diff --git a/adb/Android.bp b/adb/Android.bp
index 9d47b8b..b1ca8af 100644
--- a/adb/Android.bp
+++ b/adb/Android.bp
@@ -133,7 +133,6 @@
     "transport.cpp",
     "transport_fd.cpp",
     "transport_local.cpp",
-    "transport_usb.cpp",
     "types.cpp",
 ]
 
@@ -169,6 +168,7 @@
         "client/usb_libusb.cpp",
         "client/usb_dispatch.cpp",
         "client/transport_mdns.cpp",
+        "client/transport_usb.cpp",
         "client/pairing/pairing_client.cpp",
     ],
 
@@ -381,10 +381,6 @@
         "daemon/adb_wifi.cpp",
     ],
 
-    local_include_dirs: [
-        "daemon/include",
-    ],
-
     generated_headers: ["platform_tools_version"],
 
     static_libs: [
@@ -414,12 +410,6 @@
                 "daemon/transport_qemu.cpp",
                 "daemon/usb.cpp",
                 "daemon/usb_ffs.cpp",
-                "daemon/usb_legacy.cpp",
-            ]
-        },
-        linux_glibc: {
-            srcs: [
-                "daemon/usb_dummy.cpp",
             ]
         },
         recovery: {
@@ -544,8 +534,9 @@
         "libmdnssd",
     ],
 
-    export_include_dirs: [
-        "daemon/include",
+    visibility: [
+        "//bootable/recovery/minadbd",
+        "//system/core/adb",
     ],
 }
 
diff --git a/adb/adb.cpp b/adb/adb.cpp
index 98db191..44e5dac 100644
--- a/adb/adb.cpp
+++ b/adb/adb.cpp
@@ -66,6 +66,10 @@
 #include "daemon/logging.h"
 #endif
 
+#if ADB_HOST
+#include "client/usb.h"
+#endif
+
 std::string adb_version() {
     // Don't change the format of this --- it's parsed by ddmlib.
     return android::base::StringPrintf(
diff --git a/adb/adb.h b/adb/adb.h
index 86d205c..ce12a55 100644
--- a/adb/adb.h
+++ b/adb/adb.h
@@ -29,7 +29,6 @@
 #include "fdevent/fdevent.h"
 #include "socket.h"
 #include "types.h"
-#include "usb.h"
 
 constexpr size_t MAX_PAYLOAD_V1 = 4 * 1024;
 constexpr size_t MAX_PAYLOAD = 1024 * 1024;
@@ -139,7 +138,6 @@
 
 /* initialize a transport object's func pointers and state */
 int init_socket_transport(atransport* t, unique_fd s, int port, int local);
-void init_usb_transport(atransport* t, usb_handle* usb);
 
 std::string getEmulatorSerialString(int console_port);
 #if ADB_HOST
@@ -252,4 +250,5 @@
 // Wait until device scan has completed and every transport is ready, or a timeout elapses.
 void adb_wait_for_device_initialization();
 
+void usb_init();
 #endif
diff --git a/adb/client/main.cpp b/adb/client/main.cpp
index a85a18c..78f7b8f 100644
--- a/adb/client/main.cpp
+++ b/adb/client/main.cpp
@@ -36,6 +36,7 @@
 #include "adb_listeners.h"
 #include "adb_utils.h"
 #include "adb_wifi.h"
+#include "client/usb.h"
 #include "commandline.h"
 #include "sysdeps/chrono.h"
 #include "transport.h"
diff --git a/adb/transport_usb.cpp b/adb/client/transport_usb.cpp
similarity index 96%
rename from adb/transport_usb.cpp
rename to adb/client/transport_usb.cpp
index fb81b37..777edde 100644
--- a/adb/transport_usb.cpp
+++ b/adb/client/transport_usb.cpp
@@ -16,6 +16,10 @@
 
 #define TRACE_TAG TRANSPORT
 
+#include "sysdeps.h"
+
+#include "client/usb.h"
+
 #include <memory>
 
 #include "sysdeps.h"
@@ -135,8 +139,8 @@
         }
 
         p->payload.resize(p->msg.data_length);
-        if (usb_read(usb, &p->payload[0], p->payload.size())
-                != static_cast<int>(p->payload.size())) {
+        if (usb_read(usb, &p->payload[0], p->payload.size()) !=
+            static_cast<int>(p->payload.size())) {
             PLOG(ERROR) << "remote usb: terminated (data)";
             return -1;
         }
diff --git a/adb/usb.h b/adb/client/usb.h
similarity index 72%
rename from adb/usb.h
rename to adb/client/usb.h
index eb8ca6c..b371788 100644
--- a/adb/usb.h
+++ b/adb/client/usb.h
@@ -18,6 +18,9 @@
 
 #include <sys/types.h>
 
+#include "adb.h"
+#include "transport.h"
+
 // USB host/client interface.
 
 #define ADB_USB_INTERFACE(handle_ref_type)                       \
@@ -30,35 +33,38 @@
     void usb_kick(handle_ref_type h);                            \
     size_t usb_get_max_packet_size(handle_ref_type)
 
-#if !ADB_HOST
-// The daemon has a single implementation.
-
-struct usb_handle;
-ADB_USB_INTERFACE(usb_handle*);
-
-#else // linux host || darwin
 // Linux and Darwin clients have native and libusb implementations.
 
 namespace libusb {
-    struct usb_handle;
-    ADB_USB_INTERFACE(libusb::usb_handle*);
-}
+struct usb_handle;
+ADB_USB_INTERFACE(libusb::usb_handle*);
+}  // namespace libusb
 
 namespace native {
-    struct usb_handle;
-    ADB_USB_INTERFACE(native::usb_handle*);
-}
+struct usb_handle;
+ADB_USB_INTERFACE(native::usb_handle*);
+}  // namespace native
 
 // Empty base that both implementations' opaque handles inherit from.
-struct usb_handle {
-};
+struct usb_handle {};
 
 ADB_USB_INTERFACE(::usb_handle*);
 
-#endif // linux host || darwin
-
-
 // USB device detection.
 int is_adb_interface(int usb_class, int usb_subclass, int usb_protocol);
 
 bool should_use_libusb();
+
+struct UsbConnection : public BlockingConnection {
+    explicit UsbConnection(usb_handle* handle) : handle_(handle) {}
+    ~UsbConnection();
+
+    bool Read(apacket* packet) override final;
+    bool Write(apacket* packet) override final;
+    bool DoTlsHandshake(RSA* key, std::string* auth_key) override final;
+
+    void Close() override final;
+    virtual void Reset() override final;
+
+    usb_handle* handle_;
+};
diff --git a/adb/client/usb_dispatch.cpp b/adb/client/usb_dispatch.cpp
index f55ae90..7b97117 100644
--- a/adb/client/usb_dispatch.cpp
+++ b/adb/client/usb_dispatch.cpp
@@ -15,7 +15,8 @@
  */
 
 #include <android-base/logging.h>
-#include "usb.h"
+
+#include "client/usb.h"
 
 void usb_init() {
     if (should_use_libusb()) {
diff --git a/adb/client/usb_libusb.cpp b/adb/client/usb_libusb.cpp
index 53f01a0..07cbc94 100644
--- a/adb/client/usb_libusb.cpp
+++ b/adb/client/usb_libusb.cpp
@@ -14,10 +14,10 @@
  * limitations under the License.
  */
 
-#include "usb.h"
-
 #include "sysdeps.h"
 
+#include "client/usb.h"
+
 #include <stdint.h>
 #include <stdlib.h>
 
@@ -40,7 +40,6 @@
 #include "adb.h"
 #include "adb_utils.h"
 #include "transport.h"
-#include "usb.h"
 
 using android::base::StringPrintf;
 
diff --git a/adb/client/usb_linux.cpp b/adb/client/usb_linux.cpp
index 343e7b5..95b1817 100644
--- a/adb/client/usb_linux.cpp
+++ b/adb/client/usb_linux.cpp
@@ -18,6 +18,8 @@
 
 #include "sysdeps.h"
 
+#include "client/usb.h"
+
 #include <ctype.h>
 #include <dirent.h>
 #include <errno.h>
@@ -48,7 +50,6 @@
 
 #include "adb.h"
 #include "transport.h"
-#include "usb.h"
 
 using namespace std::chrono_literals;
 using namespace std::literals;
diff --git a/adb/client/usb_osx.cpp b/adb/client/usb_osx.cpp
index 7207ca7..a93fa3a 100644
--- a/adb/client/usb_osx.cpp
+++ b/adb/client/usb_osx.cpp
@@ -18,6 +18,8 @@
 
 #include "sysdeps.h"
 
+#include "client/usb.h"
+
 #include <CoreFoundation/CoreFoundation.h>
 
 #include <IOKit/IOKitLib.h>
diff --git a/adb/client/usb_windows.cpp b/adb/client/usb_windows.cpp
index 197c6fa..e209230 100644
--- a/adb/client/usb_windows.cpp
+++ b/adb/client/usb_windows.cpp
@@ -18,6 +18,8 @@
 
 #include "sysdeps.h"
 
+#include "client/usb.h"
+
 // clang-format off
 #include <winsock2.h>  // winsock.h *must* be included before windows.h.
 #include <windows.h>
diff --git a/adb/daemon/include/adbd/usb.h b/adb/daemon/include/adbd/usb.h
deleted file mode 100644
index 2204246..0000000
--- a/adb/daemon/include/adbd/usb.h
+++ /dev/null
@@ -1,68 +0,0 @@
-#pragma once
-
-/*
- * Copyright (C) 2017 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <linux/usb/functionfs.h>
-
-#include <atomic>
-#include <condition_variable>
-#include <mutex>
-#include <vector>
-
-#include <android-base/unique_fd.h>
-#include <asyncio/AsyncIO.h>
-
-struct aio_block {
-    std::vector<struct iocb> iocb;
-    std::vector<struct iocb*> iocbs;
-    std::vector<struct io_event> events;
-    aio_context_t ctx;
-    int num_submitted;
-    int fd;
-};
-
-struct usb_handle {
-    usb_handle() : kicked(false) {
-    }
-
-    std::condition_variable notify;
-    std::mutex lock;
-    std::atomic<bool> kicked;
-    bool open_new_connection = true;
-
-    int (*write)(usb_handle* h, const void* data, int len);
-    int (*read)(usb_handle* h, void* data, int len, bool allow_partial);
-    void (*kick)(usb_handle* h);
-    void (*close)(usb_handle* h);
-
-    // FunctionFS
-    android::base::unique_fd control;
-    android::base::unique_fd bulk_out;  // "out" from the host's perspective => source for adbd
-    android::base::unique_fd bulk_in;   // "in" from the host's perspective => sink for adbd
-
-    // Access to these blocks is very not thread safe. Have one block for each of the
-    // read and write threads.
-    struct aio_block read_aiob;
-    struct aio_block write_aiob;
-
-    bool reads_zero_packets;
-    size_t io_size;
-};
-
-usb_handle *create_usb_handle(unsigned num_bufs, unsigned io_size);
-bool open_functionfs(android::base::unique_fd* control, android::base::unique_fd* bulk_out,
-                     android::base::unique_fd* bulk_in);
diff --git a/adb/daemon/usb.cpp b/adb/daemon/usb.cpp
index 87937fb..7fff05a 100644
--- a/adb/daemon/usb.cpp
+++ b/adb/daemon/usb.cpp
@@ -45,19 +45,15 @@
 #include <android-base/properties.h>
 #include <android-base/thread_annotations.h>
 
-#include <adbd/usb.h>
-
 #include "adb_unique_fd.h"
 #include "adb_utils.h"
+#include "daemon/usb_ffs.h"
 #include "sysdeps/chrono.h"
 #include "transport.h"
 #include "types.h"
 
 using android::base::StringPrintf;
 
-// We can't find out whether we have support for AIO on ffs endpoints until we submit a read.
-static std::optional<bool> gFfsAioSupported;
-
 // Not all USB controllers support operations larger than 16k, so don't go above that.
 // Also, each submitted operation does an allocation in the kernel of that size, so we want to
 // minimize our queue depth while still maintaining a deep enough queue to keep the USB stack fed.
@@ -612,17 +608,10 @@
         block->pending = true;
         struct iocb* iocb = &block->control;
         if (io_submit(aio_context_.get(), 1, &iocb) != 1) {
-            if (errno == EINVAL && !gFfsAioSupported.has_value()) {
-                HandleError("failed to submit first read, AIO on FFS not supported");
-                gFfsAioSupported = false;
-                return false;
-            }
-
             HandleError(StringPrintf("failed to submit read: %s", strerror(errno)));
             return false;
         }
 
-        gFfsAioSupported = true;
         return true;
     }
 
@@ -741,17 +730,10 @@
     static constexpr int kInterruptionSignal = SIGUSR1;
 };
 
-void usb_init_legacy();
-
 static void usb_ffs_open_thread() {
     adb_thread_setname("usb ffs open");
 
     while (true) {
-        if (gFfsAioSupported.has_value() && !gFfsAioSupported.value()) {
-            LOG(INFO) << "failed to use nonblocking ffs, falling back to legacy";
-            return usb_init_legacy();
-        }
-
         unique_fd control;
         unique_fd bulk_out;
         unique_fd bulk_in;
@@ -773,13 +755,5 @@
 }
 
 void usb_init() {
-    bool use_nonblocking = android::base::GetBoolProperty(
-            "persist.adb.nonblocking_ffs",
-            android::base::GetBoolProperty("ro.adb.nonblocking_ffs", true));
-
-    if (use_nonblocking) {
-        std::thread(usb_ffs_open_thread).detach();
-    } else {
-        usb_init_legacy();
-    }
+    std::thread(usb_ffs_open_thread).detach();
 }
diff --git a/adb/daemon/usb_dummy.cpp b/adb/daemon/usb_dummy.cpp
deleted file mode 100644
index c9bf797..0000000
--- a/adb/daemon/usb_dummy.cpp
+++ /dev/null
@@ -1,42 +0,0 @@
-/*
- * Copyright (C) 2019 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#include <adbd/usb.h>
-
-#include <android-base/logging.h>
-
-int usb_write(usb_handle*, const void*, int) {
-    LOG(FATAL) << "unimplemented";
-    return -1;
-}
-
-int usb_read(usb_handle*, void*, int) {
-    LOG(FATAL) << "unimplemented";
-    return -1;
-}
-
-int usb_close(usb_handle*) {
-    LOG(FATAL) << "unimplemented";
-    return -1;
-}
-
-void usb_reset(usb_handle*) {
-    LOG(FATAL) << "unimplemented";
-}
-
-void usb_kick(usb_handle*) {
-    LOG(FATAL) << "unimplemented";
-}
diff --git a/adb/daemon/usb_ffs.cpp b/adb/daemon/usb_ffs.cpp
index cb7e2fb..7bd611b 100644
--- a/adb/daemon/usb_ffs.cpp
+++ b/adb/daemon/usb_ffs.cpp
@@ -18,6 +18,8 @@
 
 #include "sysdeps.h"
 
+#include "daemon/usb_ffs.h"
+
 #include <linux/usb/ch9.h>
 #include <linux/usb/functionfs.h>
 
@@ -26,7 +28,6 @@
 #include <android-base/unique_fd.h>
 
 #include "adb.h"
-#include "adbd/usb.h"
 
 #define MAX_PACKET_SIZE_FS 64
 #define MAX_PACKET_SIZE_HS 512
diff --git a/adb/daemon/usb_ffs.h b/adb/daemon/usb_ffs.h
new file mode 100644
index 0000000..a19d7cc
--- /dev/null
+++ b/adb/daemon/usb_ffs.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <android-base/unique_fd.h>
+
+bool open_functionfs(android::base::unique_fd* control, android::base::unique_fd* bulk_out,
+                     android::base::unique_fd* bulk_in);
diff --git a/adb/daemon/usb_legacy.cpp b/adb/daemon/usb_legacy.cpp
deleted file mode 100644
index fe80e7d..0000000
--- a/adb/daemon/usb_legacy.cpp
+++ /dev/null
@@ -1,327 +0,0 @@
-/*
- * Copyright (C) 2007 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#define TRACE_TAG USB
-
-#include "sysdeps.h"
-
-#include <dirent.h>
-#include <errno.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/ioctl.h>
-#include <sys/mman.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#include <linux/usb/ch9.h>
-#include <linux/usb/functionfs.h>
-
-#include <algorithm>
-#include <atomic>
-#include <chrono>
-#include <condition_variable>
-#include <mutex>
-#include <thread>
-
-#include <android-base/logging.h>
-#include <android-base/properties.h>
-
-#include "adb.h"
-#include "adbd/usb.h"
-#include "transport.h"
-
-using namespace std::chrono_literals;
-
-#define MAX_PACKET_SIZE_FS 64
-#define MAX_PACKET_SIZE_HS 512
-#define MAX_PACKET_SIZE_SS 1024
-
-#define USB_FFS_BULK_SIZE 16384
-
-// Number of buffers needed to fit MAX_PAYLOAD, with an extra for ZLPs.
-#define USB_FFS_NUM_BUFS ((4 * MAX_PAYLOAD / USB_FFS_BULK_SIZE) + 1)
-
-static unique_fd& dummy_fd = *new unique_fd();
-
-static void aio_block_init(aio_block* aiob, unsigned num_bufs) {
-    aiob->iocb.resize(num_bufs);
-    aiob->iocbs.resize(num_bufs);
-    aiob->events.resize(num_bufs);
-    aiob->num_submitted = 0;
-    for (unsigned i = 0; i < num_bufs; i++) {
-        aiob->iocbs[i] = &aiob->iocb[i];
-    }
-    memset(&aiob->ctx, 0, sizeof(aiob->ctx));
-    if (io_setup(num_bufs, &aiob->ctx)) {
-        D("[ aio: got error on io_setup (%d) ]", errno);
-    }
-}
-
-static int getMaxPacketSize(int ffs_fd) {
-    usb_endpoint_descriptor desc;
-    if (ioctl(ffs_fd, FUNCTIONFS_ENDPOINT_DESC, reinterpret_cast<unsigned long>(&desc))) {
-        D("[ could not get endpoint descriptor! (%d) ]", errno);
-        return MAX_PACKET_SIZE_HS;
-    } else {
-        return desc.wMaxPacketSize;
-    }
-}
-
-static bool init_functionfs(struct usb_handle* h) {
-    LOG(INFO) << "initializing functionfs";
-    if (!open_functionfs(&h->control, &h->bulk_out, &h->bulk_in)) {
-        return false;
-    }
-
-    h->read_aiob.fd = h->bulk_out.get();
-    h->write_aiob.fd = h->bulk_in.get();
-    h->reads_zero_packets = true;
-    return true;
-}
-
-static void usb_legacy_ffs_open_thread(usb_handle* usb) {
-    adb_thread_setname("usb legacy ffs open");
-
-    while (true) {
-        // wait until the USB device needs opening
-        std::unique_lock<std::mutex> lock(usb->lock);
-        while (!usb->open_new_connection) {
-            usb->notify.wait(lock);
-        }
-        usb->open_new_connection = false;
-        lock.unlock();
-
-        while (true) {
-            if (init_functionfs(usb)) {
-                LOG(INFO) << "functionfs successfully initialized";
-                break;
-            }
-            std::this_thread::sleep_for(1s);
-        }
-
-        LOG(INFO) << "registering usb transport";
-        register_usb_transport(usb, nullptr, nullptr, 1);
-    }
-
-    // never gets here
-    abort();
-}
-
-static int usb_ffs_write(usb_handle* h, const void* data, int len) {
-    D("about to write (fd=%d, len=%d)", h->bulk_in.get(), len);
-
-    const char* buf = static_cast<const char*>(data);
-    int orig_len = len;
-    while (len > 0) {
-        int write_len = std::min(USB_FFS_BULK_SIZE, len);
-        int n = adb_write(h->bulk_in, buf, write_len);
-        if (n < 0) {
-            D("ERROR: fd = %d, n = %d: %s", h->bulk_in.get(), n, strerror(errno));
-            return -1;
-        }
-        buf += n;
-        len -= n;
-    }
-
-    D("[ done fd=%d ]", h->bulk_in.get());
-    return orig_len;
-}
-
-static int usb_ffs_read(usb_handle* h, void* data, int len, bool allow_partial) {
-    D("about to read (fd=%d, len=%d)", h->bulk_out.get(), len);
-
-    char* buf = static_cast<char*>(data);
-    int orig_len = len;
-    unsigned count = 0;
-    while (len > 0) {
-        int read_len = std::min(USB_FFS_BULK_SIZE, len);
-        int n = adb_read(h->bulk_out, buf, read_len);
-        if (n < 0) {
-            D("ERROR: fd = %d, n = %d: %s", h->bulk_out.get(), n, strerror(errno));
-            return -1;
-        }
-        buf += n;
-        len -= n;
-        count += n;
-
-        // For fastbootd command such as "getvar all", len parameter is always set 64.
-        // But what we read is actually less than 64.
-        // For example, length 10 for "getvar all" command.
-        // If we get less data than expected, this means there should be no more data.
-        if (allow_partial && n < read_len) {
-            orig_len = count;
-            break;
-        }
-    }
-
-    D("[ done fd=%d ]", h->bulk_out.get());
-    return orig_len;
-}
-
-static int usb_ffs_do_aio(usb_handle* h, const void* data, int len, bool read) {
-    aio_block* aiob = read ? &h->read_aiob : &h->write_aiob;
-    bool zero_packet = false;
-
-    int num_bufs = len / h->io_size + (len % h->io_size == 0 ? 0 : 1);
-    const char* cur_data = reinterpret_cast<const char*>(data);
-    int packet_size = getMaxPacketSize(aiob->fd);
-
-    if (posix_madvise(const_cast<void*>(data), len, POSIX_MADV_SEQUENTIAL | POSIX_MADV_WILLNEED) <
-        0) {
-        D("[ Failed to madvise: %d ]", errno);
-    }
-
-    for (int i = 0; i < num_bufs; i++) {
-        int buf_len = std::min(len, static_cast<int>(h->io_size));
-        io_prep(&aiob->iocb[i], aiob->fd, cur_data, buf_len, 0, read);
-
-        len -= buf_len;
-        cur_data += buf_len;
-
-        if (len == 0 && buf_len % packet_size == 0 && read) {
-            // adb does not expect the device to send a zero packet after data transfer,
-            // but the host *does* send a zero packet for the device to read.
-            zero_packet = h->reads_zero_packets;
-        }
-    }
-    if (zero_packet) {
-        io_prep(&aiob->iocb[num_bufs], aiob->fd, reinterpret_cast<const void*>(cur_data),
-                packet_size, 0, read);
-        num_bufs += 1;
-    }
-
-    while (true) {
-        if (TEMP_FAILURE_RETRY(io_submit(aiob->ctx, num_bufs, aiob->iocbs.data())) < num_bufs) {
-            PLOG(ERROR) << "aio: got error submitting " << (read ? "read" : "write");
-            return -1;
-        }
-        if (TEMP_FAILURE_RETRY(io_getevents(aiob->ctx, num_bufs, num_bufs, aiob->events.data(),
-                                            nullptr)) < num_bufs) {
-            PLOG(ERROR) << "aio: got error waiting " << (read ? "read" : "write");
-            return -1;
-        }
-        if (num_bufs == 1 && aiob->events[0].res == -EINTR) {
-            continue;
-        }
-        int ret = 0;
-        for (int i = 0; i < num_bufs; i++) {
-            if (aiob->events[i].res < 0) {
-                errno = -aiob->events[i].res;
-                PLOG(ERROR) << "aio: got error event on " << (read ? "read" : "write")
-                            << " total bufs " << num_bufs;
-                return -1;
-            }
-            ret += aiob->events[i].res;
-        }
-        return ret;
-    }
-}
-
-static int usb_ffs_aio_read(usb_handle* h, void* data, int len, bool allow_partial) {
-    return usb_ffs_do_aio(h, data, len, true);
-}
-
-static int usb_ffs_aio_write(usb_handle* h, const void* data, int len) {
-    return usb_ffs_do_aio(h, data, len, false);
-}
-
-static void usb_ffs_kick(usb_handle* h) {
-    int err;
-
-    err = ioctl(h->bulk_in.get(), FUNCTIONFS_CLEAR_HALT);
-    if (err < 0) {
-        D("[ kick: source (fd=%d) clear halt failed (%d) ]", h->bulk_in.get(), errno);
-    }
-
-    err = ioctl(h->bulk_out.get(), FUNCTIONFS_CLEAR_HALT);
-    if (err < 0) {
-        D("[ kick: sink (fd=%d) clear halt failed (%d) ]", h->bulk_out.get(), errno);
-    }
-
-    // don't close ep0 here, since we may not need to reinitialize it with
-    // the same descriptors again. if however ep1/ep2 fail to re-open in
-    // init_functionfs, only then would we close and open ep0 again.
-    // Ditto the comment in usb_adb_kick.
-    h->kicked = true;
-    TEMP_FAILURE_RETRY(dup2(dummy_fd.get(), h->bulk_out.get()));
-    TEMP_FAILURE_RETRY(dup2(dummy_fd.get(), h->bulk_in.get()));
-}
-
-static void usb_ffs_close(usb_handle* h) {
-    LOG(INFO) << "closing functionfs transport";
-
-    h->kicked = false;
-    h->bulk_out.reset();
-    h->bulk_in.reset();
-
-    // Notify usb_adb_open_thread to open a new connection.
-    h->lock.lock();
-    h->open_new_connection = true;
-    h->lock.unlock();
-    h->notify.notify_one();
-}
-
-usb_handle* create_usb_handle(unsigned num_bufs, unsigned io_size) {
-    usb_handle* h = new usb_handle();
-
-    if (android::base::GetBoolProperty("sys.usb.ffs.aio_compat", false)) {
-        // Devices on older kernels (< 3.18) will not have aio support for ffs
-        // unless backported. Fall back on the non-aio functions instead.
-        h->write = usb_ffs_write;
-        h->read = usb_ffs_read;
-    } else {
-        h->write = usb_ffs_aio_write;
-        h->read = usb_ffs_aio_read;
-        aio_block_init(&h->read_aiob, num_bufs);
-        aio_block_init(&h->write_aiob, num_bufs);
-    }
-    h->io_size = io_size;
-    h->kick = usb_ffs_kick;
-    h->close = usb_ffs_close;
-    return h;
-}
-
-void usb_init_legacy() {
-    D("[ usb_init - using legacy FunctionFS ]");
-    dummy_fd.reset(adb_open("/dev/null", O_WRONLY | O_CLOEXEC));
-    CHECK_NE(-1, dummy_fd.get());
-
-    std::thread(usb_legacy_ffs_open_thread, create_usb_handle(USB_FFS_NUM_BUFS, USB_FFS_BULK_SIZE))
-            .detach();
-}
-
-int usb_write(usb_handle* h, const void* data, int len) {
-    return h->write(h, data, len);
-}
-
-int usb_read(usb_handle* h, void* data, int len) {
-    return h->read(h, data, len, false /* allow_partial */);
-}
-
-int usb_close(usb_handle* h) {
-    h->close(h);
-    return 0;
-}
-
-void usb_reset(usb_handle* h) {
-    usb_close(h);
-}
-
-void usb_kick(usb_handle* h) {
-    h->kick(h);
-}
diff --git a/adb/transport.cpp b/adb/transport.cpp
index 460faf0..61467cb 100644
--- a/adb/transport.cpp
+++ b/adb/transport.cpp
@@ -1454,6 +1454,7 @@
 
 #endif
 
+#if ADB_HOST
 void register_usb_transport(usb_handle* usb, const char* serial, const char* devpath,
                             unsigned writeable) {
     atransport* t = new atransport(writeable ? kCsOffline : kCsNoPerm);
@@ -1475,6 +1476,7 @@
 
     register_transport(t);
 }
+#endif
 
 #if ADB_HOST
 // This should only be used for transports with connection_state == kCsNoPerm.
diff --git a/adb/transport.h b/adb/transport.h
index 5d4e297..5bc1b5c 100644
--- a/adb/transport.h
+++ b/adb/transport.h
@@ -39,7 +39,6 @@
 #include "adb.h"
 #include "adb_unique_fd.h"
 #include "types.h"
-#include "usb.h"
 
 typedef std::unordered_set<std::string> FeatureSet;
 
@@ -202,20 +201,6 @@
     std::unique_ptr<adb::tls::TlsConnection> tls_;
 };
 
-struct UsbConnection : public BlockingConnection {
-    explicit UsbConnection(usb_handle* handle) : handle_(handle) {}
-    ~UsbConnection();
-
-    bool Read(apacket* packet) override final;
-    bool Write(apacket* packet) override final;
-    bool DoTlsHandshake(RSA* key, std::string* auth_key) override final;
-
-    void Close() override final;
-    virtual void Reset() override final;
-
-    usb_handle* handle_;
-};
-
 // Waits for a transport's connection to be not pending. This is a separate
 // object so that the transport can be destroyed and another thread can be
 // notified of it in a race-free way.
@@ -251,6 +236,10 @@
     Abort,
 };
 
+#if ADB_HOST
+struct usb_handle;
+#endif
+
 class atransport : public enable_weak_from_this<atransport> {
   public:
     // TODO(danalbert): We expose waaaaaaay too much stuff because this was
@@ -291,8 +280,10 @@
         return connection_;
     }
 
+#if ADB_HOST
     void SetUsbHandle(usb_handle* h) { usb_handle_ = h; }
     usb_handle* GetUsbHandle() { return usb_handle_; }
+#endif
 
     const TransportId id;
 
@@ -399,8 +390,10 @@
     // The underlying connection object.
     std::shared_ptr<Connection> connection_ GUARDED_BY(mutex_);
 
+#if ADB_HOST
     // USB handle for the connection, if available.
     usb_handle* usb_handle_ = nullptr;
+#endif
 
     // A callback that will be invoked when the atransport needs to reconnect.
     ReconnectCallback reconnect_;
@@ -441,8 +434,15 @@
 #endif
 
 void register_transport(atransport* transport);
-void register_usb_transport(usb_handle* h, const char* serial,
-                            const char* devpath, unsigned writeable);
+
+#if ADB_HOST
+void init_usb_transport(atransport* t, usb_handle* usb);
+void register_usb_transport(usb_handle* h, const char* serial, const char* devpath,
+                            unsigned writeable);
+
+// This should only be used for transports with connection_state == kCsNoPerm.
+void unregister_usb_transport(usb_handle* usb);
+#endif
 
 /* Connect to a network address and register it as a device */
 void connect_device(const std::string& address, std::string* response);
@@ -452,9 +452,6 @@
                                atransport::ReconnectCallback reconnect, bool use_tls,
                                int* error = nullptr);
 
-// This should only be used for transports with connection_state == kCsNoPerm.
-void unregister_usb_transport(usb_handle* usb);
-
 bool check_header(apacket* p, atransport* t);
 
 void close_usb_devices(bool reset = false);