Hi Hans, On Wednesday 15 December 2010 11:03:37 Hans Verkuil wrote: > > On Wednesday 15 December 2010 08:57:29 Hans Verkuil wrote: > > > > Hence my question, should we add a way to pass rectangles (basically a > > structv4l2_rect) through the control ioctls ? It would make sense. > > I thought it over and came to the conclusion that we should not do that. > Instead we can create four separate controls. That's not very clean, is it ? > The problem we run into when adding more complex types is that we can no > longer communicate min and max values (something that we definitely want > when dealing with coordinates). Why not ? We should still support querying min/max/def values on a struct v4l2_ctrl. This would of course require an extended queryctrl ioctl. > Another reason is how the control mechanism is designed: they only support > the basic types (int, bool, string, enum, int64 and a 'button' aka > action). And the controls are grouped into classes which are named through > the 'ctrl_class' control. > > So effectively controls represent a field in a class (or struct) and each > class can be presented as a tab page in a control panel. > > Simple and straightforward. > > If we start to add complex types, then it becomes really hard to define > the meta data of the control since you are really defining a 'mini-class'. I agree that arbitrary complex controls might not be a good idea, but v4l2_rect is a pretty standard data structure in V4L2 and something that can be useful for different controls. > It sounds nice initially, but we really should not do this since I believe > it will lead to chaos later on. You want complex types, then use ioctls, > not controls. Or split up the complex type into multiple simple types. Then let's use an ioctl for focus control. I don't like it. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
