i2c-algo-bit.c

linux 内核源代码

 * 0 chip did not answer
 * -x transmission error
 */
static int try_address(struct i2c_adapter *i2c_adap,
		       unsigned char addr, int retries)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	int i,ret = -1;
	for (i=0;i<=retries;i++) {
		ret = i2c_outb(i2c_adap,addr);
		if (ret == 1 || i == retries)
			break;
		bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
		i2c_stop(adap);
		udelay(adap->udelay);
		yield();
		bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
		i2c_start(adap);
	}
	if (i && ret)
		bit_dbg(1, &i2c_adap->dev, "Used %d tries to %s client at "
			"0x%02x: %s\n", i + 1,
			addr & 1 ? "read from" : "write to", addr >> 1,
			ret == 1 ? "success" : "failed, timeout?");
	return ret;
}

static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	const unsigned char *temp = msg->buf;
	int count = msg->len;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK; 
	int retval;
	int wrcount=0;

	while (count > 0) {
		retval = i2c_outb(i2c_adap, *temp);
		if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
			count--; 
			temp++;
			wrcount++;
		} else { /* arbitration or no acknowledge */
			dev_err(&i2c_adap->dev, "sendbytes: error - bailout.\n");
			return (retval<0)? retval : -EFAULT;
			        /* got a better one ?? */
		}
	}
	return wrcount;
}

static int acknak(struct i2c_adapter *i2c_adap, int is_ack)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	/* assert: sda is high */
	if (is_ack)		/* send ack */
		setsda(adap, 0);
	udelay((adap->udelay + 1) / 2);
	if (sclhi(adap) < 0) {	/* timeout */
		dev_err(&i2c_adap->dev, "readbytes: ack/nak timeout\n");
		return -ETIMEDOUT;
	}
	scllo(adap);
	return 0;
}

static int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	int inval;
	int rdcount=0;   	/* counts bytes read */
	unsigned char *temp = msg->buf;
	int count = msg->len;
	const unsigned flags = msg->flags;

	while (count > 0) {
		inval = i2c_inb(i2c_adap);
		if (inval>=0) {
			*temp = inval;
			rdcount++;
		} else {   /* read timed out */
			break;
		}

		temp++;
		count--;

		/* Some SMBus transactions require that we receive the
		   transaction length as the first read byte. */
		if (rdcount == 1 && (flags & I2C_M_RECV_LEN)) {
			if (inval <= 0 || inval > I2C_SMBUS_BLOCK_MAX) {
				if (!(flags & I2C_M_NO_RD_ACK))
					acknak(i2c_adap, 0);
				dev_err(&i2c_adap->dev, "readbytes: invalid "
					"block length (%d)\n", inval);
				return -EREMOTEIO;
			}
			/* The original count value accounts for the extra
			   bytes, that is, either 1 for a regular transaction,
			   or 2 for a PEC transaction. */
			count += inval;
			msg->len += inval;
		}

		bit_dbg(2, &i2c_adap->dev, "readbytes: 0x%02x %s\n",
			inval,
			(flags & I2C_M_NO_RD_ACK)
				? "(no ack/nak)"
				: (count ? "A" : "NA"));

		if (!(flags & I2C_M_NO_RD_ACK)) {
			inval = acknak(i2c_adap, count);
			if (inval < 0)
				return inval;
		}
	}
	return rdcount;
}

/* doAddress initiates the transfer by generating the start condition (in
 * try_address) and transmits the address in the necessary format to handle
 * reads, writes as well as 10bit-addresses.
 * returns:
 *  0 everything went okay, the chip ack'ed, or IGNORE_NAK flag was set
 * -x an error occurred (like: -EREMOTEIO if the device did not answer, or
 *	-ETIMEDOUT, for example if the lines are stuck...) 
 */
static int bit_doAddress(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	unsigned short flags = msg->flags;
	unsigned short nak_ok = msg->flags & I2C_M_IGNORE_NAK;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;

	unsigned char addr;
	int ret, retries;

	retries = nak_ok ? 0 : i2c_adap->retries;
	
	if ( (flags & I2C_M_TEN)  ) { 
		/* a ten bit address */
		addr = 0xf0 | (( msg->addr >> 7) & 0x03);
		bit_dbg(2, &i2c_adap->dev, "addr0: %d\n", addr);
		/* try extended address code...*/
		ret = try_address(i2c_adap, addr, retries);
		if ((ret != 1) && !nak_ok)  {
			dev_err(&i2c_adap->dev,
				"died at extended address code\n");
			return -EREMOTEIO;
		}
		/* the remaining 8 bit address */
		ret = i2c_outb(i2c_adap,msg->addr & 0x7f);
		if ((ret != 1) && !nak_ok) {
			/* the chip did not ack / xmission error occurred */
			dev_err(&i2c_adap->dev, "died at 2nd address code\n");
			return -EREMOTEIO;
		}
		if ( flags & I2C_M_RD ) {
			bit_dbg(3, &i2c_adap->dev, "emitting repeated "
				"start condition\n");
			i2c_repstart(adap);
			/* okay, now switch into reading mode */
			addr |= 0x01;
			ret = try_address(i2c_adap, addr, retries);
			if ((ret!=1) && !nak_ok) {
				dev_err(&i2c_adap->dev,
					"died at repeated address code\n");
				return -EREMOTEIO;
			}
		}
	} else {		/* normal 7bit address	*/
		addr = ( msg->addr << 1 );
		if (flags & I2C_M_RD )
			addr |= 1;
		if (flags & I2C_M_REV_DIR_ADDR )
			addr ^= 1;
		ret = try_address(i2c_adap, addr, retries);
		if ((ret!=1) && !nak_ok)
			return -EREMOTEIO;
	}

	return 0;
}

static int bit_xfer(struct i2c_adapter *i2c_adap,
		    struct i2c_msg msgs[], int num)
{
	struct i2c_msg *pmsg;
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	
	int i,ret;
	unsigned short nak_ok;

	bit_dbg(3, &i2c_adap->dev, "emitting start condition\n");
	i2c_start(adap);
	for (i=0;i<num;i++) {
		pmsg = &msgs[i];
		nak_ok = pmsg->flags & I2C_M_IGNORE_NAK; 
		if (!(pmsg->flags & I2C_M_NOSTART)) {
			if (i) {
				bit_dbg(3, &i2c_adap->dev, "emitting "
					"repeated start condition\n");
				i2c_repstart(adap);
			}
			ret = bit_doAddress(i2c_adap, pmsg);
			if ((ret != 0) && !nak_ok) {
				bit_dbg(1, &i2c_adap->dev, "NAK from "
					"device addr 0x%02x msg #%d\n",
					msgs[i].addr, i);
				goto bailout;
			}
		}
		if (pmsg->flags & I2C_M_RD ) {
			/* read bytes into buffer*/
			ret = readbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "read %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		} else {
			/* write bytes from buffer */
			ret = sendbytes(i2c_adap, pmsg);
			if (ret >= 1)
				bit_dbg(2, &i2c_adap->dev, "wrote %d byte%s\n",
					ret, ret == 1 ? "" : "s");
			if (ret < pmsg->len) {
				if (ret >= 0)
					ret = -EREMOTEIO;
				goto bailout;
			}
		}
	}
	ret = i;

bailout:
	bit_dbg(3, &i2c_adap->dev, "emitting stop condition\n");
	i2c_stop(adap);
	return ret;
}

static u32 bit_func(struct i2c_adapter *adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | 
	       I2C_FUNC_SMBUS_READ_BLOCK_DATA |
	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING;
}


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

static const struct i2c_algorithm i2c_bit_algo = {
	.master_xfer	= bit_xfer,
	.functionality	= bit_func,
};

/* 
 * registering functions to load algorithms at runtime 
 */
static int i2c_bit_prepare_bus(struct i2c_adapter *adap)
{
	struct i2c_algo_bit_data *bit_adap = adap->algo_data;

	if (bit_test) {
		int ret = test_bus(bit_adap, adap->name);
		if (ret<0)
			return -ENODEV;
	}

	/* register new adapter to i2c module... */
	adap->algo = &i2c_bit_algo;

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

	return 0;
}

int i2c_bit_add_bus(struct i2c_adapter *adap)
{
	int err;

	err = i2c_bit_prepare_bus(adap);
	if (err)
		return err;

	return i2c_add_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_bus);

int i2c_bit_add_numbered_bus(struct i2c_adapter *adap)
{
	int err;

	err = i2c_bit_prepare_bus(adap);
	if (err)
		return err;

	return i2c_add_numbered_adapter(adap);
}
EXPORT_SYMBOL(i2c_bit_add_numbered_bus);

MODULE_AUTHOR("Simon G. Vogl <[e-mail]>");
MODULE_DESCRIPTION("I2C-Bus bit-banging algorithm");
MODULE_LICENSE("GPL");