libcamera: v4l2_device: Avoid copy of V4L2ControlInfo

The V4L2Device::listControls() method creates an instance of
V4L2ControlInfo and then inserts it in the device's list of controls.
The insertion uses std::map::emplace(), but passes the V4L2ControlInfo,
resulting in a copy being performed (using the copy constructor of
V4L2ControlInfo).

Optimise this by really constructing the V4L2ControlInfo in-place. The
use of std::piecewise_construct is required for gcc-5 that seems to have
trouble with std::map::emplace() on non-copyable values in this case.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Jacopo Mondi <jacopo@jmondi.org>
Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

0 files changed, 0 insertions, 0 deletions