Move adbd's legacy USB implementation to fastboot.

This code path is effectively dead in adbd, and fastboot's dependency on
libadbd makes it hard to refactor adbd's dependencies.

Bug: http://b/150317254
Test: built and flashed aosp_walleye-eng
Change-Id: I5118136d32fdcbbd011559ed0a4a71e1dc7bf064
Merged-In: I5118136d32fdcbbd011559ed0a4a71e1dc7bf064
(cherry picked from commit 0871824de6c5b868f2a2e67c9b5673cb2181b4c6)
diff --git a/fastboot/device/usb.h b/fastboot/device/usb.h
new file mode 100644
index 0000000..6c3f542
--- /dev/null
+++ b/fastboot/device/usb.h
@@ -0,0 +1,63 @@
+#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() {}
+
+    std::condition_variable notify;
+    std::mutex lock;
+    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 (*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);