From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf1-f195.google.com ([209.85.210.195]:39425 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727777AbeIJUwl (ORCPT ); Mon, 10 Sep 2018 16:52:41 -0400 Subject: Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler To: Jonathan Cameron , Himanshu Jha Cc: zhong jiang , knaack.h@gmx.de, lars@metafoo.de, pmeerw@pmeerw.net, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org References: <1536404256-25189-1-git-send-email-zhongjiang@huawei.com> <20180908122913.GA4445@himanshu-Vostro-3559> <20180908151751.20e7396f@archlinux> From: David Frey Message-ID: Date: Mon, 10 Sep 2018 08:57:54 -0700 MIME-Version: 1.0 In-Reply-To: <20180908151751.20e7396f@archlinux> Content-Type: text/plain; charset=utf-8 Sender: linux-iio-owner@vger.kernel.org List-Id: linux-iio@vger.kernel.org On 9/8/2018 7:17 AM, Jonathan Cameron wrote: > On Sat, 8 Sep 2018 17:59:13 +0530 > Himanshu Jha wrote: > >> On Sat, Sep 08, 2018 at 06:57:36PM +0800, zhong jiang wrote: >>> The iterator in for_each_set_bit is never null, therefore, remove >>> the redundant conditional judgment. >>> >>> Signed-off-by: zhong jiang >>> --- >>> drivers/iio/humidity/am2315.c | 3 +-- >>> 1 file changed, 1 insertion(+), 2 deletions(-) >>> >>> diff --git a/drivers/iio/humidity/am2315.c b/drivers/iio/humidity/am2315.c >>> index 7d8669d..dc12e37 100644 >>> --- a/drivers/iio/humidity/am2315.c >>> +++ b/drivers/iio/humidity/am2315.c >>> @@ -176,8 +176,7 @@ static irqreturn_t am2315_trigger_handler(int irq, void *p) >>> i = 0; >>> for_each_set_bit(bit, indio_dev->active_scan_mask, >>> indio_dev->masklength) { >>> - data->buffer[i] = (bit ? sensor_data.temp_data : >>> - sensor_data.hum_data); >>> + data->buffer[i] = sensor_data.temp_data; >> >> No, this seems wrong! >> >> We have buffer support to either take both readings(temp & humid) >> simultaneously, or only single channel using specified scan mask. > > Key think is that bit most definitely can be 0 if the 0th bit is set. > This isn't a null check at all. > > I'm curious, was this a by inspection case or did some script throw > this one up? Firstly, +1 on the patch in this thread being an incorrect change. While inspecting the surrounding code, I noticed that there's a bit of questionable code in this area. I believe this whole chunk: if (*(indio_dev->active_scan_mask) == AM2315_ALL_CHANNEL_MASK) { data->buffer[0] = sensor_data.hum_data; data->buffer[1] = sensor_data.temp_data; } else { i = 0; for_each_set_bit(bit, indio_dev->active_scan_mask, indio_dev->masklength) { data->buffer[i] = (bit ? sensor_data.temp_data : sensor_data.hum_data); i++; } } could be reduced to this: for_each_set_bit(bit, indio_dev->active_scan_mask, indio_dev->masklength) data->buffer[bit] = (bit ? sensor_data.temp_data : sensor_data.hum_data); The if/else structure seems like an unnecessary optimization. Thoughts?