staging:iio:adc: Add AD7791 driver

This patch adds support for the Analog Devices AD7787, AD7788, AD7789, AD7790
and AD7791 Sigma Delta Analog-to-Digital converters.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

drivers/iio/adc/Kconfig

@@ -18,6 +18,18 @@ config AD7266
 	  Say yes here to build support for Analog Devices AD7265 and AD7266
 	  ADCs.
 
+config AD7791
+	tristate "Analog Devices AD7791 ADC driver"
+	depends on SPI
+	select AD_SIGMA_DELTA
+	help
+	  Say yes here to build support for Analog Devices AD7787, AD7788, AD7789,
+	  AD7790 and AD7791 SPI analog to digital converters (ADC). If unsure, say
+	  N (but it is safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called ad7791.
+
 config AT91_ADC
 	tristate "Atmel AT91 ADC"
 	depends on ARCH_AT91

drivers/iio/adc/Makefile

@@ -4,4 +4,5 @@
 
 obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o
 obj-$(CONFIG_AD7266) += ad7266.o
+obj-$(CONFIG_AD7791) += ad7791.o
 obj-$(CONFIG_AT91_ADC) += at91_adc.o

include/linux/platform_data/ad7791.h

+#ifndef __LINUX_PLATFORM_DATA_AD7791__
+#define __LINUX_PLATFORM_DATA_AD7791__
+
+/**
+ * struct ad7791_platform_data - AD7791 device platform data
+ * @buffered: If set to true configure the device for buffered input mode.
+ * @burnout_current: If set to true the 100mA burnout current is enabled.
+ * @unipolar: If set to true sample in unipolar mode, if set to false sample in
+ *		bipolar mode.
+ */
+struct ad7791_platform_data {
+	bool buffered;
+	bool burnout_current;
+	bool unipolar;
+};
+
+#endif