/*
 * Driver for USB ethernet port of Conexant CX82310-based ADSL routers
 * Copyright (C) 2010 by Ondrej Zary
 * some parts inspired by the cxacru driver
 *
 * 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
 */

#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 <linux/usb/usbnet.h>

enum cx82310_cmd {
        CMD_START               = 0x84, /* no effect? */
        CMD_STOP                = 0x85, /* no effect? */
        CMD_GET_STATUS          = 0x90, /* returns nothing? */
        CMD_GET_MAC_ADDR        = 0x91, /* read MAC address */
        CMD_GET_LINK_STATUS     = 0x92, /* not useful, link is always up */
        CMD_ETHERNET_MODE       = 0x99, /* unknown, needed during init */
};

enum cx82310_status {
        STATUS_UNDEFINED,
        STATUS_SUCCESS,
        STATUS_ERROR,
        STATUS_UNSUPPORTED,
        STATUS_UNIMPLEMENTED,
        STATUS_PARAMETER_ERROR,
        STATUS_DBG_LOOPBACK,
};

#define CMD_PACKET_SIZE 64
/* first command after power on can take around 8 seconds */
#define CMD_TIMEOUT     15000
#define CMD_REPLY_RETRY 5

#define CX82310_MTU     1514
#define CMD_EP          0x01

/*
 * execute control command
 *  - optionally send some data (command parameters)
 *  - optionally wait for the reply
 *  - optionally read some data from the reply
 */
static int cx82310_cmd(struct usbnet *dev, enum cx82310_cmd cmd, bool reply,
                       u8 *wdata, int wlen, u8 *rdata, int rlen)
{
        int actual_len, retries, ret;
        struct usb_device *udev = dev->udev;
        u8 *buf = kzalloc(CMD_PACKET_SIZE, GFP_KERNEL);

        if (!buf)
                return -ENOMEM;

        /* create command packet */
        buf[0] = cmd;
        if (wdata)
                memcpy(buf + 4, wdata, min_t(int, wlen, CMD_PACKET_SIZE - 4));

        /* send command packet */
        ret = usb_bulk_msg(udev, usb_sndbulkpipe(udev, CMD_EP), buf,
                           CMD_PACKET_SIZE, &actual_len, CMD_TIMEOUT);
        if (ret < 0) {
                dev_err(&dev->udev->dev, "send command %#x: error %d\n",
                        cmd, ret);
                goto end;
        }

        if (reply) {
                /* wait for reply, retry if it's empty */
                for (retries = 0; retries < CMD_REPLY_RETRY; retries++) {
                        ret = usb_bulk_msg(udev, usb_rcvbulkpipe(udev, CMD_EP),
                                           buf, CMD_PACKET_SIZE, &actual_len,
                                           CMD_TIMEOUT);
                        if (ret < 0) {
                                dev_err(&dev->udev->dev,
                                        "reply receive error %d\n", ret);
                                goto end;
                        }
                        if (actual_len > 0)
                                break;
                }
                if (actual_len == 0) {
                        dev_err(&dev->udev->dev, "no reply to command %#x\n",
                                cmd);
                        ret = -EIO;
                        goto end;
                }
                if (buf[0] != cmd) {
                        dev_err(&dev->udev->dev,
                                "got reply to command %#x, expected: %#x\n",
                                buf[0], cmd);
                        ret = -EIO;
                        goto end;
                }
                if (buf[1] != STATUS_SUCCESS) {
                        dev_err(&dev->udev->dev, "command %#x failed: %#x\n",
                                cmd, buf[1]);
                        ret = -EIO;
                        goto end;
                }
                if (rdata)
                        memcpy(rdata, buf + 4,
                               min_t(int, rlen, CMD_PACKET_SIZE - 4));
        }
end:
        kfree(buf);
        return ret;
}

#define partial_len     data[0]         /* length of partial packet data */
#define partial_rem     data[1]         /* remaining (missing) data length */
#define partial_data    data[2]         /* partial packet data */

static int cx82310_bind(struct usbnet *dev, struct usb_interface *intf)
{
        int ret;
        char buf[15];
        struct usb_device *udev = dev->udev;

        /* avoid ADSL modems - continue only if iProduct is "USB NET CARD" */
        if (usb_string(udev, udev->descriptor.iProduct, buf, sizeof(buf)) > 0
            && strcmp(buf, "USB NET CARD")) {
                dev_info(&udev->dev, "ignoring: probably an ADSL modem\n");
                return -ENODEV;
        }

        ret = usbnet_get_endpoints(dev, intf);
        if (ret)
                return ret;

        /*
         * this must not include ethernet header as the device can send partial
         * packets with no header (and sometimes even empty URBs)
         */
        dev->net->hard_header_len = 0;
        /* we can send at most 1514 bytes of data (+ 2-byte header) per URB */
        dev->hard_mtu = CX82310_MTU + 2;
        /* we can receive URBs up to 4KB from the device */
        dev->rx_urb_size = 4096;

        dev->partial_data = (unsigned long) kmalloc(dev->hard_mtu, GFP_KERNEL);
        if (!dev->partial_data)
                return -ENOMEM;

        /* enable ethernet mode (?) */
        ret = cx82310_cmd(dev, CMD_ETHERNET_MODE, true, "\x01", 1, NULL, 0);
        if (ret) {
                dev_err(&udev->dev, "unable to enable ethernet mode: %d\n",
                        ret);
                goto err;
        }

        /* get the MAC address */
        ret = cx82310_cmd(dev, CMD_GET_MAC_ADDR, true, NULL, 0,
                          dev->net->dev_addr, ETH_ALEN);
        if (ret) {
                dev_err(&udev->dev, "unable to read MAC address: %d\n", ret);
                goto err;
        }

        /* start (does not seem to have any effect?) */
        ret = cx82310_cmd(dev, CMD_START, false, NULL, 0, NULL, 0);
        if (ret)
                goto err;

        return 0;
err:
        kfree((void *)dev->partial_data);
        return ret;
}

static void cx82310_unbind(struct usbnet *dev, struct usb_interface *intf)
{
        kfree((void *)dev->partial_data);
}

/*
 * RX is NOT easy - we can receive multiple packets per skb, each having 2-byte
 * packet length at the beginning.
 * The last packet might be incomplete (when it crosses the 4KB URB size),
 * continuing in the next skb (without any headers).
 * If a packet has odd length, there is one extra byte at the end (before next
 * packet or at the end of the URB).
 */
static int cx82310_rx_fixup(struct usbnet *dev, struct sk_buff *skb)
{
        int len;
        struct sk_buff *skb2;

        /*
         * If the last skb ended with an incomplete packet, this skb contains
         * end of that packet at the beginning.
         */
        if (dev->partial_rem) {
                len = dev->partial_len + dev->partial_rem;
                skb2 = alloc_skb(len, GFP_ATOMIC);
                if (!skb2)
                        return 0;
                skb_put(skb2, len);
                memcpy(skb2->data, (void *)dev->partial_data,
                       dev->partial_len);
                memcpy(skb2->data + dev->partial_len, skb->data,
                       dev->partial_rem);
                usbnet_skb_return(dev, skb2);
                skb_pull(skb, (dev->partial_rem + 1) & ~1);
                dev->partial_rem = 0;
                if (skb->len < 2)
                        return 1;
        }

        /* a skb can contain multiple packets */
        while (skb->len > 1) {
                /* first two bytes are packet length */
                len = skb->data[0] | (skb->data[1] << 8);
                skb_pull(skb, 2);

                /* if last packet in the skb, let usbnet to process it */
                if (len == skb->len || len + 1 == skb->len) {
                        skb_trim(skb, len);
                        break;
                }

                if (len > CX82310_MTU) {
                        dev_err(&dev->udev->dev, "RX packet too long: %d B\n",
                                len);
                        return 0;
                }

                /* incomplete packet, save it for the next skb */
                if (len > skb->len) {
                        dev->partial_len = skb->len;
                        dev->partial_rem = len - skb->len;
                        memcpy((void *)dev->partial_data, skb->data,
                               dev->partial_len);
                        skb_pull(skb, skb->len);
                        break;
                }

                skb2 = alloc_skb(len, GFP_ATOMIC);
                if (!skb2)
                        return 0;
                skb_put(skb2, len);
                memcpy(skb2->data, skb->data, len);
                /* process the packet */
                usbnet_skb_return(dev, skb2);

                skb_pull(skb, (len + 1) & ~1);
        }

        /* let usbnet process the last packet */
        return 1;
}

/* TX is easy, just add 2 bytes of length at the beginning */
static struct sk_buff *cx82310_tx_fixup(struct usbnet *dev, struct sk_buff *skb,
                                       gfp_t flags)
{
        int len = skb->len;

        if (skb_headroom(skb) < 2) {
                struct sk_buff *skb2 = skb_copy_expand(skb, 2, 0, flags);
                dev_kfree_skb_any(skb);
                skb = skb2;
                if (!skb)
                        return NULL;
        }
        skb_push(skb, 2);

        skb->data[0] = len;
        skb->data[1] = len >> 8;

        return skb;
}


static const struct driver_info cx82310_info = {
        .description    = "Conexant CX82310 USB ethernet",
        .flags          = FLAG_ETHER,
        .bind           = cx82310_bind,
        .unbind         = cx82310_unbind,
        .rx_fixup       = cx82310_rx_fixup,
        .tx_fixup       = cx82310_tx_fixup,
};

static const struct usb_device_id products[] = {
        {
                USB_DEVICE_AND_INTERFACE_INFO(0x0572, 0xcb01, 0xff, 0, 0),
                .driver_info = (unsigned long) &cx82310_info
        },
        { },
};
MODULE_DEVICE_TABLE(usb, products);

static struct usb_driver cx82310_driver = {
        .name           = "cx82310_eth",
        .id_table       = products,
        .probe          = usbnet_probe,
        .disconnect     = usbnet_disconnect,
        .suspend        = usbnet_suspend,
        .resume         = usbnet_resume,
        .disable_hub_initiated_lpm = 1,
};

module_usb_driver(cx82310_driver);

MODULE_AUTHOR("Ondrej Zary");
MODULE_DESCRIPTION("Conexant CX82310-based ADSL router USB ethernet driver");
MODULE_LICENSE("GPL");