/*
 * Symbol USB barcode to serial driver
 *
 * Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
 * Copyright (C) 2009 Greg Kroah-Hartman <gregkh@suse.de>
 * Copyright (C) 2009 Novell Inc.
 *
 *      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.
 */

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

static const struct usb_device_id id_table[] = {
        { USB_DEVICE(0x05e0, 0x0600) },
        { },
};
MODULE_DEVICE_TABLE(usb, id_table);

struct symbol_private {
        spinlock_t lock;        /* protects the following flags */
        bool throttled;
        bool actually_throttled;
};

static void symbol_int_callback(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        struct symbol_private *priv = usb_get_serial_port_data(port);
        unsigned char *data = urb->transfer_buffer;
        int status = urb->status;
        int result;
        int data_length;

        switch (status) {
        case 0:
                /* success */
                break;
        case -ECONNRESET:
        case -ENOENT:
        case -ESHUTDOWN:
                /* this urb is terminated, clean up */
                dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
                        __func__, status);
                return;
        default:
                dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
                        __func__, status);
                goto exit;
        }

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

        if (urb->actual_length > 1) {
                data_length = urb->actual_length - 1;

                /*
                 * Data from the device comes with a 1 byte header:
                 *
                 * <size of data>data...
                 *      This is real data to be sent to the tty layer
                 * we pretty much just ignore the size and send everything
                 * else to the tty layer.
                 */
                tty_insert_flip_string(&port->port, &data[1], data_length);
                tty_flip_buffer_push(&port->port);
        } else {
                dev_dbg(&port->dev,
                        "Improper amount of data received from the device, "
                        "%d bytes", urb->actual_length);
        }

exit:
        spin_lock(&priv->lock);

        /* Continue trying to always read if we should */
        if (!priv->throttled) {
                result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
                if (result)
                        dev_err(&port->dev,
                            "%s - failed resubmitting read urb, error %d\n",
                                                        __func__, result);
        } else
                priv->actually_throttled = true;
        spin_unlock(&priv->lock);
}

static int symbol_open(struct tty_struct *tty, struct usb_serial_port *port)
{
        struct symbol_private *priv = usb_get_serial_data(port->serial);
        unsigned long flags;
        int result = 0;

        spin_lock_irqsave(&priv->lock, flags);
        priv->throttled = false;
        priv->actually_throttled = false;
        spin_unlock_irqrestore(&priv->lock, flags);

        /* Start reading from the device */
        result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
        if (result)
                dev_err(&port->dev,
                        "%s - failed resubmitting read urb, error %d\n",
                        __func__, result);
        return result;
}

static void symbol_close(struct usb_serial_port *port)
{
        usb_kill_urb(port->interrupt_in_urb);
}

static void symbol_throttle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct symbol_private *priv = usb_get_serial_data(port->serial);

        spin_lock_irq(&priv->lock);
        priv->throttled = true;
        spin_unlock_irq(&priv->lock);
}

static void symbol_unthrottle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        struct symbol_private *priv = usb_get_serial_data(port->serial);
        int result;
        bool was_throttled;

        spin_lock_irq(&priv->lock);
        priv->throttled = false;
        was_throttled = priv->actually_throttled;
        priv->actually_throttled = false;
        spin_unlock_irq(&priv->lock);

        if (was_throttled) {
                result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
                if (result)
                        dev_err(&port->dev,
                                "%s - failed submitting read urb, error %d\n",
                                                        __func__, result);
        }
}

static int symbol_startup(struct usb_serial *serial)
{
        if (!serial->num_interrupt_in) {
                dev_err(&serial->dev->dev, "no interrupt-in endpoint\n");
                return -ENODEV;
        }

        return 0;
}

static int symbol_port_probe(struct usb_serial_port *port)
{
        struct symbol_private *priv;

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

        spin_lock_init(&priv->lock);

        usb_set_serial_port_data(port, priv);

        return 0;
}

static int symbol_port_remove(struct usb_serial_port *port)
{
        struct symbol_private *priv = usb_get_serial_port_data(port);

        kfree(priv);

        return 0;
}

static struct usb_serial_driver symbol_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "symbol",
        },
        .id_table =             id_table,
        .num_ports =            1,
        .attach =               symbol_startup,
        .port_probe =           symbol_port_probe,
        .port_remove =          symbol_port_remove,
        .open =                 symbol_open,
        .close =                symbol_close,
        .throttle =             symbol_throttle,
        .unthrottle =           symbol_unthrottle,
        .read_int_callback =    symbol_int_callback,
};

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

module_usb_serial_driver(serial_drivers, id_table);

MODULE_LICENSE("GPL");