1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * AIRcable USB Bluetooth Dongle Driver.
  4 *
  5 * Copyright (C) 2010 Johan Hovold <jhovold@gmail.com>
  6 * Copyright (C) 2006 Manuel Francisco Naranjo (naranjo.manuel@gmail.com)
  7 *
  8 * The device works as an standard CDC device, it has 2 interfaces, the first
  9 * one is for firmware access and the second is the serial one.
 10 * The protocol is very simply, there are two possibilities reading or writing.
 11 * When writing the first urb must have a Header that starts with 0x20 0x29 the
 12 * next two bytes must say how much data will be sent.
 13 * When reading the process is almost equal except that the header starts with
 14 * 0x00 0x20.
 15 *
 16 * The device simply need some stuff to understand data coming from the usb
 17 * buffer: The First and Second byte is used for a Header, the Third and Fourth
 18 * tells the  device the amount of information the package holds.
 19 * Packages are 60 bytes long Header Stuff.
 20 * When writing to the device the first two bytes of the header are 0x20 0x29
 21 * When reading the bytes are 0x00 0x20, or 0x00 0x10, there is an strange
 22 * situation, when too much data arrives to the device because it sends the data
 23 * but with out the header. I will use a simply hack to override this situation,
 24 * if there is data coming that does not contain any header, then that is data
 25 * that must go directly to the tty, as there is no documentation about if there
 26 * is any other control code, I will simply check for the first
 27 * one.
 28 *
 29 * I have taken some info from a Greg Kroah-Hartman article:
 30 * http://www.linuxjournal.com/article/6573
 31 * And from Linux Device Driver Kit CD, which is a great work, the authors taken
 32 * the work to recompile lots of information an knowledge in drivers development
 33 * and made it all available inside a cd.
 34 * URL: http://kernel.org/pub/linux/kernel/people/gregkh/ddk/
 35 *
 36 */
 37
 38#include <asm/unaligned.h>
 39#include <linux/tty.h>
 40#include <linux/slab.h>
 41#include <linux/module.h>
 42#include <linux/tty_flip.h>
 43#include <linux/usb.h>
 44#include <linux/usb/serial.h>
 45
 46/* Vendor and Product ID */
 47#define AIRCABLE_VID		0x16CA
 48#define AIRCABLE_USB_PID	0x1502
 49
 50/* Protocol Stuff */
 51#define HCI_HEADER_LENGTH	0x4
 52#define TX_HEADER_0		0x20
 53#define TX_HEADER_1		0x29
 54#define RX_HEADER_0		0x00
 55#define RX_HEADER_1		0x20
 56#define HCI_COMPLETE_FRAME	64
 57
 58/* rx_flags */
 59#define THROTTLED		0x01
 60#define ACTUALLY_THROTTLED	0x02
 61
 62#define DRIVER_AUTHOR "Naranjo, Manuel Francisco <naranjo.manuel@gmail.com>, Johan Hovold <jhovold@gmail.com>"
 63#define DRIVER_DESC "AIRcable USB Driver"
 64
 65/* ID table that will be registered with USB core */
 66static const struct usb_device_id id_table[] = {
 67	{ USB_DEVICE(AIRCABLE_VID, AIRCABLE_USB_PID) },
 68	{ },
 69};
 70MODULE_DEVICE_TABLE(usb, id_table);
 71
 72static int aircable_prepare_write_buffer(struct usb_serial_port *port,
 73						void *dest, size_t size)
 74{
 75	int count;
 76	unsigned char *buf = dest;
 77
 78	count = kfifo_out_locked(&port->write_fifo, buf + HCI_HEADER_LENGTH,
 79					size - HCI_HEADER_LENGTH, &port->lock);
 80	buf[0] = TX_HEADER_0;
 81	buf[1] = TX_HEADER_1;
 82	put_unaligned_le16(count, &buf[2]);
 83
 84	return count + HCI_HEADER_LENGTH;
 85}
 86
 87static int aircable_calc_num_ports(struct usb_serial *serial,
 88					struct usb_serial_endpoints *epds)
 89{
 90	/* Ignore the first interface, which has no bulk endpoints. */
 91	if (epds->num_bulk_out == 0) {
 92		dev_dbg(&serial->interface->dev,
 93			"ignoring interface with no bulk-out endpoints\n");
 94		return -ENODEV;
 95	}
 96
 97	return 1;
 98}
 99
100static int aircable_process_packet(struct usb_serial_port *port,
101		int has_headers, char *packet, int len)
102{
103	if (has_headers) {
104		len -= HCI_HEADER_LENGTH;
105		packet += HCI_HEADER_LENGTH;
106	}
107	if (len <= 0) {
108		dev_dbg(&port->dev, "%s - malformed packet\n", __func__);
109		return 0;
110	}
111
112	tty_insert_flip_string(&port->port, packet, len);
113
114	return len;
115}
116
117static void aircable_process_read_urb(struct urb *urb)
118{
119	struct usb_serial_port *port = urb->context;
120	char *data = (char *)urb->transfer_buffer;
121	int has_headers;
122	int count;
123	int len;
124	int i;
125
126	has_headers = (urb->actual_length > 2 && data[0] == RX_HEADER_0);
127
128	count = 0;
129	for (i = 0; i < urb->actual_length; i += HCI_COMPLETE_FRAME) {
130		len = min_t(int, urb->actual_length - i, HCI_COMPLETE_FRAME);
131		count += aircable_process_packet(port, has_headers,
132								&data[i], len);
133	}
134
135	if (count)
136		tty_flip_buffer_push(&port->port);
137}
138
139static struct usb_serial_driver aircable_device = {
140	.driver = {
141		.owner =	THIS_MODULE,
142		.name =		"aircable",
143	},
144	.id_table = 		id_table,
145	.bulk_out_size =	HCI_COMPLETE_FRAME,
146	.calc_num_ports =	aircable_calc_num_ports,
147	.process_read_urb =	aircable_process_read_urb,
148	.prepare_write_buffer =	aircable_prepare_write_buffer,
149	.throttle =		usb_serial_generic_throttle,
150	.unthrottle =		usb_serial_generic_unthrottle,
151};
152
153static struct usb_serial_driver * const serial_drivers[] = {
154	&aircable_device, NULL
155};
156
157module_usb_serial_driver(serial_drivers, id_table);
158
159MODULE_AUTHOR(DRIVER_AUTHOR);
160MODULE_DESCRIPTION(DRIVER_DESC);
161MODULE_LICENSE("GPL v2");