/*
   * Driver for the Diolan u2c-12 USB-I2C adapter
   *
   * Copyright (c) 2010-2011 Ericsson AB
   *
   * Derived from:
   *  i2c-tiny-usb.c
   *  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/types.h>
  #include <linux/slab.h>
  #include <linux/usb.h>
  #include <linux/i2c.h>
  
  #define DRIVER_NAME		"i2c-diolan-u2c"
  
  #define USB_VENDOR_ID_DIOLAN		0x0abf
  #define USB_DEVICE_ID_DIOLAN_U2C	0x3370
  
  
  /* commands via USB, must match command ids in the firmware */
  #define CMD_I2C_READ		0x01
  #define CMD_I2C_WRITE		0x02
  #define CMD_I2C_SCAN		0x03	/* Returns list of detected devices */
  #define CMD_I2C_RELEASE_SDA	0x04
  #define CMD_I2C_RELEASE_SCL	0x05
  #define CMD_I2C_DROP_SDA	0x06
  #define CMD_I2C_DROP_SCL	0x07
  #define CMD_I2C_READ_SDA	0x08
  #define CMD_I2C_READ_SCL	0x09
  #define CMD_GET_FW_VERSION	0x0a
  #define CMD_GET_SERIAL		0x0b
  #define CMD_I2C_START		0x0c
  #define CMD_I2C_STOP		0x0d
  #define CMD_I2C_REPEATED_START	0x0e
  #define CMD_I2C_PUT_BYTE	0x0f
  #define CMD_I2C_GET_BYTE	0x10
  #define CMD_I2C_PUT_ACK		0x11
  #define CMD_I2C_GET_ACK		0x12
  #define CMD_I2C_PUT_BYTE_ACK	0x13
  #define CMD_I2C_GET_BYTE_ACK	0x14
  #define CMD_I2C_SET_SPEED	0x1b
  #define CMD_I2C_GET_SPEED	0x1c
  #define CMD_I2C_SET_CLK_SYNC	0x24
  #define CMD_I2C_GET_CLK_SYNC	0x25
  #define CMD_I2C_SET_CLK_SYNC_TO	0x26
  #define CMD_I2C_GET_CLK_SYNC_TO	0x27
  
  #define RESP_OK			0x00
  #define RESP_FAILED		0x01
  #define RESP_BAD_MEMADDR	0x04
  #define RESP_DATA_ERR		0x05
  #define RESP_NOT_IMPLEMENTED	0x06
  #define RESP_NACK		0x07
  #define RESP_TIMEOUT		0x09
  
  #define U2C_I2C_SPEED_FAST	0	/* 400 kHz */
  #define U2C_I2C_SPEED_STD	1	/* 100 kHz */
  #define U2C_I2C_SPEED_2KHZ	242	/* 2 kHz, minimum speed */
  #define U2C_I2C_SPEED(f)	((DIV_ROUND_UP(1000000, (f)) - 10) / 2 + 1)
  
  #define U2C_I2C_FREQ_FAST	400000
  #define U2C_I2C_FREQ_STD	100000
  #define U2C_I2C_FREQ(s)		(1000000 / (2 * (s - 1) + 10))
  
  #define DIOLAN_USB_TIMEOUT	100	/* in ms */
  #define DIOLAN_SYNC_TIMEOUT	20	/* in ms */
  
  #define DIOLAN_OUTBUF_LEN	128
  #define DIOLAN_FLUSH_LEN	(DIOLAN_OUTBUF_LEN - 4)
  #define DIOLAN_INBUF_LEN	256	/* Maximum supported receive length */
  
  /* Structure to hold all of our device specific stuff */
  struct i2c_diolan_u2c {
  	u8 obuffer[DIOLAN_OUTBUF_LEN];	/* output buffer */
  	u8 ibuffer[DIOLAN_INBUF_LEN];	/* input buffer */
  	int ep_in, ep_out;              /* Endpoints    */
  	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 */
  	int olen;			/* Output buffer length */
  	int ocount;			/* Number of enqueued messages */
  };
  
  static uint frequency = U2C_I2C_FREQ_STD;	/* I2C clock frequency in Hz */
  
  module_param(frequency, uint, S_IRUGO | S_IWUSR);
  MODULE_PARM_DESC(frequency, "I2C clock frequency in hertz");
  
  /* usb layer */
  
  /* Send command to device, and get response. */
  static int diolan_usb_transfer(struct i2c_diolan_u2c *dev)
  {
  	int ret = 0;
  	int actual;
  	int i;
  
  	if (!dev->olen || !dev->ocount)
  		return -EINVAL;
  
  	ret = usb_bulk_msg(dev->usb_dev,
  			   usb_sndbulkpipe(dev->usb_dev, dev->ep_out),
  			   dev->obuffer, dev->olen, &actual,
  			   DIOLAN_USB_TIMEOUT);
  	if (!ret) {
  		for (i = 0; i < dev->ocount; i++) {
  			int tmpret;
  
  			tmpret = usb_bulk_msg(dev->usb_dev,
  					      usb_rcvbulkpipe(dev->usb_dev,
  							      dev->ep_in),
  					      dev->ibuffer,
  					      sizeof(dev->ibuffer), &actual,
  					      DIOLAN_USB_TIMEOUT);
  			/*
  			 * Stop command processing if a previous command
  			 * returned an error.
  			 * Note that we still need to retrieve all messages.
  			 */
  			if (ret < 0)
  				continue;
  			ret = tmpret;
  			if (ret == 0 && actual > 0) {
  				switch (dev->ibuffer[actual - 1]) {
  				case RESP_NACK:
  					/*
  					 * Return ENXIO if NACK was received as
  					 * response to the address phase,
  					 * EIO otherwise
  					 */
  					ret = i == 1 ? -ENXIO : -EIO;
  					break;
  				case RESP_TIMEOUT:
  					ret = -ETIMEDOUT;
  					break;
  				case RESP_OK:
  					/* strip off return code */
  					ret = actual - 1;
  					break;
  				default:
  					ret = -EIO;
  					break;
  				}
  			}
  		}
  	}
  	dev->olen = 0;
  	dev->ocount = 0;
  	return ret;
  }
  
  static int diolan_write_cmd(struct i2c_diolan_u2c *dev, bool flush)
  {
  	if (flush || dev->olen >= DIOLAN_FLUSH_LEN)
  		return diolan_usb_transfer(dev);
  	return 0;
  }
  
  /* Send command (no data) */
  static int diolan_usb_cmd(struct i2c_diolan_u2c *dev, u8 command, bool flush)
  {
  	dev->obuffer[dev->olen++] = command;
  	dev->ocount++;
  	return diolan_write_cmd(dev, flush);
  }
  
  /* Send command with one byte of data */
  static int diolan_usb_cmd_data(struct i2c_diolan_u2c *dev, u8 command, u8 data,
  			       bool flush)
  {
  	dev->obuffer[dev->olen++] = command;
  	dev->obuffer[dev->olen++] = data;
  	dev->ocount++;
  	return diolan_write_cmd(dev, flush);
  }
  
  /* Send command with two bytes of data */
  static int diolan_usb_cmd_data2(struct i2c_diolan_u2c *dev, u8 command, u8 d1,
  				u8 d2, bool flush)
  {
  	dev->obuffer[dev->olen++] = command;
  	dev->obuffer[dev->olen++] = d1;
  	dev->obuffer[dev->olen++] = d2;
  	dev->ocount++;
  	return diolan_write_cmd(dev, flush);
  }
  
  /*
   * Flush input queue.
   * If we don't do this at startup and the controller has queued up
   * messages which were not retrieved, it will stop responding
   * at some point.
   */
  static void diolan_flush_input(struct i2c_diolan_u2c *dev)
  {
  	int i;
  
  	for (i = 0; i < 10; i++) {
  		int actual = 0;
  		int ret;
  
  		ret = usb_bulk_msg(dev->usb_dev,
  				   usb_rcvbulkpipe(dev->usb_dev, dev->ep_in),
  				   dev->ibuffer, sizeof(dev->ibuffer), &actual,
  				   DIOLAN_USB_TIMEOUT);
  		if (ret < 0 || actual == 0)
  			break;
  	}
  	if (i == 10)
  		dev_err(&dev->interface->dev, "Failed to flush input buffer
  ");
  }
  
  static int diolan_i2c_start(struct i2c_diolan_u2c *dev)
  {
  	return diolan_usb_cmd(dev, CMD_I2C_START, false);
  }
  
  static int diolan_i2c_repeated_start(struct i2c_diolan_u2c *dev)
  {
  	return diolan_usb_cmd(dev, CMD_I2C_REPEATED_START, false);
  }
  
  static int diolan_i2c_stop(struct i2c_diolan_u2c *dev)
  {
  	return diolan_usb_cmd(dev, CMD_I2C_STOP, true);
  }
  
  static int diolan_i2c_get_byte_ack(struct i2c_diolan_u2c *dev, bool ack,
  				   u8 *byte)
  {
  	int ret;
  
  	ret = diolan_usb_cmd_data(dev, CMD_I2C_GET_BYTE_ACK, ack, true);
  	if (ret > 0)
  		*byte = dev->ibuffer[0];
  	else if (ret == 0)
  		ret = -EIO;
  
  	return ret;
  }
  
  static int diolan_i2c_put_byte_ack(struct i2c_diolan_u2c *dev, u8 byte)
  {
  	return diolan_usb_cmd_data(dev, CMD_I2C_PUT_BYTE_ACK, byte, false);
  }
  
  static int diolan_set_speed(struct i2c_diolan_u2c *dev, u8 speed)
  {
  	return diolan_usb_cmd_data(dev, CMD_I2C_SET_SPEED, speed, true);
  }
  
  /* Enable or disable clock synchronization (stretching) */
  static int diolan_set_clock_synch(struct i2c_diolan_u2c *dev, bool enable)
  {
  	return diolan_usb_cmd_data(dev, CMD_I2C_SET_CLK_SYNC, enable, true);
  }
  
  /* Set clock synchronization timeout in ms */
  static int diolan_set_clock_synch_timeout(struct i2c_diolan_u2c *dev, int ms)
  {
  	int to_val = ms * 10;
  
  	return diolan_usb_cmd_data2(dev, CMD_I2C_SET_CLK_SYNC_TO,
  				    to_val & 0xff, (to_val >> 8) & 0xff, true);
  }
  
  static void diolan_fw_version(struct i2c_diolan_u2c *dev)
  {
  	int ret;
  
  	ret = diolan_usb_cmd(dev, CMD_GET_FW_VERSION, true);
  	if (ret >= 2)
  		dev_info(&dev->interface->dev,
  			 "Diolan U2C firmware version %u.%u
  ",
  			 (unsigned int)dev->ibuffer[0],
  			 (unsigned int)dev->ibuffer[1]);
  }
  
  static void diolan_get_serial(struct i2c_diolan_u2c *dev)
  {
  	int ret;
  	u32 serial;
  
  	ret = diolan_usb_cmd(dev, CMD_GET_SERIAL, true);
  	if (ret >= 4) {
  		serial = le32_to_cpu(*(u32 *)dev->ibuffer);
  		dev_info(&dev->interface->dev,
  			 "Diolan U2C serial number %u
  ", serial);
  	}
  }
  
  static int diolan_init(struct i2c_diolan_u2c *dev)
  {
  	int speed, ret;
  
  	if (frequency >= 200000) {
  		speed = U2C_I2C_SPEED_FAST;
  		frequency = U2C_I2C_FREQ_FAST;
  	} else if (frequency >= 100000 || frequency == 0) {
  		speed = U2C_I2C_SPEED_STD;
  		frequency = U2C_I2C_FREQ_STD;
  	} else {
  		speed = U2C_I2C_SPEED(frequency);
  		if (speed > U2C_I2C_SPEED_2KHZ)
  			speed = U2C_I2C_SPEED_2KHZ;
  		frequency = U2C_I2C_FREQ(speed);
  	}
  
  	dev_info(&dev->interface->dev,
  		 "Diolan U2C at USB bus %03d address %03d speed %d Hz
  ",
  		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum, frequency);
  
  	diolan_flush_input(dev);
  	diolan_fw_version(dev);
  	diolan_get_serial(dev);
  
  	/* Set I2C speed */
  	ret = diolan_set_speed(dev, speed);
  	if (ret < 0)
  		return ret;
  
  	/* Configure I2C clock synchronization */
  	ret = diolan_set_clock_synch(dev, speed != U2C_I2C_SPEED_FAST);
  	if (ret < 0)
  		return ret;
  
  	if (speed != U2C_I2C_SPEED_FAST)
  		ret = diolan_set_clock_synch_timeout(dev, DIOLAN_SYNC_TIMEOUT);
  
  	return ret;
  }
  
  /* i2c layer */
  
  static int diolan_usb_xfer(struct i2c_adapter *adapter, struct i2c_msg *msgs,
  			   int num)
  {
  	struct i2c_diolan_u2c *dev = i2c_get_adapdata(adapter);
  	struct i2c_msg *pmsg;
  	int i, j;
  	int ret, sret;
  
  	ret = diolan_i2c_start(dev);
  	if (ret < 0)
  		return ret;
  
  	for (i = 0; i < num; i++) {
  		pmsg = &msgs[i];
  		if (i) {
  			ret = diolan_i2c_repeated_start(dev);
  			if (ret < 0)
  				goto abort;
  		}
  		if (pmsg->flags & I2C_M_RD) {
  			ret =
  			    diolan_i2c_put_byte_ack(dev, (pmsg->addr << 1) | 1);
  			if (ret < 0)
  				goto abort;
  			for (j = 0; j < pmsg->len; j++) {
  				u8 byte;
  				bool ack = j < pmsg->len - 1;
  
  				/*
  				 * Don't send NACK if this is the first byte
  				 * of a SMBUS_BLOCK message.
  				 */
  				if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN))
  					ack = true;
  
  				ret = diolan_i2c_get_byte_ack(dev, ack, &byte);
  				if (ret < 0)
  					goto abort;
  				/*
  				 * Adjust count if first received byte is length
  				 */
  				if (j == 0 && (pmsg->flags & I2C_M_RECV_LEN)) {
  					if (byte == 0
  					    || byte > I2C_SMBUS_BLOCK_MAX) {
  						ret = -EPROTO;
  						goto abort;
  					}
  					pmsg->len += byte;
  				}
  				pmsg->buf[j] = byte;
  			}
  		} else {
  			ret = diolan_i2c_put_byte_ack(dev, pmsg->addr << 1);
  			if (ret < 0)
  				goto abort;
  			for (j = 0; j < pmsg->len; j++) {
  				ret = diolan_i2c_put_byte_ack(dev,
  							      pmsg->buf[j]);
  				if (ret < 0)
  					goto abort;
  			}
  		}
  	}
  	ret = num;
  abort:
  	sret = diolan_i2c_stop(dev);
  	if (sret < 0 && ret >= 0)
  		ret = sret;
  	return ret;
  }
  
  /*
   * Return list of supported functionality.
   */
  static u32 diolan_usb_func(struct i2c_adapter *a)
  {
  	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
  	       I2C_FUNC_SMBUS_READ_BLOCK_DATA | I2C_FUNC_SMBUS_BLOCK_PROC_CALL;
  }
  
  static const struct i2c_algorithm diolan_usb_algorithm = {
  	.master_xfer = diolan_usb_xfer,
  	.functionality = diolan_usb_func,
  };
  
  /* device layer */
  
  static const struct usb_device_id diolan_u2c_table[] = {
  	{ USB_DEVICE(USB_VENDOR_ID_DIOLAN, USB_DEVICE_ID_DIOLAN_U2C) },
  	{ }
  };
  
  MODULE_DEVICE_TABLE(usb, diolan_u2c_table);
  
  static void diolan_u2c_free(struct i2c_diolan_u2c *dev)
  {
  	usb_put_dev(dev->usb_dev);
  	kfree(dev);
  }
  
  static int diolan_u2c_probe(struct usb_interface *interface,
  			    const struct usb_device_id *id)
  {
  	struct usb_host_interface *hostif = interface->cur_altsetting;
  	struct i2c_diolan_u2c *dev;
  	int ret;
  
  	if (hostif->desc.bInterfaceNumber != 0
  	    || hostif->desc.bNumEndpoints < 2)
  		return -ENODEV;
  
  	/* allocate memory for our device state and initialize it */
  	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
  	if (dev == NULL) {
  		ret = -ENOMEM;
  		goto error;
  	}
  	dev->ep_out = hostif->endpoint[0].desc.bEndpointAddress;
  	dev->ep_in = hostif->endpoint[1].desc.bEndpointAddress;
  
  	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);
  
  	/* setup i2c adapter description */
  	dev->adapter.owner = THIS_MODULE;
  	dev->adapter.class = I2C_CLASS_HWMON;
  	dev->adapter.algo = &diolan_usb_algorithm;
  	i2c_set_adapdata(&dev->adapter, dev);
  	snprintf(dev->adapter.name, sizeof(dev->adapter.name),
  		 DRIVER_NAME " at bus %03d device %03d",
  		 dev->usb_dev->bus->busnum, dev->usb_dev->devnum);
  
  	dev->adapter.dev.parent = &dev->interface->dev;
  
  	/* initialize diolan i2c interface */
  	ret = diolan_init(dev);
  	if (ret < 0) {
  		dev_err(&interface->dev, "failed to initialize adapter
  ");
  		goto error_free;
  	}
  
  	/* and finally attach to i2c layer */
  	ret = i2c_add_adapter(&dev->adapter);
  	if (ret < 0) {
  		dev_err(&interface->dev, "failed to add I2C adapter
  ");
  		goto error_free;
  	}
  
  	dev_dbg(&interface->dev, "connected " DRIVER_NAME "
  ");
  
  	return 0;
  
  error_free:
  	usb_set_intfdata(interface, NULL);
  	diolan_u2c_free(dev);
  error:
  	return ret;
  }
  
  static void diolan_u2c_disconnect(struct usb_interface *interface)
  {
  	struct i2c_diolan_u2c *dev = usb_get_intfdata(interface);
  
  	i2c_del_adapter(&dev->adapter);
  	usb_set_intfdata(interface, NULL);
  	diolan_u2c_free(dev);
  
  	dev_dbg(&interface->dev, "disconnected
  ");
  }
  
  static struct usb_driver diolan_u2c_driver = {
  	.name = DRIVER_NAME,
  	.probe = diolan_u2c_probe,
  	.disconnect = diolan_u2c_disconnect,
  	.id_table = diolan_u2c_table,
  };
  
  module_usb_driver(diolan_u2c_driver);
  
  MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
  MODULE_DESCRIPTION(DRIVER_NAME " driver");
  MODULE_LICENSE("GPL");