[PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[zhong jiang]

The iterator in for_each_set_bit is never null, therefore, remove
the redundant conditional judgment.

Signed-off-by: zhong jiang <zhongjiang@huawei.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;
 			i++;
 		}
 	}
-- 
1.7.12.4

Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[Himanshu Jha]

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@huawei.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.

Patch title should be:

"iio: humidity: am2315: .... .. "


Thanks
-- 
Himanshu Jha
Undergraduate Student
Department of Electronics & Communication
Guru Tegh Bahadur Institute of Technology

Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[Jonathan Cameron]

On Sat, 8 Sep 2018 17:59:13 +0530
Himanshu Jha <himanshujha199640@gmail.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@huawei.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?

Thanks,

Jonathan

> 
> Patch title should be:
> 
> "iio: humidity: am2315: .... .. "
> 
> 
> Thanks

Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[zhong jiang]

On 2018/9/8 22:17, Jonathan Cameron wrote:
> On Sat, 8 Sep 2018 17:59:13 +0530
> Himanshu Jha <himanshujha199640@gmail.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@huawei.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.

 Yep.  I find the issue with the help of Coccinelle.

 Thanks
zhong jiang
> Thanks,
>
> Jonathan
>
>> Patch title should be:
>>
>> "iio: humidity: am2315: .... .. "
>>
>>
>> Thanks
>
> .
>

Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[David Frey]

On 9/8/2018 7:17 AM, Jonathan Cameron wrote:
> On Sat, 8 Sep 2018 17:59:13 +0530
> Himanshu Jha <himanshujha199640@gmail.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@huawei.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?

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?

Re: [PATCH] iio: remove unnecessary condition judgment in am2315_trigger_handler

[zhong jiang]

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@gmail.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@huawei.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
>> .
>>
>
>
> .
>