Re: [RFC v3 02/19] media/v4l2-core: add new ioctl VIDIOC_G_DEF_EXT_CTRLS

Ricardo Ribalda Delgado
2015-08-19T13:24:55Z

ping?

On Mon, Aug 10, 2015 at 2:04 PM, Ricardo Ribalda Delgado
<ricardo.ribalda@gmail.com> wrote:
> Hello Hans, Sakari and Laurent:
>
> I am back from holidays :). Shall I prepare a new patchset with the
> suggestion from Hans?
>
> Thanks!
>
> On Mon, Jul 20, 2015 at 4:31 PM, Hans Verkuil <hverkuil@xs4all.nl> wrote:
>> On 07/20/2015 03:52 PM, Ricardo Ribalda Delgado wrote:
>>> Hello
>>>
>>> I have no preference over the two implementations, but I see an issue
>>> with this suggestion.
>>>
>>>
>>> What happens to out out tree drivers, or drivers that don't support
>>> this functionality?
>>>
>>> With the ioctl, the user receives a -ENOTTY. So he knows there is
>>> something wrong with the driver.
>>>
>>> With this class, the driver might interpret this a simple G_VAL and
>>> return he current value with no way for the user to know what is going
>>> on.
>>
>> Drivers that implement the current API correctly will return an error
>> if V4L2_CTRL_WHICH_DEF_VAL was specified. Such drivers will interpret
>> the value as a control class, and no control classes in that range exist.
>> See also class_check() in v4l2-ctrls.c.
>>
>> The exception here is uvc which doesn't have this class check and it will
>> just return the current value :-(
>>
>> I don't see a way around this, unfortunately.
>>
>> Out-of-tree drivers that use the control framework are fine, and I don't
>> really care about drivers (out-of-tree or otherwise) that do not use the
>> control framework.
>>
>>> Regarding the new implementation.... I can make some code next week,
>>> this week I am 120% busy :)
>>
>> Wait until there is a decision first :-)
>>
>> It's not a lot of work, I think.
>>
>> Regards,
>>
>> Hans
>>
>>> What do you think?
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>>
>
>
>
> --
> Ricardo Ribalda

--
Ricardo Ribalda