linux-kernel - Re: [PATCH 2/4] staging: atomisp: simplify if statement in atomisp_get_sensor

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Date:   Mon, 20 Mar 2017 14:11:33 +0100
From:   walter harms <wharms@....de>
To:     DaeSeok Youn <daeseok.youn@...il.com>
CC:     mchehab@...nel.org, Greg KH <gregkh@...uxfoundation.org>,
        Alan Cox <alan@...ux.intel.com>,
        SIMRAN SINGHAL <singhalsimran0@...il.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-media@...r.kernel.org, devel <devel@...verdev.osuosl.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        kernel-janitors <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH 2/4] staging: atomisp: simplify if statement in atomisp_get_sensor_fps()



Am 20.03.2017 13:51, schrieb DaeSeok Youn:
> 2017-03-20 21:04 GMT+09:00 walter harms <wharms@....de>:
>>
>>
>> Am 20.03.2017 11:59, schrieb Daeseok Youn:
>>> If v4l2_subdev_call() gets the global frame interval values,
>>> it returned 0 and it could be checked whether numerator is zero or not.
>>>
>>> If the numerator is not zero, the fps could be calculated in this function.
>>> If not, it just returns 0.
>>>
>>> Signed-off-by: Daeseok Youn <daeseok.youn@...il.com>
>>> ---
>>>  .../media/atomisp/pci/atomisp2/atomisp_cmd.c       | 22 ++++++++++------------
>>>  1 file changed, 10 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c b/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
>>> index 8bdb224..6bdd19e 100644
>>> --- a/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
>>> +++ b/drivers/staging/media/atomisp/pci/atomisp2/atomisp_cmd.c
>>> @@ -153,20 +153,18 @@ struct atomisp_acc_pipe *atomisp_to_acc_pipe(struct video_device *dev)
>>>
>>>  static unsigned short atomisp_get_sensor_fps(struct atomisp_sub_device *asd)
>>>  {
>>> -     struct v4l2_subdev_frame_interval frame_interval;
>>> +     struct v4l2_subdev_frame_interval fi;
>>>       struct atomisp_device *isp = asd->isp;
>>> -     unsigned short fps;
>>>
>>> -     if (v4l2_subdev_call(isp->inputs[asd->input_curr].camera,
>>> -         video, g_frame_interval, &frame_interval)) {
>>> -             fps = 0;
>>> -     } else {
>>> -             if (frame_interval.interval.numerator)
>>> -                     fps = frame_interval.interval.denominator /
>>> -                         frame_interval.interval.numerator;
>>> -             else
>>> -                     fps = 0;
>>> -     }
>>> +     unsigned short fps = 0;
>>> +     int ret;
>>> +
>>> +     ret = v4l2_subdev_call(isp->inputs[asd->input_curr].camera,
>>> +                            video, g_frame_interval, &fi);
>>> +
>>> +     if (!ret && fi.interval.numerator)
>>> +             fps = fi.interval.denominator / fi.interval.numerator;
>>> +
>>>       return fps;
>>>  }
>>
>>
>>
>> do you need to check ret at all ? if an error occurs can fi.interval.numerator
>> be something else than 0 ?
> the return value from the v4l2_subdev_call() function is zero when it
> is done without any error. and also I checked
> the ret value whether is 0 or not. if the ret is 0 then the value of
> numerator should be checked to avoid for dividing by 0.
>>
>> if ret is an ERRNO it would be wise to return ret not fps, but this may require
>> changes at other places also.
> hmm.., yes, you are right. but I think it is ok because the
> atomisp_get_sensor_fps() function is needed to get fps value.
> (originally, zero or calculated fps value was returned.)

maybe its better to divide this in:
	if (ret)
	   return 0; // error case

	return (fi.interval.numerator>0)?fi.interval.denominator / fi.interval.numerator:0;

So there is a chance that someone will a) understand and b) fix the error return.

re,
 wh

> 
>>
>> re,
>>  wh
>>
>>>
>