linux-kernel - Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger

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Message-ID: <5B97177A.6010301@huawei.com>
Date:   Tue, 11 Sep 2018 09:16:42 +0800
From:   zhong jiang <zhongjiang@...wei.com>
To:     Jonathan Cameron <jic23@...nel.org>
CC:     Himanshu Jha <himanshujha199640@...il.com>, <knaack.h@....de>,
        <lars@...afoo.de>, <pmeerw@...erw.net>,
        <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

On 2018/9/10 21:49, zhong jiang wrote:
> On 2018/9/8 22:17, Jonathan Cameron wrote:
>> On Sat, 8 Sep 2018 17:59:13 +0530
>> Himanshu Jha <himanshujha199640@...il.com> 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 <zhongjiang@...wei.com>
>>>> ---
>>>>  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?
>  Hi,  Jonathan
>
>  bit is a iterator that find the non-zero bit in indio_dev->active_scan_mask. if  all bit is
>  zero ,  it should return the masklength.
 That's my stupid fault.   The patch is totally wrong.:-(

Thanks,
zhong jiang
>  Yep.  I find the issue with the help of Coccinelle.
>
>  Thanks
> zhong jiang
>> Thanks,
>>
>> Jonathan
>>
>>> Patch title should be:
>>>
>>> "iio: humidity: am2315: .... .. "
>>>
>>>
>>> Thanks
>> .
>>
>
>
> .
>