2018-09-08 11:11:32

by zhong jiang

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

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

Signed-off-by: zhong jiang <[email protected]>
---
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

2018-09-08 12:31:52

by Himanshu Jha

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

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 <[email protected]>
> ---
> 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

2018-09-08 14:19:20

by Jonathan Cameron

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

On Sat, 8 Sep 2018 17:59:13 +0530
Himanshu Jha <[email protected]> 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 <[email protected]>
> > ---
> > 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

2018-09-10 13:51:59

by zhong jiang

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

On 2018/9/8 22:17, Jonathan Cameron wrote:
> On Sat, 8 Sep 2018 17:59:13 +0530
> Himanshu Jha <[email protected]> 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 <[email protected]>
>>> ---
>>> 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
>
> .
>

2018-09-10 15:59:55

by David Frey

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

On 9/8/2018 7:17 AM, Jonathan Cameron wrote:
> On Sat, 8 Sep 2018 17:59:13 +0530
> Himanshu Jha <[email protected]> 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 <[email protected]>
>>> ---
>>> 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?

2018-09-11 01:17:08

by zhong jiang

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 <[email protected]> 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 <[email protected]>
>>>> ---
>>>> 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
>> .
>>
>
>
> .
>