ad7779_spi_read
ret = ad7779_spi_read(st, reg, &data);
ret = ad7779_spi_read(st, reg, &rval);
ret = ad7779_spi_read(st, AD7779_REG_GENERAL_USER_CONFIG_2, &temp);
ret = ad7779_spi_read(st, AD7779_REG_CH_GAIN_LOWER_BYTE(channel),
ret = ad7779_spi_read(st, AD7779_REG_CH_GAIN_MID_BYTE(channel),
ret = ad7779_spi_read(st, AD7779_REG_CH_GAIN_UPPER_BYTE(channel),
ret = ad7779_spi_read(st, AD7779_REG_CH_OFFSET_LOWER_BYTE(channel),
ret = ad7779_spi_read(st, AD7779_REG_CH_OFFSET_MID_BYTE(channel),
ret = ad7779_spi_read(st, AD7779_REG_CH_OFFSET_UPPER_BYTE(channel),