Re: [PATCH] media: v4l2-subdev: Fix stream handling for crop API

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

On 02/04/2024 23:11, Laurent Pinchart wrote:
> On Tue, Apr 02, 2024 at 03:23:03PM +0000, Sakari Ailus wrote:
>> On Tue, Apr 02, 2024 at 12:11:30PM +0300, Tomi Valkeinen wrote:
>>> On 02/04/2024 11:46, Sakari Ailus wrote:
>>>> On Tue, Apr 02, 2024 at 11:44:07AM +0300, Laurent Pinchart wrote:
>>>>> On Tue, Apr 02, 2024 at 08:20:22AM +0000, Sakari Ailus wrote:
>>>>>> Moi,
>>>>>>
>>>>>> On Tue, Apr 02, 2024 at 02:37:25AM +0300, Laurent Pinchart wrote:
>>>>>>> When support for streams was added to the V4L2 subdev API, the
>>>>>>> v4l2_subdev_crop structure was extended with a stream field, but the
>>>>>>> field was not handled in the core code that translates the
>>>>>>> VIDIOC_SUBDEV_[GS]_CROP ioctls to the selection API. Fix it.
>>>>>>
>>>>>> The field is indeed in the UAPI headers. But do we want to support the CROP
>>>>>> IOCTL for streams? Shouldn't the callers be using the [GS]_SELECTION
>>>>>> instead?
>>>>>
>>>>> They should, but if the field is there, we should support it :-) The
>>>>> alternative is to remove it. It will cause failures in v4l2-compliance
>>>>> that we'll need to handle though.
>>>>
>>>> I'd prefer to stick to selections here, this is new functionality so
>>>> [GS]_CROP support isn't required. I don't have a strong opinion on the
>>>> matter though.
>>>
>>> Maybe it's easier to just support the stream field, instead of making
>>> [GS]_CROP the odd case which looks like it should support streams, but then
>>> doesn't...
>>
>> It's an old IOCTL already replaced by the [GS]_SELECTION. I mainly write
>> kernel space software but overall I think it's better if we can provide a
>> single API for controlling cropping instead of two with similar
>> functionality, of which the user then should choose from.
>>
>> It should be also documented in this context if we choose support
>> [GS]_CROP.
>>
>> So I believe we have less work to do and have a better result if we just
>> drop the stream field there. :-)
> 
> I tend to agree, even if that's only a slight preference. Tomi, if
> you're fine with this, I'll update the patch.

I'm fine with it. So we now should move the 'stream' field back to 
reserved, and add documentation saying that [GS]_CROP works differently 
than the other ioctls?

  Tomi