linux-kernel - Re: [PATCH] v4l2-core/v4l2-ctrls: Filter NOOP CH

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Date:	Wed, 11 Nov 2015 13:33:16 +0100
From:	Hans Verkuil <hansverk@...co.com>
To:	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>,
	Hans Verkuil <hverkuil@...all.nl>
Cc:	Hans Verkuil <hans.verkuil@...co.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	linux-media <linux-media@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dimitrios Katsaros <patcherwork@...il.com>
Subject: Re: [PATCH] v4l2-core/v4l2-ctrls: Filter NOOP CH_RANGE events

On 11/11/15 13:20, Ricardo Ribalda Delgado wrote:
> Hello Hans
> 
> On my cameras, the framerate can be controlled in very fine steps (so
> you can be in sync with the conveyor belt). The exposure time is
> dependent on the framerate. I was calling modify_range every time
> there was a change on the framerate on all the different heads.
> Leading to invalid/noop events.
> 
> I have already fixed it on my sensor code, but there is a lot of copy
> paste.... I thought that check belong to the framework. It also will
> give some consistency, because If my memory is good, set_ctrl does not
> send and event if the value is unchanged.

Ah, OK. That makes sense. Thanks for the explanation.

	Hans

> 
> 
> Thanks :)
> 
> And take as much time as you need for   V4L2_CTRL_WHICH_DEF_VAL :-)
> 
> 
> 
> On Wed, Nov 11, 2015 at 1:11 PM, Hans Verkuil <hverkuil@...all.nl> wrote:
>> On 11/11/15 12:58, Ricardo Ribalda Delgado wrote:
>>> If modify_range is called but no range is changed, do not send the
>>> CH_RANGE event.
>>
>> While not opposed to this patch, I do wonder what triggered this patch?
>> Is it just a matter of efficiency? And since it is a driver that calls
>> this, shouldn't the driver only call this function when something
>> actually changes?
>>
>> In other words, can you give some background information?
>>
>> Regards,
>>
>>         Hans
>>
>> PS: still haven't processed your V4L2_CTRL_WHICH_DEF_VAL patch series. Hope
>> to do this next week at the latest.
>>
>>>
>>> Reported-by: Dimitrios Katsaros <patcherwork@...il.com>
>>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
>>> ---
>>>  drivers/media/v4l2-core/v4l2-ctrls.c | 23 ++++++++++++++---------
>>>  1 file changed, 14 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
>>> index 4a1d9fdd14bb..f9c0e8150bd1 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
>>> @@ -3300,7 +3300,8 @@ EXPORT_SYMBOL(v4l2_ctrl_notify);
>>>  int __v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
>>>                       s64 min, s64 max, u64 step, s64 def)
>>>  {
>>> -     bool changed;
>>> +     bool value_changed;
>>> +     bool range_changed = false;
>>>       int ret;
>>>
>>>       lockdep_assert_held(ctrl->handler->lock);
>>> @@ -3324,10 +3325,14 @@ int __v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
>>>       default:
>>>               return -EINVAL;
>>>       }
>>> -     ctrl->minimum = min;
>>> -     ctrl->maximum = max;
>>> -     ctrl->step = step;
>>> -     ctrl->default_value = def;
>>> +     if ((ctrl->minimum != min) || (ctrl->maximum != max) ||
>>> +             (ctrl->step != step) || ctrl->default_value != def) {
>>> +             range_changed = true;
>>> +             ctrl->minimum = min;
>>> +             ctrl->maximum = max;
>>> +             ctrl->step = step;
>>> +             ctrl->default_value = def;
>>> +     }
>>>       cur_to_new(ctrl);
>>>       if (validate_new(ctrl, ctrl->p_new)) {
>>>               if (ctrl->type == V4L2_CTRL_TYPE_INTEGER64)
>>> @@ -3337,12 +3342,12 @@ int __v4l2_ctrl_modify_range(struct v4l2_ctrl *ctrl,
>>>       }
>>>
>>>       if (ctrl->type == V4L2_CTRL_TYPE_INTEGER64)
>>> -             changed = *ctrl->p_new.p_s64 != *ctrl->p_cur.p_s64;
>>> +             value_changed = *ctrl->p_new.p_s64 != *ctrl->p_cur.p_s64;
>>>       else
>>> -             changed = *ctrl->p_new.p_s32 != *ctrl->p_cur.p_s32;
>>> -     if (changed)
>>> +             value_changed = *ctrl->p_new.p_s32 != *ctrl->p_cur.p_s32;
>>> +     if (value_changed)
>>>               ret = set_ctrl(NULL, ctrl, V4L2_EVENT_CTRL_CH_RANGE);
>>> -     else
>>> +     else if (range_changed)
>>>               send_event(NULL, ctrl, V4L2_EVENT_CTRL_CH_RANGE);
>>>       return ret;
>>>  }
>>>
> 
> 
> 
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