On Thursday, December 23, 2010 10:19:38 Laurent Pinchart wrote: > 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 ? Why not? It's perfectly consistent with the way controls work. > > 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. Which will make apps even more complicated. I thought about this as well, but it's a road that will lead to chaos. > > 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. I would vote for 4 controls. Since FOCUS_MODE_AUTO is a control it makes no sense to make an ioctl to set the rectangle. That would be a strange mix. And having 4 controls for the rectangle will actually look good in GUIs, and with S_EXT_CTRLS you can set all focus-related controls in one call. Regards, Hans -- Hans Verkuil - video4linux developer - sponsored by Cisco -- 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
