Audio: Introduce Codec abstraction.

Now that we have two hardware variants with different audio codecs.

firmware/application/audio.hpp

@@ -25,9 +25,34 @@
 #include "volume.hpp"
 
 #include <cstdint>
+#include <cstddef>
+
+#include <string>
 
 namespace audio {
 
+class Codec {
+public:
+	virtual ~Codec() { }
+
+	virtual std::string name() const = 0;
+
+	virtual bool reset() = 0;
+	virtual void init() = 0;
+
+	virtual void headphone_enable() = 0;
+	virtual void headphone_disable() = 0;
+	virtual volume_range_t headphone_gain_range() const = 0;
+	virtual void set_headphone_volume(const volume_t volume) = 0;
+
+	virtual void microphone_enable() = 0;
+	virtual void microphone_disable() = 0;
+
+	virtual size_t reg_count() const = 0;
+	virtual size_t reg_bits() const = 0;
+	virtual uint32_t reg_read(const size_t register_number) = 0;
+};
+
 namespace output {
 
 void start();