drivers/media/common/saa7146_i2c.c - maze/linux - Git at Google

 #include <media/saa7146_vv.h>

 static u32 saa7146_i2c_func(struct i2c_adapter *adapter)
 {
 //fm	DEB_I2C(("'%s'.\n", adapter->name));

 	return	  I2C_FUNC_I2C
 		| I2C_FUNC_SMBUS_QUICK
 		| I2C_FUNC_SMBUS_READ_BYTE	| I2C_FUNC_SMBUS_WRITE_BYTE
 		| I2C_FUNC_SMBUS_READ_BYTE_DATA | I2C_FUNC_SMBUS_WRITE_BYTE_DATA;
 }

 /* this function returns the status-register of our i2c-device */
 static inline u32 saa7146_i2c_status(struct saa7146_dev *dev)
 {
 	u32 iicsta = saa7146_read(dev, I2C_STATUS);
 /*
 	DEB_I2C(("status: 0x%08x\n",iicsta));
 */
 	return iicsta;
 }

 /* this function runs through the i2c-messages and prepares the data to be
    sent through the saa7146. have a look at the specifications p. 122 ff
    to understand this. it returns the number of u32s to send, or -1
    in case of an error. */
 static int saa7146_i2c_msg_prepare(const struct i2c_msg *m, int num, __le32 *op)
 {
 	int h1, h2;
 	int i, j, addr;
 	int mem = 0, op_count = 0;

 	/* first determine size of needed memory */
 	for(i = 0; i < num; i++) {
 		mem += m[i].len + 1;
 	}

 	/* worst case: we need one u32 for three bytes to be send
 	   plus one extra byte to address the device */
 	mem = 1 + ((mem-1) / 3);

 	/* we assume that op points to a memory of at least SAA7146_I2C_MEM bytes
 	   size. if we exceed this limit... */
 	if ( (4*mem) > SAA7146_I2C_MEM ) {
 //fm		DEB_I2C(("cannot prepare i2c-message.\n"));
 		return -ENOMEM;
 	}

 	/* be careful: clear out the i2c-mem first */
 	memset(op,0,sizeof(__le32)*mem);

 	/* loop through all messages */
 	for(i = 0; i < num; i++) {

 		/* insert the address of the i2c-slave.
 		   note: we get 7 bit i2c-addresses,
 		   so we have to perform a translation */
 		addr = (m[i].addr*2) + ( (0 != (m[i].flags & I2C_M_RD)) ? 1 : 0);
 		h1 = op_count/3; h2 = op_count%3;
 		op[h1] |= cpu_to_le32(	    (u8)addr << ((3-h2)*8));
 		op[h1] |= cpu_to_le32(SAA7146_I2C_START << ((3-h2)*2));
 		op_count++;

 		/* loop through all bytes of message i */
 		for(j = 0; j < m[i].len; j++) {
 			/* insert the data bytes */
 			h1 = op_count/3; h2 = op_count%3;
 			op[h1] |= cpu_to_le32( (u32)((u8)m[i].buf[j]) << ((3-h2)*8));
 			op[h1] |= cpu_to_le32(       SAA7146_I2C_CONT << ((3-h2)*2));
 			op_count++;
 		}

 	}

 	/* have a look at the last byte inserted:
 	  if it was: ...CONT change it to ...STOP */
 	h1 = (op_count-1)/3; h2 = (op_count-1)%3;
 	if ( SAA7146_I2C_CONT == (0x3 & (le32_to_cpu(op[h1]) >> ((3-h2)*2))) ) {
 		op[h1] &= ~cpu_to_le32(0x2 << ((3-h2)*2));
 		op[h1] |= cpu_to_le32(SAA7146_I2C_STOP << ((3-h2)*2));
 	}

 	/* return the number of u32s to send */
 	return mem;
 }

 /* this functions loops through all i2c-messages. normally, it should determine
    which bytes were read through the adapter and write them back to the corresponding
    i2c-message. but instead, we simply write back all bytes.
    fixme: this could be improved. */
 static int saa7146_i2c_msg_cleanup(const struct i2c_msg *m, int num, __le32 *op)
 {
 	int i, j;
 	int op_count = 0;

 	/* loop through all messages */
 	for(i = 0; i < num; i++) {

 		op_count++;

 		/* loop through all bytes of message i */
 		for(j = 0; j < m[i].len; j++) {
 			/* write back all bytes that could have been read */
 			m[i].buf[j] = (le32_to_cpu(op[op_count/3]) >> ((3-(op_count%3))*8));
 			op_count++;
 		}
 	}

 	return 0;
 }

 /* this functions resets the i2c-device and returns 0 if everything was fine, otherwise -1 */
 static int saa7146_i2c_reset(struct saa7146_dev *dev)
 {
 	/* get current status */
 	u32 status = saa7146_i2c_status(dev);

 	/* clear registers for sure */
 	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
 	saa7146_write(dev, I2C_TRANSFER, 0);

 	/* check if any operation is still in progress */
 	if ( 0 != ( status & SAA7146_I2C_BUSY) ) {

 		/* yes, kill ongoing operation */
 		DEB_I2C(("busy_state detected.\n"));

 		/* set "ABORT-OPERATION"-bit (bit 7)*/
 		saa7146_write(dev, I2C_STATUS, (dev->i2c_bitrate | MASK_07));
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));
 		msleep(SAA7146_I2C_DELAY);

 		/* clear all error-bits pending; this is needed because p.123, note 1 */
 		saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));
 		msleep(SAA7146_I2C_DELAY);
 	}

 	/* check if any error is (still) present. (this can be necessary because p.123, note 1) */
 	status = saa7146_i2c_status(dev);

 	if ( dev->i2c_bitrate != status ) {

 		DEB_I2C(("error_state detected. status:0x%08x\n",status));

 		/* Repeat the abort operation. This seems to be necessary
 		   after serious protocol errors caused by e.g. the SAA7740 */
 		saa7146_write(dev, I2C_STATUS, (dev->i2c_bitrate | MASK_07));
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));
 		msleep(SAA7146_I2C_DELAY);

 		/* clear all error-bits pending */
 		saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));
 		msleep(SAA7146_I2C_DELAY);

 		/* the data sheet says it might be necessary to clear the status
 		   twice after an abort */
 		saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));
 		msleep(SAA7146_I2C_DELAY);
 	}

 	/* if any error is still present, a fatal error has occured ... */
 	status = saa7146_i2c_status(dev);
 	if ( dev->i2c_bitrate != status ) {
 		DEB_I2C(("fatal error. status:0x%08x\n",status));
 		return -1;
 	}

 	return 0;
 }

 /* this functions writes out the data-byte 'dword' to the i2c-device.
    it returns 0 if ok, -1 if the transfer failed, -2 if the transfer
    failed badly (e.g. address error) */
 static int saa7146_i2c_writeout(struct saa7146_dev *dev, __le32 *dword, int short_delay)
 {
 	u32 status = 0, mc2 = 0;
 	int trial = 0;
 	unsigned long timeout;

 	/* write out i2c-command */
 	DEB_I2C(("before: 0x%08x (status: 0x%08x), %d\n",*dword,saa7146_read(dev, I2C_STATUS), dev->i2c_op));

 	if( 0 != (SAA7146_USE_I2C_IRQ & dev->ext->flags)) {

 		saa7146_write(dev, I2C_STATUS,	 dev->i2c_bitrate);
 		saa7146_write(dev, I2C_TRANSFER, le32_to_cpu(*dword));

 		dev->i2c_op = 1;
 		SAA7146_ISR_CLEAR(dev, MASK_16|MASK_17);
 		SAA7146_IER_ENABLE(dev, MASK_16|MASK_17);
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));

 		timeout = HZ/100 + 1; /* 10ms */
 		timeout = wait_event_interruptible_timeout(dev->i2c_wq, dev->i2c_op == 0, timeout);
 		if (timeout == -ERESTARTSYS || dev->i2c_op) {
 			SAA7146_IER_DISABLE(dev, MASK_16|MASK_17);
 			SAA7146_ISR_CLEAR(dev, MASK_16|MASK_17);
 			if (timeout == -ERESTARTSYS)
 				/* a signal arrived */
 				return -ERESTARTSYS;

 			printk(KERN_WARNING "%s %s [irq]: timed out waiting for end of xfer\n",
 				dev->name, __func__);
 			return -EIO;
 		}
 		status = saa7146_read(dev, I2C_STATUS);
 	} else {
 		saa7146_write(dev, I2C_STATUS,	 dev->i2c_bitrate);
 		saa7146_write(dev, I2C_TRANSFER, le32_to_cpu(*dword));
 		saa7146_write(dev, MC2, (MASK_00 | MASK_16));

 		/* do not poll for i2c-status before upload is complete */
 		timeout = jiffies + HZ/100 + 1; /* 10ms */
 		while(1) {
 			mc2 = (saa7146_read(dev, MC2) & 0x1);
 			if( 0 != mc2 ) {
 				break;
 			}
 			if (time_after(jiffies,timeout)) {
 				printk(KERN_WARNING "%s %s: timed out waiting for MC2\n",
 					dev->name, __func__);
 				return -EIO;
 			}
 		}
 		/* wait until we get a transfer done or error */
 		timeout = jiffies + HZ/100 + 1; /* 10ms */
 		/* first read usually delivers bogus results... */
 		saa7146_i2c_status(dev);
 		while(1) {
 			status = saa7146_i2c_status(dev);
 			if ((status & 0x3) != 1)
 				break;
 			if (time_after(jiffies,timeout)) {
 				/* this is normal when probing the bus
 				 * (no answer from nonexisistant device...)
 				 */
 				printk(KERN_WARNING "%s %s [poll]: timed out waiting for end of xfer\n",
 					dev->name, __func__);
 				return -EIO;
 			}
 			if (++trial < 50 && short_delay)
 				udelay(10);
 			else
 				msleep(1);
 		}
 	}

 	/* give a detailed status report */
 	if ( 0 != (status & (SAA7146_I2C_SPERR | SAA7146_I2C_APERR |
 			     SAA7146_I2C_DTERR | SAA7146_I2C_DRERR |
 			     SAA7146_I2C_AL    | SAA7146_I2C_ERR   |
 			     SAA7146_I2C_BUSY)) ) {

 		if ( 0 == (status & SAA7146_I2C_ERR) ||
 		     0 == (status & SAA7146_I2C_BUSY) ) {
 			/* it may take some time until ERR goes high - ignore */
 			DEB_I2C(("unexpected i2c status %04x\n", status));
 		}
 		if( 0 != (status & SAA7146_I2C_SPERR) ) {
 			DEB_I2C(("error due to invalid start/stop condition.\n"));
 		}
 		if( 0 != (status & SAA7146_I2C_DTERR) ) {
 			DEB_I2C(("error in data transmission.\n"));
 		}
 		if( 0 != (status & SAA7146_I2C_DRERR) ) {
 			DEB_I2C(("error when receiving data.\n"));
 		}
 		if( 0 != (status & SAA7146_I2C_AL) ) {
 			DEB_I2C(("error because arbitration lost.\n"));
 		}

 		/* we handle address-errors here */
 		if( 0 != (status & SAA7146_I2C_APERR) ) {
 			DEB_I2C(("error in address phase.\n"));
 			return -EREMOTEIO;
 		}

 		return -EIO;
 	}

 	/* read back data, just in case we were reading ... */
 	*dword = cpu_to_le32(saa7146_read(dev, I2C_TRANSFER));

 	DEB_I2C(("after: 0x%08x\n",*dword));
 	return 0;
 }

 static int saa7146_i2c_transfer(struct saa7146_dev *dev, const struct i2c_msg *msgs, int num, int retries)
 {
 	int i = 0, count = 0;
 	__le32 *buffer = dev->d_i2c.cpu_addr;
 	int err = 0;
 	int short_delay = 0;

 	if (mutex_lock_interruptible(&dev->i2c_lock))
 		return -ERESTARTSYS;

 	for(i=0;i<num;i++) {
 		DEB_I2C(("msg:%d/%d\n",i+1,num));
 	}

 	/* prepare the message(s), get number of u32s to transfer */
 	count = saa7146_i2c_msg_prepare(msgs, num, buffer);
 	if ( 0 > count ) {
 		err = -1;
 		goto out;
 	}

 	if ( count > 3 || 0 != (SAA7146_I2C_SHORT_DELAY & dev->ext->flags) )
 		short_delay = 1;

 	do {
 		/* reset the i2c-device if necessary */
 		err = saa7146_i2c_reset(dev);
 		if ( 0 > err ) {
 			DEB_I2C(("could not reset i2c-device.\n"));
 			goto out;
 		}

 		/* write out the u32s one after another */
 		for(i = 0; i < count; i++) {
 			err = saa7146_i2c_writeout(dev, &buffer[i], short_delay);
 			if ( 0 != err) {
 				/* this one is unsatisfying: some i2c slaves on some
 				   dvb cards don't acknowledge correctly, so the saa7146
 				   thinks that an address error occured. in that case, the
 				   transaction should be retrying, even if an address error
 				   occured. analog saa7146 based cards extensively rely on
 				   i2c address probing, however, and address errors indicate that a
 				   device is really *not* there. retrying in that case
 				   increases the time the device needs to probe greatly, so
 				   it should be avoided. So we bail out in irq mode after an
 				   address error and trust the saa7146 address error detection. */
 				if (-EREMOTEIO == err && 0 != (SAA7146_USE_I2C_IRQ & dev->ext->flags))
 					goto out;
 				DEB_I2C(("error while sending message(s). starting again.\n"));
 				break;
 			}
 		}
 		if( 0 == err ) {
 			err = num;
 			break;
 		}

 		/* delay a bit before retrying */
 		msleep(10);

 	} while (err != num && retries--);

 	/* quit if any error occurred */
 	if (err != num)
 		goto out;

 	/* if any things had to be read, get the results */
 	if ( 0 != saa7146_i2c_msg_cleanup(msgs, num, buffer)) {
 		DEB_I2C(("could not cleanup i2c-message.\n"));
 		err = -1;
 		goto out;
 	}

 	/* return the number of delivered messages */
 	DEB_I2C(("transmission successful. (msg:%d).\n",err));
 out:
 	/* another bug in revision 0: the i2c-registers get uploaded randomly by other
 	   uploads, so we better clear them out before continueing */
 	if( 0 == dev->revision ) {
 		__le32 zero = 0;
 		saa7146_i2c_reset(dev);
 		if( 0 != saa7146_i2c_writeout(dev, &zero, short_delay)) {
 			INFO(("revision 0 error. this should never happen.\n"));
 		}
 	}

 	mutex_unlock(&dev->i2c_lock);
 	return err;
 }

 /* utility functions */
 static int saa7146_i2c_xfer(struct i2c_adapter* adapter, struct i2c_msg *msg, int num)
 {
 	struct v4l2_device *v4l2_dev = i2c_get_adapdata(adapter);
 	struct saa7146_dev *dev = to_saa7146_dev(v4l2_dev);

 	/* use helper function to transfer data */
 	return saa7146_i2c_transfer(dev, msg, num, adapter->retries);
 }


 /*****************************************************************************/
 /* i2c-adapter helper functions                                              */

 /* exported algorithm data */
 static struct i2c_algorithm saa7146_algo = {
 	.master_xfer	= saa7146_i2c_xfer,
 	.functionality	= saa7146_i2c_func,
 };

 int saa7146_i2c_adapter_prepare(struct saa7146_dev *dev, struct i2c_adapter *i2c_adapter, u32 bitrate)
 {
 	DEB_EE(("bitrate: 0x%08x\n",bitrate));

 	/* enable i2c-port pins */
 	saa7146_write(dev, MC1, (MASK_08 | MASK_24));

 	dev->i2c_bitrate = bitrate;
 	saa7146_i2c_reset(dev);

 	if (i2c_adapter) {
 		i2c_set_adapdata(i2c_adapter, &dev->v4l2_dev);
 		i2c_adapter->dev.parent    = &dev->pci->dev;
 		i2c_adapter->algo	   = &saa7146_algo;
 		i2c_adapter->algo_data     = NULL;
 		i2c_adapter->timeout = SAA7146_I2C_TIMEOUT;
 		i2c_adapter->retries = SAA7146_I2C_RETRIES;
 	}

 	return 0;
 }
	#include <media/saa7146_vv.h>

	static u32 saa7146_i2c_func(struct i2c_adapter *adapter)
	{
	//fm DEB_I2C(("'%s'.\n", adapter->name));

	return I2C_FUNC_I2C
	\| I2C_FUNC_SMBUS_QUICK
	\| I2C_FUNC_SMBUS_READ_BYTE \| I2C_FUNC_SMBUS_WRITE_BYTE
	\| I2C_FUNC_SMBUS_READ_BYTE_DATA \| I2C_FUNC_SMBUS_WRITE_BYTE_DATA;
	}

	/* this function returns the status-register of our i2c-device */
	static inline u32 saa7146_i2c_status(struct saa7146_dev *dev)
	{
	u32 iicsta = saa7146_read(dev, I2C_STATUS);
	/*
	DEB_I2C(("status: 0x%08x\n",iicsta));
	*/
	return iicsta;
	}

	/* this function runs through the i2c-messages and prepares the data to be
	sent through the saa7146. have a look at the specifications p. 122 ff
	to understand this. it returns the number of u32s to send, or -1
	in case of an error. */
	static int saa7146_i2c_msg_prepare(const struct i2c_msg m, int num, __le32 op)
	{
	int h1, h2;
	int i, j, addr;
	int mem = 0, op_count = 0;

	/* first determine size of needed memory */
	for(i = 0; i < num; i++) {
	mem += m[i].len + 1;
	}

	/* worst case: we need one u32 for three bytes to be send
	plus one extra byte to address the device */
	mem = 1 + ((mem-1) / 3);

	/* we assume that op points to a memory of at least SAA7146_I2C_MEM bytes
	size. if we exceed this limit... */
	if ( (4*mem) > SAA7146_I2C_MEM ) {
	//fm DEB_I2C(("cannot prepare i2c-message.\n"));
	return -ENOMEM;
	}

	/* be careful: clear out the i2c-mem first */
	memset(op,0,sizeof(__le32)*mem);

	/* loop through all messages */
	for(i = 0; i < num; i++) {

	/* insert the address of the i2c-slave.
	note: we get 7 bit i2c-addresses,
	so we have to perform a translation */
	addr = (m[i].addr*2) + ( (0 != (m[i].flags & I2C_M_RD)) ? 1 : 0);
	h1 = op_count/3; h2 = op_count%3;
	op[h1] \|= cpu_to_le32( (u8)addr << ((3-h2)*8));
	op[h1] \|= cpu_to_le32(SAA7146_I2C_START << ((3-h2)*2));
	op_count++;

	/* loop through all bytes of message i */
	for(j = 0; j < m[i].len; j++) {
	/* insert the data bytes */
	h1 = op_count/3; h2 = op_count%3;
	op[h1] \|= cpu_to_le32( (u32)((u8)m[i].buf[j]) << ((3-h2)*8));
	op[h1] \|= cpu_to_le32( SAA7146_I2C_CONT << ((3-h2)*2));
	op_count++;
	}

	}

	/* have a look at the last byte inserted:
	if it was: ...CONT change it to ...STOP */
	h1 = (op_count-1)/3; h2 = (op_count-1)%3;
	if ( SAA7146_I2C_CONT == (0x3 & (le32_to_cpu(op[h1]) >> ((3-h2)*2))) ) {
	op[h1] &= ~cpu_to_le32(0x2 << ((3-h2)*2));
	op[h1] \|= cpu_to_le32(SAA7146_I2C_STOP << ((3-h2)*2));
	}

	/* return the number of u32s to send */
	return mem;
	}

	/* this functions loops through all i2c-messages. normally, it should determine
	which bytes were read through the adapter and write them back to the corresponding
	i2c-message. but instead, we simply write back all bytes.
	fixme: this could be improved. */
	static int saa7146_i2c_msg_cleanup(const struct i2c_msg m, int num, __le32 op)
	{
	int i, j;
	int op_count = 0;

	/* loop through all messages */
	for(i = 0; i < num; i++) {

	op_count++;

	/* loop through all bytes of message i */
	for(j = 0; j < m[i].len; j++) {
	/* write back all bytes that could have been read */
	m[i].buf[j] = (le32_to_cpu(op[op_count/3]) >> ((3-(op_count%3))*8));
	op_count++;
	}
	}

	return 0;
	}

	/* this functions resets the i2c-device and returns 0 if everything was fine, otherwise -1 */
	static int saa7146_i2c_reset(struct saa7146_dev *dev)
	{
	/* get current status */
	u32 status = saa7146_i2c_status(dev);

	/* clear registers for sure */
	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, I2C_TRANSFER, 0);

	/* check if any operation is still in progress */
	if ( 0 != ( status & SAA7146_I2C_BUSY) ) {

	/* yes, kill ongoing operation */
	DEB_I2C(("busy_state detected.\n"));

	/* set "ABORT-OPERATION"-bit (bit 7)*/
	saa7146_write(dev, I2C_STATUS, (dev->i2c_bitrate \| MASK_07));
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));
	msleep(SAA7146_I2C_DELAY);

	/* clear all error-bits pending; this is needed because p.123, note 1 */
	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));
	msleep(SAA7146_I2C_DELAY);
	}

	/* check if any error is (still) present. (this can be necessary because p.123, note 1) */
	status = saa7146_i2c_status(dev);

	if ( dev->i2c_bitrate != status ) {

	DEB_I2C(("error_state detected. status:0x%08x\n",status));

	/* Repeat the abort operation. This seems to be necessary
	after serious protocol errors caused by e.g. the SAA7740 */
	saa7146_write(dev, I2C_STATUS, (dev->i2c_bitrate \| MASK_07));
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));
	msleep(SAA7146_I2C_DELAY);

	/* clear all error-bits pending */
	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));
	msleep(SAA7146_I2C_DELAY);

	/* the data sheet says it might be necessary to clear the status
	twice after an abort */
	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));
	msleep(SAA7146_I2C_DELAY);
	}

	/* if any error is still present, a fatal error has occured ... */
	status = saa7146_i2c_status(dev);
	if ( dev->i2c_bitrate != status ) {
	DEB_I2C(("fatal error. status:0x%08x\n",status));
	return -1;
	}

	return 0;
	}

	/* this functions writes out the data-byte 'dword' to the i2c-device.
	it returns 0 if ok, -1 if the transfer failed, -2 if the transfer
	failed badly (e.g. address error) */
	static int saa7146_i2c_writeout(struct saa7146_dev dev, __le32 dword, int short_delay)
	{
	u32 status = 0, mc2 = 0;
	int trial = 0;
	unsigned long timeout;

	/* write out i2c-command */
	DEB_I2C(("before: 0x%08x (status: 0x%08x), %d\n",*dword,saa7146_read(dev, I2C_STATUS), dev->i2c_op));

	if( 0 != (SAA7146_USE_I2C_IRQ & dev->ext->flags)) {

	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, I2C_TRANSFER, le32_to_cpu(*dword));

	dev->i2c_op = 1;
	SAA7146_ISR_CLEAR(dev, MASK_16\|MASK_17);
	SAA7146_IER_ENABLE(dev, MASK_16\|MASK_17);
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));

	timeout = HZ/100 + 1; /* 10ms */
	timeout = wait_event_interruptible_timeout(dev->i2c_wq, dev->i2c_op == 0, timeout);
	if (timeout == -ERESTARTSYS \|\| dev->i2c_op) {
	SAA7146_IER_DISABLE(dev, MASK_16\|MASK_17);
	SAA7146_ISR_CLEAR(dev, MASK_16\|MASK_17);
	if (timeout == -ERESTARTSYS)
	/* a signal arrived */
	return -ERESTARTSYS;

	printk(KERN_WARNING "%s %s [irq]: timed out waiting for end of xfer\n",
	dev->name, __func__);
	return -EIO;
	}
	status = saa7146_read(dev, I2C_STATUS);
	} else {
	saa7146_write(dev, I2C_STATUS, dev->i2c_bitrate);
	saa7146_write(dev, I2C_TRANSFER, le32_to_cpu(*dword));
	saa7146_write(dev, MC2, (MASK_00 \| MASK_16));

	/* do not poll for i2c-status before upload is complete */
	timeout = jiffies + HZ/100 + 1; /* 10ms */
	while(1) {
	mc2 = (saa7146_read(dev, MC2) & 0x1);
	if( 0 != mc2 ) {
	break;
	}
	if (time_after(jiffies,timeout)) {
	printk(KERN_WARNING "%s %s: timed out waiting for MC2\n",
	dev->name, __func__);
	return -EIO;
	}
	}
	/* wait until we get a transfer done or error */
	timeout = jiffies + HZ/100 + 1; /* 10ms */
	/* first read usually delivers bogus results... */
	saa7146_i2c_status(dev);
	while(1) {
	status = saa7146_i2c_status(dev);
	if ((status & 0x3) != 1)
	break;
	if (time_after(jiffies,timeout)) {
	/* this is normal when probing the bus
	* (no answer from nonexisistant device...)
	*/
	printk(KERN_WARNING "%s %s [poll]: timed out waiting for end of xfer\n",
	dev->name, __func__);
	return -EIO;
	}
	if (++trial < 50 && short_delay)
	udelay(10);
	else
	msleep(1);
	}
	}

	/* give a detailed status report */
	if ( 0 != (status & (SAA7146_I2C_SPERR \| SAA7146_I2C_APERR \|
	SAA7146_I2C_DTERR \| SAA7146_I2C_DRERR \|
	SAA7146_I2C_AL \| SAA7146_I2C_ERR \|
	SAA7146_I2C_BUSY)) ) {

	if ( 0 == (status & SAA7146_I2C_ERR) \|\|
	0 == (status & SAA7146_I2C_BUSY) ) {
	/* it may take some time until ERR goes high - ignore */
	DEB_I2C(("unexpected i2c status %04x\n", status));
	}
	if( 0 != (status & SAA7146_I2C_SPERR) ) {
	DEB_I2C(("error due to invalid start/stop condition.\n"));
	}
	if( 0 != (status & SAA7146_I2C_DTERR) ) {
	DEB_I2C(("error in data transmission.\n"));
	}
	if( 0 != (status & SAA7146_I2C_DRERR) ) {
	DEB_I2C(("error when receiving data.\n"));
	}
	if( 0 != (status & SAA7146_I2C_AL) ) {
	DEB_I2C(("error because arbitration lost.\n"));
	}

	/* we handle address-errors here */
	if( 0 != (status & SAA7146_I2C_APERR) ) {
	DEB_I2C(("error in address phase.\n"));
	return -EREMOTEIO;
	}

	return -EIO;
	}

	/* read back data, just in case we were reading ... */
	*dword = cpu_to_le32(saa7146_read(dev, I2C_TRANSFER));

	DEB_I2C(("after: 0x%08x\n",*dword));
	return 0;
	}

	static int saa7146_i2c_transfer(struct saa7146_dev dev, const struct i2c_msg msgs, int num, int retries)
	{
	int i = 0, count = 0;
	__le32 *buffer = dev->d_i2c.cpu_addr;
	int err = 0;
	int short_delay = 0;

	if (mutex_lock_interruptible(&dev->i2c_lock))
	return -ERESTARTSYS;

	for(i=0;i<num;i++) {
	DEB_I2C(("msg:%d/%d\n",i+1,num));
	}

	/* prepare the message(s), get number of u32s to transfer */
	count = saa7146_i2c_msg_prepare(msgs, num, buffer);
	if ( 0 > count ) {
	err = -1;
	goto out;
	}

	if ( count > 3 \|\| 0 != (SAA7146_I2C_SHORT_DELAY & dev->ext->flags) )
	short_delay = 1;

	do {
	/* reset the i2c-device if necessary */
	err = saa7146_i2c_reset(dev);
	if ( 0 > err ) {
	DEB_I2C(("could not reset i2c-device.\n"));
	goto out;
	}

	/* write out the u32s one after another */
	for(i = 0; i < count; i++) {
	err = saa7146_i2c_writeout(dev, &buffer[i], short_delay);
	if ( 0 != err) {
	/* this one is unsatisfying: some i2c slaves on some
	dvb cards don't acknowledge correctly, so the saa7146
	thinks that an address error occured. in that case, the
	transaction should be retrying, even if an address error
	occured. analog saa7146 based cards extensively rely on
	i2c address probing, however, and address errors indicate that a
	device is really not there. retrying in that case
	increases the time the device needs to probe greatly, so
	it should be avoided. So we bail out in irq mode after an
	address error and trust the saa7146 address error detection. */
	if (-EREMOTEIO == err && 0 != (SAA7146_USE_I2C_IRQ & dev->ext->flags))
	goto out;
	DEB_I2C(("error while sending message(s). starting again.\n"));
	break;
	}
	}
	if( 0 == err ) {
	err = num;
	break;
	}

	/* delay a bit before retrying */
	msleep(10);

	} while (err != num && retries--);

	/* quit if any error occurred */
	if (err != num)
	goto out;

	/* if any things had to be read, get the results */
	if ( 0 != saa7146_i2c_msg_cleanup(msgs, num, buffer)) {
	DEB_I2C(("could not cleanup i2c-message.\n"));
	err = -1;
	goto out;
	}

	/* return the number of delivered messages */
	DEB_I2C(("transmission successful. (msg:%d).\n",err));
	out:
	/* another bug in revision 0: the i2c-registers get uploaded randomly by other
	uploads, so we better clear them out before continueing */
	if( 0 == dev->revision ) {
	__le32 zero = 0;
	saa7146_i2c_reset(dev);
	if( 0 != saa7146_i2c_writeout(dev, &zero, short_delay)) {
	INFO(("revision 0 error. this should never happen.\n"));
	}
	}

	mutex_unlock(&dev->i2c_lock);
	return err;
	}

	/* utility functions */
	static int saa7146_i2c_xfer(struct i2c_adapter* adapter, struct i2c_msg *msg, int num)
	{
	struct v4l2_device *v4l2_dev = i2c_get_adapdata(adapter);
	struct saa7146_dev *dev = to_saa7146_dev(v4l2_dev);

	/* use helper function to transfer data */
	return saa7146_i2c_transfer(dev, msg, num, adapter->retries);
	}


	/*****************************************************************************/
	/* i2c-adapter helper functions */

	/* exported algorithm data */
	static struct i2c_algorithm saa7146_algo = {
	.master_xfer = saa7146_i2c_xfer,
	.functionality = saa7146_i2c_func,
	};

	int saa7146_i2c_adapter_prepare(struct saa7146_dev dev, struct i2c_adapter i2c_adapter, u32 bitrate)
	{
	DEB_EE(("bitrate: 0x%08x\n",bitrate));

	/* enable i2c-port pins */
	saa7146_write(dev, MC1, (MASK_08 \| MASK_24));

	dev->i2c_bitrate = bitrate;
	saa7146_i2c_reset(dev);

	if (i2c_adapter) {
	i2c_set_adapdata(i2c_adapter, &dev->v4l2_dev);
	i2c_adapter->dev.parent = &dev->pci->dev;
	i2c_adapter->algo = &saa7146_algo;
	i2c_adapter->algo_data = NULL;
	i2c_adapter->timeout = SAA7146_I2C_TIMEOUT;
	i2c_adapter->retries = SAA7146_I2C_RETRIES;
	}

	return 0;
	}