps (Exim 4.85_2 #1 (Red Hat Linux)) id 1cI1rc-0003Eb-Bq for linux-arm-kernel@lists.infradead.org; Fri, 16 Dec 2016 23:24:35 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Sender:In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date; bh=X/x3LS1kvmk3bjZLXGL5lKKPn6JZoLg1dyAeR47gKq4=; b=fQCX6S+HUABj1T7FXNb0rkHuxRyU5T8aASVPdQ1OC8uOOON8TfyoYm8KPvFbcJam52YtrFLt5NM5TQX4poB510cOhX9otNU/DU8bTwvP/pQzLejfnhGk5DwhH108W2Tiaruxdjq59o7rzZ2g6C2MOyRxYAmE1ZzmegcdLgM5N+I=; Received: from n2100.armlinux.org.uk ([2002:4e20:1eda:1:214:fdff:fe10:4f86]:44127) by pandora.armlinux.org.uk with esmtpsa (TLSv1:DHE-RSA-AES256-SHA:256) (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1cI1r7-0002lS-45; Fri, 16 Dec 2016 23:24:01 +0000 Received: from linux by n2100.armlinux.org.uk with local (Exim 4.76) (envelope-from ) id 1cI1r2-0005No-Kw; Fri, 16 Dec 2016 23:23:56 +0000 Date: Fri, 16 Dec 2016 23:23:56 +0000 From: Russell King - ARM Linux To: Peter Rosin Subject: Re: [PATCH] i2c: mux: pca954x: fix i2c mux selection caching Message-ID: <20161216232355.GO14217@n2100.armlinux.org.uk> References: <251c31e3-141c-8884-d56a-fa539714d1ff@axentia.se> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <251c31e3-141c-8884-d56a-fa539714d1ff@axentia.se> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20161216_152432_935949_ECABFE9B X-CRM114-Status: GOOD ( 19.05 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Wolfram Sang Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP On Fri, Dec 16, 2016 at 10:20:35PM +0100, Peter Rosin wrote: > On 2016-12-16 21:06, Russell King wrote: > > smbus functions return -ve on error, 0 on success. However, > > __i2c_transfer() have a different return signature - -ve on error, or > > number of buffers transferred (which may be zero or greater.) > > > > The upshot of this is that the sense of the test is reversed when using > > the mux on a bus supporting the master_xfer method: we cache the value > > and never retry if we fail to transfer any buffers, but if we succeed, > > we clear the cached value. > > Ouch! Thanks for catching this. > > > Fix this. > > But lets fix the corner case of __i2c_transfer returning 0 instead of > the expected 1 as well (not sure if that's even possible, but lets close > the possibility just in case), so I'd prefer if you could fix > pca954x_reg_write() to return 0 iff __i2c_transfer(...) returns 1 > instead, and -EREMOTEIO on other non-negative return values. Thanks! So you want something like this instead? Acked-by: Peter Rosin diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c index 8bc3d36d2837..9c4ac26c014e 100644 --- a/drivers/i2c/muxes/i2c-mux-pca954x.c +++ b/drivers/i2c/muxes/i2c-mux-pca954x.c @@ -151,6 +151,9 @@ static int pca954x_reg_write(struct i2c_adapter *adap, buf[0] = val; msg.buf = buf; ret = __i2c_transfer(adap, &msg, 1); + + if (ret >= 0 && ret != 1) + ret = -EREMOTEIO; } else { union i2c_smbus_data data; ret = adap->algo->smbus_xfer(adap, client->addr, @@ -179,7 +182,7 @@ static int pca954x_select_chan(struct i2c_mux_core *muxc, u32 chan) /* Only select the channel if its different from the last channel */ if (data->last_chan != regval) { ret = pca954x_reg_write(muxc->parent, client, regval); - data->last_chan = ret ? 0 : regval; + data->last_chan = ret < 0 ? 0 : regval; } return ret;