/*
   * 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, see <http://www.gnu.org/licenses/>.
   */
  
  #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>
  
  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
  #define CMD_TIMEOUT	100
  #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) {
  		if (cmd != CMD_GET_LINK_STATUS)
  			dev_err(&dev->udev->dev, "send command %#x: error %d
  ",
  				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) {
  				if (cmd != CMD_GET_LINK_STATUS)
  					dev_err(&dev->udev->dev,
  						"reply receive error %d
  ",
  						ret);
  				goto end;
  			}
  			if (actual_len > 0)
  				break;
  		}
  		if (actual_len == 0) {
  			dev_err(&dev->udev->dev, "no reply to command %#x
  ",
  				cmd);
  			ret = -EIO;
  			goto end;
  		}
  		if (buf[0] != cmd) {
  			dev_err(&dev->udev->dev,
  				"got reply to command %#x, expected: %#x
  ",
  				buf[0], cmd);
  			ret = -EIO;
  			goto end;
  		}
  		if (buf[1] != STATUS_SUCCESS) {
  			dev_err(&dev->udev->dev, "command %#x failed: %#x
  ",
  				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;
  	u8 link[3];
  	int timeout = 50;
  
  	/* 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
  ");
  		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;
  
  	/* wait for firmware to become ready (indicated by the link being up) */
  	while (--timeout) {
  		ret = cx82310_cmd(dev, CMD_GET_LINK_STATUS, true, NULL, 0,
  				  link, sizeof(link));
  		/* the command can time out during boot - it's not an error */
  		if (!ret && link[0] == 1 && link[2] == 1)
  			break;
  		msleep(500);
  	}
  	if (!timeout) {
  		dev_err(&udev->dev, "firmware not ready in time
  ");
  		return -ETIMEDOUT;
  	}
  
  	/* 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
  ",
  			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
  ", 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
  ",
  				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,
  };
  
  #define USB_DEVICE_CLASS(vend, prod, cl, sc, pr) \
  	.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
  		       USB_DEVICE_ID_MATCH_DEV_INFO, \
  	.idVendor = (vend), \
  	.idProduct = (prod), \
  	.bDeviceClass = (cl), \
  	.bDeviceSubClass = (sc), \
  	.bDeviceProtocol = (pr)
  
  static const struct usb_device_id products[] = {
  	{
  		USB_DEVICE_CLASS(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");