From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754150AbeDWGoZ (ORCPT ); Mon, 23 Apr 2018 02:44:25 -0400 Received: from mail-wr0-f195.google.com ([209.85.128.195]:34153 "EHLO mail-wr0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752393AbeDWGoV (ORCPT ); Mon, 23 Apr 2018 02:44:21 -0400 X-Google-Smtp-Source: AIpwx49u0OS3NVTVAjf6If9I9nnZ697MWAjRlI8nJaLWmCVNU6wHR3LC7KEGxekQ9/zwXjNarEZZ/Q== Date: Mon, 23 Apr 2018 07:44:17 +0100 From: Lee Jones To: Dan Carpenter Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH v2] mfd: tps65911-comparator: Fix an off by one bug Message-ID: <20180423064417.2e2ng3su23w4i7hx@dell> References: <20180420083909.66a6t63s5q6vpwp7@dell> <20180420090910.GA26071@mwanda> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20180420090910.GA26071@mwanda> User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 20 Apr 2018, Dan Carpenter wrote: > The COMP1 and COMP2 elements are in 0 and 1 respectively so this code is > accessing the wrong elements and one space beyond the end of the array. > We should be using "id - 1" instead. > > The "id" variable is never COMP (0) so that code can be removed. > > Fixes: 6851ad3ab346 ("TPS65911: Comparator: Add comparator driver") > Signed-off-by: Dan Carpenter > --- > v2: we can fix the bug and save memory. Looks like it's as we feared: http://www.ti.com/lit/ds/symlink/tps65911.pdf (page 52) There are only 2 comparators 1 and 2. > diff --git a/drivers/mfd/tps65911-comparator.c b/drivers/mfd/tps65911-comparator.c > index c0789f81a1c5..887409c3938d 100644 > --- a/drivers/mfd/tps65911-comparator.c > +++ b/drivers/mfd/tps65911-comparator.c > @@ -22,7 +22,6 @@ > #include > #include > > -#define COMP 0 > #define COMP1 1 > #define COMP2 2 Sorry, but I think these defines should describe the indexes into the supplied struct directly, especially as in this case it is their only reason for being. I completely agree with you that defining something that is named '1' as '0' is not ideal, but IMHO it's better than jumping through hoops using arithmetic in array indexes. > @@ -58,14 +57,11 @@ static struct comparator tps_comparators[] = { > > static int comp_threshold_set(struct tps65910 *tps65910, int id, int voltage) > { > - struct comparator tps_comp = tps_comparators[id]; > + struct comparator tps_comp = tps_comparators[id - 1]; > int curr_voltage = 0; > int ret; > u8 index = 0, val; > > - if (id == COMP) > - return 0; > - > while (curr_voltage < tps_comp.uV_max) { > curr_voltage = tps_comp.vsel_table[index]; > if (curr_voltage >= voltage) > @@ -85,13 +81,10 @@ static int comp_threshold_set(struct tps65910 *tps65910, int id, int voltage) > > static int comp_threshold_get(struct tps65910 *tps65910, int id) > { > - struct comparator tps_comp = tps_comparators[id]; > + struct comparator tps_comp = tps_comparators[id - 1]; > int ret; > u8 val; > > - if (id == COMP) > - return 0; > - > ret = tps65910->read(tps65910, tps_comp.reg, 1, &val); > if (ret < 0) > return ret; -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog