/*
 * USB ZyXEL omni.net LCD PLUS driver
 *
 *      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.
 *
 * See Documentation/usb/usb-serial.txt for more information on using this
 * driver
 *
 * Please report both successes and troubles to the author at omninet@kroah.com
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/uaccess.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>

#define DRIVER_AUTHOR "Alessandro Zummo"
#define DRIVER_DESC "USB ZyXEL omni.net LCD PLUS Driver"

#define ZYXEL_VENDOR_ID         0x0586
#define ZYXEL_OMNINET_ID        0x1000
/* This one seems to be a re-branded ZyXEL device */
#define BT_IGNITIONPRO_ID       0x2000

/* function prototypes */
static int  omninet_open(struct tty_struct *tty, struct usb_serial_port *port);
static void omninet_process_read_urb(struct urb *urb);
static void omninet_write_bulk_callback(struct urb *urb);
static int  omninet_write(struct tty_struct *tty, struct usb_serial_port *port,
                                const unsigned char *buf, int count);
static int  omninet_write_room(struct tty_struct *tty);
static void omninet_disconnect(struct usb_serial *serial);
static int omninet_port_probe(struct usb_serial_port *port);
static int omninet_port_remove(struct usb_serial_port *port);

static const struct usb_device_id id_table[] = {
        { USB_DEVICE(ZYXEL_VENDOR_ID, ZYXEL_OMNINET_ID) },
        { USB_DEVICE(ZYXEL_VENDOR_ID, BT_IGNITIONPRO_ID) },
        { }                                             /* Terminating entry */
};
MODULE_DEVICE_TABLE(usb, id_table);

static struct usb_serial_driver zyxel_omninet_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "omninet",
        },
        .description =          "ZyXEL - omni.net lcd plus usb",
        .id_table =             id_table,
        .num_ports =            1,
        .port_probe =           omninet_port_probe,
        .port_remove =          omninet_port_remove,
        .open =                 omninet_open,
        .write =                omninet_write,
        .write_room =           omninet_write_room,
        .write_bulk_callback =  omninet_write_bulk_callback,
        .process_read_urb =     omninet_process_read_urb,
        .disconnect =           omninet_disconnect,
};

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


/*
 * The protocol.
 *
 * The omni.net always exchange 64 bytes of data with the host. The first
 * four bytes are the control header.
 *
 * oh_seq is a sequence number. Don't know if/how it's used.
 * oh_len is the length of the data bytes in the packet.
 * oh_xxx Bit-mapped, related to handshaking and status info.
 *      I normally set it to 0x03 in transmitted frames.
 *      7: Active when the TA is in a CONNECTed state.
 *      6: unknown
 *      5: handshaking, unknown
 *      4: handshaking, unknown
 *      3: unknown, usually 0
 *      2: unknown, usually 0
 *      1: handshaking, unknown, usually set to 1 in transmitted frames
 *      0: handshaking, unknown, usually set to 1 in transmitted frames
 * oh_pad Probably a pad byte.
 *
 * After the header you will find data bytes if oh_len was greater than zero.
 */
struct omninet_header {
        __u8    oh_seq;
        __u8    oh_len;
        __u8    oh_xxx;
        __u8    oh_pad;
};

struct omninet_data {
        __u8    od_outseq;      /* Sequence number for bulk_out URBs */
};

static int omninet_port_probe(struct usb_serial_port *port)
{
        struct omninet_data *od;

        od = kzalloc(sizeof(*od), GFP_KERNEL);
        if (!od)
                return -ENOMEM;

        usb_set_serial_port_data(port, od);

        return 0;
}

static int omninet_port_remove(struct usb_serial_port *port)
{
        struct omninet_data *od;

        od = usb_get_serial_port_data(port);
        kfree(od);

        return 0;
}

static int omninet_open(struct tty_struct *tty, struct usb_serial_port *port)
{
        struct usb_serial       *serial = port->serial;
        struct usb_serial_port  *wport;

        wport = serial->port[1];
        tty_port_tty_set(&wport->port, tty);

        return usb_serial_generic_open(tty, port);
}

#define OMNINET_HEADERLEN       4
#define OMNINET_BULKOUTSIZE     64
#define OMNINET_PAYLOADSIZE     (OMNINET_BULKOUTSIZE - OMNINET_HEADERLEN)

static void omninet_process_read_urb(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        const struct omninet_header *hdr = urb->transfer_buffer;
        const unsigned char *data;
        size_t data_len;

        if (urb->actual_length <= OMNINET_HEADERLEN || !hdr->oh_len)
                return;

        data = (char *)urb->transfer_buffer + OMNINET_HEADERLEN;
        data_len = min_t(size_t, urb->actual_length - OMNINET_HEADERLEN,
                                                                hdr->oh_len);
        tty_insert_flip_string(&port->port, data, data_len);
        tty_flip_buffer_push(&port->port);
}

static int omninet_write(struct tty_struct *tty, struct usb_serial_port *port,
                                        const unsigned char *buf, int count)
{
        struct usb_serial *serial = port->serial;
        struct usb_serial_port *wport = serial->port[1];

        struct omninet_data *od = usb_get_serial_port_data(port);
        struct omninet_header *header = (struct omninet_header *)
                                        wport->write_urb->transfer_buffer;

        int                     result;

        if (count == 0) {
                dev_dbg(&port->dev, "%s - write request of 0 bytes\n", __func__);
                return 0;
        }

        if (!test_and_clear_bit(0, &port->write_urbs_free)) {
                dev_dbg(&port->dev, "%s - already writing\n", __func__);
                return 0;
        }

        count = (count > OMNINET_PAYLOADSIZE) ? OMNINET_PAYLOADSIZE : count;

        memcpy(wport->write_urb->transfer_buffer + OMNINET_HEADERLEN,
                                                                buf, count);

        usb_serial_debug_data(&port->dev, __func__, count,
                              wport->write_urb->transfer_buffer);

        header->oh_seq  = od->od_outseq++;
        header->oh_len  = count;
        header->oh_xxx  = 0x03;
        header->oh_pad  = 0x00;

        /* send the data out the bulk port, always 64 bytes */
        wport->write_urb->transfer_buffer_length = OMNINET_BULKOUTSIZE;

        result = usb_submit_urb(wport->write_urb, GFP_ATOMIC);
        if (result) {
                set_bit(0, &wport->write_urbs_free);
                dev_err_console(port,
                        "%s - failed submitting write urb, error %d\n",
                        __func__, result);
        } else
                result = count;

        return result;
}


static int omninet_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct usb_serial       *serial = port->serial;
        struct usb_serial_port  *wport  = serial->port[1];

        int room = 0; /* Default: no room */

        if (test_bit(0, &wport->write_urbs_free))
                room = wport->bulk_out_size - OMNINET_HEADERLEN;

        dev_dbg(&port->dev, "%s - returns %d\n", __func__, room);

        return room;
}

static void omninet_write_bulk_callback(struct urb *urb)
{
/*      struct omninet_header   *header = (struct omninet_header  *)
                                                urb->transfer_buffer; */
        struct usb_serial_port  *port   =  urb->context;
        int status = urb->status;

        set_bit(0, &port->write_urbs_free);
        if (status) {
                dev_dbg(&port->dev, "%s - nonzero write bulk status received: %d\n",
                        __func__, status);
                return;
        }

        usb_serial_port_softint(port);
}


static void omninet_disconnect(struct usb_serial *serial)
{
        struct usb_serial_port *wport = serial->port[1];

        usb_kill_urb(wport->write_urb);
}

module_usb_serial_driver(serial_drivers, id_table);

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