root/drivers/usb/serial/aircable.c

DEFINITIONS

1. aircable_prepare_write_buffer
2. aircable_calc_num_ports
3. aircable_process_packet
4. aircable_process_read_urb

   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 */
  66 static const struct usb_device_id id_table[] = {
  67         { USB_DEVICE(AIRCABLE_VID, AIRCABLE_USB_PID) },
  68         { },
  69 };
  70 MODULE_DEVICE_TABLE(usb, id_table);
  71 
  72 static 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 
  87 static 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 
 100 static 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 
 117 static 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 
 139 static 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 
 153 static struct usb_serial_driver * const serial_drivers[] = {
 154         &aircable_device, NULL
 155 };
 156 
 157 module_usb_serial_driver(serial_drivers, id_table);
 158 
 159 MODULE_AUTHOR(DRIVER_AUTHOR);
 160 MODULE_DESCRIPTION(DRIVER_DESC);
 161 MODULE_LICENSE("GPL v2");