/*
 * Safe Encapsulated USB Serial Driver
 *
 *      Copyright (C) 2001 Lineo
 *      Copyright (C) 2001 Hewlett-Packard
 *
 *      This program is free software; you can redistribute it and/or modify
 *      it under the terms of the GNU General Public License as published by
 *      the Free Software Foundation; either version 2 of the License, or
 *      (at your option) any later version.
 *
 * By:
 *      Stuart Lynne <sl@lineo.com>, Tom Rushworth <tbr@lineo.com>
 */

/*
 * The encapsultaion is designed to overcome difficulties with some USB
 * hardware.
 *
 * While the USB protocol has a CRC over the data while in transit, i.e. while
 * being carried over the bus, there is no end to end protection. If the
 * hardware has any problems getting the data into or out of the USB transmit
 * and receive FIFO's then data can be lost.
 *
 * This protocol adds a two byte trailer to each USB packet to specify the
 * number of bytes of valid data and a 10 bit CRC that will allow the receiver
 * to verify that the entire USB packet was received without error.
 *
 * Because in this case the sender and receiver are the class and function
 * drivers there is now end to end protection.
 *
 * There is an additional option that can be used to force all transmitted
 * packets to be padded to the maximum packet size. This provides a work
 * around for some devices which have problems with small USB packets.
 *
 * Assuming a packetsize of N:
 *
 *      0..N-2  data and optional padding
 *
 *      N-2     bits 7-2 - number of bytes of valid data
 *              bits 1-0 top two bits of 10 bit CRC
 *      N-1     bottom 8 bits of 10 bit CRC
 *
 *
 *      | Data Length       | 10 bit CRC                                |
 *      + 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 | 7 . 6 . 5 . 4 . 3 . 2 . 1 . 0 +
 *
 * The 10 bit CRC is computed across the sent data, followed by the trailer
 * with the length set and the CRC set to zero. The CRC is then OR'd into
 * the trailer.
 *
 * When received a 10 bit CRC is computed over the entire frame including
 * the trailer and should be equal to zero.
 *
 * Two module parameters are used to control the encapsulation, if both are
 * turned of the module works as a simple serial device with NO
 * encapsulation.
 *
 * See linux/drivers/usbd/serial_fd for a device function driver
 * implementation of this.
 *
 */


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


#ifndef CONFIG_USB_SERIAL_SAFE_PADDED
#define CONFIG_USB_SERIAL_SAFE_PADDED 0
#endif

static int debug;
static int safe = 1;
static int padded = CONFIG_USB_SERIAL_SAFE_PADDED;

#define DRIVER_VERSION "v0.0b"
#define DRIVER_AUTHOR "sl@lineo.com, tbr@lineo.com"
#define DRIVER_DESC "USB Safe Encapsulated Serial"

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

static __u16 vendor;            /* no default */
static __u16 product;           /* no default */
module_param(vendor, ushort, 0);
MODULE_PARM_DESC(vendor, "User specified USB idVendor (required)");
module_param(product, ushort, 0);
MODULE_PARM_DESC(product, "User specified USB idProduct (required)");

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

module_param(safe, bool, 0);
MODULE_PARM_DESC(safe, "Turn Safe Encapsulation On/Off");

module_param(padded, bool, 0);
MODULE_PARM_DESC(padded, "Pad to full wMaxPacketSize On/Off");

#define CDC_DEVICE_CLASS                        0x02

#define CDC_INTERFACE_CLASS                     0x02
#define CDC_INTERFACE_SUBCLASS                  0x06

#define LINEO_INTERFACE_CLASS                   0xff

#define LINEO_INTERFACE_SUBCLASS_SAFENET        0x01
#define LINEO_SAFENET_CRC                       0x01
#define LINEO_SAFENET_CRC_PADDED                0x02

#define LINEO_INTERFACE_SUBCLASS_SAFESERIAL     0x02
#define LINEO_SAFESERIAL_CRC                    0x01
#define LINEO_SAFESERIAL_CRC_PADDED             0x02


#define MY_USB_DEVICE(vend, prod, dc, ic, isc) \
        .match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
                       USB_DEVICE_ID_MATCH_DEV_CLASS | \
                       USB_DEVICE_ID_MATCH_INT_CLASS | \
                       USB_DEVICE_ID_MATCH_INT_SUBCLASS, \
        .idVendor = (vend), \
        .idProduct = (prod),\
        .bDeviceClass = (dc),\
        .bInterfaceClass = (ic), \
        .bInterfaceSubClass = (isc),

static struct usb_device_id id_table[] = {
        {MY_USB_DEVICE(0x49f, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Itsy */
        {MY_USB_DEVICE(0x3f0, 0x2101, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Calypso */
        {MY_USB_DEVICE(0x4dd, 0x8001, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Iris */
        {MY_USB_DEVICE(0x4dd, 0x8002, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
        {MY_USB_DEVICE(0x4dd, 0x8003, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
        {MY_USB_DEVICE(0x4dd, 0x8004, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Collie */
        {MY_USB_DEVICE(0x5f9, 0xffff, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},   /* Sharp tmp */
        /* extra null entry for module vendor/produc parameters */
        {MY_USB_DEVICE(0, 0, CDC_DEVICE_CLASS, LINEO_INTERFACE_CLASS, LINEO_INTERFACE_SUBCLASS_SAFESERIAL)},
        {}                      /* terminating entry  */
};

MODULE_DEVICE_TABLE(usb, id_table);

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

static const __u16 crc10_table[256] = {
        0x000, 0x233, 0x255, 0x066, 0x299, 0x0aa, 0x0cc, 0x2ff,
        0x301, 0x132, 0x154, 0x367, 0x198, 0x3ab, 0x3cd, 0x1fe,
        0x031, 0x202, 0x264, 0x057, 0x2a8, 0x09b, 0x0fd, 0x2ce,
        0x330, 0x103, 0x165, 0x356, 0x1a9, 0x39a, 0x3fc, 0x1cf,
        0x062, 0x251, 0x237, 0x004, 0x2fb, 0x0c8, 0x0ae, 0x29d,
        0x363, 0x150, 0x136, 0x305, 0x1fa, 0x3c9, 0x3af, 0x19c,
        0x053, 0x260, 0x206, 0x035, 0x2ca, 0x0f9, 0x09f, 0x2ac,
        0x352, 0x161, 0x107, 0x334, 0x1cb, 0x3f8, 0x39e, 0x1ad,
        0x0c4, 0x2f7, 0x291, 0x0a2, 0x25d, 0x06e, 0x008, 0x23b,
        0x3c5, 0x1f6, 0x190, 0x3a3, 0x15c, 0x36f, 0x309, 0x13a,
        0x0f5, 0x2c6, 0x2a0, 0x093, 0x26c, 0x05f, 0x039, 0x20a,
        0x3f4, 0x1c7, 0x1a1, 0x392, 0x16d, 0x35e, 0x338, 0x10b,
        0x0a6, 0x295, 0x2f3, 0x0c0, 0x23f, 0x00c, 0x06a, 0x259,
        0x3a7, 0x194, 0x1f2, 0x3c1, 0x13e, 0x30d, 0x36b, 0x158,
        0x097, 0x2a4, 0x2c2, 0x0f1, 0x20e, 0x03d, 0x05b, 0x268,
        0x396, 0x1a5, 0x1c3, 0x3f0, 0x10f, 0x33c, 0x35a, 0x169,
        0x188, 0x3bb, 0x3dd, 0x1ee, 0x311, 0x122, 0x144, 0x377,
        0x289, 0x0ba, 0x0dc, 0x2ef, 0x010, 0x223, 0x245, 0x076,
        0x1b9, 0x38a, 0x3ec, 0x1df, 0x320, 0x113, 0x175, 0x346,
        0x2b8, 0x08b, 0x0ed, 0x2de, 0x021, 0x212, 0x274, 0x047,
        0x1ea, 0x3d9, 0x3bf, 0x18c, 0x373, 0x140, 0x126, 0x315,
        0x2eb, 0x0d8, 0x0be, 0x28d, 0x072, 0x241, 0x227, 0x014,
        0x1db, 0x3e8, 0x38e, 0x1bd, 0x342, 0x171, 0x117, 0x324,
        0x2da, 0x0e9, 0x08f, 0x2bc, 0x043, 0x270, 0x216, 0x025,
        0x14c, 0x37f, 0x319, 0x12a, 0x3d5, 0x1e6, 0x180, 0x3b3,
        0x24d, 0x07e, 0x018, 0x22b, 0x0d4, 0x2e7, 0x281, 0x0b2,
        0x17d, 0x34e, 0x328, 0x11b, 0x3e4, 0x1d7, 0x1b1, 0x382,
        0x27c, 0x04f, 0x029, 0x21a, 0x0e5, 0x2d6, 0x2b0, 0x083,
        0x12e, 0x31d, 0x37b, 0x148, 0x3b7, 0x184, 0x1e2, 0x3d1,
        0x22f, 0x01c, 0x07a, 0x249, 0x0b6, 0x285, 0x2e3, 0x0d0,
        0x11f, 0x32c, 0x34a, 0x179, 0x386, 0x1b5, 0x1d3, 0x3e0,
        0x21e, 0x02d, 0x04b, 0x278, 0x087, 0x2b4, 0x2d2, 0x0e1,
};

#define CRC10_INITFCS     0x000 /* Initial FCS value */
#define CRC10_GOODFCS     0x000 /* Good final FCS value */
#define CRC10_FCS(fcs, c) ((((fcs) << 8) & 0x3ff) ^ crc10_table[((fcs) >> 2) & 0xff] ^ (c))

/**
 * fcs_compute10 - memcpy and calculate 10 bit CRC across buffer
 * @sp: pointer to buffer
 * @len: number of bytes
 * @fcs: starting FCS
 *
 * Perform a memcpy and calculate fcs using ppp 10bit CRC algorithm. Return
 * new 10 bit FCS.
 */
static __u16 __inline__ fcs_compute10(unsigned char *sp, int len, __u16 fcs)
{
        for (; len-- > 0; fcs = CRC10_FCS(fcs, *sp++));
        return fcs;
}

static void safe_read_bulk_callback(struct urb *urb)
{
        struct usb_serial_port *port =  urb->context;
        unsigned char *data = urb->transfer_buffer;
        unsigned char length = urb->actual_length;
        struct tty_struct *tty;
        int result;
        int status = urb->status;

        dbg("%s", __func__);

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

        dbg("safe_read_bulk_callback length: %d",
                                        port->read_urb->actual_length);
#ifdef ECHO_RCV
        {
                int i;
                unsigned char *cp = port->read_urb->transfer_buffer;
                for (i = 0; i < port->read_urb->actual_length; i++) {
                        if ((i % 32) == 0)
                                printk("\nru[%02x] ", i);
                        printk("%02x ", *cp++);
                }
                printk("\n");
        }
#endif
        tty = tty_port_tty_get(&port->port);
        if (safe) {
                __u16 fcs;
                fcs = fcs_compute10(data, length, CRC10_INITFCS);
                if (!fcs) {
                        int actual_length = data[length - 2] >> 2;
                        if (actual_length <= (length - 2)) {
                                dev_info(&urb->dev->dev, "%s - actual: %d\n",
                                         __func__, actual_length);
                                tty_insert_flip_string(tty,
                                                        data, actual_length);
                                tty_flip_buffer_push(tty);
                        } else {
                                dev_err(&port->dev,
                                        "%s - inconsistent lengths %d:%d\n",
                                        __func__, actual_length, length);
                        }
                } else {
                        dev_err(&port->dev, "%s - bad CRC %x\n", __func__, fcs);
                }
        } else {
                tty_insert_flip_string(tty, data, length);
                tty_flip_buffer_push(tty);
        }
        tty_kref_put(tty);

        /* Continue trying to always read  */
        usb_fill_bulk_urb(urb, port->serial->dev,
                        usb_rcvbulkpipe(port->serial->dev,
                                        port->bulk_in_endpointAddress),
                        urb->transfer_buffer, urb->transfer_buffer_length,
                        safe_read_bulk_callback, port);

        result = usb_submit_urb(urb, GFP_ATOMIC);
        if (result)
                dev_err(&port->dev,
                        "%s - failed resubmitting read urb, error %d\n",
                        __func__, result);
                /* FIXME: Need a mechanism to retry later if this happens */
}

static int safe_write(struct tty_struct *tty, struct usb_serial_port *port,
                                        const unsigned char *buf, int count)
{
        unsigned char *data;
        int result;
        int i;
        int packet_length;

        dbg("safe_write port: %p %d urb: %p count: %d",
                                port, port->number, port->write_urb, count);

        if (!port->write_urb) {
                dbg("%s - write urb NULL", __func__);
                return 0;
        }

        dbg("safe_write write_urb: %d transfer_buffer_length",
             port->write_urb->transfer_buffer_length);

        if (!port->write_urb->transfer_buffer_length) {
                dbg("%s - write urb transfer_buffer_length zero", __func__);
                return 0;
        }
        if (count == 0) {
                dbg("%s - write request of 0 bytes", __func__);
                return 0;
        }
        spin_lock_bh(&port->lock);
        if (port->write_urb_busy) {
                spin_unlock_bh(&port->lock);
                dbg("%s - already writing", __func__);
                return 0;
        }
        port->write_urb_busy = 1;
        spin_unlock_bh(&port->lock);

        packet_length = port->bulk_out_size;    /* get max packetsize */

        i = packet_length - (safe ? 2 : 0);     /* get bytes to send */
        count = (count > i) ? i : count;


        /* get the data into the transfer buffer */
        data = port->write_urb->transfer_buffer;
        memset(data, '0', packet_length);

        memcpy(data, buf, count);

        if (safe) {
                __u16 fcs;

                /* pad if necessary */
                if (!padded)
                        packet_length = count + 2;
                /* set count */
                data[packet_length - 2] = count << 2;
                data[packet_length - 1] = 0;

                /* compute fcs and insert into trailer */
                fcs = fcs_compute10(data, packet_length, CRC10_INITFCS);
                data[packet_length - 2] |= fcs >> 8;
                data[packet_length - 1] |= fcs & 0xff;

                /* set length to send */
                port->write_urb->transfer_buffer_length = packet_length;
        } else {
                port->write_urb->transfer_buffer_length = count;
        }

        usb_serial_debug_data(debug, &port->dev, __func__, count,
                                        port->write_urb->transfer_buffer);
#ifdef ECHO_TX
        {
                int i;
                unsigned char *cp = port->write_urb->transfer_buffer;
                for (i = 0; i < port->write_urb->transfer_buffer_length; i++) {
                        if ((i % 32) == 0)
                                printk("\nsu[%02x] ", i);
                        printk("%02x ", *cp++);
                }
                printk("\n");
        }
#endif
        port->write_urb->dev = port->serial->dev;
        result = usb_submit_urb(port->write_urb, GFP_KERNEL);
        if (result) {
                port->write_urb_busy = 0;
                dev_err(&port->dev,
                        "%s - failed submitting write urb, error %d\n",
                        __func__, result);
                return 0;
        }
        dbg("%s urb: %p submitted", __func__, port->write_urb);

        return count;
}

static int safe_write_room(struct tty_struct *tty)
{
        struct usb_serial_port *port = tty->driver_data;
        int room = 0;           /* Default: no room */
        unsigned long flags;

        dbg("%s", __func__);

        spin_lock_irqsave(&port->lock, flags);
        if (port->write_urb_busy)
                room = port->bulk_out_size - (safe ? 2 : 0);
        spin_unlock_irqrestore(&port->lock, flags);

        if (room)
                dbg("safe_write_room returns %d", room);
        return room;
}

static int safe_startup(struct usb_serial *serial)
{
        switch (serial->interface->cur_altsetting->desc.bInterfaceProtocol) {
        case LINEO_SAFESERIAL_CRC:
                break;
        case LINEO_SAFESERIAL_CRC_PADDED:
                padded = 1;
                break;
        default:
                return -EINVAL;
        }
        return 0;
}

static struct usb_serial_driver safe_device = {
        .driver = {
                .owner =        THIS_MODULE,
                .name =         "safe_serial",
        },
        .id_table =             id_table,
        .usb_driver =           &safe_driver,
        .num_ports =            1,
        .write =                safe_write,
        .write_room =           safe_write_room,
        .read_bulk_callback =   safe_read_bulk_callback,
        .attach =               safe_startup,
};

static int __init safe_init(void)
{
        int i, retval;

        printk(KERN_INFO KBUILD_MODNAME ": " DRIVER_VERSION ":"
               DRIVER_DESC "\n");

        /* if we have vendor / product parameters patch them into id list */
        if (vendor || product) {
                printk(KERN_INFO KBUILD_MODNAME ": vendor: %x product: %x\n",
                       vendor, product);

                for (i = 0; i < ARRAY_SIZE(id_table); i++) {
                        if (!id_table[i].idVendor && !id_table[i].idProduct) {
                                id_table[i].idVendor = vendor;
                                id_table[i].idProduct = product;
                                break;
                        }
                }
        }

        retval = usb_serial_register(&safe_device);
        if (retval)
                goto failed_usb_serial_register;
        retval = usb_register(&safe_driver);
        if (retval)
                goto failed_usb_register;

        return 0;
failed_usb_register:
        usb_serial_deregister(&safe_device);
failed_usb_serial_register:
        return retval;
}

static void __exit safe_exit(void)
{
        usb_deregister(&safe_driver);
        usb_serial_deregister(&safe_device);
}

module_init(safe_init);
module_exit(safe_exit);