Added bit-bashing i2c interface code

src/include/gpxe/i2c.h

@@ -0,0 +1,109 @@
+#ifndef _GPXE_I2C_H
+#define _GPXE_I2C_H
+
+/** @file
+ *
+ * I2C interface
+ *
+ */
+
+#include <stdint.h>
+
+/** An I2C device
+ *
+ * An I2C device represents a specific slave device on an I2C bus.  It
+ * is accessed via an I2C interface.
+ */
+struct i2c_device {
+	/** Address of this device */
+	unsigned int address;
+	/** Flag indicating a ten-bit address format */
+	int tenbit;
+};
+
+/** An I2C interface
+ *
+ * An I2C interface provides access to an I2C bus, via which I2C
+ * devices may be reached.
+ */
+struct i2c_interface {
+	/**
+	 * Read data from I2C device
+	 *
+	 * @v i2c		I2C interface
+	 * @v i2cdev		I2C device
+	 * @v offset		Starting offset within the device
+	 * @v data		Data buffer
+	 * @v len		Length of data buffer
+	 * @ret rc		Return status code
+	 */
+	int ( * read ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
+			 unsigned int offset, uint8_t *data,
+			 unsigned int len );
+	/**
+	 * Write data to I2C device
+	 *
+	 * @v i2c		I2C interface
+	 * @v i2cdev		I2C device
+	 * @v offset		Starting offset within the device
+	 * @v data		Data buffer
+	 * @v len		Length of data buffer
+	 * @ret rc		Return status code
+	 */
+	int ( * write ) ( struct i2c_interface *i2c, struct i2c_device *i2cdev,
+			  unsigned int offset, const uint8_t *data,
+			  unsigned int len );
+};
+
+/** A bit-bashing I2C interface
+ *
+ * This provides a standardised way to construct I2C buses via a
+ * bit-bashing interface.
+ */
+struct i2c_bit_basher {
+	/** I2C interface */
+	struct i2c_interface i2c;
+	/** Bit-bashing interface */
+	struct bit_basher basher;
+};
+
+/** Ten-bit address marker
+ *
+ * This value is ORed with the I2C device address to indicate a
+ * ten-bit address format on the bus.
+ */
+#define I2C_TENBIT_ADDRESS 0x7800
+
+/** An I2C write command */
+#define I2C_WRITE 0
+
+/** An I2C read command */
+#define I2C_READ 1
+
+/** Bit indices used for I2C bit-bashing interface */
+enum {
+	I2C_BIT_SCL = 0,
+	I2C_BIT_SDA,
+};
+
+/** Delay required for bit-bashing operation */
+#define I2C_UDELAY 5
+
+/**
+ * Check presence of I2C device
+ *
+ * @v i2c		I2C interface
+ * @v i2cdev		I2C device
+ * @ret rc		Return status code
+ *
+ * Checks for the presence of the device on the I2C bus by attempting
+ * a zero-length write.
+ */
+static inline int i2c_check_presence ( struct i2c_interface *i2c,
+				       struct i2c_device *i2cdev ) {
+	return i2c->write ( i2c, i2cdev, 0, NULL, 0 );
+}
+
+extern void init_i2c_bit_basher ( struct i2c_bit_basher *i2cbit );
+
+#endif /* _GPXE_I2C_H */