// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Net1080 based USB host-to-host cables
 * Copyright (C) 2000-2005 by David Brownell
 */

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

#include <linux/module.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 <linux/usb/usbnet.h>
#include <linux/slab.h>

#include <linux/unaligned.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;
} __packed;

#define PAD_BYTE        ((unsigned char)0xAC)

struct nc_trailer {
        __le16  packet_id;
} __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 = usbnet_read_cmd(dev, req,
                                     USB_DIR_IN | USB_TYPE_VENDOR |
                                     USB_RECIP_DEVICE,
                                     0, regnum, retval_ptr,
                                     sizeof *retval_ptr);
        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);
}

static void
nc_vendor_write(struct usbnet *dev, u8 req, u8 regnum, u16 value)
{
        usbnet_write_cmd(dev, req,
                         USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
                         value, regnum, NULL, 0);
}

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)
                return;

        netdev_dbg(dev->net, "registers:\n");
        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)
                        netdev_dbg(dev->net, "reg [0x%x] ==> error %d\n",
                                   reg, retval);
                else
                        netdev_dbg(dev->net, "reg [0x%x] = 0x%x\n", 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)
{
        netif_dbg(dev, link, dev->net,
                  "net1080 %s-%s usbctl 0x%x:%s%s%s%s%s; this%s%s; other%s%s; r/o 0x%x\n",
                  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_THIS) ? " FLUSH" : "",
                  (usbctl & USBCTL_DISCONN_THIS) ? " DIS" : "",

                  (usbctl & USBCTL_FLUSH_OTHER) ? " FLUSH" : "",
                  (usbctl & USBCTL_DISCONN_OTHER) ? " 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)
{
        netif_dbg(dev, link, dev->net,
                  "net1080 %s-%s status 0x%x: this (%c) PKT=%d%s%s%s; other PKT=%d%s%s%s; unspec 0x%x\n",
                  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_OTHER(ttl)  (0x00ff & (ttl >> 8))
#define MK_TTL(this,other)      ((u16)(((other)<<8)|(0x00ff&(this))))

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

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

        // nc_dump_registers(dev);

        if ((retval = nc_register_read(dev, REG_STATUS, &vp)) < 0) {
                netdev_dbg(dev->net, "can't read %s-%s status: %d\n",
                           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) {
                netdev_dbg(dev->net, "can't read USBCTL, %d\n", 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) {
                netdev_dbg(dev->net, "can't read TTL, %d\n", retval);
                goto done;
        }
        ttl = vp;

        nc_register_write(dev, REG_TTL,
                        MK_TTL(NC_READ_TTL_MS, TTL_OTHER(ttl)) );
        netdev_dbg(dev->net, "assigned TTL, %d ms\n", NC_READ_TTL_MS);

        netif_info(dev, link, dev->net, "port %c, peer %sconnected\n",
                   (status & STATUS_PORT_A) ? 'A' : 'B',
                   (status & STATUS_CONN_OTHER) ? "" : "dis");
        retval = 0;

done:
        return retval;
}

static int net1080_check_connect(struct usbnet *dev)
{
        int                     retval;
        u16                     status;
        u16                     vp;

        retval = nc_register_read(dev, REG_STATUS, &vp);
        status = vp;
        if (retval != 0) {
                netdev_dbg(dev->net, "net1080_check_conn read - %d\n", retval);
                return retval;
        }
        if ((status & STATUS_CONN_OTHER) != STATUS_CONN_OTHER)
                return -ENOLINK;
        return 0;
}

static void nc_ensure_sync(struct usbnet *dev)
{
        if (++dev->frame_errors <= 5)
                return;

        if (usbnet_write_cmd_async(dev, REQUEST_REGISTER,
                                        USB_DIR_OUT | USB_TYPE_VENDOR |
                                        USB_RECIP_DEVICE,
                                        USBCTL_FLUSH_THIS |
                                        USBCTL_FLUSH_OTHER,
                                        REG_USBCTL, NULL, 0))
                return;

        netif_dbg(dev, rx_err, dev->net,
                  "flush net1080; too many framing errors\n");
        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;

        /* This check is no longer done by usbnet */
        if (skb->len < dev->net->hard_header_len)
                return 0;

        if (!(skb->len & 0x01)) {
                netdev_dbg(dev->net, "rx framesize %d range %d..%d mtu %d\n",
                           skb->len, dev->net->hard_header_len, dev->hard_mtu,
                           dev->net->mtu);
                dev->net->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->net->stats.rx_frame_errors++;
                netdev_dbg(dev->net, "packet too big, %d\n", packet_len);
                nc_ensure_sync(dev);
                return 0;
        } else if (hdr_len < MIN_HEADER) {
                dev->net->stats.rx_frame_errors++;
                netdev_dbg(dev->net, "header too short, %d\n", hdr_len);
                nc_ensure_sync(dev);
                return 0;
        } else if (hdr_len > MIN_HEADER) {
                // out of band data for us?
                netdev_dbg(dev->net, "header OOB, %d bytes\n", 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 (packet_len >= skb->len || skb->data[packet_len] != PAD_BYTE) {
                        dev->net->stats.rx_frame_errors++;
                        netdev_dbg(dev->net, "bad pad\n");
                        return 0;
                }
                skb_trim(skb, skb->len - 1);
        }
        if (skb->len != packet_len) {
                dev->net->stats.rx_frame_errors++;
                netdev_dbg(dev->net, "bad packet len %d (expected %d)\n",
                           skb->len, packet_len);
                nc_ensure_sync(dev);
                return 0;
        }
        if (header->packet_id != get_unaligned(&trailer->packet_id)) {
                dev->net->stats.rx_fifo_errors++;
                netdev_dbg(dev->net, "(2+ dropped) rx packet_id mismatch 0x%x 0x%x\n",
                           le16_to_cpu(header->packet_id),
                           le16_to_cpu(trailer->packet_id));
                return 0;
        }
#if 0
        netdev_dbg(dev->net, "frame <rx h %d p %d id %d\n", 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 = 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_u8(skb, PAD_BYTE);
        trailer = skb_put(skb, sizeof *trailer);
        put_unaligned(header->packet_id, &trailer->packet_id);
#if 0
        netdev_dbg(dev->net, "frame >tx h %d p %d id %d\n",
                   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_POINTTOPOINT | 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,
        .disable_hub_initiated_lpm = 1,
};

module_usb_driver(net1080_driver);

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