Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751903AbaBBQVM (ORCPT ); Sun, 2 Feb 2014 11:21:12 -0500 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:55265 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751751AbaBBQVL (ORCPT ); Sun, 2 Feb 2014 11:21:11 -0500 Date: Sun, 2 Feb 2014 16:20:58 +0000 From: Russell King - ARM Linux To: Jean-Francois Moine Cc: dri-devel@lists.freedesktop.org, Dave Airlie , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Rob Clark Subject: Re: [PATCH v5 02/23] drm/i2c: tda998x: check more I/O errors Message-ID: <20140202162057.GE26684@n2100.arm.linux.org.uk> References: <9ebf1fdd613b5747aefb3ee21c9c246d102f1a47.1390986082.git.moinejf@free.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9ebf1fdd613b5747aefb3ee21c9c246d102f1a47.1390986082.git.moinejf@free.fr> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jan 25, 2014 at 06:14:45PM +0100, Jean-Francois Moine wrote: > This patch adds more error checking inn I2C I/O functions. > In case of I/O error, this permits to avoid writing in bad controller > pages, a bad chipset detection or looping when getting the EDID. I've just looked at this again, and spotted something: > -static uint8_t > +static int > reg_read(struct tda998x_priv *priv, uint16_t reg) > { > uint8_t val = 0; > - reg_read_range(priv, reg, &val, sizeof(val)); > + int ret; > + > + ret = reg_read_range(priv, reg, &val, sizeof(val)); > + if (ret < 0) > + return ret; So yes, this can return negative numbers. > @@ -1158,8 +1184,11 @@ tda998x_encoder_init(struct i2c_client *client, > tda998x_reset(priv); > > /* read version: */ > - priv->rev = reg_read(priv, REG_VERSION_LSB) | > - reg_read(priv, REG_VERSION_MSB) << 8; > + ret = reg_read(priv, REG_VERSION_LSB) | > + (reg_read(priv, REG_VERSION_MSB) << 8); > + if (ret < 0) > + goto fail; > + priv->rev = ret; Two issues here: 1. The additional parens are /really/ not required. 2. What if reg_read(priv, REG_VERSION_MSB) returns a negative number? If we're going to the extent of attempting to make the read/write functions return errors, we should at least handle errors generated by them properly, otherwise it's pointless making them return errors. ret = reg_read(priv, REG_VERSION_LSB); if (ret < 0) goto fail; priv->rev = ret; ret = reg_read(priv, REG_VERSION_MSB); if (ret < 0) goto fail; priv->rev |= ret << 8; If you want it to look slightly nicer: int rev_lo, rev_hi; rev_lo = reg_read(priv, REG_VERSION_LSB); rev_hi = reg_read(priv, REG_VERSION_MSB); if (rev_lo < 0 || rev_hi < 0) { ret = rev_lo < 0 ? rev_lo : rev_hi; goto fail; } priv->rev = rev_lo | rev_hi << 8; I'm happy to commit such a change after this patch to clean it up, or if you want to regenerate your patch 2 and post /just/ that incorporating this change. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/