/*
 * 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/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/spinlock.h>
#include <asm/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;
	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
	if (safe) {
		__u16 fcs;
		if (!(fcs = fcs_compute10 (data, length, CRC10_INITFCS))) {
			int actual_length = data[length - 2] >> 2;
			if (actual_length <= (length - 2)) {
				info ("%s - actual: %d", __func__, actual_length);
				tty_insert_flip_string(port->tty, data, actual_length);
				tty_flip_buffer_push (port->tty);
			} else {
				err ("%s - inconsistent lengths %d:%d", __func__,
				     actual_length, length);
			}
		} else {
			err ("%s - bad CRC %x", __func__, fcs);
		}
	} else {
		tty_insert_flip_string(port->tty, data, length);
		tty_flip_buffer_push (port->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);

	if ((result = usb_submit_urb (urb, GFP_ATOMIC))) {
		err ("%s - failed resubmitting read urb, error %d", __func__, result);
		/* FIXME: Need a mechanism to retry later if this happens */
	}
}

static int safe_write (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;
	if ((result = usb_submit_urb (port->write_urb, GFP_KERNEL))) {
		port->write_urb_busy = 0;
		err ("%s - failed submitting write urb, error %d", __func__, result);
		return 0;
	}
	dbg ("%s urb: %p submitted", __func__, port->write_urb);

	return (count);
}

static int safe_write_room (struct usb_serial_port *port)
{
	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;

	info (DRIVER_VERSION " " DRIVER_AUTHOR);
	info (DRIVER_DESC);
	info ("vendor: %x product: %x safe: %d padded: %d\n", vendor, product, safe, padded);

	// if we have vendor / product parameters patch them into id list
	if (vendor || product) {
		info ("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);