v4.19.13 snapshot.
diff --git a/drivers/usb/serial/usb_debug.c b/drivers/usb/serial/usb_debug.c
new file mode 100644
index 0000000..aaf4813
--- /dev/null
+++ b/drivers/usb/serial/usb_debug.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Debug cable driver
+ *
+ * Copyright (C) 2006 Greg Kroah-Hartman <greg@kroah.com>
+ */
+
+#include <linux/gfp.h>
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define USB_DEBUG_MAX_PACKET_SIZE 8
+#define USB_DEBUG_BRK_SIZE 8
+static const char USB_DEBUG_BRK[USB_DEBUG_BRK_SIZE] = {
+ 0x00,
+ 0xff,
+ 0x01,
+ 0xfe,
+ 0x00,
+ 0xfe,
+ 0x01,
+ 0xff,
+};
+
+static const struct usb_device_id id_table[] = {
+ { USB_DEVICE(0x0525, 0x127a) },
+ { },
+};
+
+static const struct usb_device_id dbc_id_table[] = {
+ { USB_DEVICE(0x1d6b, 0x0010) },
+ { USB_DEVICE(0x1d6b, 0x0011) },
+ { },
+};
+
+static const struct usb_device_id id_table_combined[] = {
+ { USB_DEVICE(0x0525, 0x127a) },
+ { USB_DEVICE(0x1d6b, 0x0010) },
+ { USB_DEVICE(0x1d6b, 0x0011) },
+ { },
+};
+MODULE_DEVICE_TABLE(usb, id_table_combined);
+
+/* This HW really does not support a serial break, so one will be
+ * emulated when ever the break state is set to true.
+ */
+static void usb_debug_break_ctl(struct tty_struct *tty, int break_state)
+{
+ struct usb_serial_port *port = tty->driver_data;
+ if (!break_state)
+ return;
+ usb_serial_generic_write(tty, port, USB_DEBUG_BRK, USB_DEBUG_BRK_SIZE);
+}
+
+static void usb_debug_process_read_urb(struct urb *urb)
+{
+ struct usb_serial_port *port = urb->context;
+
+ if (urb->actual_length == USB_DEBUG_BRK_SIZE &&
+ memcmp(urb->transfer_buffer, USB_DEBUG_BRK,
+ USB_DEBUG_BRK_SIZE) == 0) {
+ usb_serial_handle_break(port);
+ return;
+ }
+
+ usb_serial_generic_process_read_urb(urb);
+}
+
+static struct usb_serial_driver debug_device = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "debug",
+ },
+ .id_table = id_table,
+ .num_ports = 1,
+ .bulk_out_size = USB_DEBUG_MAX_PACKET_SIZE,
+ .break_ctl = usb_debug_break_ctl,
+ .process_read_urb = usb_debug_process_read_urb,
+};
+
+static struct usb_serial_driver dbc_device = {
+ .driver = {
+ .owner = THIS_MODULE,
+ .name = "xhci_dbc",
+ },
+ .id_table = dbc_id_table,
+ .num_ports = 1,
+ .break_ctl = usb_debug_break_ctl,
+ .process_read_urb = usb_debug_process_read_urb,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+ &debug_device, &dbc_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table_combined);
+MODULE_LICENSE("GPL v2");