libcamera: v4l2_device: List valid controls at open

Enumerate all the valid controls a device supports at open() time.
A control is valid only if its type is supported.

Store the control information in a map inside the device to save
querying the control when setting or getting its value from the device
and provide an operation to retrieve information by control ID.

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

src/libcamera/include/v4l2_device.h

@@ -7,18 +7,23 @@
 #ifndef __LIBCAMERA_V4L2_DEVICE_H__
 #define __LIBCAMERA_V4L2_DEVICE_H__
 
+#include <map>
 #include <string>
 
 #include "log.h"
 
 namespace libcamera {
 
+class V4L2ControlInfo;
+
 class V4L2Device : protected Loggable
 {
 public:
 	void close();
 	bool isOpen() const { return fd_ != -1; }
 
+	const V4L2ControlInfo *getControlInfo(unsigned int id) const;
+
 	const std::string &deviceNode() const { return deviceNode_; }
 
 protected:
@@ -32,6 +37,9 @@ protected:
 	int fd() { return fd_; }
 
 private:
+	void listControls();
+
+	std::map<unsigned int, V4L2ControlInfo> controls_;
 	std::string deviceNode_;
 	int fd_;
 };