/*
 * USB Serial Converter Generic functions
 *
 * Copyright (C) 2010 Johan Hovold (jhovold@gmail.com)
 * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.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.
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/uaccess.h>
#include <linux/kfifo.h>
#include <linux/serial.h>

static int debug;

#ifdef CONFIG_USB_SERIAL_GENERIC

static int generic_probe(struct usb_interface *interface,
                         const struct usb_device_id *id);

static __u16 vendor  = 0x05f9;
static __u16 product = 0xffff;

module_param(vendor, ushort, 0);
MODULE_PARM_DESC(vendor, "User specified USB idVendor");

module_param(product, ushort, 0);
MODULE_PARM_DESC(product, "User specified USB idProduct");

static struct usb_device_id generic_device_ids[2]; /* Initially all zeroes. */

/* we want to look at all devices, as the vendor/product id can change
 * depending on the command line argument */
static const struct usb_device_id generic_serial_ids[] = {
        {.driver_info = 42},
        {}
};

static struct usb_driver generic_driver = {
        .name =         "usbserial_generic",
        .probe =        generic_probe,
        .disconnect =   usb_serial_disconnect,
        .id_table =     generic_serial_ids,
        .no_dynamic_id =        1,
};

/* All of the device info needed for the Generic Serial Converter */
struct usb_serial_driver usb_serial_generic_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "generic",
        },
        .id_table =             generic_device_ids,
        .usb_driver =           &generic_driver,
        .num_ports =            1,
        .disconnect =           usb_serial_generic_disconnect,
        .release =              usb_serial_generic_release,
        .throttle =             usb_serial_generic_throttle,
        .unthrottle =           usb_serial_generic_unthrottle,
        .resume =               usb_serial_generic_resume,
};

static int generic_probe(struct usb_interface *interface,
                               const struct usb_device_id *id)
{
        const struct usb_device_id *id_pattern;

        id_pattern = usb_match_id(interface, generic_device_ids);
        if (id_pattern != NULL)
                return usb_serial_probe(interface, id);
        return -ENODEV;
}
#endif

int usb_serial_generic_register(int _debug)
{
        int retval = 0;

        debug = _debug;
#ifdef CONFIG_USB_SERIAL_GENERIC
        generic_device_ids[0].idVendor = vendor;
        generic_device_ids[0].idProduct = product;
        generic_device_ids[0].match_flags =
                USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT;

        /* register our generic driver with ourselves */
        retval = usb_serial_register(&usb_serial_generic_device);
        if (retval)
                goto exit;
        retval = usb_register(&generic_driver);
        if (retval)
                usb_serial_deregister(&usb_serial_generic_device);
exit:
#endif
        return retval;
}

void usb_serial_generic_deregister(void)
{
#ifdef CONFIG_USB_SERIAL_GENERIC
        /* remove our generic driver */
        usb_deregister(&generic_driver);
        usb_serial_deregister(&usb_serial_generic_device);
#endif
}

int usb_serial_generic_open(struct tty_struct *tty, struct usb_serial_port *port)
{
        int result = 0;
        unsigned long flags;

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

        /* clear the throttle flags */
        spin_lock_irqsave(&port->lock, flags);
        port->throttled = 0;
        port->throttle_req = 0;
        spin_unlock_irqrestore(&port->lock, flags);

        /* if we have a bulk endpoint, start reading from it */
        if (port->bulk_in_size)
                result = usb_serial_generic_submit_read_urb(port, GFP_KERNEL);

        return result;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_open);

static void generic_cleanup(struct usb_serial_port *port)
{
        struct usb_serial *serial = port->serial;
        unsigned long flags;
        int i;

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

        if (serial->dev) {
                /* shutdown any bulk transfers that might be going on */
                if (port->bulk_out_size) {
                        usb_kill_urb(port->write_urb);
                        for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
                                usb_kill_urb(port->write_urbs[i]);

                        spin_lock_irqsave(&port->lock, flags);
                        kfifo_reset_out(&port->write_fifo);
                        spin_unlock_irqrestore(&port->lock, flags);
                }
                if (port->bulk_in_size)
                        usb_kill_urb(port->read_urb);
        }
}

void usb_serial_generic_close(struct usb_serial_port *port)
{
        dbg("%s - port %d", __func__, port->number);
        generic_cleanup(port);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_close);

int usb_serial_generic_prepare_write_buffer(struct usb_serial_port *port,
                                                void *dest, size_t size)
{
        return kfifo_out_locked(&port->write_fifo, dest, size, &port->lock);
}

/**
 * usb_serial_generic_write_start - kick off an URB write
 * @port:       Pointer to the &struct usb_serial_port data
 *
 * Returns zero on success, or a negative errno value
 */
static int usb_serial_generic_write_start(struct usb_serial_port *port)
{
        struct urb *urb;
        int count, result;
        unsigned long flags;
        int i;

        if (test_and_set_bit_lock(USB_SERIAL_WRITE_BUSY, &port->flags))
                return 0;
retry:
        spin_lock_irqsave(&port->lock, flags);
        if (!port->write_urbs_free || !kfifo_len(&port->write_fifo)) {
                clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
                spin_unlock_irqrestore(&port->lock, flags);
                return 0;
        }
        i = (int)find_first_bit(&port->write_urbs_free,
                                                ARRAY_SIZE(port->write_urbs));
        spin_unlock_irqrestore(&port->lock, flags);

        urb = port->write_urbs[i];
        count = port->serial->type->prepare_write_buffer(port,
                                                urb->transfer_buffer,
                                                port->bulk_out_size);
        urb->transfer_buffer_length = count;
        usb_serial_debug_data(debug, &port->dev, __func__, count,
                                                urb->transfer_buffer);
        spin_lock_irqsave(&port->lock, flags);
        port->tx_bytes += count;
        spin_unlock_irqrestore(&port->lock, flags);

        clear_bit(i, &port->write_urbs_free);
        result = usb_submit_urb(urb, GFP_ATOMIC);
        if (result) {
                dev_err(&port->dev, "%s - error submitting urb: %d\n",
                                                __func__, result);
                set_bit(i, &port->write_urbs_free);
                spin_lock_irqsave(&port->lock, flags);
                port->tx_bytes -= count;
                spin_unlock_irqrestore(&port->lock, flags);

                clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);
                return result;
        }

        /* Try sending off another urb, unless in irq context (in which case
         * there will be no free urb). */
        if (!in_irq())
                goto retry;

        clear_bit_unlock(USB_SERIAL_WRITE_BUSY, &port->flags);

        return 0;
}

/**
 * usb_serial_generic_write - generic write function for serial USB devices
 * @tty:        Pointer to &struct tty_struct for the device
 * @port:       Pointer to the &usb_serial_port structure for the device
 * @buf:        Pointer to the data to write
 * @count:      Number of bytes to write
 *
 * Returns the number of characters actually written, which may be anything
 * from zero to @count. If an error occurs, it returns the negative errno
 * value.
 */
int usb_serial_generic_write(struct tty_struct *tty,
        struct usb_serial_port *port, const unsigned char *buf, int count)
{
        int result;

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

        /* only do something if we have a bulk out endpoint */
        if (!port->bulk_out_size)
                return -ENODEV;

        if (!count)
                return 0;

        count = kfifo_in_locked(&port->write_fifo, buf, count, &port->lock);
        result = usb_serial_generic_write_start(port);
        if (result)
                return result;

        return count;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_write);

int usb_serial_generic_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        unsigned long flags;
        int room;

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

        if (!port->bulk_out_size)
                return 0;

        spin_lock_irqsave(&port->lock, flags);
        room = kfifo_avail(&port->write_fifo);
        spin_unlock_irqrestore(&port->lock, flags);

        dbg("%s - returns %d", __func__, room);
        return room;
}

int usb_serial_generic_chars_in_buffer(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        unsigned long flags;
        int chars;

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

        if (!port->bulk_out_size)
                return 0;

        spin_lock_irqsave(&port->lock, flags);
        chars = kfifo_len(&port->write_fifo) + port->tx_bytes;
        spin_unlock_irqrestore(&port->lock, flags);

        dbg("%s - returns %d", __func__, chars);
        return chars;
}

int usb_serial_generic_submit_read_urb(struct usb_serial_port *port,
                                        gfp_t mem_flags)
{
        int result;

        result = usb_submit_urb(port->read_urb, mem_flags);
        if (result && result != -EPERM) {
                dev_err(&port->dev, "%s - error submitting urb: %d\n",
                                                        __func__, result);
        }
        return result;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_submit_read_urb);

void usb_serial_generic_process_read_urb(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        struct tty_struct *tty;
        char *ch = (char *)urb->transfer_buffer;
        int i;

        if (!urb->actual_length)
                return;

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

        /* The per character mucking around with sysrq path it too slow for
           stuff like 3G modems, so shortcircuit it in the 99.9999999% of cases
           where the USB serial is not a console anyway */
        if (!port->port.console || !port->sysrq)
                tty_insert_flip_string(tty, ch, urb->actual_length);
        else {
                for (i = 0; i < urb->actual_length; i++, ch++) {
                        if (!usb_serial_handle_sysrq_char(port, *ch))
                                tty_insert_flip_char(tty, *ch, TTY_NORMAL);
                }
        }
        tty_flip_buffer_push(tty);
        tty_kref_put(tty);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_process_read_urb);

void usb_serial_generic_read_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port = urb->context;
        unsigned char *data = urb->transfer_buffer;
        int status = urb->status;
        unsigned long flags;

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

        if (unlikely(status != 0)) {
                dbg("%s - nonzero read bulk status received: %d",
                    __func__, status);
                return;
        }

        usb_serial_debug_data(debug, &port->dev, __func__,
                                                urb->actual_length, data);
        port->serial->type->process_read_urb(urb);

        /* Throttle the device if requested by tty */
        spin_lock_irqsave(&port->lock, flags);
        port->throttled = port->throttle_req;
        if (!port->throttled) {
                spin_unlock_irqrestore(&port->lock, flags);
                usb_serial_generic_submit_read_urb(port, GFP_ATOMIC);
        } else
                spin_unlock_irqrestore(&port->lock, flags);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_read_bulk_callback);

void usb_serial_generic_write_bulk_callback(struct urb *urb)
{
        unsigned long flags;
        struct usb_serial_port *port = urb->context;
        int status = urb->status;
        int i;

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

        for (i = 0; i < ARRAY_SIZE(port->write_urbs); ++i)
                if (port->write_urbs[i] == urb)
                        break;

        spin_lock_irqsave(&port->lock, flags);
        port->tx_bytes -= urb->transfer_buffer_length;
        set_bit(i, &port->write_urbs_free);
        spin_unlock_irqrestore(&port->lock, flags);

        if (status) {
                dbg("%s - non-zero urb status: %d", __func__, status);

                spin_lock_irqsave(&port->lock, flags);
                kfifo_reset_out(&port->write_fifo);
                spin_unlock_irqrestore(&port->lock, flags);
        } else {
                usb_serial_generic_write_start(port);
        }

        usb_serial_port_softint(port);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_write_bulk_callback);

void usb_serial_generic_throttle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        unsigned long flags;

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

        /* Set the throttle request flag. It will be picked up
         * by usb_serial_generic_read_bulk_callback(). */
        spin_lock_irqsave(&port->lock, flags);
        port->throttle_req = 1;
        spin_unlock_irqrestore(&port->lock, flags);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_throttle);

void usb_serial_generic_unthrottle(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        int was_throttled;

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

        /* Clear the throttle flags */
        spin_lock_irq(&port->lock);
        was_throttled = port->throttled;
        port->throttled = port->throttle_req = 0;
        spin_unlock_irq(&port->lock);

        if (was_throttled)
                usb_serial_generic_submit_read_urb(port, GFP_KERNEL);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_unthrottle);

#ifdef CONFIG_MAGIC_SYSRQ
int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
{
        if (port->sysrq && port->port.console) {
                if (ch && time_before(jiffies, port->sysrq)) {
                        handle_sysrq(ch);
                        port->sysrq = 0;
                        return 1;
                }
                port->sysrq = 0;
        }
        return 0;
}
#else
int usb_serial_handle_sysrq_char(struct usb_serial_port *port, unsigned int ch)
{
        return 0;
}
#endif
EXPORT_SYMBOL_GPL(usb_serial_handle_sysrq_char);

int usb_serial_handle_break(struct usb_serial_port *port)
{
        if (!port->sysrq) {
                port->sysrq = jiffies + HZ*5;
                return 1;
        }
        port->sysrq = 0;
        return 0;
}
EXPORT_SYMBOL_GPL(usb_serial_handle_break);

/**
 *      usb_serial_handle_dcd_change - handle a change of carrier detect state
 *      @port: usb_serial_port structure for the open port
 *      @tty: tty_struct structure for the port
 *      @status: new carrier detect status, nonzero if active
 */
void usb_serial_handle_dcd_change(struct usb_serial_port *usb_port,
                                struct tty_struct *tty, unsigned int status)
{
        struct tty_port *port = &usb_port->port;

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

        if (status)
                wake_up_interruptible(&port->open_wait);
        else if (tty && !C_CLOCAL(tty))
                tty_hangup(tty);
}
EXPORT_SYMBOL_GPL(usb_serial_handle_dcd_change);

int usb_serial_generic_resume(struct usb_serial *serial)
{
        struct usb_serial_port *port;
        int i, c = 0, r;

        for (i = 0; i < serial->num_ports; i++) {
                port = serial->port[i];
                if (!test_bit(ASYNCB_INITIALIZED, &port->port.flags))
                        continue;

                if (port->read_urb) {
                        r = usb_submit_urb(port->read_urb, GFP_NOIO);
                        if (r < 0)
                                c++;
                }

                if (port->bulk_out_size) {
                        r = usb_serial_generic_write_start(port);
                        if (r < 0)
                                c++;
                }
        }

        return c ? -EIO : 0;
}
EXPORT_SYMBOL_GPL(usb_serial_generic_resume);

void usb_serial_generic_disconnect(struct usb_serial *serial)
{
        int i;

        dbg("%s", __func__);

        /* stop reads and writes on all ports */
        for (i = 0; i < serial->num_ports; ++i)
                generic_cleanup(serial->port[i]);
}
EXPORT_SYMBOL_GPL(usb_serial_generic_disconnect);

void usb_serial_generic_release(struct usb_serial *serial)
{
        dbg("%s", __func__);
}