drivers/usb/net/net1080.c - kernel/msm-5.4 - Gitiles

 /*
  * Net1080 based USB host-to-host cables
  * Copyright (C) 2000-2005 by David Brownell
  *
  * 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.
  *
  * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 // #define	DEBUG			// error path messages, extra info
 // #define	VERBOSE			// more; success messages

 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/ethtool.h>
 #include <linux/workqueue.h>
 #include <linux/mii.h>
 #include <linux/usb.h>

 #include <asm/unaligned.h>

 #include "usbnet.h"


 /*
  * Netchip 1080 driver ... http://www.netchip.com
  * (Sept 2004:  End-of-life announcement has been sent.)
  * Used in (some) LapLink cables
  */

 #define frame_errors	data[1]

 /*
  * NetChip framing of ethernet packets, supporting additional error
  * checks for links that may drop bulk packets from inside messages.
  * Odd USB length == always short read for last usb packet.
  *	- nc_header
  *	- Ethernet header (14 bytes)
  *	- payload
  *	- (optional padding byte, if needed so length becomes odd)
  *	- nc_trailer
  *
  * This framing is to be avoided for non-NetChip devices.
  */

 struct nc_header {		// packed:
 	__le16	hdr_len;		// sizeof nc_header (LE, all)
 	__le16	packet_len;		// payload size (including ethhdr)
 	__le16	packet_id;		// detects dropped packets
 #define MIN_HEADER	6

 	// all else is optional, and must start with:
 	// __le16	vendorId;	// from usb-if
 	// __le16	productId;
 } __attribute__((__packed__));

 #define	PAD_BYTE	((unsigned char)0xAC)

 struct nc_trailer {
 	__le16	packet_id;
 } __attribute__((__packed__));

 // packets may use FLAG_FRAMING_NC and optional pad
 #define FRAMED_SIZE(mtu) (sizeof (struct nc_header) \
 				+ sizeof (struct ethhdr) \
 				+ (mtu) \
 				+ 1 \
 				+ sizeof (struct nc_trailer))

 #define MIN_FRAMED	FRAMED_SIZE(0)

 /* packets _could_ be up to 64KB... */
 #define NC_MAX_PACKET	32767


 /*
  * Zero means no timeout; else, how long a 64 byte bulk packet may be queued
  * before the hardware drops it.  If that's done, the driver will need to
  * frame network packets to guard against the dropped USB packets.  The win32
  * driver sets this for both sides of the link.
  */
 #define	NC_READ_TTL_MS	((u8)255)	// ms

 /*
  * We ignore most registers and EEPROM contents.
  */
 #define	REG_USBCTL	((u8)0x04)
 #define REG_TTL		((u8)0x10)
 #define REG_STATUS	((u8)0x11)

 /*
  * Vendor specific requests to read/write data
  */
 #define	REQUEST_REGISTER	((u8)0x10)
 #define	REQUEST_EEPROM		((u8)0x11)

 static int
 nc_vendor_read(struct usbnet *dev, u8 req, u8 regnum, u16 *retval_ptr)
 {
 	int status = usb_control_msg(dev->udev,
 		usb_rcvctrlpipe(dev->udev, 0),
 		req,
 		USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		0, regnum,
 		retval_ptr, sizeof *retval_ptr,
 		USB_CTRL_GET_TIMEOUT);
 	if (status > 0)
 		status = 0;
 	if (!status)
 		le16_to_cpus(retval_ptr);
 	return status;
 }

 static inline int
 nc_register_read(struct usbnet *dev, u8 regnum, u16 *retval_ptr)
 {
 	return nc_vendor_read(dev, REQUEST_REGISTER, regnum, retval_ptr);
 }

 // no retval ... can become async, usable in_interrupt()
 static void
 nc_vendor_write(struct usbnet *dev, u8 req, u8 regnum, u16 value)
 {
 	usb_control_msg(dev->udev,
 		usb_sndctrlpipe(dev->udev, 0),
 		req,
 		USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		value, regnum,
 		NULL, 0,			// data is in setup packet
 		USB_CTRL_SET_TIMEOUT);
 }

 static inline void
 nc_register_write(struct usbnet *dev, u8 regnum, u16 value)
 {
 	nc_vendor_write(dev, REQUEST_REGISTER, regnum, value);
 }


 #if 0
 static void nc_dump_registers(struct usbnet *dev)
 {
 	u8	reg;
 	u16	*vp = kmalloc(sizeof (u16));

 	if (!vp) {
 		dbg("no memory?");
 		return;
 	}

 	dbg("%s registers:", dev->net->name);
 	for (reg = 0; reg < 0x20; reg++) {
 		int retval;

 		// reading some registers is trouble
 		if (reg >= 0x08 && reg <= 0xf)
 			continue;
 		if (reg >= 0x12 && reg <= 0x1e)
 			continue;

 		retval = nc_register_read(dev, reg, vp);
 		if (retval < 0)
 			dbg("%s reg [0x%x] ==> error %d",
 				dev->net->name, reg, retval);
 		else
 			dbg("%s reg [0x%x] = 0x%x",
 				dev->net->name, reg, *vp);
 	}
 	kfree(vp);
 }
 #endif


 /*-------------------------------------------------------------------------*/

 /*
  * Control register
  */

 #define	USBCTL_WRITABLE_MASK	0x1f0f
 // bits 15-13 reserved, r/o
 #define	USBCTL_ENABLE_LANG	(1 << 12)
 #define	USBCTL_ENABLE_MFGR	(1 << 11)
 #define	USBCTL_ENABLE_PROD	(1 << 10)
 #define	USBCTL_ENABLE_SERIAL	(1 << 9)
 #define	USBCTL_ENABLE_DEFAULTS	(1 << 8)
 // bits 7-4 reserved, r/o
 #define	USBCTL_FLUSH_OTHER	(1 << 3)
 #define	USBCTL_FLUSH_THIS	(1 << 2)
 #define	USBCTL_DISCONN_OTHER	(1 << 1)
 #define	USBCTL_DISCONN_THIS	(1 << 0)

 static inline void nc_dump_usbctl(struct usbnet *dev, u16 usbctl)
 {
 	if (!netif_msg_link(dev))
 		return;
 	devdbg(dev, "net1080 %s-%s usbctl 0x%x:%s%s%s%s%s;"
 			" this%s%s;"
 			" other%s%s; r/o 0x%x",
 		dev->udev->bus->bus_name, dev->udev->devpath,
 		usbctl,
 		(usbctl & USBCTL_ENABLE_LANG) ? " lang" : "",
 		(usbctl & USBCTL_ENABLE_MFGR) ? " mfgr" : "",
 		(usbctl & USBCTL_ENABLE_PROD) ? " prod" : "",
 		(usbctl & USBCTL_ENABLE_SERIAL) ? " serial" : "",
 		(usbctl & USBCTL_ENABLE_DEFAULTS) ? " defaults" : "",

 		(usbctl & USBCTL_FLUSH_OTHER) ? " FLUSH" : "",
 		(usbctl & USBCTL_DISCONN_OTHER) ? " DIS" : "",
 		(usbctl & USBCTL_FLUSH_THIS) ? " FLUSH" : "",
 		(usbctl & USBCTL_DISCONN_THIS) ? " DIS" : "",
 		usbctl & ~USBCTL_WRITABLE_MASK
 		);
 }

 /*-------------------------------------------------------------------------*/

 /*
  * Status register
  */

 #define	STATUS_PORT_A		(1 << 15)

 #define	STATUS_CONN_OTHER	(1 << 14)
 #define	STATUS_SUSPEND_OTHER	(1 << 13)
 #define	STATUS_MAILBOX_OTHER	(1 << 12)
 #define	STATUS_PACKETS_OTHER(n)	(((n) >> 8) & 0x03)

 #define	STATUS_CONN_THIS	(1 << 6)
 #define	STATUS_SUSPEND_THIS	(1 << 5)
 #define	STATUS_MAILBOX_THIS	(1 << 4)
 #define	STATUS_PACKETS_THIS(n)	(((n) >> 0) & 0x03)

 #define	STATUS_UNSPEC_MASK	0x0c8c
 #define	STATUS_NOISE_MASK 	((u16)~(0x0303|STATUS_UNSPEC_MASK))


 static inline void nc_dump_status(struct usbnet *dev, u16 status)
 {
 	if (!netif_msg_link(dev))
 		return;
 	devdbg(dev, "net1080 %s-%s status 0x%x:"
 			" this (%c) PKT=%d%s%s%s;"
 			" other PKT=%d%s%s%s; unspec 0x%x",
 		dev->udev->bus->bus_name, dev->udev->devpath,
 		status,

 		// XXX the packet counts don't seem right
 		// (1 at reset, not 0); maybe UNSPEC too

 		(status & STATUS_PORT_A) ? 'A' : 'B',
 		STATUS_PACKETS_THIS(status),
 		(status & STATUS_CONN_THIS) ? " CON" : "",
 		(status & STATUS_SUSPEND_THIS) ? " SUS" : "",
 		(status & STATUS_MAILBOX_THIS) ? " MBOX" : "",

 		STATUS_PACKETS_OTHER(status),
 		(status & STATUS_CONN_OTHER) ? " CON" : "",
 		(status & STATUS_SUSPEND_OTHER) ? " SUS" : "",
 		(status & STATUS_MAILBOX_OTHER) ? " MBOX" : "",

 		status & STATUS_UNSPEC_MASK
 		);
 }

 /*-------------------------------------------------------------------------*/

 /*
  * TTL register
  */

 #define	TTL_THIS(ttl)	(0x00ff & ttl)
 #define	TTL_OTHER(ttl)	(0x00ff & (ttl >> 8))
 #define MK_TTL(this,other)	((u16)(((other)<<8)|(0x00ff&(this))))

 static inline void nc_dump_ttl(struct usbnet *dev, u16 ttl)
 {
 	if (netif_msg_link(dev))
 		devdbg(dev, "net1080 %s-%s ttl 0x%x this = %d, other = %d",
 			dev->udev->bus->bus_name, dev->udev->devpath,
 			ttl, TTL_THIS(ttl), TTL_OTHER(ttl));
 }

 /*-------------------------------------------------------------------------*/

 static int net1080_reset(struct usbnet *dev)
 {
 	u16		usbctl, status, ttl;
 	u16		*vp = kmalloc(sizeof (u16), GFP_KERNEL);
 	int		retval;

 	if (!vp)
 		return -ENOMEM;

 	// nc_dump_registers(dev);

 	if ((retval = nc_register_read(dev, REG_STATUS, vp)) < 0) {
 		dbg("can't read %s-%s status: %d",
 			dev->udev->bus->bus_name, dev->udev->devpath, retval);
 		goto done;
 	}
 	status = *vp;
 	nc_dump_status(dev, status);

 	if ((retval = nc_register_read(dev, REG_USBCTL, vp)) < 0) {
 		dbg("can't read USBCTL, %d", retval);
 		goto done;
 	}
 	usbctl = *vp;
 	nc_dump_usbctl(dev, usbctl);

 	nc_register_write(dev, REG_USBCTL,
 			USBCTL_FLUSH_THIS | USBCTL_FLUSH_OTHER);

 	if ((retval = nc_register_read(dev, REG_TTL, vp)) < 0) {
 		dbg("can't read TTL, %d", retval);
 		goto done;
 	}
 	ttl = *vp;
 	// nc_dump_ttl(dev, ttl);

 	nc_register_write(dev, REG_TTL,
 			MK_TTL(NC_READ_TTL_MS, TTL_OTHER(ttl)) );
 	dbg("%s: assigned TTL, %d ms", dev->net->name, NC_READ_TTL_MS);

 	if (netif_msg_link(dev))
 		devinfo(dev, "port %c, peer %sconnected",
 			(status & STATUS_PORT_A) ? 'A' : 'B',
 			(status & STATUS_CONN_OTHER) ? "" : "dis"
 			);
 	retval = 0;

 done:
 	kfree(vp);
 	return retval;
 }

 static int net1080_check_connect(struct usbnet *dev)
 {
 	int			retval;
 	u16			status;
 	u16			*vp = kmalloc(sizeof (u16), GFP_KERNEL);

 	if (!vp)
 		return -ENOMEM;
 	retval = nc_register_read(dev, REG_STATUS, vp);
 	status = *vp;
 	kfree(vp);
 	if (retval != 0) {
 		dbg("%s net1080_check_conn read - %d", dev->net->name, retval);
 		return retval;
 	}
 	if ((status & STATUS_CONN_OTHER) != STATUS_CONN_OTHER)
 		return -ENOLINK;
 	return 0;
 }

 static void nc_flush_complete(struct urb *urb)
 {
 	kfree(urb->context);
 	usb_free_urb(urb);
 }

 static void nc_ensure_sync(struct usbnet *dev)
 {
 	dev->frame_errors++;
 	if (dev->frame_errors > 5) {
 		struct urb		*urb;
 		struct usb_ctrlrequest	*req;
 		int			status;

 		/* Send a flush */
 		urb = usb_alloc_urb(0, GFP_ATOMIC);
 		if (!urb)
 			return;

 		req = kmalloc(sizeof *req, GFP_ATOMIC);
 		if (!req) {
 			usb_free_urb(urb);
 			return;
 		}

 		req->bRequestType = USB_DIR_OUT
 			| USB_TYPE_VENDOR
 			| USB_RECIP_DEVICE;
 		req->bRequest = REQUEST_REGISTER;
 		req->wValue = cpu_to_le16(USBCTL_FLUSH_THIS
 				| USBCTL_FLUSH_OTHER);
 		req->wIndex = cpu_to_le16(REG_USBCTL);
 		req->wLength = cpu_to_le16(0);

 		/* queue an async control request, we don't need
 		 * to do anything when it finishes except clean up.
 		 */
 		usb_fill_control_urb(urb, dev->udev,
 			usb_sndctrlpipe(dev->udev, 0),
 			(unsigned char *) req,
 			NULL, 0,
 			nc_flush_complete, req);
 		status = usb_submit_urb(urb, GFP_ATOMIC);
 		if (status) {
 			kfree(req);
 			usb_free_urb(urb);
 			return;
 		}

 		if (netif_msg_rx_err(dev))
 			devdbg(dev, "flush net1080; too many framing errors");
 		dev->frame_errors = 0;
 	}
 }

 static int net1080_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
 {
 	struct nc_header	*header;
 	struct nc_trailer	*trailer;
 	u16			hdr_len, packet_len;

 	if (!(skb->len & 0x01)) {
 #ifdef DEBUG
 		struct net_device	*net = dev->net;
 		dbg("rx framesize %d range %d..%d mtu %d", skb->len,
 			net->hard_header_len, dev->hard_mtu, net->mtu);
 #endif
 		dev->stats.rx_frame_errors++;
 		nc_ensure_sync(dev);
 		return 0;
 	}

 	header = (struct nc_header *) skb->data;
 	hdr_len = le16_to_cpup(&header->hdr_len);
 	packet_len = le16_to_cpup(&header->packet_len);
 	if (FRAMED_SIZE(packet_len) > NC_MAX_PACKET) {
 		dev->stats.rx_frame_errors++;
 		dbg("packet too big, %d", packet_len);
 		nc_ensure_sync(dev);
 		return 0;
 	} else if (hdr_len < MIN_HEADER) {
 		dev->stats.rx_frame_errors++;
 		dbg("header too short, %d", hdr_len);
 		nc_ensure_sync(dev);
 		return 0;
 	} else if (hdr_len > MIN_HEADER) {
 		// out of band data for us?
 		dbg("header OOB, %d bytes", hdr_len - MIN_HEADER);
 		nc_ensure_sync(dev);
 		// switch (vendor/product ids) { ... }
 	}
 	skb_pull(skb, hdr_len);

 	trailer = (struct nc_trailer *)
 		(skb->data + skb->len - sizeof *trailer);
 	skb_trim(skb, skb->len - sizeof *trailer);

 	if ((packet_len & 0x01) == 0) {
 		if (skb->data [packet_len] != PAD_BYTE) {
 			dev->stats.rx_frame_errors++;
 			dbg("bad pad");
 			return 0;
 		}
 		skb_trim(skb, skb->len - 1);
 	}
 	if (skb->len != packet_len) {
 		dev->stats.rx_frame_errors++;
 		dbg("bad packet len %d (expected %d)",
 			skb->len, packet_len);
 		nc_ensure_sync(dev);
 		return 0;
 	}
 	if (header->packet_id != get_unaligned(&trailer->packet_id)) {
 		dev->stats.rx_fifo_errors++;
 		dbg("(2+ dropped) rx packet_id mismatch 0x%x 0x%x",
 			le16_to_cpu(header->packet_id),
 			le16_to_cpu(trailer->packet_id));
 		return 0;
 	}
 #if 0
 	devdbg(dev, "frame <rx h %d p %d id %d", header->hdr_len,
 		header->packet_len, header->packet_id);
 #endif
 	dev->frame_errors = 0;
 	return 1;
 }

 static struct sk_buff *
 net1080_tx_fixup(struct usbnet *dev, struct sk_buff *skb, gfp_t flags)
 {
 	struct sk_buff		*skb2;
 	struct nc_header	*header = NULL;
 	struct nc_trailer	*trailer = NULL;
 	int			padlen = sizeof (struct nc_trailer);
 	int			len = skb->len;

 	if (!((len + padlen + sizeof (struct nc_header)) & 0x01))
 		padlen++;
 	if (!skb_cloned(skb)) {
 		int	headroom = skb_headroom(skb);
 		int	tailroom = skb_tailroom(skb);

 		if (padlen <= tailroom &&
 		    sizeof(struct nc_header) <= headroom)
 			/* There's enough head and tail room */
 			goto encapsulate;

 		if ((sizeof (struct nc_header) + padlen) <
 				(headroom + tailroom)) {
 			/* There's enough total room, so just readjust */
 			skb->data = memmove(skb->head
 						+ sizeof (struct nc_header),
 					    skb->data, skb->len);
 			skb_set_tail_pointer(skb, len);
 			goto encapsulate;
 		}
 	}

 	/* Create a new skb to use with the correct size */
 	skb2 = skb_copy_expand(skb,
 				sizeof (struct nc_header),
 				padlen,
 				flags);
 	dev_kfree_skb_any(skb);
 	if (!skb2)
 		return skb2;
 	skb = skb2;

 encapsulate:
 	/* header first */
 	header = (struct nc_header *) skb_push(skb, sizeof *header);
 	header->hdr_len = cpu_to_le16(sizeof (*header));
 	header->packet_len = cpu_to_le16(len);
 	header->packet_id = cpu_to_le16((u16)dev->xid++);

 	/* maybe pad; then trailer */
 	if (!((skb->len + sizeof *trailer) & 0x01))
 		*skb_put(skb, 1) = PAD_BYTE;
 	trailer = (struct nc_trailer *) skb_put(skb, sizeof *trailer);
 	put_unaligned(header->packet_id, &trailer->packet_id);
 #if 0
 	devdbg(dev, "frame >tx h %d p %d id %d",
 		header->hdr_len, header->packet_len,
 		header->packet_id);
 #endif
 	return skb;
 }

 static int net1080_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	unsigned	extra = sizeof (struct nc_header)
 				+ 1
 				+ sizeof (struct nc_trailer);

 	dev->net->hard_header_len += extra;
 	dev->rx_urb_size = dev->net->hard_header_len + dev->net->mtu;
 	dev->hard_mtu = NC_MAX_PACKET;
 	return usbnet_get_endpoints (dev, intf);
 }

 static const struct driver_info	net1080_info = {
 	.description =	"NetChip TurboCONNECT",
 	.flags =	FLAG_FRAMING_NC,
 	.bind =		net1080_bind,
 	.reset =	net1080_reset,
 	.check_connect = net1080_check_connect,
 	.rx_fixup =	net1080_rx_fixup,
 	.tx_fixup =	net1080_tx_fixup,
 };

 static const struct usb_device_id	products [] = {
 {
 	USB_DEVICE(0x0525, 0x1080),	// NetChip ref design
 	.driver_info =	(unsigned long) &net1080_info,
 }, {
 	USB_DEVICE(0x06D0, 0x0622),	// Laplink Gold
 	.driver_info =	(unsigned long) &net1080_info,
 },
 	{ },		// END
 };
 MODULE_DEVICE_TABLE(usb, products);

 static struct usb_driver net1080_driver = {
 	.name =		"net1080",
 	.id_table =	products,
 	.probe =	usbnet_probe,
 	.disconnect =	usbnet_disconnect,
 	.suspend =	usbnet_suspend,
 	.resume =	usbnet_resume,
 };

 static int __init net1080_init(void)
 {
  	return usb_register(&net1080_driver);
 }
 module_init(net1080_init);

 static void __exit net1080_exit(void)
 {
  	usb_deregister(&net1080_driver);
 }
 module_exit(net1080_exit);

 MODULE_AUTHOR("David Brownell");
 MODULE_DESCRIPTION("NetChip 1080 based USB Host-to-Host Links");
 MODULE_LICENSE("GPL");
	/*
	* Net1080 based USB host-to-host cables
	* Copyright (C) 2000-2005 by David Brownell
	*
	* 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.
	*
	* 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	// #define DEBUG // error path messages, extra info
	// #define VERBOSE // more; success messages

	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/netdevice.h>
	#include <linux/etherdevice.h>
	#include <linux/ethtool.h>
	#include <linux/workqueue.h>
	#include <linux/mii.h>
	#include <linux/usb.h>

	#include <asm/unaligned.h>

	#include "usbnet.h"


	/*
	* Netchip 1080 driver ... http://www.netchip.com
	* (Sept 2004: End-of-life announcement has been sent.)
	* Used in (some) LapLink cables
	*/

	#define frame_errors data[1]

	/*
	* NetChip framing of ethernet packets, supporting additional error
	* checks for links that may drop bulk packets from inside messages.
	* Odd USB length == always short read for last usb packet.
	* - nc_header
	* - Ethernet header (14 bytes)
	* - payload
	* - (optional padding byte, if needed so length becomes odd)
	* - nc_trailer
	*
	* This framing is to be avoided for non-NetChip devices.
	*/

	struct nc_header { // packed:
	__le16 hdr_len; // sizeof nc_header (LE, all)
	__le16 packet_len; // payload size (including ethhdr)
	__le16 packet_id; // detects dropped packets
	#define MIN_HEADER 6

	// all else is optional, and must start with:
	// __le16 vendorId; // from usb-if
	// __le16 productId;
	} __attribute__((__packed__));

	#define PAD_BYTE ((unsigned char)0xAC)

	struct nc_trailer {
	__le16 packet_id;
	} __attribute__((__packed__));

	// packets may use FLAG_FRAMING_NC and optional pad
	#define FRAMED_SIZE(mtu) (sizeof (struct nc_header) \
	+ sizeof (struct ethhdr) \
	+ (mtu) \
	+ 1 \
	+ sizeof (struct nc_trailer))

	#define MIN_FRAMED FRAMED_SIZE(0)

	/* packets _could_ be up to 64KB... */
	#define NC_MAX_PACKET 32767


	/*
	* Zero means no timeout; else, how long a 64 byte bulk packet may be queued
	* before the hardware drops it. If that's done, the driver will need to
	* frame network packets to guard against the dropped USB packets. The win32
	* driver sets this for both sides of the link.
	*/
	#define NC_READ_TTL_MS ((u8)255) // ms

	/*
	* We ignore most registers and EEPROM contents.
	*/
	#define REG_USBCTL ((u8)0x04)
	#define REG_TTL ((u8)0x10)
	#define REG_STATUS ((u8)0x11)

	/*
	* Vendor specific requests to read/write data
	*/
	#define REQUEST_REGISTER ((u8)0x10)
	#define REQUEST_EEPROM ((u8)0x11)

	static int
	nc_vendor_read(struct usbnet dev, u8 req, u8 regnum, u16 retval_ptr)
	{
	int status = usb_control_msg(dev->udev,
	usb_rcvctrlpipe(dev->udev, 0),
	req,
	USB_DIR_IN \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	0, regnum,
	retval_ptr, sizeof *retval_ptr,
	USB_CTRL_GET_TIMEOUT);
	if (status > 0)
	status = 0;
	if (!status)
	le16_to_cpus(retval_ptr);
	return status;
	}

	static inline int
	nc_register_read(struct usbnet dev, u8 regnum, u16 retval_ptr)
	{
	return nc_vendor_read(dev, REQUEST_REGISTER, regnum, retval_ptr);
	}

	// no retval ... can become async, usable in_interrupt()
	static void
	nc_vendor_write(struct usbnet *dev, u8 req, u8 regnum, u16 value)
	{
	usb_control_msg(dev->udev,
	usb_sndctrlpipe(dev->udev, 0),
	req,
	USB_DIR_OUT \| USB_TYPE_VENDOR \| USB_RECIP_DEVICE,
	value, regnum,
	NULL, 0, // data is in setup packet
	USB_CTRL_SET_TIMEOUT);
	}

	static inline void
	nc_register_write(struct usbnet *dev, u8 regnum, u16 value)
	{
	nc_vendor_write(dev, REQUEST_REGISTER, regnum, value);
	}


	#if 0
	static void nc_dump_registers(struct usbnet *dev)
	{
	u8 reg;
	u16 *vp = kmalloc(sizeof (u16));

	if (!vp) {
	dbg("no memory?");
	return;
	}

	dbg("%s registers:", dev->net->name);
	for (reg = 0; reg < 0x20; reg++) {
	int retval;

	// reading some registers is trouble
	if (reg >= 0x08 && reg <= 0xf)
	continue;
	if (reg >= 0x12 && reg <= 0x1e)
	continue;

	retval = nc_register_read(dev, reg, vp);
	if (retval < 0)
	dbg("%s reg [0x%x] ==> error %d",
	dev->net->name, reg, retval);
	else
	dbg("%s reg [0x%x] = 0x%x",
	dev->net->name, reg, *vp);
	}
	kfree(vp);
	}
	#endif


	/-------------------------------------------------------------------------/

	/*
	* Control register
	*/

	#define USBCTL_WRITABLE_MASK 0x1f0f
	// bits 15-13 reserved, r/o
	#define USBCTL_ENABLE_LANG (1 << 12)
	#define USBCTL_ENABLE_MFGR (1 << 11)
	#define USBCTL_ENABLE_PROD (1 << 10)
	#define USBCTL_ENABLE_SERIAL (1 << 9)
	#define USBCTL_ENABLE_DEFAULTS (1 << 8)
	// bits 7-4 reserved, r/o
	#define USBCTL_FLUSH_OTHER (1 << 3)
	#define USBCTL_FLUSH_THIS (1 << 2)
	#define USBCTL_DISCONN_OTHER (1 << 1)
	#define USBCTL_DISCONN_THIS (1 << 0)

	static inline void nc_dump_usbctl(struct usbnet *dev, u16 usbctl)
	{
	if (!netif_msg_link(dev))
	return;
	devdbg(dev, "net1080 %s-%s usbctl 0x%x:%s%s%s%s%s;"
	" this%s%s;"
	" other%s%s; r/o 0x%x",
	dev->udev->bus->bus_name, dev->udev->devpath,
	usbctl,
	(usbctl & USBCTL_ENABLE_LANG) ? " lang" : "",
	(usbctl & USBCTL_ENABLE_MFGR) ? " mfgr" : "",
	(usbctl & USBCTL_ENABLE_PROD) ? " prod" : "",
	(usbctl & USBCTL_ENABLE_SERIAL) ? " serial" : "",
	(usbctl & USBCTL_ENABLE_DEFAULTS) ? " defaults" : "",

	(usbctl & USBCTL_FLUSH_OTHER) ? " FLUSH" : "",
	(usbctl & USBCTL_DISCONN_OTHER) ? " DIS" : "",
	(usbctl & USBCTL_FLUSH_THIS) ? " FLUSH" : "",
	(usbctl & USBCTL_DISCONN_THIS) ? " DIS" : "",
	usbctl & ~USBCTL_WRITABLE_MASK
	);
	}

	/-------------------------------------------------------------------------/

	/*
	* Status register
	*/

	#define STATUS_PORT_A (1 << 15)

	#define STATUS_CONN_OTHER (1 << 14)
	#define STATUS_SUSPEND_OTHER (1 << 13)
	#define STATUS_MAILBOX_OTHER (1 << 12)
	#define STATUS_PACKETS_OTHER(n) (((n) >> 8) & 0x03)

	#define STATUS_CONN_THIS (1 << 6)
	#define STATUS_SUSPEND_THIS (1 << 5)
	#define STATUS_MAILBOX_THIS (1 << 4)
	#define STATUS_PACKETS_THIS(n) (((n) >> 0) & 0x03)

	#define STATUS_UNSPEC_MASK 0x0c8c
	#define STATUS_NOISE_MASK ((u16)~(0x0303\|STATUS_UNSPEC_MASK))


	static inline void nc_dump_status(struct usbnet *dev, u16 status)
	{
	if (!netif_msg_link(dev))
	return;
	devdbg(dev, "net1080 %s-%s status 0x%x:"
	" this (%c) PKT=%d%s%s%s;"
	" other PKT=%d%s%s%s; unspec 0x%x",
	dev->udev->bus->bus_name, dev->udev->devpath,
	status,

	// XXX the packet counts don't seem right
	// (1 at reset, not 0); maybe UNSPEC too

	(status & STATUS_PORT_A) ? 'A' : 'B',
	STATUS_PACKETS_THIS(status),
	(status & STATUS_CONN_THIS) ? " CON" : "",
	(status & STATUS_SUSPEND_THIS) ? " SUS" : "",
	(status & STATUS_MAILBOX_THIS) ? " MBOX" : "",

	STATUS_PACKETS_OTHER(status),
	(status & STATUS_CONN_OTHER) ? " CON" : "",
	(status & STATUS_SUSPEND_OTHER) ? " SUS" : "",
	(status & STATUS_MAILBOX_OTHER) ? " MBOX" : "",

	status & STATUS_UNSPEC_MASK
	);
	}

	/-------------------------------------------------------------------------/

	/*
	* TTL register
	*/

	#define TTL_THIS(ttl) (0x00ff & ttl)
	#define TTL_OTHER(ttl) (0x00ff & (ttl >> 8))
	#define MK_TTL(this,other) ((u16)(((other)<<8)\|(0x00ff&(this))))

	static inline void nc_dump_ttl(struct usbnet *dev, u16 ttl)
	{
	if (netif_msg_link(dev))
	devdbg(dev, "net1080 %s-%s ttl 0x%x this = %d, other = %d",
	dev->udev->bus->bus_name, dev->udev->devpath,
	ttl, TTL_THIS(ttl), TTL_OTHER(ttl));
	}

	/-------------------------------------------------------------------------/

	static int net1080_reset(struct usbnet *dev)
	{
	u16 usbctl, status, ttl;
	u16 *vp = kmalloc(sizeof (u16), GFP_KERNEL);
	int retval;

	if (!vp)
	return -ENOMEM;

	// nc_dump_registers(dev);

	if ((retval = nc_register_read(dev, REG_STATUS, vp)) < 0) {
	dbg("can't read %s-%s status: %d",
	dev->udev->bus->bus_name, dev->udev->devpath, retval);
	goto done;
	}
	status = *vp;
	nc_dump_status(dev, status);

	if ((retval = nc_register_read(dev, REG_USBCTL, vp)) < 0) {
	dbg("can't read USBCTL, %d", retval);
	goto done;
	}
	usbctl = *vp;
	nc_dump_usbctl(dev, usbctl);

	nc_register_write(dev, REG_USBCTL,
	USBCTL_FLUSH_THIS \| USBCTL_FLUSH_OTHER);

	if ((retval = nc_register_read(dev, REG_TTL, vp)) < 0) {
	dbg("can't read TTL, %d", retval);
	goto done;
	}
	ttl = *vp;
	// nc_dump_ttl(dev, ttl);

	nc_register_write(dev, REG_TTL,
	MK_TTL(NC_READ_TTL_MS, TTL_OTHER(ttl)) );
	dbg("%s: assigned TTL, %d ms", dev->net->name, NC_READ_TTL_MS);

	if (netif_msg_link(dev))
	devinfo(dev, "port %c, peer %sconnected",
	(status & STATUS_PORT_A) ? 'A' : 'B',
	(status & STATUS_CONN_OTHER) ? "" : "dis"
	);
	retval = 0;

	done:
	kfree(vp);
	return retval;
	}

	static int net1080_check_connect(struct usbnet *dev)
	{
	int retval;
	u16 status;
	u16 *vp = kmalloc(sizeof (u16), GFP_KERNEL);

	if (!vp)
	return -ENOMEM;
	retval = nc_register_read(dev, REG_STATUS, vp);
	status = *vp;
	kfree(vp);
	if (retval != 0) {
	dbg("%s net1080_check_conn read - %d", dev->net->name, retval);
	return retval;
	}
	if ((status & STATUS_CONN_OTHER) != STATUS_CONN_OTHER)
	return -ENOLINK;
	return 0;
	}

	static void nc_flush_complete(struct urb *urb)
	{
	kfree(urb->context);
	usb_free_urb(urb);
	}

	static void nc_ensure_sync(struct usbnet *dev)
	{
	dev->frame_errors++;
	if (dev->frame_errors > 5) {
	struct urb *urb;
	struct usb_ctrlrequest *req;
	int status;

	/* Send a flush */
	urb = usb_alloc_urb(0, GFP_ATOMIC);
	if (!urb)
	return;

	req = kmalloc(sizeof *req, GFP_ATOMIC);
	if (!req) {
	usb_free_urb(urb);
	return;
	}

	req->bRequestType = USB_DIR_OUT
	\| USB_TYPE_VENDOR
	\| USB_RECIP_DEVICE;
	req->bRequest = REQUEST_REGISTER;
	req->wValue = cpu_to_le16(USBCTL_FLUSH_THIS
	\| USBCTL_FLUSH_OTHER);
	req->wIndex = cpu_to_le16(REG_USBCTL);
	req->wLength = cpu_to_le16(0);

	/* queue an async control request, we don't need
	* to do anything when it finishes except clean up.
	*/
	usb_fill_control_urb(urb, dev->udev,
	usb_sndctrlpipe(dev->udev, 0),
	(unsigned char *) req,
	NULL, 0,
	nc_flush_complete, req);
	status = usb_submit_urb(urb, GFP_ATOMIC);
	if (status) {
	kfree(req);
	usb_free_urb(urb);
	return;
	}

	if (netif_msg_rx_err(dev))
	devdbg(dev, "flush net1080; too many framing errors");
	dev->frame_errors = 0;
	}
	}

	static int net1080_rx_fixup(struct usbnet dev, struct sk_buff skb)
	{
	struct nc_header *header;
	struct nc_trailer *trailer;
	u16 hdr_len, packet_len;

	if (!(skb->len & 0x01)) {
	#ifdef DEBUG
	struct net_device *net = dev->net;
	dbg("rx framesize %d range %d..%d mtu %d", skb->len,
	net->hard_header_len, dev->hard_mtu, net->mtu);
	#endif
	dev->stats.rx_frame_errors++;
	nc_ensure_sync(dev);
	return 0;
	}

	header = (struct nc_header *) skb->data;
	hdr_len = le16_to_cpup(&header->hdr_len);
	packet_len = le16_to_cpup(&header->packet_len);
	if (FRAMED_SIZE(packet_len) > NC_MAX_PACKET) {
	dev->stats.rx_frame_errors++;
	dbg("packet too big, %d", packet_len);
	nc_ensure_sync(dev);
	return 0;
	} else if (hdr_len < MIN_HEADER) {
	dev->stats.rx_frame_errors++;
	dbg("header too short, %d", hdr_len);
	nc_ensure_sync(dev);
	return 0;
	} else if (hdr_len > MIN_HEADER) {
	// out of band data for us?
	dbg("header OOB, %d bytes", hdr_len - MIN_HEADER);
	nc_ensure_sync(dev);
	// switch (vendor/product ids) { ... }
	}
	skb_pull(skb, hdr_len);

	trailer = (struct nc_trailer *)
	(skb->data + skb->len - sizeof *trailer);
	skb_trim(skb, skb->len - sizeof *trailer);

	if ((packet_len & 0x01) == 0) {
	if (skb->data [packet_len] != PAD_BYTE) {
	dev->stats.rx_frame_errors++;
	dbg("bad pad");
	return 0;
	}
	skb_trim(skb, skb->len - 1);
	}
	if (skb->len != packet_len) {
	dev->stats.rx_frame_errors++;
	dbg("bad packet len %d (expected %d)",
	skb->len, packet_len);
	nc_ensure_sync(dev);
	return 0;
	}
	if (header->packet_id != get_unaligned(&trailer->packet_id)) {
	dev->stats.rx_fifo_errors++;
	dbg("(2+ dropped) rx packet_id mismatch 0x%x 0x%x",
	le16_to_cpu(header->packet_id),
	le16_to_cpu(trailer->packet_id));
	return 0;
	}
	#if 0
	devdbg(dev, "frame <rx h %d p %d id %d", header->hdr_len,
	header->packet_len, header->packet_id);
	#endif
	dev->frame_errors = 0;
	return 1;
	}

	static struct sk_buff *
	net1080_tx_fixup(struct usbnet dev, struct sk_buff skb, gfp_t flags)
	{
	struct sk_buff *skb2;
	struct nc_header *header = NULL;
	struct nc_trailer *trailer = NULL;
	int padlen = sizeof (struct nc_trailer);
	int len = skb->len;

	if (!((len + padlen + sizeof (struct nc_header)) & 0x01))
	padlen++;
	if (!skb_cloned(skb)) {
	int headroom = skb_headroom(skb);
	int tailroom = skb_tailroom(skb);

	if (padlen <= tailroom &&
	sizeof(struct nc_header) <= headroom)
	/* There's enough head and tail room */
	goto encapsulate;

	if ((sizeof (struct nc_header) + padlen) <
	(headroom + tailroom)) {
	/* There's enough total room, so just readjust */
	skb->data = memmove(skb->head
	+ sizeof (struct nc_header),
	skb->data, skb->len);
	skb_set_tail_pointer(skb, len);
	goto encapsulate;
	}
	}

	/* Create a new skb to use with the correct size */
	skb2 = skb_copy_expand(skb,
	sizeof (struct nc_header),
	padlen,
	flags);
	dev_kfree_skb_any(skb);
	if (!skb2)
	return skb2;
	skb = skb2;

	encapsulate:
	/* header first */
	header = (struct nc_header ) skb_push(skb, sizeof header);
	header->hdr_len = cpu_to_le16(sizeof (*header));
	header->packet_len = cpu_to_le16(len);
	header->packet_id = cpu_to_le16((u16)dev->xid++);

	/* maybe pad; then trailer */
	if (!((skb->len + sizeof *trailer) & 0x01))
	*skb_put(skb, 1) = PAD_BYTE;
	trailer = (struct nc_trailer ) skb_put(skb, sizeof trailer);
	put_unaligned(header->packet_id, &trailer->packet_id);
	#if 0
	devdbg(dev, "frame >tx h %d p %d id %d",
	header->hdr_len, header->packet_len,
	header->packet_id);
	#endif
	return skb;
	}

	static int net1080_bind(struct usbnet dev, struct usb_interface intf)
	{
	unsigned extra = sizeof (struct nc_header)
	+ 1
	+ sizeof (struct nc_trailer);

	dev->net->hard_header_len += extra;
	dev->rx_urb_size = dev->net->hard_header_len + dev->net->mtu;
	dev->hard_mtu = NC_MAX_PACKET;
	return usbnet_get_endpoints (dev, intf);
	}

	static const struct driver_info net1080_info = {
	.description = "NetChip TurboCONNECT",
	.flags = FLAG_FRAMING_NC,
	.bind = net1080_bind,
	.reset = net1080_reset,
	.check_connect = net1080_check_connect,
	.rx_fixup = net1080_rx_fixup,
	.tx_fixup = net1080_tx_fixup,
	};

	static const struct usb_device_id products [] = {
	{
	USB_DEVICE(0x0525, 0x1080), // NetChip ref design
	.driver_info = (unsigned long) &net1080_info,
	}, {
	USB_DEVICE(0x06D0, 0x0622), // Laplink Gold
	.driver_info = (unsigned long) &net1080_info,
	},
	{ }, // END
	};
	MODULE_DEVICE_TABLE(usb, products);

	static struct usb_driver net1080_driver = {
	.name = "net1080",
	.id_table = products,
	.probe = usbnet_probe,
	.disconnect = usbnet_disconnect,
	.suspend = usbnet_suspend,
	.resume = usbnet_resume,
	};

	static int __init net1080_init(void)
	{
	return usb_register(&net1080_driver);
	}
	module_init(net1080_init);

	static void __exit net1080_exit(void)
	{
	usb_deregister(&net1080_driver);
	}
	module_exit(net1080_exit);

	MODULE_AUTHOR("David Brownell");
	MODULE_DESCRIPTION("NetChip 1080 based USB Host-to-Host Links");
	MODULE_LICENSE("GPL");