i2c.c

来自「linux-2.4.29操作系统的源码」· C语言 代码 · 共 731 行 · 第 1/2 页

	/*
	 * switch off I2C
	 */
	i2c_data(1);
	i2c_disable();
	i2c_dir_in();
	/*
	 * now wait for ack
	 */
	i2c_delay(CLOCK_HIGH_TIME/2);
	/*
	 * check for ack
	 */
	if(i2c_getbit())
		ack = 0;
	i2c_delay(CLOCK_HIGH_TIME/2);
	if(!ack){
		if(!i2c_getbit()) /* receiver pulld SDA low */
			ack = 1;
		i2c_delay(CLOCK_HIGH_TIME/2);
	}

   /*
    * our clock is high now, make sure data is low
    * before we enable our output. If we keep data high
    * and enable output, we would generate a stop condition.
    */
   i2c_data(I2C_DATA_LOW);
   
	/*
	 * end clock pulse
	 */
	i2c_enable();
	i2c_dir_out();
	i2c_clk(I2C_CLOCK_LOW);
	i2c_delay(CLOCK_HIGH_TIME/4);
	/*
	 * enable output
	 */
	i2c_dir_out();
	/*
	 * remove ACK clock pulse
	 */
	i2c_data(I2C_DATA_HIGH);
	i2c_delay(CLOCK_LOW_TIME/2);
	return ack;
}

/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: I2C::sendAck
*#
*# DESCRIPTION  : Send ACK on received data
*#
*#--------------------------------------------------------------------------*/
void
i2c_sendack(void)
{
	/*
	 * enable output
	 */
	i2c_delay(CLOCK_LOW_TIME);
	i2c_dir_out();
	/*
	 * set ack pulse high
	 */
	i2c_data(I2C_DATA_LOW);
	/*
	 * generate clock pulse
	 */
	i2c_delay(CLOCK_HIGH_TIME/6);
	i2c_clk(I2C_CLOCK_HIGH);
	i2c_delay(CLOCK_HIGH_TIME);
	i2c_clk(I2C_CLOCK_LOW);
	i2c_delay(CLOCK_LOW_TIME/6);
	/*
	 * reset data out
	 */
	i2c_data(I2C_DATA_HIGH);
	i2c_delay(CLOCK_LOW_TIME);
	
	i2c_dir_in();
}

/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_sendnack
*#
*# DESCRIPTION  : Sends NACK on received data
*#
*#--------------------------------------------------------------------------*/
void
i2c_sendnack(void)
{
	/*
	 * enable output
	 */
	i2c_delay(CLOCK_LOW_TIME);
	i2c_dir_out();
	/*
	 * set data high
	 */
	i2c_data(I2C_DATA_HIGH);
	/*
	 * generate clock pulse
	 */
	i2c_delay(CLOCK_HIGH_TIME/6);
	i2c_clk(I2C_CLOCK_HIGH);
	i2c_delay(CLOCK_HIGH_TIME);
	i2c_clk(I2C_CLOCK_LOW);
	i2c_delay(CLOCK_LOW_TIME);
	
	i2c_dir_in();
}

/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_writereg
*#
*# DESCRIPTION  : Writes a value to an I2C device
*#
*#--------------------------------------------------------------------------*/
int
i2c_writereg(unsigned char theSlave, unsigned char theReg, 
	     unsigned char theValue)
{
	int error, cntr = 3;
	unsigned long flags;

	do {
		error = 0;
		/*
		 * we don't like to be interrupted
		 */
		save_flags(flags);
		cli();

		i2c_start();
		/*
		 * send slave address
		 */
		i2c_outbyte((theSlave & 0xfe));
		/*
		 * wait for ack
		 */
		if(!i2c_getack())
			error = 1;
		/*
		 * now select register
		 */
		i2c_dir_out();
		i2c_outbyte(theReg);
		/*
		 * now it's time to wait for ack
		 */
		if(!i2c_getack())
			error |= 2;
		/*
		 * send register register data
		 */
		i2c_outbyte(theValue);
		/*
		 * now it's time to wait for ack
		 */
		if(!i2c_getack())
			error |= 4;
		/*
		 * end byte stream
		 */
		i2c_stop();
		/*
		 * enable interrupt again
		 */
		restore_flags(flags);
		
	} while(error && cntr--);

	i2c_delay(CLOCK_LOW_TIME);
	
	return -error;
}

/*#---------------------------------------------------------------------------
*#
*# FUNCTION NAME: i2c_readreg
*#
*# DESCRIPTION  : Reads a value from the decoder registers.
*#
*#--------------------------------------------------------------------------*/
unsigned char
i2c_readreg(unsigned char theSlave, unsigned char theReg)
{
	unsigned char b = 0;
	int error, cntr = 3;
	unsigned long flags;

	do {
		error = 0;
		/*
		 * we don't like to be interrupted
		 */
		save_flags(flags);
		cli();
		/*
		 * generate start condition
		 */
		i2c_start();
    
		/*
		 * send slave address
		 */
		i2c_outbyte((theSlave & 0xfe));
		/*
		 * wait for ack
		 */
		if(!i2c_getack())
			error = 1;
		/*
		 * now select register
		 */
		i2c_dir_out();
		i2c_outbyte(theReg);
		/*
		 * now it's time to wait for ack
		 */
		if(!i2c_getack())
			error = 1;
		/*
		 * repeat start condition
		 */
		i2c_delay(CLOCK_LOW_TIME);
		i2c_start();
		/*
		 * send slave address
		 */
		i2c_outbyte(theSlave | 0x01);
		/*
		 * wait for ack
		 */
		if(!i2c_getack())
			error = 1;
		/*
		 * fetch register
		 */
		b = i2c_inbyte();
		/*
		 * last received byte needs to be nacked
		 * instead of acked
		 */
		i2c_sendnack();
		/*
		 * end sequence
		 */
		i2c_stop();
		/*
		 * enable interrupt again
		 */
		restore_flags(flags);
		
	} while(error && cntr--);

	return b;
}

static int
i2c_open(struct inode *inode, struct file *filp)
{
	return 0;
}

static int
i2c_release(struct inode *inode, struct file *filp)
{
	return 0;
}

/* Main device API. ioctl's to write or read to/from i2c registers.
 */

static int
i2c_ioctl(struct inode *inode, struct file *file,
	  unsigned int cmd, unsigned long arg)
{
	if(_IOC_TYPE(cmd) != ETRAXI2C_IOCTYPE) {
		return -EINVAL;
	}

	switch (_IOC_NR(cmd)) {
		case I2C_WRITEREG:
			/* write to an i2c slave */
			D(printk("i2cw %d %d %d\n", 
				 I2C_ARGSLAVE(arg),
				 I2C_ARGREG(arg),
				 I2C_ARGVALUE(arg)));

			return i2c_writereg(I2C_ARGSLAVE(arg),
					    I2C_ARGREG(arg),
					    I2C_ARGVALUE(arg));
		case I2C_READREG:
		{
			unsigned char val;
			/* read from an i2c slave */
			D(printk("i2cr %d %d ", 
				I2C_ARGSLAVE(arg),
				I2C_ARGREG(arg)));
			val = i2c_readreg(I2C_ARGSLAVE(arg), I2C_ARGREG(arg));
			D(printk("= %d\n", val));
			return val;
		}					    
		default:
			return -EINVAL;

	}
	
	return 0;
}

static struct file_operations i2c_fops = {
	owner:    THIS_MODULE,
	ioctl:    i2c_ioctl,
	open:     i2c_open,
	release:  i2c_release,
};

int __init
i2c_init(void)
{
	int res;

	/* Setup and enable the Port B I2C interface */

#ifndef CONFIG_ETRAX_I2C_USES_PB_NOT_PB_I2C
	*R_PORT_PB_I2C = port_pb_i2c_shadow |= 
		IO_STATE(R_PORT_PB_I2C, i2c_en,  on) |
		IO_FIELD(R_PORT_PB_I2C, i2c_d,   1)  |
		IO_FIELD(R_PORT_PB_I2C, i2c_clk, 1)  |
		IO_STATE(R_PORT_PB_I2C, i2c_oe_, enable);
#endif

	port_pb_dir_shadow &= ~IO_MASK(R_PORT_PB_DIR, dir0);
	port_pb_dir_shadow &= ~IO_MASK(R_PORT_PB_DIR, dir1);

	*R_PORT_PB_DIR = (port_pb_dir_shadow |=
			  IO_STATE(R_PORT_PB_DIR, dir0, input)  |
			  IO_STATE(R_PORT_PB_DIR, dir1, output));

	/* register char device */

	res = register_chrdev(I2C_MAJOR, i2c_name, &i2c_fops);
	if(res < 0) {
		printk(KERN_ERR "i2c: couldn't get a major number.\n");
		return res;
	}

	printk(KERN_INFO "I2C driver v2.2, (c) 1999-2001 Axis Communications AB\n");
	
	return 0;
}

/* this makes sure that i2c_init is called during boot */

module_init(i2c_init);

/****************** END OF FILE i2c.c ********************************/