ks959-sir.c

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/*****************************************************************************
*
* Filename:      ks959-sir.c
* Version:       0.1.2
* Description:   Irda KingSun KS-959 USB Dongle
* Status:        Experimental
* Author:        Alex Villacís Lasso <[e-mail]>
*         with help from Domen Puncer <[e-mail]>
*
*    Based on stir4200, mcs7780, kingsun-sir drivers.
*
*    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.
*
*    This program is distributed in the hope that it will be useful,
*    but WITHOUT ANY WARRANTY; without even the implied warranty of
*    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
*    GNU General Public License for more details.
*
*    You should have received a copy of the GNU General Public License
*    along with this program; if not, write to the Free Software
*    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*****************************************************************************/

/*
 * Following is my most current (2007-07-17) understanding of how the Kingsun
 * KS-959 dongle is supposed to work. This information was deduced by
 * reverse-engineering and examining the USB traffic captured with USBSnoopy
 * from the WinXP driver. Feel free to update here as more of the dongle is
 * known.
 *
 * My most sincere thanks must go to Domen Puncer <[e-mail]> for
 * invaluable help in cracking the obfuscation and padding required for this
 * dongle.
 *
 * General: This dongle exposes one interface with one interrupt IN endpoint.
 * However, the interrupt endpoint is NOT used at all for this dongle. Instead,
 * this dongle uses control transfers for everything, including sending and
 * receiving the IrDA frame data. Apparently the interrupt endpoint is just a
 * dummy to ensure the dongle has a valid interface to present to the PC.And I
 * thought the DonShine dongle was weird... In addition, this dongle uses
 * obfuscation (?!?!), applied at the USB level, to hide the traffic, both sent
 * and received, from the dongle. I call it obfuscation because the XOR keying
 * and padding required to produce an USB traffic acceptable for the dongle can
 * not be explained by any other technical requirement.
 *
 * Transmission: To transmit an IrDA frame, the driver must prepare a control
 * URB with the following as a setup packet:
 *    bRequestType    USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE
 *    bRequest        0x09
 *    wValue          <length of valid data before padding, little endian>
 *    wIndex          0x0000
 *    wLength         <length of padded data>
 * The payload packet must be manually wrapped and escaped (as in stir4200.c),
 * then padded and obfuscated before being sent. Both padding and obfuscation
 * are implemented in the procedure obfuscate_tx_buffer(). Suffice to say, the
 * designer/programmer of the dongle used his name as a source for the
 * obfuscation. WTF?!
 * Apparently the dongle cannot handle payloads larger than 256 bytes. The
 * driver has to perform fragmentation in order to send anything larger than
 * this limit.
 *
 * Reception: To receive data, the driver must poll the dongle regularly (like
 * kingsun-sir.c) with control URBs and the following as a setup packet:
 *    bRequestType    USB_DIR_IN | USB_TYPE_CLASS | USB_RECIP_INTERFACE
 *    bRequest        0x01
 *    wValue          0x0200
 *    wIndex          0x0000
 *    wLength         0x0800 (size of available buffer)
 * If there is data to be read, it will be returned as the response payload.
 * This data is (apparently) not padded, but it is obfuscated. To de-obfuscate
 * it, the driver must XOR every byte, in sequence, with a value that starts at
 * 1 and is incremented with each byte processed, and then with 0x55. The value
 * incremented with each byte processed overflows as an unsigned char. The
 * resulting bytes form a wrapped SIR frame that is unwrapped and unescaped
 * as in stir4200.c The incremented value is NOT reset with each frame, but is
 * kept across the entire session with the dongle. Also, the dongle inserts an
 * extra garbage byte with value 0x95 (after decoding) every 0xff bytes, which
 * must be skipped.
 *
 * Speed change: To change the speed of the dongle, the driver prepares a
 * control URB with the following as a setup packet:
 *    bRequestType    USB_DIR_OUT | USB_TYPE_CLASS | USB_RECIP_INTERFACE
 *    bRequest        0x09
 *    wValue          0x0200
 *    wIndex          0x0001
 *    wLength         0x0008 (length of the payload)
 * The payload is a 8-byte record, apparently identical to the one used in
 * drivers/usb/serial/cypress_m8.c to change speed:
 *     __u32 baudSpeed;
 *    unsigned int dataBits : 2;    // 0 - 5 bits 3 - 8 bits
 *    unsigned int : 1;
 *    unsigned int stopBits : 1;
 *    unsigned int parityEnable : 1;
 *    unsigned int parityType : 1;
 *    unsigned int : 1;
 *    unsigned int reset : 1;
 *    unsigned char reserved[3];    // set to 0
 *
 * For now only SIR speeds have been observed with this dongle. Therefore,
 * nothing is known on what changes (if any) must be done to frame wrapping /
 * unwrapping for higher than SIR speeds. This driver assumes no change is
 * necessary and announces support for all the way to 57600 bps. Although the
 * package announces support for up to 4MBps, tests with a Sony Ericcson K300
 * phone show corruption when receiving large frames at 115200 bps, the highest
 * speed announced by the phone. However, transmission at 115200 bps is OK. Go
 * figure. Since I don't know whether the phone or the dongle is at fault, max
 * announced speed is 57600 bps until someone produces a device that can run
 * at higher speeds with this dongle.
 */

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/kernel.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <linux/usb.h>
#include <linux/device.h>
#include <linux/crc32.h>

#include <asm/unaligned.h>
#include <asm/byteorder.h>
#include <asm/uaccess.h>

#include <net/irda/irda.h>
#include <net/irda/wrapper.h>
#include <net/irda/crc.h>

#define KS959_VENDOR_ID 0x07d0
#define KS959_PRODUCT_ID 0x4959

/* These are the currently known USB ids */
static struct usb_device_id dongles[] = {
	/* KingSun Co,Ltd  IrDA/USB Bridge */
	{USB_DEVICE(KS959_VENDOR_ID, KS959_PRODUCT_ID)},
	{}
};

MODULE_DEVICE_TABLE(usb, dongles);

#define KINGSUN_MTT 0x07
#define KINGSUN_REQ_RECV 0x01
#define KINGSUN_REQ_SEND 0x09

#define KINGSUN_RCV_FIFO_SIZE    2048	/* Max length we can receive */
#define KINGSUN_SND_FIFO_SIZE    2048	/* Max packet we can send */
#define KINGSUN_SND_PACKET_SIZE    256	/* Max packet dongle can handle */

struct ks959_speedparams {
	__le32 baudrate;	/* baud rate, little endian */
	__u8 flags;
	__u8 reserved[3];
} __attribute__ ((packed));

#define KS_DATA_5_BITS 0x00
#define KS_DATA_6_BITS 0x01
#define KS_DATA_7_BITS 0x02
#define KS_DATA_8_BITS 0x03

#define KS_STOP_BITS_1 0x00
#define KS_STOP_BITS_2 0x08

#define KS_PAR_DISABLE    0x00
#define KS_PAR_EVEN    0x10
#define KS_PAR_ODD    0x30
#define KS_RESET    0x80

struct ks959_cb {
	struct usb_device *usbdev;	/* init: probe_irda */
	struct net_device *netdev;	/* network layer */
	struct irlap_cb *irlap;	/* The link layer we are binded to */
	struct net_device_stats stats;	/* network statistics */
	struct qos_info qos;

	struct usb_ctrlrequest *tx_setuprequest;
	struct urb *tx_urb;
	__u8 *tx_buf_clear;
	unsigned int tx_buf_clear_used;
	unsigned int tx_buf_clear_sent;
	__u8 *tx_buf_xored;

	struct usb_ctrlrequest *rx_setuprequest;
	struct urb *rx_urb;
	__u8 *rx_buf;
	__u8 rx_variable_xormask;
	iobuff_t rx_unwrap_buff;
	struct timeval rx_time;

	struct usb_ctrlrequest *speed_setuprequest;
	struct urb *speed_urb;
	struct ks959_speedparams speedparams;
	unsigned int new_speed;

	spinlock_t lock;
	int receiving;
};

/* Procedure to perform the obfuscation/padding expected by the dongle
 *
 * buf_cleartext    (IN) Cleartext version of the IrDA frame to transmit
 * len_cleartext    (IN) Length of the cleartext version of IrDA frame
 * buf_xoredtext    (OUT) Obfuscated version of frame built by proc
 * len_maxbuf        (OUT) Maximum space available at buf_xoredtext
 *
 * (return)         length of obfuscated frame with padding
 *
 * If not enough space (as indicated by len_maxbuf vs. required padding),
 * zero is returned
 *
 * The value of lookup_string is actually a required portion of the algorithm.
 * Seems the designer of the dongle wanted to state who exactly is responsible
 * for implementing obfuscation. Send your best (or other) wishes to him ]:-)
 */
static unsigned int obfuscate_tx_buffer(const __u8 * buf_cleartext,
					unsigned int len_cleartext,
					__u8 * buf_xoredtext,
					unsigned int len_maxbuf)
{
	unsigned int len_xoredtext;

	/* Calculate required length with padding, check for necessary space */
	len_xoredtext = ((len_cleartext + 7) & ~0x7) + 0x10;
	if (len_xoredtext <= len_maxbuf) {
		static const __u8 lookup_string[] = "wangshuofei19710";
		__u8 xor_mask;

		/* Unlike the WinXP driver, we *do* clear out the padding */
		memset(buf_xoredtext, 0, len_xoredtext);

		xor_mask = lookup_string[(len_cleartext & 0x0f) ^ 0x06] ^ 0x55;

		while (len_cleartext-- > 0) {
			*buf_xoredtext++ = *buf_cleartext++ ^ xor_mask;
		}
	} else {
		len_xoredtext = 0;
	}
	return len_xoredtext;
}

/* Callback transmission routine */
static void ks959_speed_irq(struct urb *urb)
{
	/* unlink, shutdown, unplug, other nasties */
	if (urb->status != 0) {
		err("ks959_speed_irq: urb asynchronously failed - %d",
		    urb->status);
	}
}

/* Send a control request to change speed of the dongle */
static int ks959_change_speed(struct ks959_cb *kingsun, unsigned speed)
{
	static unsigned int supported_speeds[] = { 2400, 9600, 19200, 38400,
		57600, 115200, 576000, 1152000, 4000000, 0
	};
	int err;
	unsigned int i;

	if (kingsun->speed_setuprequest == NULL || kingsun->speed_urb == NULL)
		return -ENOMEM;

	/* Check that requested speed is among the supported ones */
	for (i = 0; supported_speeds[i] && supported_speeds[i] != speed; i++) ;
	if (supported_speeds[i] == 0)
		return -EOPNOTSUPP;

	memset(&(kingsun->speedparams), 0, sizeof(struct ks959_speedparams));
	kingsun->speedparams.baudrate = cpu_to_le32(speed);
	kingsun->speedparams.flags = KS_DATA_8_BITS;

	/* speed_setuprequest pre-filled in ks959_probe */
	usb_fill_control_urb(kingsun->speed_urb, kingsun->usbdev,
			     usb_sndctrlpipe(kingsun->usbdev, 0),
			     (unsigned char *)kingsun->speed_setuprequest,
			     &(kingsun->speedparams),
			     sizeof(struct ks959_speedparams), ks959_speed_irq,
			     kingsun);
	kingsun->speed_urb->status = 0;
	err = usb_submit_urb(kingsun->speed_urb, GFP_ATOMIC);

	return err;
}

/* Submit one fragment of an IrDA frame to the dongle */
static void ks959_send_irq(struct urb *urb);
static int ks959_submit_tx_fragment(struct ks959_cb *kingsun)
{
	unsigned int padlen;
	unsigned int wraplen;
	int ret;

	/* Check whether current plaintext can produce a padded buffer that fits
	   within the range handled by the dongle */
	wraplen = (KINGSUN_SND_PACKET_SIZE & ~0x7) - 0x10;
	if (wraplen > kingsun->tx_buf_clear_used)
		wraplen = kingsun->tx_buf_clear_used;

	/* Perform dongle obfuscation. Also remove the portion of the frame that
	   was just obfuscated and will now be sent to the dongle. */
	padlen = obfuscate_tx_buffer(kingsun->tx_buf_clear, wraplen,
				     kingsun->tx_buf_xored,
				     KINGSUN_SND_PACKET_SIZE);

	/* Calculate how much data can be transmitted in this urb */
	kingsun->tx_setuprequest->wValue = cpu_to_le16(wraplen);
	kingsun->tx_setuprequest->wLength = cpu_to_le16(padlen);
	/* Rest of the fields were filled in ks959_probe */
	usb_fill_control_urb(kingsun->tx_urb, kingsun->usbdev,
			     usb_sndctrlpipe(kingsun->usbdev, 0),
			     (unsigned char *)kingsun->tx_setuprequest,
			     kingsun->tx_buf_xored, padlen,
			     ks959_send_irq, kingsun);
	kingsun->tx_urb->status = 0;
	ret = usb_submit_urb(kingsun->tx_urb, GFP_ATOMIC);

	/* Remember how much data was sent, in order to update at callback */
	kingsun->tx_buf_clear_sent = (ret == 0) ? wraplen : 0;
	return ret;
}

/* Callback transmission routine */
static void ks959_send_irq(struct urb *urb)
{
	struct ks959_cb *kingsun = urb->context;
	struct net_device *netdev = kingsun->netdev;
	int ret = 0;

	/* in process of stopping, just drop data */
	if (!netif_running(kingsun->netdev)) {
		err("ks959_send_irq: Network not running!");
		return;
	}

	/* unlink, shutdown, unplug, other nasties */
	if (urb->status != 0) {
		err("ks959_send_irq: urb asynchronously failed - %d",
		    urb->status);
		return;
	}

	if (kingsun->tx_buf_clear_used > 0) {
		/* Update data remaining to be sent */
		if (kingsun->tx_buf_clear_sent < kingsun->tx_buf_clear_used) {
			memmove(kingsun->tx_buf_clear,
				kingsun->tx_buf_clear +
				kingsun->tx_buf_clear_sent,
				kingsun->tx_buf_clear_used -
				kingsun->tx_buf_clear_sent);
		}
		kingsun->tx_buf_clear_used -= kingsun->tx_buf_clear_sent;
		kingsun->tx_buf_clear_sent = 0;

		if (kingsun->tx_buf_clear_used > 0) {
			/* There is more data to be sent */
			if ((ret = ks959_submit_tx_fragment(kingsun)) != 0) {
				err("ks959_send_irq: failed tx_urb submit: %d",
				    ret);
				switch (ret) {
				case -ENODEV:
				case -EPIPE:
					break;
				default:
					kingsun->stats.tx_errors++;
					netif_start_queue(netdev);
				}
			}
		} else {
			/* All data sent, send next speed && wake network queue */
			if (kingsun->new_speed != -1 &&
			    cpu_to_le32(kingsun->new_speed) !=
			    kingsun->speedparams.baudrate)
				ks959_change_speed(kingsun, kingsun->new_speed);

			netif_wake_queue(netdev);
		}
	}
}

/*
 * Called from net/core when new frame is available.
 */
static int ks959_hard_xmit(struct sk_buff *skb, struct net_device *netdev)
{
	struct ks959_cb *kingsun;
	unsigned int wraplen;
	int ret = 0;

	if (skb == NULL || netdev == NULL)
		return -EINVAL;

	netif_stop_queue(netdev);

	/* the IRDA wrapping routines don't deal with non linear skb */
	SKB_LINEAR_ASSERT(skb);

	kingsun = netdev_priv(netdev);

	spin_lock(&kingsun->lock);
	kingsun->new_speed = irda_get_next_speed(skb);

	/* Append data to the end of whatever data remains to be transmitted */
	wraplen =
	    async_wrap_skb(skb, kingsun->tx_buf_clear, KINGSUN_SND_FIFO_SIZE);
	kingsun->tx_buf_clear_used = wraplen;

	if ((ret = ks959_submit_tx_fragment(kingsun)) != 0) {
		err("ks959_hard_xmit: failed tx_urb submit: %d", ret);
		switch (ret) {
		case -ENODEV:
		case -EPIPE:
			break;
		default:
			kingsun->stats.tx_errors++;
			netif_start_queue(netdev);
		}
	} else {
		kingsun->stats.tx_packets++;
		kingsun->stats.tx_bytes += skb->len;

	}

	dev_kfree_skb(skb);
	spin_unlock(&kingsun->lock);

	return ret;
}

/* Receive callback function */
static void ks959_rcv_irq(struct urb *urb)
{
	struct ks959_cb *kingsun = urb->context;
	int ret;

	/* in process of stopping, just drop data */
	if (!netif_running(kingsun->netdev)) {
		kingsun->receiving = 0;
		return;
	}

	/* unlink, shutdown, unplug, other nasties */
	if (urb->status != 0) {
		err("kingsun_rcv_irq: urb asynchronously failed - %d",
		    urb->status);
		kingsun->receiving = 0;
		return;
	}

	if (urb->actual_length > 0) {
		__u8 *bytes = urb->transfer_buffer;
		unsigned int i;

		for (i = 0; i < urb->actual_length; i++) {
			/* De-obfuscation implemented here: variable portion of
			   xormask is incremented, and then used with the encoded
			   byte for the XOR. The result of the operation is used
			   to unwrap the SIR frame. */
			kingsun->rx_variable_xormask++;
			bytes[i] =
			    bytes[i] ^ kingsun->rx_variable_xormask ^ 0x55u;

			/* rx_variable_xormask doubles as an index counter so we
			   can skip the byte at 0xff (wrapped around to 0).
			 */