drivers/media/usb/usbvision/usbvision-i2c.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * usbvision_i2c.c
  *  i2c algorithm for USB-I2C Bridges
  *
  * Copyright (c) 1999-2007 Joerg Heckenbach <joerg@heckenbach-aw.de>
  *                         Dwaine Garden <dwainegarden@rogers.com>
  *
  * This module is part of usbvision driver project.
  * Updates to driver completed by Dwaine P. Garden
  */


 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/uaccess.h>
 #include <linux/ioport.h>
 #include <linux/errno.h>
 #include <linux/usb.h>
 #include <linux/i2c.h>
 #include "usbvision.h"

 #define DBG_I2C		(1 << 0)

 static int i2c_debug;

 module_param(i2c_debug, int, 0644);			/* debug_i2c_usb mode of the device driver */
 MODULE_PARM_DESC(i2c_debug, "enable debug messages [i2c]");

 #define PDEBUG(level, fmt, args...) { \
 		if (i2c_debug & (level)) \
 			printk(KERN_INFO KBUILD_MODNAME ":[%s:%d] " fmt, \
 				__func__, __LINE__ , ## args); \
 	}

 static int usbvision_i2c_write(struct usb_usbvision *usbvision, unsigned char addr, char *buf,
 			    short len);
 static int usbvision_i2c_read(struct usb_usbvision *usbvision, unsigned char addr, char *buf,
 			   short len);

 static inline int try_write_address(struct i2c_adapter *i2c_adap,
 				    unsigned char addr, int retries)
 {
 	struct usb_usbvision *usbvision;
 	int i, ret = -1;
 	char buf[4];

 	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);
 	buf[0] = 0x00;
 	for (i = 0; i <= retries; i++) {
 		ret = (usbvision_i2c_write(usbvision, addr, buf, 1));
 		if (ret == 1)
 			break;	/* success! */
 		udelay(5);
 		if (i == retries)	/* no success */
 			break;
 		udelay(10);
 	}
 	if (i) {
 		PDEBUG(DBG_I2C, "Needed %d retries for address %#2x", i, addr);
 		PDEBUG(DBG_I2C, "Maybe there's no device at this address");
 	}
 	return ret;
 }

 static inline int try_read_address(struct i2c_adapter *i2c_adap,
 				   unsigned char addr, int retries)
 {
 	struct usb_usbvision *usbvision;
 	int i, ret = -1;
 	char buf[4];

 	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);
 	for (i = 0; i <= retries; i++) {
 		ret = (usbvision_i2c_read(usbvision, addr, buf, 1));
 		if (ret == 1)
 			break;	/* success! */
 		udelay(5);
 		if (i == retries)	/* no success */
 			break;
 		udelay(10);
 	}
 	if (i) {
 		PDEBUG(DBG_I2C, "Needed %d retries for address %#2x", i, addr);
 		PDEBUG(DBG_I2C, "Maybe there's no device at this address");
 	}
 	return ret;
 }

 static inline int usb_find_address(struct i2c_adapter *i2c_adap,
 				   struct i2c_msg *msg, int retries,
 				   unsigned char *add)
 {
 	unsigned short flags = msg->flags;

 	unsigned char addr;
 	int ret;

 	addr = (msg->addr << 1);
 	if (flags & I2C_M_RD)
 		addr |= 1;

 	add[0] = addr;
 	if (flags & I2C_M_RD)
 		ret = try_read_address(i2c_adap, addr, retries);
 	else
 		ret = try_write_address(i2c_adap, addr, retries);

 	if (ret != 1)
 		return -EREMOTEIO;

 	return 0;
 }

 static int
 usbvision_i2c_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[], int num)
 {
 	struct i2c_msg *pmsg;
 	struct usb_usbvision *usbvision;
 	int i, ret;
 	unsigned char addr = 0;

 	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);

 	for (i = 0; i < num; i++) {
 		pmsg = &msgs[i];
 		ret = usb_find_address(i2c_adap, pmsg, i2c_adap->retries, &addr);
 		if (ret != 0) {
 			PDEBUG(DBG_I2C, "got NAK from device, message #%d", i);
 			return (ret < 0) ? ret : -EREMOTEIO;
 		}

 		if (pmsg->flags & I2C_M_RD) {
 			/* read bytes into buffer */
 			ret = (usbvision_i2c_read(usbvision, addr, pmsg->buf, pmsg->len));
 			if (ret < pmsg->len)
 				return (ret < 0) ? ret : -EREMOTEIO;
 		} else {
 			/* write bytes from buffer */
 			ret = (usbvision_i2c_write(usbvision, addr, pmsg->buf, pmsg->len));
 			if (ret < pmsg->len)
 				return (ret < 0) ? ret : -EREMOTEIO;
 		}
 	}
 	return num;
 }

 static u32 functionality(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 }

 /* -----exported algorithm data: -------------------------------------	*/

 static const struct i2c_algorithm usbvision_algo = {
 	.master_xfer   = usbvision_i2c_xfer,
 	.smbus_xfer    = NULL,
 	.functionality = functionality,
 };


 /* ----------------------------------------------------------------------- */
 /* usbvision specific I2C functions                                        */
 /* ----------------------------------------------------------------------- */
 static const struct i2c_adapter i2c_adap_template;

 int usbvision_i2c_register(struct usb_usbvision *usbvision)
 {
 	static unsigned short saa711x_addrs[] = {
 		0x4a >> 1, 0x48 >> 1,	/* SAA7111, SAA7111A and SAA7113 */
 		0x42 >> 1, 0x40 >> 1,	/* SAA7114, SAA7115 and SAA7118 */
 		I2C_CLIENT_END };

 	if (usbvision->registered_i2c)
 		return 0;

 	usbvision->i2c_adap = i2c_adap_template;

 	snprintf(usbvision->i2c_adap.name, sizeof(usbvision->i2c_adap.name),
 		 "usbvision-%d-%s",
 		 usbvision->dev->bus->busnum, usbvision->dev->devpath);
 	PDEBUG(DBG_I2C, "Adaptername: %s", usbvision->i2c_adap.name);
 	usbvision->i2c_adap.dev.parent = &usbvision->dev->dev;

 	i2c_set_adapdata(&usbvision->i2c_adap, &usbvision->v4l2_dev);

 	if (usbvision_write_reg(usbvision, USBVISION_SER_MODE, USBVISION_IIC_LRNACK) < 0) {
 		printk(KERN_ERR "usbvision_i2c_register: can't write reg\n");
 		return -EBUSY;
 	}

 	PDEBUG(DBG_I2C, "I2C   debugging is enabled [i2c]");
 	PDEBUG(DBG_I2C, "ALGO   debugging is enabled [i2c]");

 	/* register new adapter to i2c module... */

 	usbvision->i2c_adap.algo = &usbvision_algo;

 	usbvision->i2c_adap.timeout = 100;	/* default values, should       */
 	usbvision->i2c_adap.retries = 3;	/* be replaced by defines       */

 	i2c_add_adapter(&usbvision->i2c_adap);

 	PDEBUG(DBG_I2C, "i2c bus for %s registered", usbvision->i2c_adap.name);

 	/* Request the load of the i2c modules we need */
 	switch (usbvision_device_data[usbvision->dev_model].codec) {
 	case CODEC_SAA7113:
 	case CODEC_SAA7111:
 		/* Without this delay the detection of the saa711x is
 		   hit-and-miss. */
 		mdelay(10);
 		v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
 				&usbvision->i2c_adap,
 				"saa7115_auto", 0, saa711x_addrs);
 		break;
 	}
 	if (usbvision_device_data[usbvision->dev_model].tuner == 1) {
 		struct v4l2_subdev *sd;
 		enum v4l2_i2c_tuner_type type;
 		struct tuner_setup tun_setup;

 		sd = v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
 				&usbvision->i2c_adap,
 				"tuner", 0, v4l2_i2c_tuner_addrs(ADDRS_DEMOD));
 		/* depending on whether we found a demod or not, select
 		   the tuner type. */
 		type = sd ? ADDRS_TV_WITH_DEMOD : ADDRS_TV;

 		sd = v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
 				&usbvision->i2c_adap,
 				"tuner", 0, v4l2_i2c_tuner_addrs(type));

 		if (sd == NULL)
 			return -ENODEV;
 		if (usbvision->tuner_type != -1) {
 			tun_setup.mode_mask = T_ANALOG_TV | T_RADIO;
 			tun_setup.type = usbvision->tuner_type;
 			tun_setup.addr = v4l2_i2c_subdev_addr(sd);
 			call_all(usbvision, tuner, s_type_addr, &tun_setup);
 		}
 	}
 	usbvision->registered_i2c = 1;

 	return 0;
 }

 int usbvision_i2c_unregister(struct usb_usbvision *usbvision)
 {
 	if (!usbvision->registered_i2c)
 		return 0;

 	i2c_del_adapter(&(usbvision->i2c_adap));
 	usbvision->registered_i2c = 0;

 	PDEBUG(DBG_I2C, "i2c bus for %s unregistered", usbvision->i2c_adap.name);

 	return 0;
 }

 static int
 usbvision_i2c_read_max4(struct usb_usbvision *usbvision, unsigned char addr,
 		     char *buf, short len)
 {
 	int rc, retries;

 	for (retries = 5;;) {
 		rc = usbvision_write_reg(usbvision, USBVISION_SER_ADRS, addr);
 		if (rc < 0)
 			return rc;

 		/* Initiate byte read cycle                    */
 		/* USBVISION_SER_CONT <- d0-d2 n. of bytes to r/w */
 		/*                    d3 0=Wr 1=Rd             */
 		rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT,
 				      (len & 0x07) | 0x18);
 		if (rc < 0)
 			return rc;

 		/* Test for Busy and ACK */
 		do {
 			/* USBVISION_SER_CONT -> d4 == 0 busy */
 			rc = usbvision_read_reg(usbvision, USBVISION_SER_CONT);
 		} while (rc > 0 && ((rc & 0x10) != 0));	/* Retry while busy */
 		if (rc < 0)
 			return rc;

 		/* USBVISION_SER_CONT -> d5 == 1 Not ack */
 		if ((rc & 0x20) == 0)	/* Ack? */
 			break;

 		/* I2C abort */
 		rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT, 0x00);
 		if (rc < 0)
 			return rc;

 		if (--retries < 0)
 			return -1;
 	}

 	switch (len) {
 	case 4:
 		buf[3] = usbvision_read_reg(usbvision, USBVISION_SER_DAT4);
 		/* fall through */
 	case 3:
 		buf[2] = usbvision_read_reg(usbvision, USBVISION_SER_DAT3);
 		/* fall through */
 	case 2:
 		buf[1] = usbvision_read_reg(usbvision, USBVISION_SER_DAT2);
 		/* fall through */
 	case 1:
 		buf[0] = usbvision_read_reg(usbvision, USBVISION_SER_DAT1);
 		break;
 	default:
 		printk(KERN_ERR
 		       "usbvision_i2c_read_max4: buffer length > 4\n");
 	}

 	if (i2c_debug & DBG_I2C) {
 		int idx;

 		for (idx = 0; idx < len; idx++)
 			PDEBUG(DBG_I2C, "read %x from address %x", (unsigned char)buf[idx], addr);
 	}
 	return len;
 }


 static int usbvision_i2c_write_max4(struct usb_usbvision *usbvision,
 				 unsigned char addr, const char *buf,
 				 short len)
 {
 	int rc, retries;
 	int i;
 	unsigned char *value = usbvision->ctrl_urb_buffer;
 	unsigned char ser_cont;

 	ser_cont = (len & 0x07) | 0x10;

 	value[0] = addr;
 	value[1] = ser_cont;
 	for (i = 0; i < len; i++)
 		value[i + 2] = buf[i];

 	for (retries = 5;;) {
 		rc = usb_control_msg(usbvision->dev,
 				     usb_sndctrlpipe(usbvision->dev, 1),
 				     USBVISION_OP_CODE,
 				     USB_DIR_OUT | USB_TYPE_VENDOR |
 				     USB_RECIP_ENDPOINT, 0,
 				     (__u16) USBVISION_SER_ADRS, value,
 				     len + 2, HZ);

 		if (rc < 0)
 			return rc;

 		rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT,
 				      (len & 0x07) | 0x10);
 		if (rc < 0)
 			return rc;

 		/* Test for Busy and ACK */
 		do {
 			rc = usbvision_read_reg(usbvision, USBVISION_SER_CONT);
 		} while (rc > 0 && ((rc & 0x10) != 0));	/* Retry while busy */
 		if (rc < 0)
 			return rc;

 		if ((rc & 0x20) == 0)	/* Ack? */
 			break;

 		/* I2C abort */
 		usbvision_write_reg(usbvision, USBVISION_SER_CONT, 0x00);

 		if (--retries < 0)
 			return -1;

 	}

 	if (i2c_debug & DBG_I2C) {
 		int idx;

 		for (idx = 0; idx < len; idx++)
 			PDEBUG(DBG_I2C, "wrote %x at address %x", (unsigned char)buf[idx], addr);
 	}
 	return len;
 }

 static int usbvision_i2c_write(struct usb_usbvision *usbvision, unsigned char addr, char *buf,
 			    short len)
 {
 	char *buf_ptr = buf;
 	int retval;
 	int wrcount = 0;
 	int count;
 	int max_len = 4;

 	while (len > 0) {
 		count = (len > max_len) ? max_len : len;
 		retval = usbvision_i2c_write_max4(usbvision, addr, buf_ptr, count);
 		if (retval > 0) {
 			len -= count;
 			buf_ptr += count;
 			wrcount += count;
 		} else
 			return (retval < 0) ? retval : -EFAULT;
 	}
 	return wrcount;
 }

 static int usbvision_i2c_read(struct usb_usbvision *usbvision, unsigned char addr, char *buf,
 			   short len)
 {
 	char temp[4];
 	int retval, i;
 	int rdcount = 0;
 	int count;

 	while (len > 0) {
 		count = (len > 3) ? 4 : len;
 		retval = usbvision_i2c_read_max4(usbvision, addr, temp, count);
 		if (retval > 0) {
 			for (i = 0; i < len; i++)
 				buf[rdcount + i] = temp[i];
 			len -= count;
 			rdcount += count;
 		} else
 			return (retval < 0) ? retval : -EFAULT;
 	}
 	return rdcount;
 }

 static const struct i2c_adapter i2c_adap_template = {
 	.owner = THIS_MODULE,
 	.name              = "usbvision",
 };
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* usbvision_i2c.c
	* i2c algorithm for USB-I2C Bridges
	*
	* Copyright (c) 1999-2007 Joerg Heckenbach <joerg@heckenbach-aw.de>
	* Dwaine Garden <dwainegarden@rogers.com>
	*
	* This module is part of usbvision driver project.
	* Updates to driver completed by Dwaine P. Garden
	*/


	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/delay.h>
	#include <linux/init.h>
	#include <linux/uaccess.h>
	#include <linux/ioport.h>
	#include <linux/errno.h>
	#include <linux/usb.h>
	#include <linux/i2c.h>
	#include "usbvision.h"

	#define DBG_I2C (1 << 0)

	static int i2c_debug;

	module_param(i2c_debug, int, 0644); /* debug_i2c_usb mode of the device driver */
	MODULE_PARM_DESC(i2c_debug, "enable debug messages [i2c]");

	#define PDEBUG(level, fmt, args...) { \
	if (i2c_debug & (level)) \
	printk(KERN_INFO KBUILD_MODNAME ":[%s:%d] " fmt, \
	__func__, __LINE__ , ## args); \
	}

	static int usbvision_i2c_write(struct usb_usbvision usbvision, unsigned char addr, char buf,
	short len);
	static int usbvision_i2c_read(struct usb_usbvision usbvision, unsigned char addr, char buf,
	short len);

	static inline int try_write_address(struct i2c_adapter *i2c_adap,
	unsigned char addr, int retries)
	{
	struct usb_usbvision *usbvision;
	int i, ret = -1;
	char buf[4];

	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);
	buf[0] = 0x00;
	for (i = 0; i <= retries; i++) {
	ret = (usbvision_i2c_write(usbvision, addr, buf, 1));
	if (ret == 1)
	break; /* success! */
	udelay(5);
	if (i == retries) /* no success */
	break;
	udelay(10);
	}
	if (i) {
	PDEBUG(DBG_I2C, "Needed %d retries for address %#2x", i, addr);
	PDEBUG(DBG_I2C, "Maybe there's no device at this address");
	}
	return ret;
	}

	static inline int try_read_address(struct i2c_adapter *i2c_adap,
	unsigned char addr, int retries)
	{
	struct usb_usbvision *usbvision;
	int i, ret = -1;
	char buf[4];

	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);
	for (i = 0; i <= retries; i++) {
	ret = (usbvision_i2c_read(usbvision, addr, buf, 1));
	if (ret == 1)
	break; /* success! */
	udelay(5);
	if (i == retries) /* no success */
	break;
	udelay(10);
	}
	if (i) {
	PDEBUG(DBG_I2C, "Needed %d retries for address %#2x", i, addr);
	PDEBUG(DBG_I2C, "Maybe there's no device at this address");
	}
	return ret;
	}

	static inline int usb_find_address(struct i2c_adapter *i2c_adap,
	struct i2c_msg *msg, int retries,
	unsigned char *add)
	{
	unsigned short flags = msg->flags;

	unsigned char addr;
	int ret;

	addr = (msg->addr << 1);
	if (flags & I2C_M_RD)
	addr \|= 1;

	add[0] = addr;
	if (flags & I2C_M_RD)
	ret = try_read_address(i2c_adap, addr, retries);
	else
	ret = try_write_address(i2c_adap, addr, retries);

	if (ret != 1)
	return -EREMOTEIO;

	return 0;
	}

	static int
	usbvision_i2c_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[], int num)
	{
	struct i2c_msg *pmsg;
	struct usb_usbvision *usbvision;
	int i, ret;
	unsigned char addr = 0;

	usbvision = (struct usb_usbvision *)i2c_get_adapdata(i2c_adap);

	for (i = 0; i < num; i++) {
	pmsg = &msgs[i];
	ret = usb_find_address(i2c_adap, pmsg, i2c_adap->retries, &addr);
	if (ret != 0) {
	PDEBUG(DBG_I2C, "got NAK from device, message #%d", i);
	return (ret < 0) ? ret : -EREMOTEIO;
	}

	if (pmsg->flags & I2C_M_RD) {
	/* read bytes into buffer */
	ret = (usbvision_i2c_read(usbvision, addr, pmsg->buf, pmsg->len));
	if (ret < pmsg->len)
	return (ret < 0) ? ret : -EREMOTEIO;
	} else {
	/* write bytes from buffer */
	ret = (usbvision_i2c_write(usbvision, addr, pmsg->buf, pmsg->len));
	if (ret < pmsg->len)
	return (ret < 0) ? ret : -EREMOTEIO;
	}
	}
	return num;
	}

	static u32 functionality(struct i2c_adapter *adap)
	{
	return I2C_FUNC_I2C \| I2C_FUNC_SMBUS_EMUL;
	}

	/* -----exported algorithm data: ------------------------------------- */

	static const struct i2c_algorithm usbvision_algo = {
	.master_xfer = usbvision_i2c_xfer,
	.smbus_xfer = NULL,
	.functionality = functionality,
	};


	/* ----------------------------------------------------------------------- */
	/* usbvision specific I2C functions */
	/* ----------------------------------------------------------------------- */
	static const struct i2c_adapter i2c_adap_template;

	int usbvision_i2c_register(struct usb_usbvision *usbvision)
	{
	static unsigned short saa711x_addrs[] = {
	0x4a >> 1, 0x48 >> 1, /* SAA7111, SAA7111A and SAA7113 */
	0x42 >> 1, 0x40 >> 1, /* SAA7114, SAA7115 and SAA7118 */
	I2C_CLIENT_END };

	if (usbvision->registered_i2c)
	return 0;

	usbvision->i2c_adap = i2c_adap_template;

	snprintf(usbvision->i2c_adap.name, sizeof(usbvision->i2c_adap.name),
	"usbvision-%d-%s",
	usbvision->dev->bus->busnum, usbvision->dev->devpath);
	PDEBUG(DBG_I2C, "Adaptername: %s", usbvision->i2c_adap.name);
	usbvision->i2c_adap.dev.parent = &usbvision->dev->dev;

	i2c_set_adapdata(&usbvision->i2c_adap, &usbvision->v4l2_dev);

	if (usbvision_write_reg(usbvision, USBVISION_SER_MODE, USBVISION_IIC_LRNACK) < 0) {
	printk(KERN_ERR "usbvision_i2c_register: can't write reg\n");
	return -EBUSY;
	}

	PDEBUG(DBG_I2C, "I2C debugging is enabled [i2c]");
	PDEBUG(DBG_I2C, "ALGO debugging is enabled [i2c]");

	/* register new adapter to i2c module... */

	usbvision->i2c_adap.algo = &usbvision_algo;

	usbvision->i2c_adap.timeout = 100; /* default values, should */
	usbvision->i2c_adap.retries = 3; /* be replaced by defines */

	i2c_add_adapter(&usbvision->i2c_adap);

	PDEBUG(DBG_I2C, "i2c bus for %s registered", usbvision->i2c_adap.name);

	/* Request the load of the i2c modules we need */
	switch (usbvision_device_data[usbvision->dev_model].codec) {
	case CODEC_SAA7113:
	case CODEC_SAA7111:
	/* Without this delay the detection of the saa711x is
	hit-and-miss. */
	mdelay(10);
	v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
	&usbvision->i2c_adap,
	"saa7115_auto", 0, saa711x_addrs);
	break;
	}
	if (usbvision_device_data[usbvision->dev_model].tuner == 1) {
	struct v4l2_subdev *sd;
	enum v4l2_i2c_tuner_type type;
	struct tuner_setup tun_setup;

	sd = v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
	&usbvision->i2c_adap,
	"tuner", 0, v4l2_i2c_tuner_addrs(ADDRS_DEMOD));
	/* depending on whether we found a demod or not, select
	the tuner type. */
	type = sd ? ADDRS_TV_WITH_DEMOD : ADDRS_TV;

	sd = v4l2_i2c_new_subdev(&usbvision->v4l2_dev,
	&usbvision->i2c_adap,
	"tuner", 0, v4l2_i2c_tuner_addrs(type));

	if (sd == NULL)
	return -ENODEV;
	if (usbvision->tuner_type != -1) {
	tun_setup.mode_mask = T_ANALOG_TV \| T_RADIO;
	tun_setup.type = usbvision->tuner_type;
	tun_setup.addr = v4l2_i2c_subdev_addr(sd);
	call_all(usbvision, tuner, s_type_addr, &tun_setup);
	}
	}
	usbvision->registered_i2c = 1;

	return 0;
	}

	int usbvision_i2c_unregister(struct usb_usbvision *usbvision)
	{
	if (!usbvision->registered_i2c)
	return 0;

	i2c_del_adapter(&(usbvision->i2c_adap));
	usbvision->registered_i2c = 0;

	PDEBUG(DBG_I2C, "i2c bus for %s unregistered", usbvision->i2c_adap.name);

	return 0;
	}

	static int
	usbvision_i2c_read_max4(struct usb_usbvision *usbvision, unsigned char addr,
	char *buf, short len)
	{
	int rc, retries;

	for (retries = 5;;) {
	rc = usbvision_write_reg(usbvision, USBVISION_SER_ADRS, addr);
	if (rc < 0)
	return rc;

	/* Initiate byte read cycle */
	/* USBVISION_SER_CONT <- d0-d2 n. of bytes to r/w */
	/* d3 0=Wr 1=Rd */
	rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT,
	(len & 0x07) \| 0x18);
	if (rc < 0)
	return rc;

	/* Test for Busy and ACK */
	do {
	/* USBVISION_SER_CONT -> d4 == 0 busy */
	rc = usbvision_read_reg(usbvision, USBVISION_SER_CONT);
	} while (rc > 0 && ((rc & 0x10) != 0)); /* Retry while busy */
	if (rc < 0)
	return rc;

	/* USBVISION_SER_CONT -> d5 == 1 Not ack */
	if ((rc & 0x20) == 0) /* Ack? */
	break;

	/* I2C abort */
	rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT, 0x00);
	if (rc < 0)
	return rc;

	if (--retries < 0)
	return -1;
	}

	switch (len) {
	case 4:
	buf[3] = usbvision_read_reg(usbvision, USBVISION_SER_DAT4);
	/* fall through */
	case 3:
	buf[2] = usbvision_read_reg(usbvision, USBVISION_SER_DAT3);
	/* fall through */
	case 2:
	buf[1] = usbvision_read_reg(usbvision, USBVISION_SER_DAT2);
	/* fall through */
	case 1:
	buf[0] = usbvision_read_reg(usbvision, USBVISION_SER_DAT1);
	break;
	default:
	printk(KERN_ERR
	"usbvision_i2c_read_max4: buffer length > 4\n");
	}

	if (i2c_debug & DBG_I2C) {
	int idx;

	for (idx = 0; idx < len; idx++)
	PDEBUG(DBG_I2C, "read %x from address %x", (unsigned char)buf[idx], addr);
	}
	return len;
	}


	static int usbvision_i2c_write_max4(struct usb_usbvision *usbvision,
	unsigned char addr, const char *buf,
	short len)
	{
	int rc, retries;
	int i;
	unsigned char *value = usbvision->ctrl_urb_buffer;
	unsigned char ser_cont;

	ser_cont = (len & 0x07) \| 0x10;

	value[0] = addr;
	value[1] = ser_cont;
	for (i = 0; i < len; i++)
	value[i + 2] = buf[i];

	for (retries = 5;;) {
	rc = usb_control_msg(usbvision->dev,
	usb_sndctrlpipe(usbvision->dev, 1),
	USBVISION_OP_CODE,
	USB_DIR_OUT \| USB_TYPE_VENDOR \|
	USB_RECIP_ENDPOINT, 0,
	(__u16) USBVISION_SER_ADRS, value,
	len + 2, HZ);

	if (rc < 0)
	return rc;

	rc = usbvision_write_reg(usbvision, USBVISION_SER_CONT,
	(len & 0x07) \| 0x10);
	if (rc < 0)
	return rc;

	/* Test for Busy and ACK */
	do {
	rc = usbvision_read_reg(usbvision, USBVISION_SER_CONT);
	} while (rc > 0 && ((rc & 0x10) != 0)); /* Retry while busy */
	if (rc < 0)
	return rc;

	if ((rc & 0x20) == 0) /* Ack? */
	break;

	/* I2C abort */
	usbvision_write_reg(usbvision, USBVISION_SER_CONT, 0x00);

	if (--retries < 0)
	return -1;

	}

	if (i2c_debug & DBG_I2C) {
	int idx;

	for (idx = 0; idx < len; idx++)
	PDEBUG(DBG_I2C, "wrote %x at address %x", (unsigned char)buf[idx], addr);
	}
	return len;
	}

	static int usbvision_i2c_write(struct usb_usbvision usbvision, unsigned char addr, char buf,
	short len)
	{
	char *buf_ptr = buf;
	int retval;
	int wrcount = 0;
	int count;
	int max_len = 4;

	while (len > 0) {
	count = (len > max_len) ? max_len : len;
	retval = usbvision_i2c_write_max4(usbvision, addr, buf_ptr, count);
	if (retval > 0) {
	len -= count;
	buf_ptr += count;
	wrcount += count;
	} else
	return (retval < 0) ? retval : -EFAULT;
	}
	return wrcount;
	}

	static int usbvision_i2c_read(struct usb_usbvision usbvision, unsigned char addr, char buf,
	short len)
	{
	char temp[4];
	int retval, i;
	int rdcount = 0;
	int count;

	while (len > 0) {
	count = (len > 3) ? 4 : len;
	retval = usbvision_i2c_read_max4(usbvision, addr, temp, count);
	if (retval > 0) {
	for (i = 0; i < len; i++)
	buf[rdcount + i] = temp[i];
	len -= count;
	rdcount += count;
	} else
	return (retval < 0) ? retval : -EFAULT;
	}
	return rdcount;
	}

	static const struct i2c_adapter i2c_adap_template = {
	.owner = THIS_MODULE,
	.name = "usbvision",
	};