For handling try_fmt, the values should be filled in by validating the
stream configuration, and not by recalculating them or manually checking
against the cached list of formats and sizes. Add a new
V4L2Camera::validateConfiguration() function to validate a configuration
and use it to obtain size, format, stride, and frameSize values.
If the format negotiation fails, return error from try_fmt and s_fmt.
Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>