On 23/01/14 15:23, Hans Verkuil wrote:
> On 01/23/2014 12:02 AM, Sylwester Nawrocki wrote:
>> On 01/20/2014 01:45 PM, Hans Verkuil wrote:
>>> From: Hans Verkuil<hans.verkuil@xxxxxxxxx>
>>>
>>> Add a new struct and ioctl to extend the amount of information you can
>>> get for a control.
>>>
>>> It gives back a unit string, the range is now a s64 type, and the matrix
>>> and element size can be reported through cols/rows/elem_size.
>>>
>>> Signed-off-by: Hans Verkuil<hans.verkuil@xxxxxxxxx>
>>> ---
>>> include/uapi/linux/videodev2.h | 30 ++++++++++++++++++++++++++++++
>>> 1 file changed, 30 insertions(+)
>>>
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 4d7782a..9e5b7d4 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -1272,6 +1272,34 @@ struct v4l2_queryctrl {
>>> __u32 reserved[2];
>>> };
>>>
>>> +/* Used in the VIDIOC_QUERY_EXT_CTRL ioctl for querying extended controls */
>>> +struct v4l2_query_ext_ctrl {
>>> + __u32 id;
>>> + __u32 type;
>>> + char name[32];
>>> + char unit[32];
>>
>>> + union {
>>> + __s64 val;
>>> + __u32 reserved[4];
>>> + } min;
>>> + union {
>>> + __s64 val;
>>> + __u32 reserved[4];
>>> + } max;
>>> + union {
>>> + __u64 val;
>>> + __u32 reserved[4];
>>> + } step;
>>> + union {
>>> + __s64 val;
>>> + __u32 reserved[4];
>>> + } def;
>>
>> Are these reserved[] arrays of any use ?
>
> Excellent question. I'd like to know as well :-)
>
> The idea is that if the type of the control is complex, then for certain types
> it might still make sense to have a range. E.g. say that the type is v4l2_rect,
> then you can define min/max/step/def v4l2_rect entries in the unions. Ditto
> for a v4l2_fract (it would be nice to be able to specify the min/max allowed
> scaling factors, for example).
Huh, sorry, I misread the patch. Please ignore this comment.
Certainly we need an ability to query other compound control types as well.
16 bytes seems a reasonable size, I guess it is going to be sufficient for
most cases. If not we could add a pointer member to the union...?
> The question is, am I over-engineering or is this the best idea since sliced
> bread? Without the 'reserved' part this idea will be impossible to implement,
> and I don't think it hurts to have it in.
Yes, that's how I imagined it as well, I didn't mean questioning the union
idea at all.
>>> + __u32 flags;
>>> + __u32 cols, rows;
>>
>> nit: I would put them on separate lines and use full words.
>
> Separate lines: no problem, but do I really have to write 'columns' in full? :-(
Yes, sorry, one shall abide by the rules! :-)
Really, it's up to you - as the author, I think you're entitled to decide
about such details. ;) The short version looks probably neater anyway.
--
Regards,
Sylwester
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