feat: hid rpc channel (#755)

* feat: use hidRpcChannel to save bandwidth

* chore: simplify handshake of hid rpc

* add logs

* chore: add timeout when writing to hid endpoints

* fix issues

* chore: show hid rpc version

* refactor hidrpc marshal / unmarshal

* add queues for keyboard / mouse event

* chore: change logging level of JSONRPC send event to trace

* minor changes related to logging

* fix: nil check

* chore: add comments and remove unused code

* add useMouse

* chore: log msg data only when debug or trace mode

* chore: make tslint happy

* chore: unlock keyboardStateLock before calling onKeysDownChange

* chore: remove keyPressReportApiAvailable

* chore: change version handle

* chore: clean up unused functions

* remove comments

internal/hidrpc/hidrpc.go

@@ -0,0 +1,100 @@
+package hidrpc
+
+import (
+	"fmt"
+
+	"github.com/jetkvm/kvm/internal/usbgadget"
+)
+
+// MessageType is the type of the HID RPC message
+type MessageType byte
+
+const (
+	TypeHandshake        MessageType = 0x01
+	TypeKeyboardReport   MessageType = 0x02
+	TypePointerReport    MessageType = 0x03
+	TypeWheelReport      MessageType = 0x04
+	TypeKeypressReport   MessageType = 0x05
+	TypeMouseReport      MessageType = 0x06
+	TypeKeyboardLedState MessageType = 0x32
+	TypeKeydownState     MessageType = 0x33
+)
+
+const (
+	Version byte = 0x01 // Version of the HID RPC protocol
+)
+
+// GetQueueIndex returns the index of the queue to which the message should be enqueued.
+func GetQueueIndex(messageType MessageType) int {
+	switch messageType {
+	case TypeHandshake:
+		return 0
+	case TypeKeyboardReport, TypeKeypressReport, TypeKeyboardLedState, TypeKeydownState:
+		return 1
+	case TypePointerReport, TypeMouseReport, TypeWheelReport:
+		return 2
+	default:
+		return 3
+	}
+}
+
+// Unmarshal unmarshals the HID RPC message from the data.
+func Unmarshal(data []byte, message *Message) error {
+	l := len(data)
+	if l < 1 {
+		return fmt.Errorf("invalid data length: %d", l)
+	}
+
+	message.t = MessageType(data[0])
+	message.d = data[1:]
+	return nil
+}
+
+// Marshal marshals the HID RPC message to the data.
+func Marshal(message *Message) ([]byte, error) {
+	if message.t == 0 {
+		return nil, fmt.Errorf("invalid message type: %d", message.t)
+	}
+
+	data := make([]byte, len(message.d)+1)
+	data[0] = byte(message.t)
+	copy(data[1:], message.d)
+
+	return data, nil
+}
+
+// NewHandshakeMessage creates a new handshake message.
+func NewHandshakeMessage() *Message {
+	return &Message{
+		t: TypeHandshake,
+		d: []byte{Version},
+	}
+}
+
+// NewKeyboardReportMessage creates a new keyboard report message.
+func NewKeyboardReportMessage(keys []byte, modifier uint8) *Message {
+	return &Message{
+		t: TypeKeyboardReport,
+		d: append([]byte{modifier}, keys...),
+	}
+}
+
+// NewKeyboardLedMessage creates a new keyboard LED message.
+func NewKeyboardLedMessage(state usbgadget.KeyboardState) *Message {
+	return &Message{
+		t: TypeKeyboardLedState,
+		d: []byte{state.Byte()},
+	}
+}
+
+// NewKeydownStateMessage creates a new keydown state message.
+func NewKeydownStateMessage(state usbgadget.KeysDownState) *Message {
+	data := make([]byte, len(state.Keys)+1)
+	data[0] = state.Modifier
+	copy(data[1:], state.Keys)
+
+	return &Message{
+		t: TypeKeydownState,
+		d: data,
+	}
+}