AudioServer: Handle multiple audio devices with multiple pins

This makes audio server configurable during runtime!

userspace/libraries/LibAudio/Audio.cpp

@@ -1,6 +1,7 @@
 #include <BAN/ScopeGuard.h>
 
 #include <LibAudio/Audio.h>
+#include <LibAudio/Protocol.h>
 
 #include <fcntl.h>
 #include <stdlib.h>
@@ -121,10 +122,15 @@ namespace LibAudio
 	{
 		ASSERT(m_server_fd != -1);
 
-		const ssize_t nsend = send(m_server_fd, &m_smo_key, sizeof(m_smo_key), 0);
+		LibAudio::Packet packet {
+			.type = LibAudio::Packet::RegisterBuffer,
+			.parameter = static_cast<uint64_t>(m_smo_key),
+		};
+
+		const ssize_t nsend = send(m_server_fd, &packet, sizeof(packet), 0);
 		if (nsend == -1)
 			return BAN::Error::from_errno(errno);
-		ASSERT(nsend == sizeof(m_smo_key));
+		ASSERT(nsend == sizeof(packet));
 
 		return {};
 	}
@@ -137,8 +143,12 @@ namespace LibAudio
 			return;
 		m_audio_buffer->paused = paused;
 
-		long dummy = 0;
-		send(m_server_fd, &dummy, sizeof(dummy), 0);
+		LibAudio::Packet packet {
+			.type = LibAudio::Packet::Notify,
+			.parameter = 0,
+		};
+
+		send(m_server_fd, &packet, sizeof(packet), 0);
 	}
 
 	size_t Audio::queue_samples(BAN::Span<const AudioBuffer::sample_t> samples)

userspace/libraries/LibAudio/include/LibAudio/Audio.h

@@ -9,8 +9,6 @@
 namespace LibAudio
 {
 
-	static constexpr BAN::StringView s_audio_server_socket = "/tmp/audio-server.socket"_sv;
-
 	struct AudioBuffer
 	{
 		using sample_t = double;

userspace/libraries/LibAudio/include/LibAudio/Protocol.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <BAN/StringView.h>
+
+namespace LibAudio
+{
+
+	struct Packet
+	{
+		enum : uint8_t
+		{
+			Notify,         // parameter: ignored
+			                // response: nothing
+			                // server refereshes buffered data
+
+			RegisterBuffer, // paramenter: smo key
+			                // response: nothing
+			                // register audio buffer to server
+
+			QueryDevices,   // parameter: ignored
+			                // response: (uint32_t)
+							// query the number of devices available
+
+			QueryPins,      // parameter: sink number
+			                // response: (uint32_t)
+							// query the number of pins the sink has
+
+			GetDevice,      // parameter: ignored
+			                // reponse: (uint32_t)
+							// get the currently active device
+
+			SetDevice,      // parameter: device number
+			                // reponse: nothing
+							// set the currently active device
+
+			GetPin,         // parameter: ignored
+			                // response: nothing
+							// get the active pin of the current device
+
+			SetPin,         // parameter: pin number
+			                // response: nothing
+							// set the active pin of the current device
+		} type;
+
+		uint64_t parameter;
+	};
+
+	static constexpr BAN::StringView s_audio_server_socket = "/tmp/audio-server.socket"_sv;
+
+}