l2cap: add documentation

1 files changed, 72 insertions, 18 deletions

diff --git a/pandora/l2cap.proto b/pandora/l2cap.proto
index 79332c4..055f893 100644
--- a/pandora/l2cap.proto
+++ b/pandora/l2cap.proto
@@ -22,86 +22,126 @@ import "pandora/host.proto";
 
 option java_outer_classname = "L2CAPProto";
 
+// L2CAP (Logical Link Control and Adaptation Protocol) services for managing channels
+// and data communication over ACL connections. This protocol is essential for
+// creating multiplexed data channels over the underlying ACL connections in Bluetooth.
 service L2CAP {
   // Establish an L2CAP channel on an ACL connection.
   rpc Connect(ConnectRequest) returns (ConnectResponse);
-  // Wait and accept incoming L2CAP channels on an ACL connection.
+  // Await and accept incoming L2CAP channels on an existing ACL connection.
+  // Returns a stream of channel, this accept and yield channels until the stream
+  // is closed. Every incoming L2CAP channel connection request not handled by this
+  // method should be rejected.
   rpc OnConnection(OnConnectionRequest) returns (stream OnConnectionResponse);
-  // Disconnect an L2CAP channel.
+  // Disconnect an established L2CAP channel.
   rpc Disconnect(DisconnectRequest) returns (DisconnectResponse);
-  // Wait an L2CAP channel to be disconnected.
-  rpc WaitDisconnection(WaitDisconnectionRequest)
-      returns (WaitDisconnectionResponse);
-  // Receive data from an L2CAP channel.
+  // Await an established L2CAP channel's termination.
+  rpc WaitDisconnection(WaitDisconnectionRequest) returns (WaitDisconnectionResponse);
+  // Fetch data received from an active L2CAP channel.
+  // Packets are yielded until the stream is closed, packets are droped otherwise. 
   rpc Receive(ReceiveRequest) returns (stream ReceiveResponse);
-  // Send data to an L2CAP channel.
+  // Send data over an L2CAP channel to a connected device.
   rpc Send(SendRequest) returns (SendResponse);
 }
 
+// Potential reasons for command rejections in the L2CAP protocol.
 enum CommandRejectReason {
+  // The command wasn't understood by the receiver.
   COMMAND_NOT_UNDERSTOOD = 0;
+  // The received signal exceeds the allowed MTU (Maximum Transmission Unit).
   SIGNAL_MTU_EXCEEDED = 1;
+  // The received command includes an invalid Channel Identifier (CID).
   INVALID_CID_IN_REQUEST = 2;
 }
 
+// A Token representing a unique L2CAP channel for data communication.
 message Channel {
+  // Opaque value filled by the gRPC server, must not be modified nor crafted.
   google.protobuf.Any cookie = 1;
 }
 
+// Request for establishing an L2CAP connection-oriented channel, 
+// where data is transmitted with acknowledgment.
 message ConnectionOrientedChannelRequest {
-  // Protocol/Service Multiplexer.
+  // Protocol/Service Multiplexer (PSM) for identifying the upper-layer protocol.
   uint32 psm = 1;
-  // Maximum transmission unit.
+  // Defines the maximum size of data payload (in bytes) that can be sent in a single packet.
   uint32 mtu = 2;
 }
 
+// Request for establishing a credit-based L2CAP channel, 
+// typically used in BLE (Bluetooth Low Energy) when precise flow control is required.
 message CreditBasedChannelRequest {
-  // Simplified Protocol/Service Multiplexer.
+  // Simplified Protocol/Service Multiplexer (sPSM) for identifying the upper-layer protocol in BLE.
   uint32 spsm = 1;
-  // Maximum transmission unit.
+  // Defines the maximum size of data payload (in bytes) that can be sent in a single packet.
   uint32 mtu = 2;
-  // Maximum PDU payload size.
+  // Maximum size of the PDU (Protocol Data Unit) payload.
   uint32 mps = 3;
-  // Maximum number of packets to transmit.
+  // Initial credits given for flow control, defining the number of PDUs the sender can transmit.
   uint32 initial_credit = 4;
 }
 
+// Request for establishing a fixed L2CAP channel, often pre-defined for specific purposes.
 message FixedChannelRequest {
-  // Fixed channel identifier
+  // Fixed Channel Identifier (CID). Represents the unique identifier for the fixed channel.
+  // Available CIDs are:
+  // - 0x0001: L2CAP Signaling Channel
+  // - 0x0002: Connectionless Channel
+  // - 0x0003: AMP Manager Protocol
+  // - 0x0004: Attribute Protocol (ATT) for BLE
+  // - 0x0005: L2CAP Signaling Channel for BLE
+  // - 0x0006: Security Manager Protocol for BLE
+  // - 0x0007: Security Manager Protocol for BR/EDR
+  // - CIDs in the range of 0x0007 to 0x003F are reserved for standardization purposes.
   uint32 cid = 1;
 }
 
+// Request of the `Connect` method.
 message ConnectRequest {
-  // BR/EDR or Low-Energy connection.
+  // Specifies the underlying ACL connection, either BR/EDR (Basic Rate/Enhanced Data Rate) or BLE.
   Connection connection = 1;
+  // Defines the type and specifics of the channel to establish.
   oneof type {
+    // Request a fixed channel.
     FixedChannelRequest fixed = 2;
+    // Request a connection-oriented channel.
     ConnectionOrientedChannelRequest basic = 3;
+    // Request a BLE credit-based channel.
     CreditBasedChannelRequest le_credit_based = 4;
+    // Request an enhanced credit-based channel.
     CreditBasedChannelRequest enhanced_credit_based = 5;
   }
 }
 
+// Response of the `Connect` method.
 message ConnectResponse {
   oneof result {
+    // Error details if the connection failed.
     CommandRejectReason error = 1;
+    // Details of the established channel on success.
     Channel channel = 2;
   }
 }
 
+// Request of the `OnConnection` method.
 message OnConnectionRequest {
-  // BR/EDR or Low-Energy connection.
-  // Note: On some platforms, directional server might not be applicable, so
-  // connections on other ACL connections will also be accepted but not reported
+  // Specifies the underlying ACL connection, either BR/EDR or BLE.
   Connection connection = 1;
+  // Defines the type and specifics of the channel to wait and accept.
   oneof type {
+    // Accept fixed channels.
     FixedChannelRequest fixed = 2;
+    // Accept connection-oriented channels.
     ConnectionOrientedChannelRequest basic = 3;
+    // Accept BLE credit-based channels.
     CreditBasedChannelRequest le_credit_based = 4;
+    // Accept enhanced credit-based channels.
     CreditBasedChannelRequest enhanced_credit_based = 5;
   }
 }
 
+// Response of the `OnConnection` method.
 message OnConnectionResponse {
   oneof result {
     CommandRejectReason error = 1;
@@ -109,10 +149,13 @@ message OnConnectionResponse {
   }
 }
 
+// Request of the `Disconnect` method.
 message DisconnectRequest {
+  // Specifies the channel to disconnect.
   Channel channel = 1;
 }
 
+// Response of the `Disconnect` method.
 message DisconnectResponse {
   oneof result {
     CommandRejectReason error = 1;
@@ -120,10 +163,13 @@ message DisconnectResponse {
   }
 }
 
+// Request of the `WaitDisconnection` method.
 message WaitDisconnectionRequest {
+  // Specifies the channel to await disconnection.
   Channel channel = 1;
 }
 
+// Response of the `WaitDisconnection` method.
 message WaitDisconnectionResponse {
   oneof result {
     CommandRejectReason error = 1;
@@ -131,19 +177,27 @@ message WaitDisconnectionResponse {
   }
 }
 
+// Request of the `Receive` method.
 message ReceiveRequest {
+  // Specifies the channel to fetch data from.
   Channel channel = 1;
 }
 
+// Response of the `Receive` method.
 message ReceiveResponse {
+  // Contains the data received from the channel.
   bytes data = 1;
 }
 
+// Request of the `Send` method.
 message SendRequest {
+  // Specifies the channel to send data over.
   Channel channel = 1;
+  // Data to be sent over the specified channel.
   bytes data = 2;
 }
 
+// Response of the `Send` method.
 message SendResponse {
   oneof result {
     CommandRejectReason error = 1;