libcamera: controls: Add default to ControlRange

Augment the the ControlRange class to store the control default value.

This is particularly relevant for v4l2 controls used to create
Camera properties, which are constructed using immutable video device
properties, whose value won't change at runtime.

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

include/libcamera/controls.h

@@ -114,10 +114,12 @@ class ControlRange
 {
 public:
 	explicit ControlRange(const ControlValue &min = 0,
-			      const ControlValue &max = 0);
+			      const ControlValue &max = 0,
+			      const ControlValue &def = 0);
 
 	const ControlValue &min() const { return min_; }
 	const ControlValue &max() const { return max_; }
+	const ControlValue &def() const { return def_; }
 
 	std::string toString() const;
 
@@ -134,6 +136,7 @@ public:
 private:
 	ControlValue min_;
 	ControlValue max_;
+	ControlValue def_;
 };
 
 using ControlIdMap = std::unordered_map<unsigned int, const ControlId *>;

src/libcamera/controls.cpp

@@ -357,10 +357,12 @@ Control<int64_t>::Control(unsigned int id, const char *name)
  * \brief Construct a ControlRange with minimum and maximum range parameters
  * \param[in] min The control minimum value
  * \param[in] max The control maximum value
+ * \param[in] def The control default value
  */
 ControlRange::ControlRange(const ControlValue &min,
-			   const ControlValue &max)
+			   const ControlValue &max,
-	: min_(min), max_(max)
+			   const ControlValue &def)
+	: min_(min), max_(max), def_(def)
 {
 }
 
@@ -376,6 +378,12 @@ ControlRange::ControlRange(const ControlValue &min,
  * \return A ControlValue with the maximum value for the control
  */
 
+/**
+ * \fn ControlRange::def()
+ * \brief Retrieve the default value of the control
+ * \return A ControlValue with the default value for the control
+ */
+
 /**
  * \brief Provide a string representation of the ControlRange
  */

src/libcamera/v4l2_controls.cpp

@@ -121,17 +121,20 @@ V4L2ControlRange::V4L2ControlRange(const struct v4l2_query_ext_ctrl &ctrl)
 	switch (ctrl.type) {
 	case V4L2_CTRL_TYPE_BOOLEAN:
 		ControlRange::operator=(ControlRange(static_cast<bool>(ctrl.minimum),
-						     static_cast<bool>(ctrl.maximum)));
+						     static_cast<bool>(ctrl.maximum),
+						     static_cast<bool>(ctrl.default_value)));
 		break;
 
 	case V4L2_CTRL_TYPE_INTEGER64:
 		ControlRange::operator=(ControlRange(static_cast<int64_t>(ctrl.minimum),
-						     static_cast<int64_t>(ctrl.maximum)));
+						     static_cast<int64_t>(ctrl.maximum),
+						     static_cast<int64_t>(ctrl.default_value)));
 		break;
 
 	default:
 		ControlRange::operator=(ControlRange(static_cast<int32_t>(ctrl.minimum),
-						     static_cast<int32_t>(ctrl.maximum)));
+						     static_cast<int32_t>(ctrl.maximum),
+						     static_cast<int32_t>(ctrl.default_value)));
 		break;
 	}
 }