[PATCH v3 3/5] dt-bindings: iio: ad7949: Add adi,reference-select

[Adam Michaelis <adam.michaelis@rockwellcollins.com>]

Adding optional parameter to AD7949 to specify the source for the
reference voltage signal. Default value is maintained with option '3' to
match previous version of driver.

Signed-off-by: Adam Michaelis <adam.michaelis@rockwellcollins.com>
---
	V2:
	- Add some defines to reduce use of magic numbers.
	V3:
	- Re-think usage of device tree parameter to focus on the
	actual reference sources instead of the raw hardware
	configuration.
---
 .../devicetree/bindings/iio/adc/ad7949.txt          | 21 +++++++++++++++++++--
 1 file changed, 19 insertions(+), 2 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/ad7949.txt b/Documentation/devicetree/bindings/iio/adc/ad7949.txt
index c7f5057356b1..e5152335c761 100644
--- a/Documentation/devicetree/bindings/iio/adc/ad7949.txt
+++ b/Documentation/devicetree/bindings/iio/adc/ad7949.txt
@@ -6,11 +6,28 @@ Required properties:
 	* "adi,ad7682"
 	* "adi,ad7689"
  - reg: spi chip select number for the device
- - vref-supply: The regulator supply for ADC reference voltage
 
-Example:
+Optional properties:
+ - adi,reference-select: Select the reference voltage source to use
+ when converting the input voltages. Valid values are:
+   0: Internal 2.5V reference;
+   1: Internal 4.096V reference;
+   2: External REF reference;
+   3: External REFIN reference (default);
+ - vref-supply: The regulator supply for external ADC reference voltage.
+ Required if one of the external references is selected by
+ 'adi,reference-select'.
+
+Examples:
 adc@0 {
 	compatible = "adi,ad7949";
 	reg = <0>;
+	adi,reference-select = <2>;
 	vref-supply = <&vdd_supply>;
 };
+
+adc@0 {
+	compatible = "adi,ad7949";
+	reg = <0>;
+	adi,reference-select = <0>;
+};
-- 
1.9.1