aircable.c

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/*
 * AIRcable USB Bluetooth Dongle Driver.
 *
 * Copyright (C) 2010 Johan Hovold <[email protected]>
 * Copyright (C) 2006 Manuel Francisco Naranjo ([email protected])
 *
 * This program is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License version 2 as published by the
 * Free Software Foundation.
 *
 * The device works as an standard CDC device, it has 2 interfaces, the first
 * one is for firmware access and the second is the serial one.
 * The protocol is very simply, there are two posibilities reading or writing.
 * When writing the first urb must have a Header that starts with 0x20 0x29 the
 * next two bytes must say how much data will be sended.
 * When reading the process is almost equal except that the header starts with
 * 0x00 0x20.
 *
 * The device simply need some stuff to understand data coming from the usb
 * buffer: The First and Second byte is used for a Header, the Third and Fourth
 * tells the  device the amount of information the package holds.
 * Packages are 60 bytes long Header Stuff.
 * When writing to the device the first two bytes of the header are 0x20 0x29
 * When reading the bytes are 0x00 0x20, or 0x00 0x10, there is an strange
 * situation, when too much data arrives to the device because it sends the data
 * but with out the header. I will use a simply hack to override this situation,
 * if there is data coming that does not contain any header, then that is data
 * that must go directly to the tty, as there is no documentation about if there
 * is any other control code, I will simply check for the first
 * one.
 *
 * The driver registers himself with the USB-serial core and the USB Core. I had
 * to implement a probe function against USB-serial, because other way, the
 * driver was attaching himself to both interfaces. I have tryed with different
 * configurations of usb_serial_driver with out exit, only the probe function
 * could handle this correctly.
 *
 * I have taken some info from a Greg Kroah-Hartman article:
 * http://www.linuxjournal.com/article/6573
 * And from Linux Device Driver Kit CD, which is a great work, the authors taken
 * the work to recompile lots of information an knowladge in drivers development
 * and made it all avaible inside a cd.
 * URL: http://kernel.org/pub/linux/kernel/people/gregkh/ddk/
 *
 */

#include <asm/unaligned.h>
#include <linux/tty.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/tty_flip.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

/* Vendor and Product ID */
#define AIRCABLE_VID        0x16CA
#define AIRCABLE_USB_PID    0x1502

/* Protocol Stuff */
#define HCI_HEADER_LENGTH   0x4
#define TX_HEADER_0     0x20
#define TX_HEADER_1     0x29
#define RX_HEADER_0     0x00
#define RX_HEADER_1     0x20
#define HCI_COMPLETE_FRAME  64

/* rx_flags */
#define THROTTLED       0x01
#define ACTUALLY_THROTTLED  0x02

/*
 * Version Information
 */
#define DRIVER_VERSION "v2.0"
#define DRIVER_AUTHOR "Naranjo, Manuel Francisco <[email protected]>, Johan Hovold <[email protected]>"
#define DRIVER_DESC "AIRcable USB Driver"

/* ID table that will be registered with USB core */
static const struct usb_device_id id_table[] = {
    { USB_DEVICE(AIRCABLE_VID, AIRCABLE_USB_PID) },
    { },
};
MODULE_DEVICE_TABLE(usb, id_table);

static int aircable_prepare_write_buffer(struct usb_serial_port *port,
                        void *dest, size_t size)
{
    int count;
    unsigned char *buf = dest;

    count = kfifo_out_locked(&port->write_fifo, buf + HCI_HEADER_LENGTH,
                    size - HCI_HEADER_LENGTH, &port->lock);
    buf[0] = TX_HEADER_0;
    buf[1] = TX_HEADER_1;
    put_unaligned_le16(count, &buf[2]);

    return count + HCI_HEADER_LENGTH;
}

static int aircable_probe(struct usb_serial *serial,
              const struct usb_device_id *id)
{
    struct usb_host_interface *iface_desc = serial->interface->
                                cur_altsetting;
    struct usb_endpoint_descriptor *endpoint;
    int num_bulk_out = 0;
    int i;

    for (i = 0; i < iface_desc->desc.bNumEndpoints; i++) {
        endpoint = &iface_desc->endpoint[i].desc;
        if (usb_endpoint_is_bulk_out(endpoint)) {
            dev_dbg(&serial->dev->dev,
                "found bulk out on endpoint %d\n", i);
            ++num_bulk_out;
        }
    }

    if (num_bulk_out == 0) {
        dev_dbg(&serial->dev->dev, "Invalid interface, discarding\n");
        return -ENODEV;
    }

    return 0;
}

static int aircable_process_packet(struct tty_struct *tty,
            struct usb_serial_port *port, int has_headers,
            char *packet, int len)
{
    if (has_headers) {
        len -= HCI_HEADER_LENGTH;
        packet += HCI_HEADER_LENGTH;
    }
    if (len <= 0) {
        dev_dbg(&port->dev, "%s - malformed packet\n", __func__);
        return 0;
    }

    tty_insert_flip_string(tty, packet, len);

    return len;
}

static void aircable_process_read_urb(struct urb *urb)
{
    struct usb_serial_port *port = urb->context;
    char *data = (char *)urb->transfer_buffer;
    struct tty_struct *tty;
    int has_headers;
    int count;
    int len;
    int i;

    tty = tty_port_tty_get(&port->port);
    if (!tty)
        return;

    has_headers = (urb->actual_length > 2 && data[0] == RX_HEADER_0);

    count = 0;
    for (i = 0; i < urb->actual_length; i += HCI_COMPLETE_FRAME) {
        len = min_t(int, urb->actual_length - i, HCI_COMPLETE_FRAME);
        count += aircable_process_packet(tty, port, has_headers,
                                &data[i], len);
    }

    if (count)
        tty_flip_buffer_push(tty);
    tty_kref_put(tty);
}

static struct usb_serial_driver aircable_device = {
    .driver = {
        .owner =    THIS_MODULE,
        .name =     "aircable",
    },
    .id_table =         id_table,
    .num_ports =        1,
    .bulk_out_size =    HCI_COMPLETE_FRAME,
    .probe =        aircable_probe,
    .process_read_urb = aircable_process_read_urb,
    .prepare_write_buffer = aircable_prepare_write_buffer,
    .throttle =     usb_serial_generic_throttle,
    .unthrottle =       usb_serial_generic_unthrottle,
};

static struct usb_serial_driver * const serial_drivers[] = {
    &aircable_device, NULL
};

module_usb_serial_driver(serial_drivers, id_table);

MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);
MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL");