IIO: ADC: New driver for AD7190/AD7192/AD7195 4 Channel SPI ADC

New driver for AD7190/AD7192/AD7195 4.8 kHz, Ultralow Noise, 24-Bit
Sigma-Delta ADC with PGA

These devices features a dual use data out ready DOUT/RDY output.
In order to avoid contentions on the SPI bus, it's necessary to use
spi bus locking. The DOUT/RDY output must also be wired to an
interrupt capable GPIO.

In INDIO_RING_TRIGGERED mode, this driver may block its SPI bus segment
for an extended period of time.

Changes since V1:

Add missing documentation.
Remove obsoleted include files.
Fix typos and style issues.
Fix buffer size.
Split ad7192_show() into two functions.
Avoid race condition add mutex.
Abandon IIO_CHAN macro.
Reorder elements in ad7192_platform_data.
Remove driver bus type.

Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/Documentation/sysfs-bus-iio

@@ -711,3 +711,24 @@ Contact:	linux-iio@xxxxxxxxxxxxxxx
 Description:
 		This attribute is used to read the amount of quadrature error
 		present in the device at a given time.
+
+What:		/sys/.../iio:deviceX/ac_excitation_en
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This attribute, if available, is used to enable the AC
+		excitation mode found on some converters. In ac excitation mode,
+		the polarity of the excitation voltage is reversed on
+		alternate cycles, to eliminate DC errors.
+
+What:		/sys/.../iio:deviceX/bridge_switch_en
+KernelVersion:	3.1.0
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This attribute, if available, is used to close or open the
+		bridge power down switch found on some converters.
+		In bridge applications, such as strain gauges and load cells,
+		the bridge itself consumes the majority of the current in the
+		system. To minimize the current consumption of the system,
+		the bridge can be disconnected (when it is not being used
+		using the bridge_switch_en attribute.

drivers/staging/iio/adc/Kconfig

@@ -161,6 +161,20 @@ config AD7816
 	  Say yes here to build support for Analog Devices AD7816/7/8
 	  temperature sensors and ADC.
 
+config AD7192
+	tristate "Analog Devices AD7190 AD7192 AD7195 ADC driver"
+	depends on SPI
+	select IIO_RING_BUFFER
+	select IIO_SW_RING
+	select IIO_TRIGGER
+	help
+	  Say yes here to build support for Analog Devices AD7190,
+	  AD7192 or AD7195 SPI analog to digital convertors (ADC).
+	  If unsure, say N (but it's safe to say "Y").
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called ad7192.
+
 config ADT75
 	tristate "Analog Devices ADT75 temperature sensor driver"
 	depends on I2C

drivers/staging/iio/adc/Makefile

@@ -37,6 +37,7 @@ obj-$(CONFIG_AD7745) += ad7745.o
 obj-$(CONFIG_AD7780) += ad7780.o
 obj-$(CONFIG_AD7793) += ad7793.o
 obj-$(CONFIG_AD7816) += ad7816.o
+obj-$(CONFIG_AD7192) += ad7192.o
 obj-$(CONFIG_ADT75) += adt75.o
 obj-$(CONFIG_ADT7310) += adt7310.o
 obj-$(CONFIG_ADT7410) += adt7410.o