/*
   * driver for the i2c-tiny-usb adapter - 1.0
   * http://www.harbaum.org/till/i2c_tiny_usb
   *
   * Copyright (C) 2006-2007 Till Harbaum (Till@Harbaum.org)
   *
   * 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, version 2.
   *
   */
  
  #include <linux/kernel.h>
  #include <linux/errno.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/types.h>
  
  /* include interfaces to usb layer */
  #include <linux/usb.h>
  
  /* include interface to i2c layer */
  #include <linux/i2c.h>
  
  /* commands via USB, must match command ids in the firmware */
  #define CMD_ECHO		0
  #define CMD_GET_FUNC		1
  #define CMD_SET_DELAY		2
  #define CMD_GET_STATUS		3
  
  #define CMD_I2C_IO		4
  #define CMD_I2C_IO_BEGIN	(1<<0)
  #define CMD_I2C_IO_END		(1<<1)
  
  /* i2c bit delay, default is 10us -> 100kHz max
     (in practice, due to additional delays in the i2c bitbanging
     code this results in a i2c clock of about 50kHz) */
  static unsigned short delay = 10;
  module_param(delay, ushort, 0);
  MODULE_PARM_DESC(delay, "bit delay in microseconds "
  		 "(default is 10us for 100kHz max)");
  
  static int usb_read(struct i2c_adapter *adapter, int cmd,
  		    int value, int index, void *data, int len);
  
  static int usb_write(struct i2c_adapter *adapter, int cmd,
  		     int value, int index, void *data, int len);
  
  /* ----- begin of i2c layer ---------------------------------------------- */
  
  #define STATUS_IDLE		0
  #define STATUS_ADDRESS_ACK	1
  #define STATUS_ADDRESS_NAK	2
  
  static int usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs, int num)
  {
  	unsigned char *pstatus;
  	struct i2c_msg *pmsg;
  	int i, ret;
  
  	dev_dbg(&adapter->dev, "master xfer %d messages:
  ", num);
  
  	pstatus = kmalloc(sizeof(*pstatus), GFP_KERNEL);
  	if (!pstatus)
  		return -ENOMEM;
  
  	for (i = 0 ; i < num ; i++) {
  		int cmd = CMD_I2C_IO;
  
  		if (i == 0)
  			cmd |= CMD_I2C_IO_BEGIN;
  
  		if (i == num-1)
  			cmd |= CMD_I2C_IO_END;
  
  		pmsg = &msgs[i];
  
  		dev_dbg(&adapter->dev,
  			"  %d: %s (flags %d) %d bytes to 0x%02x
  ",
  			i, pmsg->flags & I2C_M_RD ? "read" : "write",
  			pmsg->flags, pmsg->len, pmsg->addr);
  
  		/* and directly send the message */
  		if (pmsg->flags & I2C_M_RD) {
  			/* read data */
  			if (usb_read(adapter, cmd,
  				     pmsg->flags, pmsg->addr,
  				     pmsg->buf, pmsg->len) != pmsg->len) {
  				dev_err(&adapter->dev,
  					"failure reading data
  ");
  				ret = -EREMOTEIO;
  				goto out;
  			}
  		} else {
  			/* write data */
  			if (usb_write(adapter, cmd,
  				      pmsg->flags, pmsg->addr,
  				      pmsg->buf, pmsg->len) != pmsg->len) {
  				dev_err(&adapter->dev,
  					"failure writing data
  ");
  				ret = -EREMOTEIO;
  				goto out;
  			}
  		}
  
  		/* read status */
  		if (usb_read(adapter, CMD_GET_STATUS, 0, 0, pstatus, 1) != 1) {
  			dev_err(&adapter->dev, "failure reading status
  ");
  			ret = -EREMOTEIO;
  			goto out;
  		}
  
  		dev_dbg(&adapter->dev, "  status = %d
  ", *pstatus);
  		if (*pstatus == STATUS_ADDRESS_NAK) {
  			ret = -EREMOTEIO;
  			goto out;
  		}
  	}
  
  	ret = i;
  out:
  	kfree(pstatus);
  	return ret;
  }
  
  static u32 usb_func(struct i2c_adapter *adapter)
  {
  	__le32 *pfunc;
  	u32 ret;
  
  	pfunc = kmalloc(sizeof(*pfunc), GFP_KERNEL);
  
  	/* get functionality from adapter */
  	if (!pfunc || usb_read(adapter, CMD_GET_FUNC, 0, 0, pfunc,
  			       sizeof(*pfunc)) != sizeof(*pfunc)) {
  		dev_err(&adapter->dev, "failure reading functionality
  ");
  		ret = 0;
  		goto out;
  	}
  
  	ret = le32_to_cpup(pfunc);
  out:
  	kfree(pfunc);
  	return ret;
  }
  
  /* This is the actual algorithm we define */
  static const struct i2c_algorithm usb_algorithm = {
  	.master_xfer	= usb_xfer,
  	.functionality	= usb_func,
  };
  
  /* ----- end of i2c layer ------------------------------------------------ */
  
  /* ----- begin of usb layer ---------------------------------------------- */
  
  /*
   * Initially the usb i2c interface uses a vid/pid pair donated by
   * Future Technology Devices International Ltd., later a pair was
   * bought from EZPrototypes
   */
  static const struct usb_device_id i2c_tiny_usb_table[] = {
  	{ USB_DEVICE(0x0403, 0xc631) },   /* FTDI */
  	{ USB_DEVICE(0x1c40, 0x0534) },   /* EZPrototypes */
  	{ }                               /* Terminating entry */
  };
  
  MODULE_DEVICE_TABLE(usb, i2c_tiny_usb_table);
  
  /* Structure to hold all of our device specific stuff */
  struct i2c_tiny_usb {
  	struct usb_device *usb_dev; /* the usb device for this device */
  	struct usb_interface *interface; /* the interface for this device */
  	struct i2c_adapter adapter; /* i2c related things */
  };
  
  static int usb_read(struct i2c_adapter *adapter, int cmd,
  		    int value, int index, void *data, int len)
  {
  	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
  
  	/* do control transfer */
  	return usb_control_msg(dev->usb_dev, usb_rcvctrlpipe(dev->usb_dev, 0),
  			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE |
  			       USB_DIR_IN, value, index, data, len, 2000);
  }
  
  static int usb_write(struct i2c_adapter *adapter, int cmd,
  		     int value, int index, void *data, int len)
  {
  	struct i2c_tiny_usb *dev = (struct i2c_tiny_usb *)adapter->algo_data;
  
  	/* do control transfer */
  	return usb_control_msg(dev->usb_dev, usb_sndctrlpipe(dev->usb_dev, 0),
  			       cmd, USB_TYPE_VENDOR | USB_RECIP_INTERFACE,
  			       value, index, data, len, 2000);
  }
  
  static void i2c_tiny_usb_free(struct i2c_tiny_usb *dev)
  {
  	usb_put_dev(dev->usb_dev);
  	kfree(dev);
  }
  
  static int i2c_tiny_usb_probe(struct usb_interface *interface,
  			      const struct usb_device_id *id)
  {
  	struct i2c_tiny_usb *dev;
  	int retval = -ENOMEM;
  	u16 version;
  
  	dev_dbg(&interface->dev, "probing usb device
  ");
  
  	/* allocate memory for our device state and initialize it */
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (dev == NULL) {
  		dev_err(&interface->dev, "Out of memory
  ");
  		goto error;
  	}
  
  	dev->usb_dev = usb_get_dev(interface_to_usbdev(interface));
  	dev->interface = interface;
  
  	/* save our data pointer in this interface device */
  	usb_set_intfdata(interface, dev);
  
  	version = le16_to_cpu(dev->usb_dev->descriptor.bcdDevice);
  	dev_info(&interface->dev,
  		 "version %x.%02x found at bus %03d address %03d
  ",
  		 version >> 8, version & 0xff,
  		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
  
  	/* setup i2c adapter description */
  	dev->adapter.owner = THIS_MODULE;
  	dev->adapter.class = I2C_CLASS_HWMON;
  	dev->adapter.algo = &usb_algorithm;
  	dev->adapter.algo_data = dev;
  	snprintf(dev->adapter.name, sizeof(dev->adapter.name),
  		 "i2c-tiny-usb at bus %03d device %03d",
  		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
  
  	if (usb_write(&dev->adapter, CMD_SET_DELAY, delay, 0, NULL, 0) != 0) {
  		dev_err(&dev->adapter.dev,
  			"failure setting delay to %dus
  ", delay);
  		retval = -EIO;
  		goto error;
  	}
  
  	dev->adapter.dev.parent = &dev->interface->dev;
  
  	/* and finally attach to i2c layer */
  	i2c_add_adapter(&dev->adapter);
  
  	/* inform user about successful attachment to i2c layer */
  	dev_info(&dev->adapter.dev, "connected i2c-tiny-usb device
  ");
  
  	return 0;
  
   error:
  	if (dev)
  		i2c_tiny_usb_free(dev);
  
  	return retval;
  }
  
  static void i2c_tiny_usb_disconnect(struct usb_interface *interface)
  {
  	struct i2c_tiny_usb *dev = usb_get_intfdata(interface);
  
  	i2c_del_adapter(&dev->adapter);
  	usb_set_intfdata(interface, NULL);
  	i2c_tiny_usb_free(dev);
  
  	dev_dbg(&interface->dev, "disconnected
  ");
  }
  
  static struct usb_driver i2c_tiny_usb_driver = {
  	.name		= "i2c-tiny-usb",
  	.probe		= i2c_tiny_usb_probe,
  	.disconnect	= i2c_tiny_usb_disconnect,
  	.id_table	= i2c_tiny_usb_table,
  };
  
  module_usb_driver(i2c_tiny_usb_driver);
  
  /* ----- end of usb layer ------------------------------------------------ */
  
  MODULE_AUTHOR("Till Harbaum <Till@Harbaum.org>");
  MODULE_DESCRIPTION("i2c-tiny-usb driver v1.0");
  MODULE_LICENSE("GPL");