Add UHID keyboard support

Use the following command:

    scrcpy --keyboard=uhid

PR #4473 <https://github.com/Genymobile/scrcpy/pull/4473>

Co-authored-by: Romain Vimont <rom@rom1v.com>
Signed-off-by: Romain Vimont <rom@rom1v.com>

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

@@ -17,6 +17,8 @@ public final class ControlMessage {
     public static final int TYPE_SET_CLIPBOARD = 9;
     public static final int TYPE_SET_SCREEN_POWER_MODE = 10;
     public static final int TYPE_ROTATE_DEVICE = 11;
+    public static final int TYPE_UHID_CREATE = 12;
+    public static final int TYPE_UHID_INPUT = 13;
 
     public static final long SEQUENCE_INVALID = 0;
 
@@ -40,6 +42,8 @@ public final class ControlMessage {
     private boolean paste;
     private int repeat;
     private long sequence;
+    private int id;
+    private byte[] data;
 
     private ControlMessage() {
     }
@@ -123,6 +127,22 @@ public final class ControlMessage {
         return msg;
     }
 
+    public static ControlMessage createUhidCreate(int id, byte[] reportDesc) {
+        ControlMessage msg = new ControlMessage();
+        msg.type = TYPE_UHID_CREATE;
+        msg.id = id;
+        msg.data = reportDesc;
+        return msg;
+    }
+
+    public static ControlMessage createUhidInput(int id, byte[] data) {
+        ControlMessage msg = new ControlMessage();
+        msg.type = TYPE_UHID_INPUT;
+        msg.id = id;
+        msg.data = data;
+        return msg;
+    }
+
     public int getType() {
         return type;
     }
@@ -186,4 +206,12 @@ public final class ControlMessage {
     public long getSequence() {
         return sequence;
     }
+
+    public int getId() {
+        return id;
+    }
+
+    public byte[] getData() {
+        return data;
+    }
 }

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

@@ -15,6 +15,8 @@ public class ControlMessageReader {
     static final int SET_SCREEN_POWER_MODE_PAYLOAD_LENGTH = 1;
     static final int GET_CLIPBOARD_LENGTH = 1;
     static final int SET_CLIPBOARD_FIXED_PAYLOAD_LENGTH = 9;
+    static final int UHID_CREATE_FIXED_PAYLOAD_LENGTH = 4;
+    static final int UHID_INPUT_FIXED_PAYLOAD_LENGTH = 4;
 
     private static final int MESSAGE_MAX_SIZE = 1 << 18; // 256k
 
@@ -86,6 +88,12 @@ public class ControlMessageReader {
             case ControlMessage.TYPE_ROTATE_DEVICE:
                 msg = ControlMessage.createEmpty(type);
                 break;
+            case ControlMessage.TYPE_UHID_CREATE:
+                msg = parseUhidCreate();
+                break;
+            case ControlMessage.TYPE_UHID_INPUT:
+                msg = parseUhidInput();
+                break;
             default:
                 Ln.w("Unknown event type: " + type);
                 msg = null;
@@ -110,12 +118,21 @@ public class ControlMessageReader {
         return ControlMessage.createInjectKeycode(action, keycode, repeat, metaState);
     }
 
-    private String parseString() {
-        if (buffer.remaining() < 4) {
-            return null;
+    private int parseBufferLength(int sizeBytes) {
+        assert sizeBytes > 0 && sizeBytes <= 4;
+        if (buffer.remaining() < sizeBytes) {
+            return -1;
         }
-        int len = buffer.getInt();
-        if (buffer.remaining() < len) {
+        int value = 0;
+        for (int i = 0; i < sizeBytes; ++i) {
+            value = (value << 8) | (buffer.get() & 0xFF);
+        }
+        return value;
+    }
+
+    private String parseString() {
+        int len = parseBufferLength(4);
+        if (len == -1 || buffer.remaining() < len) {
             return null;
         }
         int position = buffer.position();
@@ -124,6 +141,16 @@ public class ControlMessageReader {
         return new String(rawBuffer, position, len, StandardCharsets.UTF_8);
     }
 
+    private byte[] parseByteArray(int sizeBytes) {
+        int len = parseBufferLength(sizeBytes);
+        if (len == -1 || buffer.remaining() < len) {
+            return null;
+        }
+        byte[] data = new byte[len];
+        buffer.get(data);
+        return data;
+    }
+
     private ControlMessage parseInjectText() {
         String text = parseString();
         if (text == null) {
@@ -193,6 +220,30 @@ public class ControlMessageReader {
         return ControlMessage.createSetScreenPowerMode(mode);
     }
 
+    private ControlMessage parseUhidCreate() {
+        if (buffer.remaining() < UHID_CREATE_FIXED_PAYLOAD_LENGTH) {
+            return null;
+        }
+        int id = buffer.getShort();
+        byte[] data = parseByteArray(2);
+        if (data == null) {
+            return null;
+        }
+        return ControlMessage.createUhidCreate(id, data);
+    }
+
+    private ControlMessage parseUhidInput() {
+        if (buffer.remaining() < UHID_INPUT_FIXED_PAYLOAD_LENGTH) {
+            return null;
+        }
+        int id = buffer.getShort();
+        byte[] data = parseByteArray(2);
+        if (data == null) {
+            return null;
+        }
+        return ControlMessage.createUhidInput(id, data);
+    }
+
     private static Position readPosition(ByteBuffer buffer) {
         int x = buffer.getInt();
         int y = buffer.getInt();

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

@@ -26,6 +26,8 @@ public class Controller implements AsyncProcessor {
 
     private Thread thread;
 
+    private final UhidManager uhidManager;
+
     private final Device device;
     private final ControlChannel controlChannel;
     private final CleanUp cleanUp;
@@ -50,6 +52,7 @@ public class Controller implements AsyncProcessor {
         this.powerOn = powerOn;
         initPointers();
         sender = new DeviceMessageSender(controlChannel);
+        uhidManager = new UhidManager();
     }
 
     private void initPointers() {
@@ -96,6 +99,7 @@ public class Controller implements AsyncProcessor {
                 Ln.e("Controller error", e);
             } finally {
                 Ln.d("Controller stopped");
+                uhidManager.closeAll();
                 listener.onTerminated(true);
             }
         }, "control-recv");
@@ -190,6 +194,12 @@ public class Controller implements AsyncProcessor {
             case ControlMessage.TYPE_ROTATE_DEVICE:
                 device.rotateDevice();
                 break;
+            case ControlMessage.TYPE_UHID_CREATE:
+                uhidManager.open(msg.getId(), msg.getData());
+                break;
+            case ControlMessage.TYPE_UHID_INPUT:
+                uhidManager.writeInput(msg.getId(), msg.getData());
+                break;
             default:
                 // do nothing
         }

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

@@ -0,0 +1,138 @@
+package com.genymobile.scrcpy;
+
+import android.system.ErrnoException;
+import android.system.Os;
+import android.system.OsConstants;
+import android.util.ArrayMap;
+
+import java.io.FileDescriptor;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.StandardCharsets;
+
+public final class UhidManager {
+
+    // Linux: include/uapi/linux/uhid.h
+    private static final int UHID_CREATE2 = 11;
+    private static final int UHID_INPUT2 = 12;
+
+    // Linux: include/uapi/linux/input.h
+    private static final short BUS_VIRTUAL = 0x06;
+
+    private final ArrayMap<Integer, FileDescriptor> fds = new ArrayMap<>();
+
+    public void open(int id, byte[] reportDesc) throws IOException {
+        try {
+            FileDescriptor fd = Os.open("/dev/uhid", OsConstants.O_RDWR, 0);
+            try {
+                FileDescriptor old = fds.put(id, fd);
+                if (old != null) {
+                    Ln.w("Duplicate UHID id: " + id);
+                    close(old);
+                }
+
+                byte[] req = buildUhidCreate2Req(reportDesc);
+                Os.write(fd, req, 0, req.length);
+            } catch (Exception e) {
+                close(fd);
+                throw e;
+            }
+        } catch (ErrnoException e) {
+            throw new IOException(e);
+        }
+    }
+
+    public void writeInput(int id, byte[] data) throws IOException {
+        FileDescriptor fd = fds.get(id);
+        if (fd == null) {
+            Ln.w("Unknown UHID id: " + id);
+            return;
+        }
+
+        try {
+            byte[] req = buildUhidInput2Req(data);
+            Os.write(fd, req, 0, req.length);
+        } catch (ErrnoException e) {
+            throw new IOException(e);
+        }
+    }
+
+    private static byte[] buildUhidCreate2Req(byte[] reportDesc) {
+        /*
+         * struct uhid_event {
+         *     uint32_t type;
+         *     union {
+         *         // ...
+         *         struct uhid_create2_req {
+         *             uint8_t name[128];
+         *             uint8_t phys[64];
+         *             uint8_t uniq[64];
+         *             uint16_t rd_size;
+         *             uint16_t bus;
+         *             uint32_t vendor;
+         *             uint32_t product;
+         *             uint32_t version;
+         *             uint32_t country;
+         *             uint8_t rd_data[HID_MAX_DESCRIPTOR_SIZE];
+         *         };
+         *     };
+         * } __attribute__((__packed__));
+         */
+
+        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());
+        buf.putShort((short) reportDesc.length);
+        buf.putShort(BUS_VIRTUAL);
+        buf.putInt(0); // vendor id
+        buf.putInt(0); // product id
+        buf.putInt(0); // version
+        buf.putInt(0); // country;
+        buf.put(reportDesc);
+        return buf.array();
+    }
+
+    private static byte[] buildUhidInput2Req(byte[] data) {
+        /*
+         * struct uhid_event {
+         *     uint32_t type;
+         *     union {
+         *         // ...
+         *         struct uhid_input2_req {
+         *             uint16_t size;
+         *             uint8_t data[UHID_DATA_MAX];
+         *         };
+         *     };
+         * } __attribute__((__packed__));
+         */
+
+        ByteBuffer buf = ByteBuffer.allocate(6 + data.length).order(ByteOrder.nativeOrder());
+        buf.putInt(UHID_INPUT2);
+        buf.putShort((short) data.length);
+        buf.put(data);
+        return buf.array();
+    }
+
+    public void close(int id) {
+        FileDescriptor fd = fds.get(id);
+        assert fd != null;
+        close(fd);
+    }
+
+    public void closeAll() {
+        for (FileDescriptor fd : fds.values()) {
+            close(fd);
+        }
+    }
+
+    private static void close(FileDescriptor fd) {
+        try {
+            Os.close(fd);
+        } catch (ErrnoException e) {
+            Ln.e("Failed to close uhid: " + e.getMessage());
+        }
+    }
+}