libcamera: Add V4L2Controls

Add libcamera V4L2 control support, implemented using the V4L2 Extended
Control APIs. This patch defines the types used to create and manage
controls.

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

src/libcamera/include/v4l2_controls.h

@@ -0,0 +1,80 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2019, Google Inc.
+ *
+ * v4l2_controls.h - V4L2 Controls Support
+ */
+
+#ifndef __LIBCAMERA_V4L2_CONTROLS_H__
+#define __LIBCAMERA_V4L2_CONTROLS_H__
+
+#include <string>
+#include <vector>
+
+#include <stdint.h>
+
+#include <linux/v4l2-controls.h>
+#include <linux/videodev2.h>
+
+namespace libcamera {
+
+class V4L2ControlInfo
+{
+public:
+	V4L2ControlInfo(const struct v4l2_query_ext_ctrl &ctrl);
+
+	unsigned int id() const { return id_; }
+	unsigned int type() const { return type_; }
+	size_t size() const { return size_; }
+	const std::string &name() const { return name_; }
+
+private:
+	unsigned int id_;
+	unsigned int type_;
+	size_t size_;
+	std::string name_;
+};
+
+class V4L2Control
+{
+public:
+	V4L2Control(unsigned int id, int value = 0)
+		: id_(id), value_(value) {}
+
+	int64_t value() const { return value_; }
+	void setValue(int64_t value) { value_ = value; }
+
+	unsigned int id() const { return id_; }
+
+private:
+	unsigned int id_;
+	int64_t value_;
+};
+
+class V4L2ControlList
+{
+public:
+	using iterator = std::vector<V4L2Control>::iterator;
+	using const_iterator = std::vector<V4L2Control>::const_iterator;
+
+	iterator begin() { return controls_.begin(); }
+	const_iterator begin() const { return controls_.begin(); }
+	iterator end() { return controls_.end(); }
+	const_iterator end() const { return controls_.end(); }
+
+	bool empty() const { return controls_.empty(); }
+	std::size_t size() const { return controls_.size(); }
+
+	void clear() { controls_.clear(); }
+	void add(unsigned int id, int64_t value = 0);
+
+	V4L2Control *getByIndex(unsigned int index);
+	V4L2Control *operator[](unsigned int id);
+
+private:
+	std::vector<V4L2Control> controls_;
+};
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_V4L2_CONTROLS_H__ */