Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754666AbbLKJgP (ORCPT ); Fri, 11 Dec 2015 04:36:15 -0500 Received: from mga03.intel.com ([134.134.136.65]:61193 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752398AbbLKJgN (ORCPT ); Fri, 11 Dec 2015 04:36:13 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,412,1444719600"; d="scan'208";a="869449426" From: Alexander Shishkin To: Chunyan Zhang Cc: "linux-kernel\@vger.kernel.org" , Mathieu Poirier Subject: Re: [PATCH] stm: the number of masters should be (sw_end - sw_start + 1) In-Reply-To: References: <1449804410-16833-1-git-send-email-zhang.chunyan@linaro.org> <87mvthxwzb.fsf@ashishki-desk.ger.corp.intel.com> <87mvthcqrm.fsf@ashishki-desk.ger.corp.intel.com> User-Agent: Notmuch/0.21 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu) Date: Fri, 11 Dec 2015 11:34:10 +0200 Message-ID: <87k2olcorx.fsf@ashishki-desk.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2997 Lines: 73 Chunyan Zhang writes: > On Fri, Dec 11, 2015 at 4:51 PM, Alexander Shishkin > wrote: >> Chunyan Zhang writes: >> >>> On Fri, Dec 11, 2015 at 3:31 PM, Alexander Shishkin >>> wrote: >>>> Chunyan Zhang writes: >>>> >>>>> sw_end represents the last software master, sw_start is index of the >>>>> first master, so the number of software masters should be >>>>> sw_end - sw_start + 1. >>>> >>>> Looks about right, but it needs to be in two separate patches. >>>> >>>>> Signed-off-by: Chunyan Zhang >>>>> --- >>>>> drivers/hwtracing/intel_th/sth.c | 2 +- >>>>> drivers/hwtracing/stm/core.c | 2 +- >>>>> 2 files changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/hwtracing/intel_th/sth.c b/drivers/hwtracing/intel_th/sth.c >>>>> index 56101c3..28917d7 100644 >>>>> --- a/drivers/hwtracing/intel_th/sth.c >>>>> +++ b/drivers/hwtracing/intel_th/sth.c >>>>> @@ -173,7 +173,7 @@ static int intel_th_sw_init(struct sth_device *sth) >>>>> sth->stm.sw_start = reg & 0xffff; >>>>> sth->stm.sw_end = reg >> 16; >>>>> >>>>> - sth->sw_nmasters = sth->stm.sw_end - sth->stm.sw_start; >>>>> + sth->sw_nmasters = sth->stm.sw_end - sth->stm.sw_start + 1; >>>>> dev_dbg(sth->dev, "sw_start: %x sw_end: %x masters: %x nchannels: %x\n", >>>>> sth->stm.sw_start, sth->stm.sw_end, sth->sw_nmasters, >>>>> sth->stm.sw_nchannels); >>>>> diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c >>>>> index 7f7bdb3..cb676f2 100644 >>>>> --- a/drivers/hwtracing/stm/core.c >>>>> +++ b/drivers/hwtracing/stm/core.c >>>>> @@ -632,7 +632,7 @@ int stm_register_device(struct device *parent, struct stm_data *stm_data, >>>>> if (!stm_data->packet || !stm_data->sw_nchannels) >>>>> return -EINVAL; >>>>> >>>>> - nmasters = stm_data->sw_end - stm_data->sw_start; >>>>> + nmasters = stm_data->sw_end - stm_data->sw_start + 1; >>>>> stm = kzalloc(sizeof(*stm) + nmasters * sizeof(void *), GFP_KERNEL); >>>> >>>> Or even offsetof(struct stm_device, masters[stm_data->sw_end]). >>>> >>> >>> This should use 'offsetofend()'. >> >> No, actually, just scratch my previous comment as it was completely >> wrong, just fix the off-by-one. If we were to use offsetof(), it should >> rather be of masters[nmasters], but all we need is to fix the off-by-one >> right now. >> > > Sorry, you may lose me here, what's 'off-by-one' ? It's an error when the result of your calculation is off by 1 (one too few or one too many). https://www.google.com/search?q=off-by-one Regards, -- Alex -- 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/