/*
 * AIRcable USB Bluetooth Dongle Driver.
 *
 * Copyright (C) 2006 Manuel Francisco Naranjo (naranjo.manuel@gmail.com)
 * 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 comming 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 agains 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 <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/circ_buf.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

static int debug;

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

/* write buffer size defines */
#define AIRCABLE_BUF_SIZE       2048

/* 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 MAX_HCI_FRAMESIZE       60
#define HCI_COMPLETE_FRAME      64

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

/*
 * Version Information
 */
#define DRIVER_VERSION "v1.0b2"
#define DRIVER_AUTHOR "Naranjo, Manuel Francisco <naranjo.manuel@gmail.com>"
#define DRIVER_DESC "AIRcable USB Driver"

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


/* Internal Structure */
struct aircable_private {
        spinlock_t rx_lock;             /* spinlock for the receive lines */
        struct circ_buf *tx_buf;        /* write buffer */
        struct circ_buf *rx_buf;        /* read buffer */
        int rx_flags;                   /* for throttilng */
        struct work_struct rx_work;     /* work cue for the receiving line */
        struct usb_serial_port *port;   /* USB port with which associated */
};

/* Private methods */

/* Circular Buffer Methods, code from ti_usb_3410_5052 used */
/*
 * serial_buf_clear
 *
 * Clear out all data in the circular buffer.
 */
static void serial_buf_clear(struct circ_buf *cb)
{
        cb->head = cb->tail = 0;
}

/*
 * serial_buf_alloc
 *
 * Allocate a circular buffer and all associated memory.
 */
static struct circ_buf *serial_buf_alloc(void)
{
        struct circ_buf *cb;
        cb = kmalloc(sizeof(struct circ_buf), GFP_KERNEL);
        if (cb == NULL)
                return NULL;
        cb->buf = kmalloc(AIRCABLE_BUF_SIZE, GFP_KERNEL);
        if (cb->buf == NULL) {
                kfree(cb);
                return NULL;
        }
        serial_buf_clear(cb);
        return cb;
}

/*
 * serial_buf_free
 *
 * Free the buffer and all associated memory.
 */
static void serial_buf_free(struct circ_buf *cb)
{
        kfree(cb->buf);
        kfree(cb);
}

/*
 * serial_buf_data_avail
 *
 * Return the number of bytes of data available in the circular
 * buffer.
 */
static int serial_buf_data_avail(struct circ_buf *cb)
{
        return CIRC_CNT(cb->head, cb->tail, AIRCABLE_BUF_SIZE);
}

/*
 * serial_buf_put
 *
 * Copy data data from a user buffer and put it into the circular buffer.
 * Restrict to the amount of space available.
 *
 * Return the number of bytes copied.
 */
static int serial_buf_put(struct circ_buf *cb, const char *buf, int count)
{
        int c, ret = 0;
        while (1) {
                c = CIRC_SPACE_TO_END(cb->head, cb->tail, AIRCABLE_BUF_SIZE);
                if (count < c)
                        c = count;
                if (c <= 0)
                        break;
                memcpy(cb->buf + cb->head, buf, c);
                cb->head = (cb->head + c) & (AIRCABLE_BUF_SIZE-1);
                buf += c;
                count -= c;
                ret = c;
        }
        return ret;
}

/*
 * serial_buf_get
 *
 * Get data from the circular buffer and copy to the given buffer.
 * Restrict to the amount of data available.
 *
 * Return the number of bytes copied.
 */
static int serial_buf_get(struct circ_buf *cb, char *buf, int count)
{
        int c, ret = 0;
        while (1) {
                c = CIRC_CNT_TO_END(cb->head, cb->tail, AIRCABLE_BUF_SIZE);
                if (count < c)
                        c = count;
                if (c <= 0)
                        break;
                memcpy(buf, cb->buf + cb->tail, c);
                cb->tail = (cb->tail + c) & (AIRCABLE_BUF_SIZE-1);
                buf += c;
                count -= c;
                ret = c;
        }
        return ret;
}

/* End of circula buffer methods */

static void aircable_send(struct usb_serial_port *port)
{
        int count, result;
        struct aircable_private *priv = usb_get_serial_port_data(port);
        unsigned char *buf;
        __le16 *dbuf;
        dbg("%s - port %d", __func__, port->number);
        if (port->write_urb_busy)
                return;

        count = min(serial_buf_data_avail(priv->tx_buf), MAX_HCI_FRAMESIZE);
        if (count == 0)
                return;

        buf = kzalloc(count + HCI_HEADER_LENGTH, GFP_ATOMIC);
        if (!buf) {
                dev_err(&port->dev, "%s- kzalloc(%d) failed.\n",
                        __func__, count + HCI_HEADER_LENGTH);
                return;
        }

        buf[0] = TX_HEADER_0;
        buf[1] = TX_HEADER_1;
        dbuf = (__le16 *)&buf[2];
        *dbuf = cpu_to_le16((u16)count);
        serial_buf_get(priv->tx_buf, buf + HCI_HEADER_LENGTH,
                                                        MAX_HCI_FRAMESIZE);

        memcpy(port->write_urb->transfer_buffer, buf,
               count + HCI_HEADER_LENGTH);

        kfree(buf);
        port->write_urb_busy = 1;
        usb_serial_debug_data(debug, &port->dev, __func__,
                              count + HCI_HEADER_LENGTH,
                              port->write_urb->transfer_buffer);
        port->write_urb->transfer_buffer_length = count + HCI_HEADER_LENGTH;
        port->write_urb->dev = port->serial->dev;
        result = usb_submit_urb(port->write_urb, GFP_ATOMIC);

        if (result) {
                dev_err(&port->dev,
                        "%s - failed submitting write urb, error %d\n",
                        __func__, result);
                port->write_urb_busy = 0;
        }

        schedule_work(&port->work);
}

static void aircable_read(struct work_struct *work)
{
        struct aircable_private *priv =
                container_of(work, struct aircable_private, rx_work);
        struct usb_serial_port *port = priv->port;
        struct tty_struct *tty;
        unsigned char *data;
        int count;
        if (priv->rx_flags & THROTTLED) {
                if (priv->rx_flags & ACTUALLY_THROTTLED)
                        schedule_work(&priv->rx_work);
                return;
        }

        /* By now I will flush data to the tty in packages of no more than
         * 64 bytes, to ensure I do not get throttled.
         * Ask USB mailing list for better aproach.
         */
        tty = tty_port_tty_get(&port->port);

        if (!tty) {
                schedule_work(&priv->rx_work);
                dev_err(&port->dev, "%s - No tty available\n", __func__);
                return ;
        }

        count = min(64, serial_buf_data_avail(priv->rx_buf));

        if (count <= 0)
                goto out; /* We have finished sending everything. */

        tty_prepare_flip_string(tty, &data, count);
        if (!data) {
                dev_err(&port->dev, "%s- kzalloc(%d) failed.",
                                                        __func__, count);
                goto out;
        }

        serial_buf_get(priv->rx_buf, data, count);

        tty_flip_buffer_push(tty);

        if (serial_buf_data_avail(priv->rx_buf))
                schedule_work(&priv->rx_work);
out:            
        tty_kref_put(tty);
        return;
}
/* End of private methods */

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)) {
                        dbg("found bulk out on endpoint %d", i);
                        ++num_bulk_out;
                }
        }

        if (num_bulk_out == 0) {
                dbg("Invalid interface, discarding");
                return -ENODEV;
        }

        return 0;
}

static int aircable_attach(struct usb_serial *serial)
{
        struct usb_serial_port *port = serial->port[0];
        struct aircable_private *priv;

        priv = kzalloc(sizeof(struct aircable_private), GFP_KERNEL);
        if (!priv) {
                dev_err(&port->dev, "%s- kmalloc(%Zd) failed.\n", __func__,
                        sizeof(struct aircable_private));
                return -ENOMEM;
        }

        /* Allocation of Circular Buffers */
        priv->tx_buf = serial_buf_alloc();
        if (priv->tx_buf == NULL) {
                kfree(priv);
                return -ENOMEM;
        }

        priv->rx_buf = serial_buf_alloc();
        if (priv->rx_buf == NULL) {
                kfree(priv->tx_buf);
                kfree(priv);
                return -ENOMEM;
        }

        priv->rx_flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
        priv->port = port;
        INIT_WORK(&priv->rx_work, aircable_read);

        usb_set_serial_port_data(serial->port[0], priv);

        return 0;
}

static void aircable_release(struct usb_serial *serial)
{

        struct usb_serial_port *port = serial->port[0];
        struct aircable_private *priv = usb_get_serial_port_data(port);

        dbg("%s", __func__);

        if (priv) {
                serial_buf_free(priv->tx_buf);
                serial_buf_free(priv->rx_buf);
                kfree(priv);
        }
}

static int aircable_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct aircable_private *priv = usb_get_serial_port_data(port);
        return serial_buf_data_avail(priv->tx_buf);
}

static int aircable_write(struct tty_struct *tty, struct usb_serial_port *port,
                          const unsigned char *source, int count)
{
        struct aircable_private *priv = usb_get_serial_port_data(port);
        int temp;

        dbg("%s - port %d, %d bytes", __func__, port->number, count);

        usb_serial_debug_data(debug, &port->dev, __func__, count, source);

        if (!count) {
                dbg("%s - write request of 0 bytes", __func__);
                return count;
        }

        temp = serial_buf_put(priv->tx_buf, source, count);

        aircable_send(port);

        if (count > AIRCABLE_BUF_SIZE)
                count = AIRCABLE_BUF_SIZE;

        return count;

}

static void aircable_write_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        int status = urb->status;
        int result;

        dbg("%s - urb status: %d", __func__ , status);

        /* This has been taken from cypress_m8.c cypress_write_int_callback */
        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* this urb is terminated, clean up */
                dbg("%s - urb shutting down with status: %d",
                    __func__, status);
                port->write_urb_busy = 0;
                return;
        default:
                /* error in the urb, so we have to resubmit it */
                dbg("%s - Overflow in write", __func__);
                dbg("%s - nonzero write bulk status received: %d",
                    __func__, status);
                port->write_urb->transfer_buffer_length = 1;
                port->write_urb->dev = port->serial->dev;
                result = usb_submit_urb(port->write_urb, GFP_ATOMIC);
                if (result)
                        dev_err(&urb->dev->dev,
                            "%s - failed resubmitting write urb, error %d\n",
                                                        __func__, result);
                else
                        return;
        }

        port->write_urb_busy = 0;

        aircable_send(port);
}

static void aircable_read_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        struct aircable_private *priv = usb_get_serial_port_data(port);
        struct tty_struct *tty;
        unsigned long no_packages, remaining, package_length, i;
        int result, shift = 0;
        unsigned char *temp;
        int status = urb->status;

        dbg("%s - port %d", __func__, port->number);

        if (status) {
                dbg("%s - urb status = %d", __func__, status);
                if (!port->port.count) {
                        dbg("%s - port is closed, exiting.", __func__);
                        return;
                }
                if (status == -EPROTO) {
                        dbg("%s - caught -EPROTO, resubmitting the urb",
                            __func__);
                        usb_fill_bulk_urb(port->read_urb, port->serial->dev,
                                usb_rcvbulkpipe(port->serial->dev,
                                        port->bulk_in_endpointAddress),
                                port->read_urb->transfer_buffer,
                                port->read_urb->transfer_buffer_length,
                                aircable_read_bulk_callback, port);

                        result = usb_submit_urb(urb, GFP_ATOMIC);
                        if (result)
                                dev_err(&urb->dev->dev,
                                        "%s - failed resubmitting read urb, error %d\n",
                                        __func__, result);
                        return;
                }
                dbg("%s - unable to handle the error, exiting.", __func__);
                return;
        }

        usb_serial_debug_data(debug, &port->dev, __func__,
                                urb->actual_length, urb->transfer_buffer);

        tty = tty_port_tty_get(&port->port);
        if (tty && urb->actual_length) {
                if (urb->actual_length <= 2) {
                        /* This is an incomplete package */
                        serial_buf_put(priv->rx_buf, urb->transfer_buffer,
                                       urb->actual_length);
                } else {
                        temp = urb->transfer_buffer;
                        if (temp[0] == RX_HEADER_0)
                                shift = HCI_HEADER_LENGTH;

                        remaining = urb->actual_length;
                        no_packages = urb->actual_length / (HCI_COMPLETE_FRAME);

                        if (urb->actual_length % HCI_COMPLETE_FRAME != 0)
                                no_packages++;

                        for (i = 0; i < no_packages; i++) {
                                if (remaining > (HCI_COMPLETE_FRAME))
                                        package_length = HCI_COMPLETE_FRAME;
                                else
                                        package_length = remaining;
                                remaining -= package_length;

                                serial_buf_put(priv->rx_buf,
                                        urb->transfer_buffer + shift +
                                        (HCI_COMPLETE_FRAME) * (i),
                                        package_length - shift);
                        }
                }
                aircable_read(&priv->rx_work);
        }
        tty_kref_put(tty);

        /* Schedule the next read _if_ we are still open */
        if (port->port.count) {
                usb_fill_bulk_urb(port->read_urb, port->serial->dev,
                                  usb_rcvbulkpipe(port->serial->dev,
                                          port->bulk_in_endpointAddress),
                                  port->read_urb->transfer_buffer,
                                  port->read_urb->transfer_buffer_length,
                                  aircable_read_bulk_callback, port);

                result = usb_submit_urb(urb, GFP_ATOMIC);
                if (result)
                        dev_err(&urb->dev->dev,
                                "%s - failed resubmitting read urb, error %d\n",
                                __func__, result);
        }

        return;
}

/* Based on ftdi_sio.c throttle */
static void aircable_throttle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct aircable_private *priv = usb_get_serial_port_data(port);

        dbg("%s - port %d", __func__, port->number);

        spin_lock_irq(&priv->rx_lock);
        priv->rx_flags |= THROTTLED;
        spin_unlock_irq(&priv->rx_lock);
}

/* Based on ftdi_sio.c unthrottle */
static void aircable_unthrottle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct aircable_private *priv = usb_get_serial_port_data(port);
        int actually_throttled;

        dbg("%s - port %d", __func__, port->number);

        spin_lock_irq(&priv->rx_lock);
        actually_throttled = priv->rx_flags & ACTUALLY_THROTTLED;
        priv->rx_flags &= ~(THROTTLED | ACTUALLY_THROTTLED);
        spin_unlock_irq(&priv->rx_lock);

        if (actually_throttled)
                schedule_work(&priv->rx_work);
}

static struct usb_driver aircable_driver = {
        .name =         "aircable",
        .probe =        usb_serial_probe,
        .disconnect =   usb_serial_disconnect,
        .id_table =     id_table,
        .no_dynamic_id =        1,
};

static struct usb_serial_driver aircable_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "aircable",
        },
        .usb_driver =           &aircable_driver,
        .id_table =             id_table,
        .num_ports =            1,
        .attach =               aircable_attach,
        .probe =                aircable_probe,
        .release =              aircable_release,
        .write =                aircable_write,
        .write_room =           aircable_write_room,
        .write_bulk_callback =  aircable_write_bulk_callback,
        .read_bulk_callback =   aircable_read_bulk_callback,
        .throttle =             aircable_throttle,
        .unthrottle =           aircable_unthrottle,
};

static int __init aircable_init(void)
{
        int retval;
        retval = usb_serial_register(&aircable_device);
        if (retval)
                goto failed_serial_register;
        retval = usb_register(&aircable_driver);
        if (retval)
                goto failed_usb_register;
        return 0;

failed_usb_register:
        usb_serial_deregister(&aircable_device);
failed_serial_register:
        return retval;
}

static void __exit aircable_exit(void)
{
        usb_deregister(&aircable_driver);
        usb_serial_deregister(&aircable_device);
}

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

module_init(aircable_init);
module_exit(aircable_exit);

module_param(debug, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(debug, "Debug enabled or not");