Introduce a participant RPC protobuf registry

.changeset/room-rpc-sip.md

@@ -0,0 +1,6 @@
+---
+"github.com/livekit/protocol": minor
+"@livekit/protocol": minor
+---
+
+Introduce a participant RPC protobuf registry for well-known LiveKit RPCs.

magefile.go

@@ -94,8 +94,16 @@ func Proto() error {
 		"rpc/sip.proto",
 	}
 
+	// mapped proto directory:
+	//    ./protobufs/livekit/roomrpc/<name>rpc
+	// and generated Go package:
+	//    ./livekit/roomrpc/<name>rpc
+	roomrpcTypeNames := []string{
+		"sip",
+	}
+
 	fmt.Println("generating protobuf")
-	target := "livekit"
+	const target = "./livekit"
 	if err := os.MkdirAll(target, 0755); err != nil {
 		return err
 	}
@@ -162,6 +170,29 @@ func Proto() error {
 		}
 	}
 
+	fmt.Println("generating protobuf (livekit/roomrpc)")
+	for _, protoName := range roomrpcTypeNames {
+		pkgName := "roomrpc/" + protoName + "rpc"
+		protoFiles, err := os.ReadDir(filepath.Join("./protobufs", pkgName))
+		if err != nil {
+			return err
+		}
+		args := []string{
+			"--go_out", target,
+			"--go_opt=paths=source_relative",
+			"--plugin=go=" + protocGoPath,
+			"-I=./protobufs",
+		}
+		for _, protoFile := range protoFiles {
+			args = append(args, filepath.Join(pkgName, protoFile.Name()))
+		}
+		cmd := exec.Command(protoc, args...)
+		connectStd(cmd)
+		if err := cmd.Run(); err != nil {
+			return err
+		}
+	}
+
 	fmt.Println("generating grpc protobuf")
 	args = append([]string{
 		"--go_out", ".",

protobufs/roomrpc/README.md

@@ -0,0 +1,25 @@
+# LiveKit participant RPCs registry (roomrpc)
+
+These protos describe a list of well-known [LiveKit participant RPCs](https://docs.livekit.io/transport/data/rpc/)
+and corresponding request/response messages.
+
+## Directory structure
+
+Each participant type or API should have its own directory under `roomrpc` with the name `<type>rpc`
+to avoid Go package name collisions and isolate types for each API.
+
+## Versioning
+
+Proto files should follow the name convention: `roomrpc_<type>_v<vers>.proto`. Version is a single sequential number, not a semver.
+For example: `roomrpc_sip_v1.proto`.
+
+Corresponding `V<vers>` should be added as a suffix to the service definition and the request/response types
+(method name should omit the version, as the versioned service name is part of the method path).
+
+```protobuf
+service MyServiceV1 {
+  rpc DoSomething(DoSomethingV1Request) returns (DoSomethingV1Response);
+}
+message DoSomethingV1Request {}
+message DoSomethingV1Response {}
+```