Refactored Mtp driver interface into multiple classes.

Added new interface for FunctionFS. This allows most of
the driver code to exist in userspace. The driver will
automatically use FunctionFS if it is enabled for that
device, otherwise it will default to the kernel driver.

The intention is to eventually deprecate the kernel driver.

Bug: 30976142
Change-Id: I36b8d16ca254fddd995b3ea1bd3d37b0ff4a28f7
Test: New automated tests for MtpFfsHandle, AsyncIO.
Manual testing on each device.
diff --git a/media/mtp/IMtpHandle.h b/media/mtp/IMtpHandle.h
new file mode 100644
index 0000000..9185255
--- /dev/null
+++ b/media/mtp/IMtpHandle.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+#ifndef _IMTP_HANDLE_H
+#define _IMTP_HANDLE_H
+
+#include <linux/usb/f_mtp.h>
+
+constexpr char FFS_MTP_EP0[] = "/dev/usb-ffs/mtp/ep0";
+
+class IMtpHandle {
+public:
+    // Return number of bytes read/written, or -1 and errno is set
+    virtual int read(void *data, int len) = 0;
+    virtual int write(const void *data, int len) = 0;
+
+    // Return 0 if send/receive is successful, or -1 and errno is set
+    virtual int receiveFile(mtp_file_range mfr) = 0;
+    virtual int sendFile(mtp_file_range mfr) = 0;
+    virtual int sendEvent(mtp_event me) = 0;
+
+    // Return 0 if operation is successful, or -1 else
+    virtual int start() = 0;
+    virtual int configure(bool ptp) = 0;
+
+    virtual void close() = 0;
+
+    virtual ~IMtpHandle() {}
+};
+
+IMtpHandle *get_ffs_handle();
+IMtpHandle *get_mtp_handle();
+
+#endif // _IMTP_HANDLE_H
+