iio: Add I/Q modifiers

I/Q modifiers can be used to denote signals which are represented by a
in-phase and a quadrature component.

The ABI documentation describes the I and Q modifiers for current and
voltage channels for now as those will be the most likely users.

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

Documentation/ABI/testing/sysfs-bus-iio

···
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_raw
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_q_raw
 KernelVersion:	2.6.35
 Contact:	[e-mail]
 Description:
···
 		versions may be used. The number must always be specified and
 		unique to allow association with event codes. Units after
 		application of scale and offset are millivolts.
+
+		Channels with 'i' and 'q' modifiers always exist in pairs and both
+		channels refer to the same signal. The 'i' channel contains the in-phase
+		component of the signal while the 'q' channel contains the quadrature
+		component.
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY-voltageZ_raw
 KernelVersion:	2.6.35
···
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_z_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_q_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_q_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_i_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_current_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_i_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_q_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_q_offset
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_i_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_tempY_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_temp_offset
 What:		/sys/bus/iio/devices/iio:deviceX/in_pressureY_offset
···
 		to the _raw output.
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_q_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_i_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_voltage_q_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_voltage-voltage_scale
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_scale
 What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_supply_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_current_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_i_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentY_q_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_i_scale
+What:		/sys/bus/iio/devices/iio:deviceX/in_current_q_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_accel_peak_scale
 What:		/sys/bus/iio/devices/iio:deviceX/in_anglvel_scale
···
 
 What		/sys/bus/iio/devices/iio:deviceX/in_voltageY_calibscale
 What		/sys/bus/iio/devices/iio:deviceX/in_voltageY_supply_calibscale
+What		/sys/bus/iio/devices/iio:deviceX/in_voltageY_i_calibscale
+What		/sys/bus/iio/devices/iio:deviceX/in_voltageY_q_calibscale
+What		/sys/bus/iio/devices/iio:deviceX/in_voltage_i_calibscale
+What		/sys/bus/iio/devices/iio:deviceX/in_voltage_q_calibscale
 What		/sys/bus/iio/devices/iio:deviceX/in_voltage_calibscale
 What		/sys/bus/iio/devices/iio:deviceX/in_accel_x_calibscale
 What		/sys/bus/iio/devices/iio:deviceX/in_accel_y_calibscale
···
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_supply_en
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_en
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY-voltageZ_en
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_i_en
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_q_en
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_i_en
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_q_en
 What:		/sys/.../iio:deviceX/scan_elements/in_incli_x_en
 What:		/sys/.../iio:deviceX/scan_elements/in_incli_y_en
 What:		/sys/.../iio:deviceX/scan_elements/in_pressureY_en
···
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_type
 What:		/sys/.../iio:deviceX/scan_elements/in_voltage_type
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_supply_type
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_i_type
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_q_type
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_i_type
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_q_type
 What:		/sys/.../iio:deviceX/scan_elements/in_timestamp_type
 What:		/sys/.../iio:deviceX/scan_elements/in_pressureY_type
 What:		/sys/.../iio:deviceX/scan_elements/in_pressure_type
···
 
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_index
 What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_supply_index
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_i_index
+What:		/sys/.../iio:deviceX/scan_elements/in_voltageY_q_index
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_i_index
+What:		/sys/.../iio:deviceX/scan_elements/in_voltage_q_index
 What:		/sys/.../iio:deviceX/scan_elements/in_accel_x_index
 What:		/sys/.../iio:deviceX/scan_elements/in_accel_y_index
 What:		/sys/.../iio:deviceX/scan_elements/in_accel_z_index
···
 		or without compensation from tilt sensors.
 
 What:		/sys/bus/iio/devices/iio:deviceX/in_currentX_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentX_i_raw
+What:		/sys/bus/iio/devices/iio:deviceX/in_currentX_q_raw
 KernelVersion:	3.18
 Contact:	[e-mail]
 Description:
···
 		after application of scale and offset. If no offset or scale is
 		present, output should be considered as processed with the
 		unit in milliamps.
+
+		Channels with 'i' and 'q' modifiers always exist in pairs and both
+		channels refer to the same signal. The 'i' channel contains the in-phase
+		component of the signal while the 'q' channel contains the quadrature
+		component.
 
 What:		/sys/.../iio:deviceX/in_energy_en
 What:		/sys/.../iio:deviceX/in_distance_en

drivers/iio/industrialio-core.c

···
 	[IIO_MOD_WALKING] = "walking",
 	[IIO_MOD_STILL] = "still",
 	[IIO_MOD_ROOT_SUM_SQUARED_X_Y_Z] = "sqrt(x^2+y^2+z^2)",
+	[IIO_MOD_I] = "i",
+	[IIO_MOD_Q] = "q",
 };
 
 /* relies on pairs of these shared then separate */

include/uapi/linux/iio/types.h

···
 	IIO_MOD_WALKING,
 	IIO_MOD_STILL,
 	IIO_MOD_ROOT_SUM_SQUARED_X_Y_Z,
+	IIO_MOD_I,
+	IIO_MOD_Q,
 };
 
 enum iio_event_type {