Comments on V4L controls

[gilles <gilles.gigan@gmail.com>]

Hi everyone,
Sorry for double posting, but I originally sent this to the old mailing
list. Here it is:

I have a couple of comments / suggestions regarding the part on controls of
the V4L2 api:
Some controls, such as pan relative and tilt relative are write-only, and
reading their value makes little sense. Yet, there is no way of knowing
about this, but to try and read a value and be greeted with EINVAL or
similar. There is already a read-only flag (V4L2_CTRL_FLAG_READ_ONLY) in
struct v4l2_query. Does it make sense to add another one for write-only
controls ?
The extended controls Pan / Tilt  reset are defined in the API as boolean
controls. Shouldnt these be defined as buttons instead, as they dont really
hold a state (enabled/disabled) ?
Comments are welcome.
Cheers,
Gilles