Mention physical gamepad names for UHID devices

Initialize UHID devices with a custom name:
 - "scrcpy: $GAMEPAD_NAME" for gamepads
 - "scrcpy" for keyboard and mouse (or if no gamepad name is available)

The name may appear in Android apps.

PR #5270 <https://github.com/Genymobile/scrcpy/pull/5270>

app/src/control_msg.c

@@ -83,15 +83,34 @@ write_position(uint8_t *buf, const struct sc_position *position) {
     sc_write16be(&buf[10], position->screen_size.height);
 }
 
-// write length (4 bytes) + string (non null-terminated)
+// Write truncated string, and return the size
+static size_t
+write_string_payload(uint8_t *payload, const char *utf8, size_t max_len) {
+    if (!utf8) {
+        return 0;
+    }
+    size_t len = sc_str_utf8_truncation_index(utf8, max_len);
+    memcpy(payload, utf8, len);
+    return len;
+}
+
+// Write length (4 bytes) + string (non null-terminated)
 static size_t
 write_string(uint8_t *buf, const char *utf8, size_t max_len) {
-    size_t len = sc_str_utf8_truncation_index(utf8, max_len);
+    size_t len = write_string_payload(buf + 4, utf8, max_len);
     sc_write32be(buf, len);
-    memcpy(&buf[4], utf8, len);
     return 4 + len;
 }
 
+// Write length (1 byte) + string (non null-terminated)
+static size_t
+write_string_tiny(uint8_t *buf, const char *utf8, size_t max_len) {
+    assert(max_len <= 0xFF);
+    size_t len = write_string_payload(buf + 1, utf8, max_len);
+    buf[0] = len;
+    return 1 + len;
+}
+
 size_t
 sc_control_msg_serialize(const struct sc_control_msg *msg, uint8_t *buf) {
     buf[0] = msg->type;
@@ -144,10 +163,18 @@ sc_control_msg_serialize(const struct sc_control_msg *msg, uint8_t *buf) {
             return 2;
         case SC_CONTROL_MSG_TYPE_UHID_CREATE:
             sc_write16be(&buf[1], msg->uhid_create.id);
-            sc_write16be(&buf[3], msg->uhid_create.report_desc_size);
+
-            memcpy(&buf[5], msg->uhid_create.report_desc,
+            size_t index = 3;
-                            msg->uhid_create.report_desc_size);
+            index += write_string_tiny(&buf[index], msg->uhid_create.name, 127);
-            return 5 + msg->uhid_create.report_desc_size;
+
+            sc_write16be(&buf[index], msg->uhid_create.report_desc_size);
+            index += 2;
+
+            memcpy(&buf[index], msg->uhid_create.report_desc,
+                                msg->uhid_create.report_desc_size);
+            index += msg->uhid_create.report_desc_size;
+
+            return index;
         case SC_CONTROL_MSG_TYPE_UHID_INPUT:
             sc_write16be(&buf[1], msg->uhid_input.id);
             sc_write16be(&buf[3], msg->uhid_input.size);
@@ -253,10 +280,15 @@ sc_control_msg_log(const struct sc_control_msg *msg) {
         case SC_CONTROL_MSG_TYPE_ROTATE_DEVICE:
             LOG_CMSG("rotate device");
             break;
-        case SC_CONTROL_MSG_TYPE_UHID_CREATE:
+        case SC_CONTROL_MSG_TYPE_UHID_CREATE: {
-            LOG_CMSG("UHID create [%" PRIu16 "] report_desc_size=%" PRIu16,
+            // Quote only if name is not null
-                     msg->uhid_create.id, msg->uhid_create.report_desc_size);
+            const char *name = msg->uhid_create.name;
+            const char *quote = name ? "\"" : "";
+            LOG_CMSG("UHID create [%" PRIu16 "] name=%s%s%s "
+                     "report_desc_size=%" PRIu16, msg->uhid_create.id,
+                     quote, name, quote, msg->uhid_create.report_desc_size);
             break;
+        }
         case SC_CONTROL_MSG_TYPE_UHID_INPUT: {
             char *hex = sc_str_to_hex_string(msg->uhid_input.data,
                                              msg->uhid_input.size);

app/src/control_msg.h

@@ -98,6 +98,7 @@ struct sc_control_msg {
         } set_screen_power_mode;
         struct {
             uint16_t id;
+            const char *name; // pointer to static data
             uint16_t report_desc_size;
             const uint8_t *report_desc; // pointer to static data
         } uhid_create;

app/src/hid/hid_event.h

@@ -15,6 +15,7 @@ struct sc_hid_input {
 
 struct sc_hid_open {
     uint16_t hid_id;
+    const char *name; // pointer to static memory
     const uint8_t *report_desc; // pointer to static memory
     size_t report_desc_size;
 };

app/src/hid/hid_gamepad.c

@@ -243,8 +243,14 @@ sc_hid_gamepad_generate_open(struct sc_hid_gamepad *hid,
 
     sc_hid_gamepad_slot_init(&hid->slots[slot_idx], gamepad_id);
 
+    SDL_GameController* game_controller =
+        SDL_GameControllerFromInstanceID(gamepad_id);
+    assert(game_controller);
+    const char *name = SDL_GameControllerName(game_controller);
+
     uint16_t hid_id = sc_hid_gamepad_slot_get_id(slot_idx);
     hid_open->hid_id = hid_id;
+    hid_open->name = name;
     hid_open->report_desc = SC_HID_GAMEPAD_REPORT_DESC;
     hid_open->report_desc_size = sizeof(SC_HID_GAMEPAD_REPORT_DESC);
 

app/src/hid/hid_keyboard.c

@@ -335,6 +335,7 @@ sc_hid_keyboard_generate_input_from_mods(struct sc_hid_input *hid_input,
 
 void sc_hid_keyboard_generate_open(struct sc_hid_open *hid_open) {
     hid_open->hid_id = SC_HID_ID_KEYBOARD;
+    hid_open->name = NULL; // No name specified after "scrcpy"
     hid_open->report_desc = SC_HID_KEYBOARD_REPORT_DESC;
     hid_open->report_desc_size = sizeof(SC_HID_KEYBOARD_REPORT_DESC);
 }

app/src/hid/hid_mouse.c

@@ -190,6 +190,7 @@ sc_hid_mouse_generate_input_from_scroll(struct sc_hid_input *hid_input,
 
 void sc_hid_mouse_generate_open(struct sc_hid_open *hid_open) {
     hid_open->hid_id = SC_HID_ID_MOUSE;
+    hid_open->name = NULL; // No name specified after "scrcpy"
     hid_open->report_desc = SC_HID_MOUSE_REPORT_DESC;
     hid_open->report_desc_size = sizeof(SC_HID_MOUSE_REPORT_DESC);
 }

app/src/uhid/gamepad_uhid.c

@@ -30,6 +30,7 @@ sc_gamepad_uhid_send_open(struct sc_gamepad_uhid *gamepad,
     struct sc_control_msg msg;
     msg.type = SC_CONTROL_MSG_TYPE_UHID_CREATE;
     msg.uhid_create.id = hid_open->hid_id;
+    msg.uhid_create.name = hid_open->name;
     msg.uhid_create.report_desc = hid_open->report_desc;
     msg.uhid_create.report_desc_size = hid_open->report_desc_size;
 

app/src/uhid/keyboard_uhid.c

@@ -152,6 +152,7 @@ sc_keyboard_uhid_init(struct sc_keyboard_uhid *kb,
     struct sc_control_msg msg;
     msg.type = SC_CONTROL_MSG_TYPE_UHID_CREATE;
     msg.uhid_create.id = SC_HID_ID_KEYBOARD;
+    msg.uhid_create.name = hid_open.name;
     msg.uhid_create.report_desc = hid_open.report_desc;
     msg.uhid_create.report_desc_size = hid_open.report_desc_size;
     if (!sc_controller_push_msg(controller, &msg)) {

app/src/uhid/mouse_uhid.c

@@ -81,6 +81,7 @@ sc_mouse_uhid_init(struct sc_mouse_uhid *mouse,
     struct sc_control_msg msg;
     msg.type = SC_CONTROL_MSG_TYPE_UHID_CREATE;
     msg.uhid_create.id = SC_HID_ID_MOUSE;
+    msg.uhid_create.name = hid_open.name;
     msg.uhid_create.report_desc = hid_open.report_desc;
     msg.uhid_create.report_desc_size = hid_open.report_desc_size;
     if (!sc_controller_push_msg(controller, &msg)) {

app/tests/test_control_msg_serialize.c

@@ -329,6 +329,7 @@ static void test_serialize_uhid_create(void) {
         .type = SC_CONTROL_MSG_TYPE_UHID_CREATE,
         .uhid_create = {
             .id = 42,
+            .name = "ABC",
             .report_desc_size = sizeof(report_desc),
             .report_desc = report_desc,
         },
@@ -336,12 +337,14 @@ static void test_serialize_uhid_create(void) {
 
     uint8_t buf[SC_CONTROL_MSG_MAX_SIZE];
     size_t size = sc_control_msg_serialize(&msg, buf);
-    assert(size == 16);
+    assert(size == 20);
 
     const uint8_t expected[] = {
         SC_CONTROL_MSG_TYPE_UHID_CREATE,
         0, 42, // id
-        0, 11, // size
+        3, // name size
+        65, 66, 67, // "ABC"
+        0, 11, // report desc size
         1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11,
     };
     assert(!memcmp(buf, expected, sizeof(expected)));

server/src/main/java/com/genymobile/scrcpy/control/ControlMessage.java

@@ -131,10 +131,11 @@ public final class ControlMessage {
         return msg;
     }
 
-    public static ControlMessage createUhidCreate(int id, byte[] reportDesc) {
+    public static ControlMessage createUhidCreate(int id, String name, byte[] reportDesc) {
         ControlMessage msg = new ControlMessage();
         msg.type = TYPE_UHID_CREATE;
         msg.id = id;
+        msg.text = name;
         msg.data = reportDesc;
         return msg;
     }

server/src/main/java/com/genymobile/scrcpy/control/ControlMessageReader.java

@@ -75,11 +75,16 @@ public class ControlMessageReader {
         return value;
     }
 
-    private String parseString() throws IOException {
+    private String parseString(int sizeBytes) throws IOException {
-        byte[] data = parseByteArray(4);
+        assert sizeBytes > 0 && sizeBytes <= 4;
+        byte[] data = parseByteArray(sizeBytes);
         return new String(data, StandardCharsets.UTF_8);
     }
 
+    private String parseString() throws IOException {
+        return parseString(4);
+    }
+
     private byte[] parseByteArray(int sizeBytes) throws IOException {
         int len = parseBufferLength(sizeBytes);
         byte[] data = new byte[len];
@@ -134,8 +139,9 @@ public class ControlMessageReader {
 
     private ControlMessage parseUhidCreate() throws IOException {
         int id = dis.readUnsignedShort();
+        String name = parseString(1);
         byte[] data = parseByteArray(2);
-        return ControlMessage.createUhidCreate(id, data);
+        return ControlMessage.createUhidCreate(id, name, data);
     }
 
     private ControlMessage parseUhidInput() throws IOException {

server/src/main/java/com/genymobile/scrcpy/control/Controller.java

@@ -210,7 +210,7 @@ public class Controller implements AsyncProcessor {
                 device.rotateDevice();
                 break;
             case ControlMessage.TYPE_UHID_CREATE:
-                getUhidManager().open(msg.getId(), msg.getData());
+                getUhidManager().open(msg.getId(), msg.getText(), msg.getData());
                 break;
             case ControlMessage.TYPE_UHID_INPUT:
                 getUhidManager().writeInput(msg.getId(), msg.getData());

server/src/main/java/com/genymobile/scrcpy/control/UhidManager.java

@@ -1,6 +1,7 @@
 package com.genymobile.scrcpy.control;
 
 import com.genymobile.scrcpy.util.Ln;
+import com.genymobile.scrcpy.util.StringUtils;
 
 import android.os.Build;
 import android.os.HandlerThread;
@@ -46,7 +47,7 @@ public final class UhidManager {
         }
     }
 
-    public void open(int id, byte[] reportDesc) throws IOException {
+    public void open(int id, String name, byte[] reportDesc) throws IOException {
         try {
             FileDescriptor fd = Os.open("/dev/uhid", OsConstants.O_RDWR, 0);
             try {
@@ -56,7 +57,7 @@ public final class UhidManager {
                     close(old);
                 }
 
-                byte[] req = buildUhidCreate2Req(reportDesc);
+                byte[] req = buildUhidCreate2Req(name, reportDesc);
                 Os.write(fd, req, 0, req.length);
 
                 registerUhidListener(id, fd);
@@ -146,7 +147,7 @@ public final class UhidManager {
         }
     }
 
-    private static byte[] buildUhidCreate2Req(byte[] reportDesc) {
+    private static byte[] buildUhidCreate2Req(String name, byte[] reportDesc) {
         /*
          * struct uhid_event {
          *     uint32_t type;
@@ -171,8 +172,14 @@ public final class UhidManager {
         byte[] empty = new byte[256];
         ByteBuffer buf = ByteBuffer.allocate(280 + reportDesc.length).order(ByteOrder.nativeOrder());
         buf.putInt(UHID_CREATE2);
-        buf.put("scrcpy".getBytes(StandardCharsets.US_ASCII));
+
-        buf.put(empty, 0, 256 - "scrcpy".length());
+        String actualName = name.isEmpty() ? "scrcpy" : "scrcpy: " + name;
+        byte[] utf8Name = actualName.getBytes(StandardCharsets.UTF_8);
+        int len = StringUtils.getUtf8TruncationIndex(utf8Name, 127);
+        assert len <= 127;
+        buf.put(utf8Name, 0, len);
+        buf.put(empty, 0, 256 - len);
+
         buf.putShort((short) reportDesc.length);
         buf.putShort(BUS_VIRTUAL);
         buf.putInt(0); // vendor id

server/src/test/java/com/genymobile/scrcpy/control/ControlMessageReaderTest.java

@@ -324,8 +324,10 @@ public class ControlMessageReaderTest {
         DataOutputStream dos = new DataOutputStream(bos);
         dos.writeByte(ControlMessage.TYPE_UHID_CREATE);
         dos.writeShort(42); // id
+        dos.writeByte(3); // name size
+        dos.write("ABC".getBytes(StandardCharsets.US_ASCII));
         byte[] data = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
-        dos.writeShort(data.length); // size
+        dos.writeShort(data.length); // report desc size
         dos.write(data);
         byte[] packet = bos.toByteArray();
 
@@ -335,6 +337,7 @@ public class ControlMessageReaderTest {
         ControlMessage event = reader.read();
         Assert.assertEquals(ControlMessage.TYPE_UHID_CREATE, event.getType());
         Assert.assertEquals(42, event.getId());
+        Assert.assertEquals("ABC", event.getText());
         Assert.assertArrayEquals(data, event.getData());
 
         Assert.assertEquals(-1, bis.read()); // EOS