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[208.81.120.1]) by smtp.gmail.com with ESMTPSA id 1-v6sm36434492pfm.145.2018.09.10.08.57.54 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Sep 2018 08:57:55 -0700 (PDT) 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 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <20180908151751.20e7396f@archlinux> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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?