#define AF901x_GETFIELD(bitf, val)		((val >> AF901x_OFFST_##bitf) &	\
					 	((1 << AF901x_WIDTH_##bitf) - 1))

#define AF901x_SETFIELD(bitf, mask, val)(mask = (mask & (~(((1 << AF901x_WIDTH_##bitf) - 1)<<	\
							AF901x_OFFST_##bitf))) | (val << AF901x_OFFST_##bitf))


#define AF901x_BYPASS_HOST2TUNER		0xd607
#define AF901x_WIDTH_BYPASS_HOST2TUNER		1
#define AF901x_OFFST_BYPASS_HOST2TUNER		2

#define AF901x_I2CREG_SEL_TUNER			0xd417
#define AF901x_WIDTH_I2CREG_SEL_TUNER		1
#define AF901x_OFFST_I2CREG_SEL_TUNER		3

/**
 * NOTE! What we do here is not a simple Tuner I2C Bus enable/disable !
 * What's performed here is a 2 way switch kind of operation where
 * the bus is switched between the demodulator and the tuner
 *
 * Of course we have a workaround (we have to), the enable bit can be
 * used for enabling the tuner, which means the demodulator is disabled.
 *
 * A case where we get totally confused is when we have MASTER/SLAVE
 * combinations
 *
 * The worst problem that we can have here: once we switch the
 * tuner bypass ON and expecting an error and the transaction aborts,
 * The driver expects the device to be communicating to the demodulator,
 * but in reality we are talking to the tuner in fact.
 *
 * A workaround for this would be to cache the gate switched state
 * into the device state structure, whereby a possible operation
 * returned success state is used to switch the gate status back to the
 * original position, such that normal communication can continue with
 * the demodulator.
 *
 * But with all these workarounds don't we look ugly ? Any better ways
 * of accomplishing this ?
 */
static int af901x_i2c_gate_ctrl(struct dvb_frontend *fe, int enable)
{
	u8 reg;

	if (slave) {
		/**
		 * Additionally, we need to tell the BCU that we are 
		 * talking to the SLAVE, How ?
		 */
		af901x_read_reg(state, AF901x_BYPASS_HOST2TUNER, &reg);

		if (enable)
			reg = AF901x_SETFIELD(BYPASS_HOST2TUNER, reg, 1);
		else 
			reg = AF901x_SETFIELD(BYPASS_HOST2TUNER, reg, 0);
		/**
		 * Additionally, we need to tell the BCU that we are 
		 * talking to the SLAVE, How ?
		 */
		af901x_write_reg(state, AF901x_BYPASS_HOST2TUNER, reg);

	} else {
		/**
		 * Additionally, we need to tell the BCU that we are 
		 * talking to the MASTER, How ?
		 */
		af901x_read_reg(state, AF901x_I2CREG_SEL_TUNER, &reg);

		if (enable)
			reg = AF901x_GETFIELD(I2CREG_SEL_TUNER, reg, 1);
		else
			reg = AF901x_GETFIELD(I2CREG_SEL_TUNER, reg, 0);

		/**
		 * Additionally, we need to tell the BCU that we are 
		 * talking to the MASTER, How ?
		 */
		af901x_write_reg(state, AF901x_I2CREG_SEL_TUNER, reg);
	}

	return 0;
}