drivers/media/video/em28xx/em28xx-i2c.c - maze/linux - Git at Google

 /*
    em28xx-i2c.c - driver for Empia EM2800/EM2820/2840 USB video capture devices

    Copyright (C) 2005 Ludovico Cavedon <cavedon@sssup.it>
 		      Markus Rechberger <mrechberger@gmail.com>
 		      Mauro Carvalho Chehab <mchehab@infradead.org>
 		      Sascha Sommer <saschasommer@freenet.de>

    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, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/usb.h>
 #include <linux/i2c.h>

 #include "em28xx.h"
 #include "tuner-xc2028.h"
 #include <media/v4l2-common.h>
 #include <media/tuner.h>

 /* ----------------------------------------------------------- */

 static unsigned int i2c_scan;
 module_param(i2c_scan, int, 0444);
 MODULE_PARM_DESC(i2c_scan, "scan i2c bus at insmod time");

 static unsigned int i2c_debug;
 module_param(i2c_debug, int, 0644);
 MODULE_PARM_DESC(i2c_debug, "enable debug messages [i2c]");


 #define dprintk1(lvl, fmt, args...)			\
 do {							\
 	if (i2c_debug >= lvl) {				\
 	printk(fmt, ##args);				\
       }							\
 } while (0)

 #define dprintk2(lvl, fmt, args...)			\
 do {							\
 	if (i2c_debug >= lvl) {				\
 		printk(KERN_DEBUG "%s at %s: " fmt,	\
 		       dev->name, __func__ , ##args);	\
       } 						\
 } while (0)

 /*
  * em2800_i2c_send_max4()
  * send up to 4 bytes to the i2c device
  */
 static int em2800_i2c_send_max4(struct em28xx *dev, unsigned char addr,
 				char *buf, int len)
 {
 	int ret;
 	int write_timeout;
 	unsigned char b2[6];
 	BUG_ON(len < 1 || len > 4);
 	b2[5] = 0x80 + len - 1;
 	b2[4] = addr;
 	b2[3] = buf[0];
 	if (len > 1)
 		b2[2] = buf[1];
 	if (len > 2)
 		b2[1] = buf[2];
 	if (len > 3)
 		b2[0] = buf[3];

 	ret = dev->em28xx_write_regs(dev, 4 - len, &b2[4 - len], 2 + len);
 	if (ret != 2 + len) {
 		em28xx_warn("writing to i2c device failed (error=%i)\n", ret);
 		return -EIO;
 	}
 	for (write_timeout = EM2800_I2C_WRITE_TIMEOUT; write_timeout > 0;
 	     write_timeout -= 5) {
 		ret = dev->em28xx_read_reg(dev, 0x05);
 		if (ret == 0x80 + len - 1)
 			return len;
 		msleep(5);
 	}
 	em28xx_warn("i2c write timed out\n");
 	return -EIO;
 }

 /*
  * em2800_i2c_send_bytes()
  */
 static int em2800_i2c_send_bytes(void *data, unsigned char addr, char *buf,
 				 short len)
 {
 	char *bufPtr = buf;
 	int ret;
 	int wrcount = 0;
 	int count;
 	int maxLen = 4;
 	struct em28xx *dev = (struct em28xx *)data;
 	while (len > 0) {
 		count = (len > maxLen) ? maxLen : len;
 		ret = em2800_i2c_send_max4(dev, addr, bufPtr, count);
 		if (ret > 0) {
 			len -= count;
 			bufPtr += count;
 			wrcount += count;
 		} else
 			return (ret < 0) ? ret : -EFAULT;
 	}
 	return wrcount;
 }

 /*
  * em2800_i2c_check_for_device()
  * check if there is a i2c_device at the supplied address
  */
 static int em2800_i2c_check_for_device(struct em28xx *dev, unsigned char addr)
 {
 	char msg;
 	int ret;
 	int write_timeout;
 	msg = addr;
 	ret = dev->em28xx_write_regs(dev, 0x04, &msg, 1);
 	if (ret < 0) {
 		em28xx_warn("setting i2c device address failed (error=%i)\n",
 			    ret);
 		return ret;
 	}
 	msg = 0x84;
 	ret = dev->em28xx_write_regs(dev, 0x05, &msg, 1);
 	if (ret < 0) {
 		em28xx_warn("preparing i2c read failed (error=%i)\n", ret);
 		return ret;
 	}
 	for (write_timeout = EM2800_I2C_WRITE_TIMEOUT; write_timeout > 0;
 	     write_timeout -= 5) {
 		unsigned reg = dev->em28xx_read_reg(dev, 0x5);

 		if (reg == 0x94)
 			return -ENODEV;
 		else if (reg == 0x84)
 			return 0;
 		msleep(5);
 	}
 	return -ENODEV;
 }

 /*
  * em2800_i2c_recv_bytes()
  * read from the i2c device
  */
 static int em2800_i2c_recv_bytes(struct em28xx *dev, unsigned char addr,
 				 char *buf, int len)
 {
 	int ret;
 	/* check for the device and set i2c read address */
 	ret = em2800_i2c_check_for_device(dev, addr);
 	if (ret) {
 		em28xx_warn
 		    ("preparing read at i2c address 0x%x failed (error=%i)\n",
 		     addr, ret);
 		return ret;
 	}
 	ret = dev->em28xx_read_reg_req_len(dev, 0x0, 0x3, buf, len);
 	if (ret < 0) {
 		em28xx_warn("reading from i2c device at 0x%x failed (error=%i)",
 			    addr, ret);
 		return ret;
 	}
 	return ret;
 }

 /*
  * em28xx_i2c_send_bytes()
  * untested for more than 4 bytes
  */
 static int em28xx_i2c_send_bytes(void *data, unsigned char addr, char *buf,
 				 short len, int stop)
 {
 	int wrcount = 0;
 	struct em28xx *dev = (struct em28xx *)data;

 	wrcount = dev->em28xx_write_regs_req(dev, stop ? 2 : 3, addr, buf, len);

 	return wrcount;
 }

 /*
  * em28xx_i2c_recv_bytes()
  * read a byte from the i2c device
  */
 static int em28xx_i2c_recv_bytes(struct em28xx *dev, unsigned char addr,
 				 char *buf, int len)
 {
 	int ret;
 	ret = dev->em28xx_read_reg_req_len(dev, 2, addr, buf, len);
 	if (ret < 0) {
 		em28xx_warn("reading i2c device failed (error=%i)\n", ret);
 		return ret;
 	}
 	if (dev->em28xx_read_reg(dev, 0x5) != 0)
 		return -ENODEV;
 	return ret;
 }

 /*
  * em28xx_i2c_check_for_device()
  * check if there is a i2c_device at the supplied address
  */
 static int em28xx_i2c_check_for_device(struct em28xx *dev, unsigned char addr)
 {
 	char msg;
 	int ret;
 	msg = addr;

 	ret = dev->em28xx_read_reg_req(dev, 2, addr);
 	if (ret < 0) {
 		em28xx_warn("reading from i2c device failed (error=%i)\n", ret);
 		return ret;
 	}
 	if (dev->em28xx_read_reg(dev, 0x5) != 0)
 		return -ENODEV;
 	return 0;
 }

 /*
  * em28xx_i2c_xfer()
  * the main i2c transfer function
  */
 static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
 			   struct i2c_msg msgs[], int num)
 {
 	struct em28xx *dev = i2c_adap->algo_data;
 	int addr, rc, i, byte;

 	if (num <= 0)
 		return 0;
 	for (i = 0; i < num; i++) {
 		addr = msgs[i].addr << 1;
 		dprintk2(2, "%s %s addr=%x len=%d:",
 			 (msgs[i].flags & I2C_M_RD) ? "read" : "write",
 			 i == num - 1 ? "stop" : "nonstop", addr, msgs[i].len);
 		if (!msgs[i].len) { /* no len: check only for device presence */
 			if (dev->board.is_em2800)
 				rc = em2800_i2c_check_for_device(dev, addr);
 			else
 				rc = em28xx_i2c_check_for_device(dev, addr);
 			if (rc < 0) {
 				dprintk2(2, " no device\n");
 				return rc;
 			}

 		} else if (msgs[i].flags & I2C_M_RD) {
 			/* read bytes */
 			if (dev->board.is_em2800)
 				rc = em2800_i2c_recv_bytes(dev, addr,
 							   msgs[i].buf,
 							   msgs[i].len);
 			else
 				rc = em28xx_i2c_recv_bytes(dev, addr,
 							   msgs[i].buf,
 							   msgs[i].len);
 			if (i2c_debug >= 2) {
 				for (byte = 0; byte < msgs[i].len; byte++)
 					printk(" %02x", msgs[i].buf[byte]);
 			}
 		} else {
 			/* write bytes */
 			if (i2c_debug >= 2) {
 				for (byte = 0; byte < msgs[i].len; byte++)
 					printk(" %02x", msgs[i].buf[byte]);
 			}
 			if (dev->board.is_em2800)
 				rc = em2800_i2c_send_bytes(dev, addr,
 							   msgs[i].buf,
 							   msgs[i].len);
 			else
 				rc = em28xx_i2c_send_bytes(dev, addr,
 							   msgs[i].buf,
 							   msgs[i].len,
 							   i == num - 1);
 		}
 		if (rc < 0)
 			goto err;
 		if (i2c_debug >= 2)
 			printk("\n");
 	}

 	return num;
 err:
 	dprintk2(2, " ERROR: %i\n", rc);
 	return rc;
 }

 /* based on linux/sunrpc/svcauth.h and linux/hash.h
  * The original hash function returns a different value, if arch is x86_64
  *  or i386.
  */
 static inline unsigned long em28xx_hash_mem(char *buf, int length, int bits)
 {
 	unsigned long hash = 0;
 	unsigned long l = 0;
 	int len = 0;
 	unsigned char c;
 	do {
 		if (len == length) {
 			c = (char)len;
 			len = -1;
 		} else
 			c = *buf++;
 		l = (l << 8) | c;
 		len++;
 		if ((len & (32 / 8 - 1)) == 0)
 			hash = ((hash^l) * 0x9e370001UL);
 	} while (len);

 	return (hash >> (32 - bits)) & 0xffffffffUL;
 }

 static int em28xx_i2c_eeprom(struct em28xx *dev, unsigned char *eedata, int len)
 {
 	unsigned char buf, *p = eedata;
 	struct em28xx_eeprom *em_eeprom = (void *)eedata;
 	int i, err, size = len, block;

 	if (dev->chip_id == CHIP_ID_EM2874) {
 		/* Empia switched to a 16-bit addressable eeprom in newer
 		   devices.  While we could certainly write a routine to read
 		   the eeprom, there is nothing of use in there that cannot be
 		   accessed through registers, and there is the risk that we
 		   could corrupt the eeprom (since a 16-bit read call is
 		   interpreted as a write call by 8-bit eeproms).
 		*/
 		return 0;
 	}

 	dev->i2c_client.addr = 0xa0 >> 1;

 	/* Check if board has eeprom */
 	err = i2c_master_recv(&dev->i2c_client, &buf, 0);
 	if (err < 0) {
 		em28xx_errdev("board has no eeprom\n");
 		memset(eedata, 0, len);
 		return -ENODEV;
 	}

 	buf = 0;

 	err = i2c_master_send(&dev->i2c_client, &buf, 1);
 	if (err != 1) {
 		printk(KERN_INFO "%s: Huh, no eeprom present (err=%d)?\n",
 		       dev->name, err);
 		return err;
 	}
 	while (size > 0) {
 		if (size > 16)
 			block = 16;
 		else
 			block = size;

 		if (block !=
 		    (err = i2c_master_recv(&dev->i2c_client, p, block))) {
 			printk(KERN_WARNING
 			       "%s: i2c eeprom read error (err=%d)\n",
 			       dev->name, err);
 			return err;
 		}
 		size -= block;
 		p += block;
 	}
 	for (i = 0; i < len; i++) {
 		if (0 == (i % 16))
 			printk(KERN_INFO "%s: i2c eeprom %02x:", dev->name, i);
 		printk(" %02x", eedata[i]);
 		if (15 == (i % 16))
 			printk("\n");
 	}

 	if (em_eeprom->id == 0x9567eb1a)
 		dev->hash = em28xx_hash_mem(eedata, len, 32);

 	printk(KERN_INFO "%s: EEPROM ID= 0x%08x, EEPROM hash = 0x%08lx\n",
 	       dev->name, em_eeprom->id, dev->hash);

 	printk(KERN_INFO "%s: EEPROM info:\n", dev->name);

 	switch (em_eeprom->chip_conf >> 4 & 0x3) {
 	case 0:
 		printk(KERN_INFO "%s:\tNo audio on board.\n", dev->name);
 		break;
 	case 1:
 		printk(KERN_INFO "%s:\tAC97 audio (5 sample rates)\n",
 				 dev->name);
 		break;
 	case 2:
 		printk(KERN_INFO "%s:\tI2S audio, sample rate=32k\n",
 				 dev->name);
 		break;
 	case 3:
 		printk(KERN_INFO "%s:\tI2S audio, 3 sample rates\n",
 				 dev->name);
 		break;
 	}

 	if (em_eeprom->chip_conf & 1 << 3)
 		printk(KERN_INFO "%s:\tUSB Remote wakeup capable\n", dev->name);

 	if (em_eeprom->chip_conf & 1 << 2)
 		printk(KERN_INFO "%s:\tUSB Self power capable\n", dev->name);

 	switch (em_eeprom->chip_conf & 0x3) {
 	case 0:
 		printk(KERN_INFO "%s:\t500mA max power\n", dev->name);
 		break;
 	case 1:
 		printk(KERN_INFO "%s:\t400mA max power\n", dev->name);
 		break;
 	case 2:
 		printk(KERN_INFO "%s:\t300mA max power\n", dev->name);
 		break;
 	case 3:
 		printk(KERN_INFO "%s:\t200mA max power\n", dev->name);
 		break;
 	}
 	printk(KERN_INFO "%s:\tTable at 0x%02x, strings=0x%04x, 0x%04x, 0x%04x\n",
 				dev->name,
 				em_eeprom->string_idx_table,
 				em_eeprom->string1,
 				em_eeprom->string2,
 				em_eeprom->string3);

 	return 0;
 }

 /* ----------------------------------------------------------- */

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

 static struct i2c_algorithm em28xx_algo = {
 	.master_xfer   = em28xx_i2c_xfer,
 	.functionality = functionality,
 };

 static struct i2c_adapter em28xx_adap_template = {
 	.owner = THIS_MODULE,
 	.name = "em28xx",
 	.algo = &em28xx_algo,
 };

 static struct i2c_client em28xx_client_template = {
 	.name = "em28xx internal",
 };

 /* ----------------------------------------------------------- */

 /*
  * i2c_devs
  * incomplete list of known devices
  */
 static char *i2c_devs[128] = {
 	[0x4a >> 1] = "saa7113h",
 	[0x60 >> 1] = "remote IR sensor",
 	[0x8e >> 1] = "remote IR sensor",
 	[0x86 >> 1] = "tda9887",
 	[0x80 >> 1] = "msp34xx",
 	[0x88 >> 1] = "msp34xx",
 	[0xa0 >> 1] = "eeprom",
 	[0xb0 >> 1] = "tda9874",
 	[0xb8 >> 1] = "tvp5150a",
 	[0xba >> 1] = "webcam sensor or tvp5150a",
 	[0xc0 >> 1] = "tuner (analog)",
 	[0xc2 >> 1] = "tuner (analog)",
 	[0xc4 >> 1] = "tuner (analog)",
 	[0xc6 >> 1] = "tuner (analog)",
 };

 /*
  * do_i2c_scan()
  * check i2c address range for devices
  */
 void em28xx_do_i2c_scan(struct em28xx *dev)
 {
 	u8 i2c_devicelist[128];
 	unsigned char buf;
 	int i, rc;

 	memset(i2c_devicelist, 0, ARRAY_SIZE(i2c_devicelist));

 	for (i = 0; i < ARRAY_SIZE(i2c_devs); i++) {
 		dev->i2c_client.addr = i;
 		rc = i2c_master_recv(&dev->i2c_client, &buf, 0);
 		if (rc < 0)
 			continue;
 		i2c_devicelist[i] = i;
 		printk(KERN_INFO "%s: found i2c device @ 0x%x [%s]\n",
 		       dev->name, i << 1, i2c_devs[i] ? i2c_devs[i] : "???");
 	}

 	dev->i2c_hash = em28xx_hash_mem(i2c_devicelist,
 					ARRAY_SIZE(i2c_devicelist), 32);
 }

 /*
  * em28xx_i2c_register()
  * register i2c bus
  */
 int em28xx_i2c_register(struct em28xx *dev)
 {
 	int retval;

 	BUG_ON(!dev->em28xx_write_regs || !dev->em28xx_read_reg);
 	BUG_ON(!dev->em28xx_write_regs_req || !dev->em28xx_read_reg_req);
 	dev->i2c_adap = em28xx_adap_template;
 	dev->i2c_adap.dev.parent = &dev->udev->dev;
 	strcpy(dev->i2c_adap.name, dev->name);
 	dev->i2c_adap.algo_data = dev;
 	i2c_set_adapdata(&dev->i2c_adap, &dev->v4l2_dev);

 	retval = i2c_add_adapter(&dev->i2c_adap);
 	if (retval < 0) {
 		em28xx_errdev("%s: i2c_add_adapter failed! retval [%d]\n",
 			__func__, retval);
 		return retval;
 	}

 	dev->i2c_client = em28xx_client_template;
 	dev->i2c_client.adapter = &dev->i2c_adap;

 	retval = em28xx_i2c_eeprom(dev, dev->eedata, sizeof(dev->eedata));
 	if ((retval < 0) && (retval != -ENODEV)) {
 		em28xx_errdev("%s: em28xx_i2_eeprom failed! retval [%d]\n",
 			__func__, retval);

 		return retval;
 	}

 	if (i2c_scan)
 		em28xx_do_i2c_scan(dev);

 	/* Instantiate the IR receiver device, if present */
 	em28xx_register_i2c_ir(dev);

 	return 0;
 }

 /*
  * em28xx_i2c_unregister()
  * unregister i2c_bus
  */
 int em28xx_i2c_unregister(struct em28xx *dev)
 {
 	i2c_del_adapter(&dev->i2c_adap);
 	return 0;
 }
	/*
	em28xx-i2c.c - driver for Empia EM2800/EM2820/2840 USB video capture devices

	Copyright (C) 2005 Ludovico Cavedon <cavedon@sssup.it>
	Markus Rechberger <mrechberger@gmail.com>
	Mauro Carvalho Chehab <mchehab@infradead.org>
	Sascha Sommer <saschasommer@freenet.de>

	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, write to the Free Software
	Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
	*/

	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/usb.h>
	#include <linux/i2c.h>

	#include "em28xx.h"
	#include "tuner-xc2028.h"
	#include <media/v4l2-common.h>
	#include <media/tuner.h>

	/* ----------------------------------------------------------- */

	static unsigned int i2c_scan;
	module_param(i2c_scan, int, 0444);
	MODULE_PARM_DESC(i2c_scan, "scan i2c bus at insmod time");

	static unsigned int i2c_debug;
	module_param(i2c_debug, int, 0644);
	MODULE_PARM_DESC(i2c_debug, "enable debug messages [i2c]");


	#define dprintk1(lvl, fmt, args...) \
	do { \
	if (i2c_debug >= lvl) { \
	printk(fmt, ##args); \
	} \
	} while (0)

	#define dprintk2(lvl, fmt, args...) \
	do { \
	if (i2c_debug >= lvl) { \
	printk(KERN_DEBUG "%s at %s: " fmt, \
	dev->name, __func__ , ##args); \
	} \
	} while (0)

	/*
	* em2800_i2c_send_max4()
	* send up to 4 bytes to the i2c device
	*/
	static int em2800_i2c_send_max4(struct em28xx *dev, unsigned char addr,
	char *buf, int len)
	{
	int ret;
	int write_timeout;
	unsigned char b2[6];
	BUG_ON(len < 1 \|\| len > 4);
	b2[5] = 0x80 + len - 1;
	b2[4] = addr;
	b2[3] = buf[0];
	if (len > 1)
	b2[2] = buf[1];
	if (len > 2)
	b2[1] = buf[2];
	if (len > 3)
	b2[0] = buf[3];

	ret = dev->em28xx_write_regs(dev, 4 - len, &b2[4 - len], 2 + len);
	if (ret != 2 + len) {
	em28xx_warn("writing to i2c device failed (error=%i)\n", ret);
	return -EIO;
	}
	for (write_timeout = EM2800_I2C_WRITE_TIMEOUT; write_timeout > 0;
	write_timeout -= 5) {
	ret = dev->em28xx_read_reg(dev, 0x05);
	if (ret == 0x80 + len - 1)
	return len;
	msleep(5);
	}
	em28xx_warn("i2c write timed out\n");
	return -EIO;
	}

	/*
	* em2800_i2c_send_bytes()
	*/
	static int em2800_i2c_send_bytes(void data, unsigned char addr, char buf,
	short len)
	{
	char *bufPtr = buf;
	int ret;
	int wrcount = 0;
	int count;
	int maxLen = 4;
	struct em28xx dev = (struct em28xx )data;
	while (len > 0) {
	count = (len > maxLen) ? maxLen : len;
	ret = em2800_i2c_send_max4(dev, addr, bufPtr, count);
	if (ret > 0) {
	len -= count;
	bufPtr += count;
	wrcount += count;
	} else
	return (ret < 0) ? ret : -EFAULT;
	}
	return wrcount;
	}

	/*
	* em2800_i2c_check_for_device()
	* check if there is a i2c_device at the supplied address
	*/
	static int em2800_i2c_check_for_device(struct em28xx *dev, unsigned char addr)
	{
	char msg;
	int ret;
	int write_timeout;
	msg = addr;
	ret = dev->em28xx_write_regs(dev, 0x04, &msg, 1);
	if (ret < 0) {
	em28xx_warn("setting i2c device address failed (error=%i)\n",
	ret);
	return ret;
	}
	msg = 0x84;
	ret = dev->em28xx_write_regs(dev, 0x05, &msg, 1);
	if (ret < 0) {
	em28xx_warn("preparing i2c read failed (error=%i)\n", ret);
	return ret;
	}
	for (write_timeout = EM2800_I2C_WRITE_TIMEOUT; write_timeout > 0;
	write_timeout -= 5) {
	unsigned reg = dev->em28xx_read_reg(dev, 0x5);

	if (reg == 0x94)
	return -ENODEV;
	else if (reg == 0x84)
	return 0;
	msleep(5);
	}
	return -ENODEV;
	}

	/*
	* em2800_i2c_recv_bytes()
	* read from the i2c device
	*/
	static int em2800_i2c_recv_bytes(struct em28xx *dev, unsigned char addr,
	char *buf, int len)
	{
	int ret;
	/* check for the device and set i2c read address */
	ret = em2800_i2c_check_for_device(dev, addr);
	if (ret) {
	em28xx_warn
	("preparing read at i2c address 0x%x failed (error=%i)\n",
	addr, ret);
	return ret;
	}
	ret = dev->em28xx_read_reg_req_len(dev, 0x0, 0x3, buf, len);
	if (ret < 0) {
	em28xx_warn("reading from i2c device at 0x%x failed (error=%i)",
	addr, ret);
	return ret;
	}
	return ret;
	}

	/*
	* em28xx_i2c_send_bytes()
	* untested for more than 4 bytes
	*/
	static int em28xx_i2c_send_bytes(void data, unsigned char addr, char buf,
	short len, int stop)
	{
	int wrcount = 0;
	struct em28xx dev = (struct em28xx )data;

	wrcount = dev->em28xx_write_regs_req(dev, stop ? 2 : 3, addr, buf, len);

	return wrcount;
	}

	/*
	* em28xx_i2c_recv_bytes()
	* read a byte from the i2c device
	*/
	static int em28xx_i2c_recv_bytes(struct em28xx *dev, unsigned char addr,
	char *buf, int len)
	{
	int ret;
	ret = dev->em28xx_read_reg_req_len(dev, 2, addr, buf, len);
	if (ret < 0) {
	em28xx_warn("reading i2c device failed (error=%i)\n", ret);
	return ret;
	}
	if (dev->em28xx_read_reg(dev, 0x5) != 0)
	return -ENODEV;
	return ret;
	}

	/*
	* em28xx_i2c_check_for_device()
	* check if there is a i2c_device at the supplied address
	*/
	static int em28xx_i2c_check_for_device(struct em28xx *dev, unsigned char addr)
	{
	char msg;
	int ret;
	msg = addr;

	ret = dev->em28xx_read_reg_req(dev, 2, addr);
	if (ret < 0) {
	em28xx_warn("reading from i2c device failed (error=%i)\n", ret);
	return ret;
	}
	if (dev->em28xx_read_reg(dev, 0x5) != 0)
	return -ENODEV;
	return 0;
	}

	/*
	* em28xx_i2c_xfer()
	* the main i2c transfer function
	*/
	static int em28xx_i2c_xfer(struct i2c_adapter *i2c_adap,
	struct i2c_msg msgs[], int num)
	{
	struct em28xx *dev = i2c_adap->algo_data;
	int addr, rc, i, byte;

	if (num <= 0)
	return 0;
	for (i = 0; i < num; i++) {
	addr = msgs[i].addr << 1;
	dprintk2(2, "%s %s addr=%x len=%d:",
	(msgs[i].flags & I2C_M_RD) ? "read" : "write",
	i == num - 1 ? "stop" : "nonstop", addr, msgs[i].len);
	if (!msgs[i].len) { /* no len: check only for device presence */
	if (dev->board.is_em2800)
	rc = em2800_i2c_check_for_device(dev, addr);
	else
	rc = em28xx_i2c_check_for_device(dev, addr);
	if (rc < 0) {
	dprintk2(2, " no device\n");
	return rc;
	}

	} else if (msgs[i].flags & I2C_M_RD) {
	/* read bytes */
	if (dev->board.is_em2800)
	rc = em2800_i2c_recv_bytes(dev, addr,
	msgs[i].buf,
	msgs[i].len);
	else
	rc = em28xx_i2c_recv_bytes(dev, addr,
	msgs[i].buf,
	msgs[i].len);
	if (i2c_debug >= 2) {
	for (byte = 0; byte < msgs[i].len; byte++)
	printk(" %02x", msgs[i].buf[byte]);
	}
	} else {
	/* write bytes */
	if (i2c_debug >= 2) {
	for (byte = 0; byte < msgs[i].len; byte++)
	printk(" %02x", msgs[i].buf[byte]);
	}
	if (dev->board.is_em2800)
	rc = em2800_i2c_send_bytes(dev, addr,
	msgs[i].buf,
	msgs[i].len);
	else
	rc = em28xx_i2c_send_bytes(dev, addr,
	msgs[i].buf,
	msgs[i].len,
	i == num - 1);
	}
	if (rc < 0)
	goto err;
	if (i2c_debug >= 2)
	printk("\n");
	}

	return num;
	err:
	dprintk2(2, " ERROR: %i\n", rc);
	return rc;
	}

	/* based on linux/sunrpc/svcauth.h and linux/hash.h
	* The original hash function returns a different value, if arch is x86_64
	* or i386.
	*/
	static inline unsigned long em28xx_hash_mem(char *buf, int length, int bits)
	{
	unsigned long hash = 0;
	unsigned long l = 0;
	int len = 0;
	unsigned char c;
	do {
	if (len == length) {
	c = (char)len;
	len = -1;
	} else
	c = *buf++;
	l = (l << 8) \| c;
	len++;
	if ((len & (32 / 8 - 1)) == 0)
	hash = ((hash^l) * 0x9e370001UL);
	} while (len);

	return (hash >> (32 - bits)) & 0xffffffffUL;
	}

	static int em28xx_i2c_eeprom(struct em28xx dev, unsigned char eedata, int len)
	{
	unsigned char buf, *p = eedata;
	struct em28xx_eeprom em_eeprom = (void )eedata;
	int i, err, size = len, block;

	if (dev->chip_id == CHIP_ID_EM2874) {
	/* Empia switched to a 16-bit addressable eeprom in newer
	devices. While we could certainly write a routine to read
	the eeprom, there is nothing of use in there that cannot be
	accessed through registers, and there is the risk that we
	could corrupt the eeprom (since a 16-bit read call is
	interpreted as a write call by 8-bit eeproms).
	*/
	return 0;
	}

	dev->i2c_client.addr = 0xa0 >> 1;

	/* Check if board has eeprom */
	err = i2c_master_recv(&dev->i2c_client, &buf, 0);
	if (err < 0) {
	em28xx_errdev("board has no eeprom\n");
	memset(eedata, 0, len);
	return -ENODEV;
	}

	buf = 0;

	err = i2c_master_send(&dev->i2c_client, &buf, 1);
	if (err != 1) {
	printk(KERN_INFO "%s: Huh, no eeprom present (err=%d)?\n",
	dev->name, err);
	return err;
	}
	while (size > 0) {
	if (size > 16)
	block = 16;
	else
	block = size;

	if (block !=
	(err = i2c_master_recv(&dev->i2c_client, p, block))) {
	printk(KERN_WARNING
	"%s: i2c eeprom read error (err=%d)\n",
	dev->name, err);
	return err;
	}
	size -= block;
	p += block;
	}
	for (i = 0; i < len; i++) {
	if (0 == (i % 16))
	printk(KERN_INFO "%s: i2c eeprom %02x:", dev->name, i);
	printk(" %02x", eedata[i]);
	if (15 == (i % 16))
	printk("\n");
	}

	if (em_eeprom->id == 0x9567eb1a)
	dev->hash = em28xx_hash_mem(eedata, len, 32);

	printk(KERN_INFO "%s: EEPROM ID= 0x%08x, EEPROM hash = 0x%08lx\n",
	dev->name, em_eeprom->id, dev->hash);

	printk(KERN_INFO "%s: EEPROM info:\n", dev->name);

	switch (em_eeprom->chip_conf >> 4 & 0x3) {
	case 0:
	printk(KERN_INFO "%s:\tNo audio on board.\n", dev->name);
	break;
	case 1:
	printk(KERN_INFO "%s:\tAC97 audio (5 sample rates)\n",
	dev->name);
	break;
	case 2:
	printk(KERN_INFO "%s:\tI2S audio, sample rate=32k\n",
	dev->name);
	break;
	case 3:
	printk(KERN_INFO "%s:\tI2S audio, 3 sample rates\n",
	dev->name);
	break;
	}

	if (em_eeprom->chip_conf & 1 << 3)
	printk(KERN_INFO "%s:\tUSB Remote wakeup capable\n", dev->name);

	if (em_eeprom->chip_conf & 1 << 2)
	printk(KERN_INFO "%s:\tUSB Self power capable\n", dev->name);

	switch (em_eeprom->chip_conf & 0x3) {
	case 0:
	printk(KERN_INFO "%s:\t500mA max power\n", dev->name);
	break;
	case 1:
	printk(KERN_INFO "%s:\t400mA max power\n", dev->name);
	break;
	case 2:
	printk(KERN_INFO "%s:\t300mA max power\n", dev->name);
	break;
	case 3:
	printk(KERN_INFO "%s:\t200mA max power\n", dev->name);
	break;
	}
	printk(KERN_INFO "%s:\tTable at 0x%02x, strings=0x%04x, 0x%04x, 0x%04x\n",
	dev->name,
	em_eeprom->string_idx_table,
	em_eeprom->string1,
	em_eeprom->string2,
	em_eeprom->string3);

	return 0;
	}

	/* ----------------------------------------------------------- */

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

	static struct i2c_algorithm em28xx_algo = {
	.master_xfer = em28xx_i2c_xfer,
	.functionality = functionality,
	};

	static struct i2c_adapter em28xx_adap_template = {
	.owner = THIS_MODULE,
	.name = "em28xx",
	.algo = &em28xx_algo,
	};

	static struct i2c_client em28xx_client_template = {
	.name = "em28xx internal",
	};

	/* ----------------------------------------------------------- */

	/*
	* i2c_devs
	* incomplete list of known devices
	*/
	static char *i2c_devs[128] = {
	[0x4a >> 1] = "saa7113h",
	[0x60 >> 1] = "remote IR sensor",
	[0x8e >> 1] = "remote IR sensor",
	[0x86 >> 1] = "tda9887",
	[0x80 >> 1] = "msp34xx",
	[0x88 >> 1] = "msp34xx",
	[0xa0 >> 1] = "eeprom",
	[0xb0 >> 1] = "tda9874",
	[0xb8 >> 1] = "tvp5150a",
	[0xba >> 1] = "webcam sensor or tvp5150a",
	[0xc0 >> 1] = "tuner (analog)",
	[0xc2 >> 1] = "tuner (analog)",
	[0xc4 >> 1] = "tuner (analog)",
	[0xc6 >> 1] = "tuner (analog)",
	};

	/*
	* do_i2c_scan()
	* check i2c address range for devices
	*/
	void em28xx_do_i2c_scan(struct em28xx *dev)
	{
	u8 i2c_devicelist[128];
	unsigned char buf;
	int i, rc;

	memset(i2c_devicelist, 0, ARRAY_SIZE(i2c_devicelist));

	for (i = 0; i < ARRAY_SIZE(i2c_devs); i++) {
	dev->i2c_client.addr = i;
	rc = i2c_master_recv(&dev->i2c_client, &buf, 0);
	if (rc < 0)
	continue;
	i2c_devicelist[i] = i;
	printk(KERN_INFO "%s: found i2c device @ 0x%x [%s]\n",
	dev->name, i << 1, i2c_devs[i] ? i2c_devs[i] : "???");
	}

	dev->i2c_hash = em28xx_hash_mem(i2c_devicelist,
	ARRAY_SIZE(i2c_devicelist), 32);
	}

	/*
	* em28xx_i2c_register()
	* register i2c bus
	*/
	int em28xx_i2c_register(struct em28xx *dev)
	{
	int retval;

	BUG_ON(!dev->em28xx_write_regs \|\| !dev->em28xx_read_reg);
	BUG_ON(!dev->em28xx_write_regs_req \|\| !dev->em28xx_read_reg_req);
	dev->i2c_adap = em28xx_adap_template;
	dev->i2c_adap.dev.parent = &dev->udev->dev;
	strcpy(dev->i2c_adap.name, dev->name);
	dev->i2c_adap.algo_data = dev;
	i2c_set_adapdata(&dev->i2c_adap, &dev->v4l2_dev);

	retval = i2c_add_adapter(&dev->i2c_adap);
	if (retval < 0) {
	em28xx_errdev("%s: i2c_add_adapter failed! retval [%d]\n",
	__func__, retval);
	return retval;
	}

	dev->i2c_client = em28xx_client_template;
	dev->i2c_client.adapter = &dev->i2c_adap;

	retval = em28xx_i2c_eeprom(dev, dev->eedata, sizeof(dev->eedata));
	if ((retval < 0) && (retval != -ENODEV)) {
	em28xx_errdev("%s: em28xx_i2_eeprom failed! retval [%d]\n",
	__func__, retval);

	return retval;
	}

	if (i2c_scan)
	em28xx_do_i2c_scan(dev);

	/* Instantiate the IR receiver device, if present */
	em28xx_register_i2c_ir(dev);

	return 0;
	}

	/*
	* em28xx_i2c_unregister()
	* unregister i2c_bus
	*/
	int em28xx_i2c_unregister(struct em28xx *dev)
	{
	i2c_del_adapter(&dev->i2c_adap);
	return 0;
	}