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112 lines
2.4 KiB
C
112 lines
2.4 KiB
C
#ifndef _GPXE_I2C_H
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#define _GPXE_I2C_H
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/** @file
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*
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* I2C interface
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*
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*/
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#include <stdint.h>
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/** An I2C device
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*
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* An I2C device represents a specific slave device on an I2C bus. It
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* is accessed via an I2C interface.
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*/
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struct i2c_device {
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/** Address of this device */
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unsigned int address;
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/** Flag indicating a ten-bit address format */
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int tenbit;
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};
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/** An I2C interface
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*
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* An I2C interface provides access to an I2C bus, via which I2C
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* devices may be reached.
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*/
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struct i2c_interface {
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/**
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* Read data from I2C device
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @v offset Starting offset within the device
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* @v data Data buffer
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* @v len Length of data buffer
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* @ret rc Return status code
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*/
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int ( * read ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
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unsigned int offset, uint8_t *data,
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unsigned int len );
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/**
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* Write data to I2C device
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @v offset Starting offset within the device
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* @v data Data buffer
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* @v len Length of data buffer
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* @ret rc Return status code
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*/
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int ( * write ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
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unsigned int offset, const uint8_t *data,
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unsigned int len );
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};
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/** A bit-bashing I2C interface
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*
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* This provides a standardised way to construct I2C buses via a
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* bit-bashing interface.
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*/
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struct i2c_bit_basher {
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/** I2C interface */
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struct i2c_interface i2c;
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/** Bit-bashing interface */
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struct bit_basher basher;
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};
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/** Ten-bit address marker
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*
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* This value is ORed with the I2C device address to indicate a
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* ten-bit address format on the bus.
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*/
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#define I2C_TENBIT_ADDRESS 0x7800
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/** An I2C write command */
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#define I2C_WRITE 0
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/** An I2C read command */
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#define I2C_READ 1
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/** Bit indices used for I2C bit-bashing interface */
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enum {
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/** Serial clock */
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I2C_BIT_SCL = 0,
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/** Serial data */
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I2C_BIT_SDA,
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};
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/** Delay required for bit-bashing operation */
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#define I2C_UDELAY 5
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/**
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* Check presence of I2C device
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*
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* @v i2c I2C interface
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* @v i2cdev I2C device
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* @ret rc Return status code
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*
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* Checks for the presence of the device on the I2C bus by attempting
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* a zero-length write.
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*/
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static inline int i2c_check_presence ( struct i2c_interface *i2c,
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struct i2c_device *i2cdev ) {
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return i2c->write ( i2c, i2cdev, 0, NULL, 0 );
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}
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extern void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit );
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#endif /* _GPXE_I2C_H */
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