drivers/i2c/busses/i2c-diolan-u2c.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * 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)
  */

 #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(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 = I2C_MAX_STANDARD_MODE_FREQ;	/* 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\n");
 }

 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\n",
 			 (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\n", serial);
 	}
 }

 static int diolan_init(struct i2c_diolan_u2c *dev)
 {
 	int speed, ret;

 	if (frequency >= 2 * I2C_MAX_STANDARD_MODE_FREQ) {
 		speed = U2C_I2C_SPEED_FAST;
 		frequency = I2C_MAX_FAST_MODE_FREQ;
 	} else if (frequency >= I2C_MAX_STANDARD_MODE_FREQ || frequency == 0) {
 		speed = U2C_I2C_SPEED_STD;
 		frequency = I2C_MAX_STANDARD_MODE_FREQ;
 	} 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\n",
 		 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;
 		}
 		ret = diolan_i2c_put_byte_ack(dev,
 					      i2c_8bit_addr_from_msg(pmsg));
 		if (ret < 0)
 			goto abort;
 		if (pmsg->flags & I2C_M_RD) {
 			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 {
 			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\n");
 		goto error_free;
 	}

 	/* and finally attach to i2c layer */
 	ret = i2c_add_adapter(&dev->adapter);
 	if (ret < 0)
 		goto error_free;

 	dev_dbg(&interface->dev, "connected " DRIVER_NAME "\n");

 	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\n");
 }

 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");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* 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)
	*/

	#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(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 = I2C_MAX_STANDARD_MODE_FREQ; /* 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\n");
	}

	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\n",
	(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\n", serial);
	}
	}

	static int diolan_init(struct i2c_diolan_u2c *dev)
	{
	int speed, ret;

	if (frequency >= 2 * I2C_MAX_STANDARD_MODE_FREQ) {
	speed = U2C_I2C_SPEED_FAST;
	frequency = I2C_MAX_FAST_MODE_FREQ;
	} else if (frequency >= I2C_MAX_STANDARD_MODE_FREQ \|\| frequency == 0) {
	speed = U2C_I2C_SPEED_STD;
	frequency = I2C_MAX_STANDARD_MODE_FREQ;
	} 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\n",
	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;
	}
	ret = diolan_i2c_put_byte_ack(dev,
	i2c_8bit_addr_from_msg(pmsg));
	if (ret < 0)
	goto abort;
	if (pmsg->flags & I2C_M_RD) {
	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 {
	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\n");
	goto error_free;
	}

	/* and finally attach to i2c layer */
	ret = i2c_add_adapter(&dev->adapter);
	if (ret < 0)
	goto error_free;

	dev_dbg(&interface->dev, "connected " DRIVER_NAME "\n");

	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\n");
	}

	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");