scripts: add script for usb backend to receive tracing data

Add script for usb backend to receive tracing stream data. This
script, trace_capture_usb.py, is based on pyusb, so install it
correctly before using the script.

Signed-off-by: Wentong Wu <wentong.wu@intel.com>

scripts/tracing/trace_capture_usb.py

@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2019 Intel Corporation.
+#
+# SPDX-License-Identifier: Apache-2.0
+"""
+Script to capture tracing data with USB backend.
+"""
+
+import usb.core
+import usb.util
+import argparse
+import sys
+
+def parse_args():
+    global args
+    parser = argparse.ArgumentParser(
+        description=__doc__,
+        formatter_class=argparse.RawDescriptionHelpFormatter)
+    parser.add_argument("-v", "--vendor_id", required=True,
+                        help="usb device vendor id")
+    parser.add_argument("-p", "--product_id", required=True,
+                        help="usb device product id")
+    parser.add_argument("-o", "--output", default='channel0_0',
+                        required=False, help="tracing data output file")
+    args = parser.parse_args()
+
+def main():
+    parse_args()
+    if args.vendor_id.isdecimal():
+        vendor_id = int(args.vendor_id)
+    else:
+        vendor_id = int(args.vendor_id, 16)
+
+    if args.product_id.isdecimal():
+        product_id = int(args.product_id)
+    else:
+        product_id = int(args.product_id, 16)
+
+    output_file = args.output
+
+    try:
+        usb_device = usb.core.find(idVendor=vendor_id, idProduct=product_id)
+    except Exception as e:
+        sys.exit("{}".format(e))
+
+    if usb_device is None:
+        sys.exit("No device found, check vendor_id and product_id")
+
+    if usb_device.is_kernel_driver_active(0):
+        try:
+            usb_device.detach_kernel_driver(0)
+        except usb.core.USBError as e:
+            sys.exit("{}".format(e))
+
+    # set the active configuration. With no arguments, the first
+    # configuration will be the active one
+    try:
+        usb_device.set_configuration()
+    except usb.core.USBError as e:
+        sys.exit("{}".format(e))
+
+    configuration = usb_device[0]
+    interface = configuration[(0, 0)]
+
+    # match the only IN endpoint
+    read_endpoint = usb.util.find_descriptor(interface, custom_match = \
+                                                lambda e: \
+                                                usb.util.endpoint_direction( \
+                                                    e.bEndpointAddress) == \
+                                                usb.util.ENDPOINT_IN)
+
+    # match the only OUT endpoint
+    write_endpoint = usb.util.find_descriptor(interface, custom_match = \
+                                                lambda e: \
+                                                usb.util.endpoint_direction( \
+                                                    e.bEndpointAddress) == \
+                                                usb.util.ENDPOINT_OUT)
+
+    usb.util.claim_interface(usb_device, interface)
+
+    #enable device tracing
+    write_endpoint.write('enable')
+
+    #try to read to avoid garbage mixed to useful stream data
+    buff = usb.util.create_buffer(8192)
+    read_endpoint.read(buff, 10000)
+
+    with open(output_file, "wb") as file_desc:
+        while True:
+            buff = usb.util.create_buffer(8192)
+            length = read_endpoint.read(buff, 100000)
+            for index in range(length):
+                file_desc.write(chr(buff[index]).encode('latin1'))
+
+    usb.util.release_interface(usb_device, interface)
+
+if __name__=="__main__":
+    try:
+        main()
+    except KeyboardInterrupt:
+        print('Data capture interrupted, data saved into {}'.format(args.output))
+        sys.exit(0)