libcamera: v4l2_controls: Turn V4L2ControlInfoMap into a class

In preparation for extending V4L2ControlInfoMap with control idmap
support, turn it into a real class. Make it inherit from std::map<>
instead of wrapping it to keep the API simple.

V4L2ControlInfoMap is meant to be constructed with a set of control
info, and never modified afterwards. To ensure this, inherit from
std::map<> with private access specifier, and explicitly expose the
std::map<> methods that do not allow insertion or removal of elements. A
custom move assignment operator is implemented to allow efficient
construction of the V4L2ControlInfoMap.

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

1 files changed, 6 insertions, 3 deletions

diff --git a/src/libcamera/v4l2_device.cpp b/src/libcamera/v4l2_device.cpp
index 8c599843..1f755f0f 100644
--- a/src/libcamera/v4l2_device.cpp
+++ b/src/libcamera/v4l2_device.cpp
@@ -340,6 +340,7 @@ int V4L2Device::ioctl(unsigned long request, void *argp)
  */
 void V4L2Device::listControls()
 {
+	std::map<unsigned int, V4L2ControlInfo> ctrls;
 	struct v4l2_query_ext_ctrl ctrl = {};
 
 	/* \todo Add support for menu and compound controls. */
@@ -368,10 +369,12 @@ void V4L2Device::listControls()
 			continue;
 		}
 
-		controls_.emplace(std::piecewise_construct,
-				  std::forward_as_tuple(ctrl.id),
-				  std::forward_as_tuple(ctrl));
+		ctrls.emplace(std::piecewise_construct,
+			      std::forward_as_tuple(ctrl.id),
+			      std::forward_as_tuple(ctrl));
 	}
+
+	controls_ = std::move(ctrls);
 }
 
 /*