iio: documentation: Add out_altvoltage and friends

Continuous frequency/clock generating devices, such as DDSs or PLLs
should use out_altvoltage.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-iio

@@ -219,6 +219,7 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_voltageY_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/out_voltageY_scale
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_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
@@ -273,6 +274,7 @@ What:		/sys/bus/iio/devices/iio:deviceX/in_accel_scale_available
 What:		/sys/.../iio:deviceX/in_voltageX_scale_available
 What:		/sys/.../iio:deviceX/in_voltage-voltage_scale_available
 What:		/sys/.../iio:deviceX/out_voltageX_scale_available
+What:		/sys/.../iio:deviceX/out_altvoltageX_scale_available
 What:		/sys/.../iio:deviceX/in_capacitance_scale_available
 KernelVersion:	2.635
 Contact:	linux-iio@vger.kernel.org
@@ -298,14 +300,19 @@ Description:
 		gives the 3dB frequency of the filter in Hz.
 
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_raw
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_raw
 KernelVersion:	2.6.37
 Contact:	linux-iio@vger.kernel.org
 Description:
 		Raw (unscaled, no bias etc.) output voltage for
 		channel Y.  The number must always be specified and
 		unique if the output corresponds to a single channel.
+		While DAC like devices typically use out_voltage,
+		a continuous frequency generating device, such as
+		a DDS or PLL should use out_altvoltage.
 
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY&Z_raw
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY&Z_raw
 KernelVersion:	2.6.37
 Contact:	linux-iio@vger.kernel.org
 Description:
@@ -316,6 +323,8 @@ Description:
 
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_powerdown_mode
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltage_powerdown_mode
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_powerdown_mode
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltage_powerdown_mode
 KernelVersion:	2.6.38
 Contact:	linux-iio@vger.kernel.org
 Description:
@@ -330,6 +339,8 @@ Description:
 
 What:		/sys/.../iio:deviceX/out_votlageY_powerdown_mode_available
 What:		/sys/.../iio:deviceX/out_voltage_powerdown_mode_available
+What:		/sys/.../iio:deviceX/out_altvotlageY_powerdown_mode_available
+What:		/sys/.../iio:deviceX/out_altvoltage_powerdown_mode_available
 KernelVersion:	2.6.38
 Contact:	linux-iio@vger.kernel.org
 Description:
@@ -338,6 +349,8 @@ Description:
 
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltageY_powerdown
 What:		/sys/bus/iio/devices/iio:deviceX/out_voltage_powerdown
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_powerdown
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltage_powerdown
 KernelVersion:	2.6.38
 Contact:	linux-iio@vger.kernel.org
 Description:
@@ -346,6 +359,24 @@ Description:
 		normal operation. Y may be suppressed if all outputs are
 		controlled together.
 
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_frequency
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Output frequency for channel Y in Hz. The number must always be
+		specified and unique if the output corresponds to a single
+		channel.
+
+What:		/sys/bus/iio/devices/iio:deviceX/out_altvoltageY_phase
+KernelVersion:	3.4.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		Phase in radians of one frequency/clock output Y
+		(out_altvoltageY) relative to another frequency/clock output
+		(out_altvoltageZ) of the device X. The number must always be
+		specified and unique if the output corresponds to a single
+		channel.
+
 What:		/sys/bus/iio/devices/iio:deviceX/events
 KernelVersion:	2.6.35
 Contact:	linux-iio@vger.kernel.org