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

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Date:   Mon, 20 Mar 2017 21:51:50 +0900
From:   DaeSeok Youn <daeseok.youn@...il.com>
To:     wharms@....de
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()

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.)

>
> re,
>  wh
>
>>