i2c-algo-bit.c

I2C总线LINUX驱动程序

}

/* ----- Utility functions
 */

/* try_address tries to contact a chip for a number of
 * times before it gives up.
 * return values:
 * 1 chip answered
 * 0 chip did not answer
 * -x transmission error
 */
static inline 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)
			break;	/* success! */
		i2c_stop(adap);
		udelay(5/*adap->udelay*/);
		if (i==retries)  /* no success */
			break;
		i2c_start(adap);
		udelay(adap->udelay);
	}
	DEB2(if (i)
	     printk(KERN_DEBUG "i2c-algo-bit.o: Used %d tries to %s client at 0x%02x : %s\n",
		    i+1, addr & 1 ? "read" : "write", addr>>1,
		    ret==1 ? "success" : ret==0 ? "no ack" : "failed, timeout?" )
	    );
	return ret;
}

static int sendbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	char c;
	const 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) {
		c = *temp;
		DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: %s sendbytes: writing %2.2X\n",
			    i2c_adap->name, c&0xff));
		retval = i2c_outb(i2c_adap,c);
		if ((retval>0) || (nak_ok && (retval==0)))  { /* ok or ignored NAK */
			count--; 
			temp++;
			wrcount++;
		} else { /* arbitration or no acknowledge */
			printk(KERN_ERR "i2c-algo-bit.o: %s sendbytes: error - bailout.\n",
			       i2c_adap->name);
			i2c_stop(adap);
			return (retval<0)? retval : -EFAULT;
			        /* got a better one ?? */
		}
#if 0
		/* from asm/delay.h */
		__delay(adap->mdelay * (loops_per_sec / 1000) );
#endif
	}
	return wrcount;
}

static inline int readbytes(struct i2c_adapter *i2c_adap, struct i2c_msg *msg)
{
	int inval;
	int rdcount=0;   	/* counts bytes read */
	struct i2c_algo_bit_data *adap = i2c_adap->algo_data;
	char *temp = msg->buf;
	int count = msg->len;
	int recv_len = 0;

	/* Receive [Count] for I2C_SMBUS_BLOCK_DATA or I2C_SMBUS_BLOCK_PROC_CALL protocol */
	if (msg->flags & I2C_M_RECV_LEN)
		recv_len = 1;

	while (count > 0) {
		inval = i2c_inb(i2c_adap);
/*printk("%#02x ",inval); if ( ! (count % 16) ) printk("\n"); */
		if (inval>=0) {
			*temp = inval;
			rdcount++;
		} else {   /* read timed out */
			printk(KERN_ERR "i2c-algo-bit.o: readbytes: i2c_inb timed out.\n");
			break;
		}

		if (recv_len) {
			recv_len = 0;
			/* [Count] should be between 1 and 31 (I2C_SMBUS_BLOCK_MAX - 1). */
			if (inval > 0 && inval < I2C_SMBUS_BLOCK_MAX) {
				count = inval + 1;	/* plus one for [Count] itself */
				msg->len = count;
				if (msg->flags & I2C_M_RECV_PEC)
					count++; /* plus one for PEC */
			} else {
				printk(KERN_ERR "i2c-algo-bit.o: readbytes: bad block count (%d).\n", inval);
				break;
			}
		}
		
		if ( count > 1 ) {		/* send ack */
			sdalo(adap);
			DEBPROTO(printk(" Am "));
		} else {
			sdahi(adap);	/* neg. ack on last byte */
			DEBPROTO(printk(" NAm "));
		}
		if (sclhi(adap)<0) {	/* timeout */
			sdahi(adap);
			printk(KERN_ERR "i2c-algo-bit.o: readbytes: Timeout at ack\n");
			return -ETIMEDOUT;
		};
		scllo(adap);
		sdahi(adap);
		temp++;
		count--;
	}
	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 inline 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);
		DEB2(printk(KERN_DEBUG "addr0: %d\n",addr));
		/* try extended address code...*/
		ret = try_address(i2c_adap, addr, retries);
		if ((ret != 1) && !nak_ok)  {
			printk(KERN_ERR "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 */
			printk(KERN_ERR "died at 2nd address code.\n");
			return -EREMOTEIO;
		}
		if ( flags & I2C_M_RD ) {
			i2c_repstart(adap);
			/* okay, now switch into reading mode */
			addr |= 0x01;
			ret = try_address(i2c_adap, addr, retries);
			if ((ret!=1) && !nak_ok) {
				printk(KERN_ERR "died at extended 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;

	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) {
				i2c_repstart(adap);
			}
			ret = bit_doAddress(i2c_adap, pmsg);
			if ((ret != 0) && !nak_ok) {
				DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: NAK from device addr %2.2x msg #%d\n",
					msgs[i].addr,i));
				return (ret<0) ? ret : -EREMOTEIO;
			}
		}
		if (pmsg->flags & I2C_M_RD ) {
			/* read bytes into buffer*/
			ret = readbytes(i2c_adap, pmsg);
			DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: read %d bytes.\n",ret));
			if (ret < pmsg->len ) {
				return (ret<0)? ret : -EREMOTEIO;
			}
		} else {
			/* write bytes from buffer */
			ret = sendbytes(i2c_adap, pmsg);
			DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: wrote %d bytes.\n",ret));
			if (ret < pmsg->len ) {
				return (ret<0) ? ret : -EREMOTEIO;
			}
		}
	}
	i2c_stop(adap);
	return num;
}

static u32 bit_func(struct i2c_adapter *i2c_adap)
{
	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL |
	       I2C_FUNC_10BIT_ADDR | I2C_FUNC_PROTOCOL_MANGLING |
	       I2C_FUNC_SMBUS_BLOCK_PROC_CALL |
	       I2C_FUNC_SMBUS_READ_BLOCK_DATA;
}


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

static struct i2c_algorithm i2c_bit_algo = {
	.name		= "Bit-shift algorithm",
	.id		= I2C_ALGO_BIT,
	.master_xfer	= bit_xfer,
	.functionality	= bit_func,
};

/* 
 * registering functions to load algorithms at runtime 
 */
int i2c_bit_add_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;
	}

	DEB2(printk(KERN_DEBUG "i2c-algo-bit.o: hw routines for %s registered.\n",
	            adap->name));

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

	adap->id |= i2c_bit_algo.id;
	adap->algo = &i2c_bit_algo;

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

	i2c_add_adapter(adap);
	return 0;
}


int i2c_bit_del_bus(struct i2c_adapter *adap)
{
	return i2c_del_adapter(adap);
}

EXPORT_SYMBOL(i2c_bit_add_bus);
EXPORT_SYMBOL(i2c_bit_del_bus);

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

MODULE_PARM(bit_test, "i");
MODULE_PARM(i2c_debug,"i");

MODULE_PARM_DESC(bit_test, "Test the lines of the bus to see if it is stuck");
MODULE_PARM_DESC(i2c_debug,
            "debug level - 0 off; 1 normal; 2,3 more verbose; 9 bit-protocol");