iio: add LM3533 ambient-light-sensor driver

Add sub-driver for the ambient-light-sensor interface on National
Semiconductor / TI LM3533 lighting power chips.

The sensor interface can be used to control the LEDs and backlights of
the chip through defining five light zones and three sets of
corresponding output-current values.

The driver provides raw and mean adc readings along with the current
light zone through sysfs. A threshold event can be generated on zone
changes. The ALS-control output values can be set per zone for the three
current output channels.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Documentation/ABI/testing/sysfs-bus-iio-light-lm3533-als

@@ -0,0 +1,62 @@
+What:		/sys/.../events/in_illuminance0_thresh_either_en
+Date:		April 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Event generated when channel passes one of the four thresholds
+		in each direction (rising|falling) and a zone change occurs.
+		The corresponding light zone can be read from
+		in_illuminance0_zone.
+
+What:		/sys/.../events/in_illuminance0_threshY_hysteresis
+Date:		May 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Get the hysteresis for thresholds Y, that is,
+
+		threshY_hysteresis = threshY_raising - threshY_falling
+
+What:		/sys/.../events/illuminance_threshY_falling_value
+What:		/sys/.../events/illuminance_threshY_raising_value
+Date:		April 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Specifies the value of threshold that the device is comparing
+		against for the events enabled by
+		in_illuminance0_thresh_either_en (0..255), where Y in 0..3.
+
+		Note that threshY_falling must be less than or equal to
+		threshY_raising.
+
+		These thresholds correspond to the eight zone-boundary
+		registers (boundaryY_{low,high}) and defines the five light
+		zones.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_illuminance0_zone
+Date:		April 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Get the current light zone (0..4) as defined by the
+		in_illuminance0_threshY_{falling,rising} thresholds.
+
+What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_raw
+Date:		May 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Get output current for channel Y (0..255), that is,
+		out_currentY_currentZ_raw, where Z is the current zone.
+
+What:		/sys/bus/iio/devices/iio:deviceX/out_currentY_currentZ_raw
+Date:		May 2012
+KernelVersion:	3.5
+Contact:	Johan Hovold <jhovold@gmail.com>
+Description:
+		Set the output current for channel out_currentY when in zone
+		Z (0..255), where Y in 0..2 and Z in 0..4.
+
+		These values correspond to the ALS-mapper target registers for
+		ALS-mapper Y + 1.

drivers/iio/Kconfig

@@ -50,5 +50,6 @@ config IIO_CONSUMERS_PER_TRIGGER
 
 source "drivers/iio/adc/Kconfig"
 source "drivers/iio/amplifiers/Kconfig"
+source "drivers/iio/light/Kconfig"
 
 endif # IIO

drivers/iio/Makefile

@@ -11,3 +11,4 @@ obj-$(CONFIG_IIO_KFIFO_BUF) += kfifo_buf.o
 
 obj-y += adc/
 obj-y += amplifiers/
+obj-y += light/

drivers/iio/light/Kconfig

@@ -0,0 +1,22 @@
+#
+# Light sensors
+#
+menu "Light sensors"
+
+config SENSORS_LM3533
+	tristate "LM3533 ambient light sensor"
+	depends on MFD_LM3533
+	help
+	  If you say yes here you get support for the ambient light sensor
+	  interface on National Semiconductor / TI LM3533 Lighting Power
+	  chips.
+
+	  The sensor interface can be used to control the LEDs and backlights
+	  of the chip through defining five light zones and three sets of
+	  corresponding output-current values.
+
+	  The driver provides raw and mean adc readings along with the current
+	  light zone through sysfs. A threshold event can be generated on zone
+	  changes. The ALS-control output values can be set per zone for the
+	  three current output channels.
+endmenu

drivers/iio/light/Makefile

@@ -0,0 +1,5 @@
+#
+# Makefile for IIO Light sensors
+#
+
+obj-$(CONFIG_SENSORS_LM3533)	+= lm3533-als.o