iio: light: isl29501: Add support for the ISL29501 ToF sensor.

This patch adds support for the ISL29501 Time of Flight sensor.
Signed-off-by: Mathieu Othacehe <m.othacehe@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Documentation/ABI/testing/sysfs-bus-iio-isl29501

+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_agc_gain
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_agc_gain_bias
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		This sensor has an automatic gain control (agc) loop
+		which sets the analog signal levels at an optimum
+		level by controlling programmable gain amplifiers. The
+		criteria for optimal gain is determined by the sensor.
+
+		Return the actual gain value as an integer in [0; 65536]
+		range when read from.
+
+		The agc gain read when measuring crosstalk shall be
+		written into in_proximity0_agc_gain_bias.
+
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_calib_phase_temp_a
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_calib_phase_temp_b
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_calib_phase_light_a
+What:		/sys/bus/iio/devices/iio:deviceX/in_proximity0_calib_phase_light_b
+KernelVersion:	4.18
+Contact:	linux-iio@vger.kernel.org
+Description:
+		The sensor is able to perform correction of distance
+		measurements due to changing temperature and ambient
+		light conditions. It can be programmed to correct for
+		a second order error polynomial.
+
+		Phase data has to be collected when temperature and
+		ambient light are modulated independently.
+
+		Then a least squares curve fit to a second order
+		polynomial has to be generated from the data. The
+		resultant curves have the form ax^2 + bx + c.
+
+		From those two curves, a and b coefficients shall be
+		stored in in_proximity0_calib_phase_temp_a and
+		in_proximity0_calib_phase_temp_b for temperature and
+		in in_proximity0_calib_phase_light_a and
+		in_proximity0_calib_phase_light_b for ambient light.
+
+		Those values must be integer in [0; 8355840] range.
+
+		Finally, the c constant is set by the sensor
+		internally.
+
+		The value stored in sensor is displayed when read from.

Documentation/devicetree/bindings/iio/light/isl29501.txt

+* ISL29501 Time-of-flight sensor.
+
+Required properties:
+
+  - compatible : should be "renesas,isl29501"
+  - reg : the I2C address of the sensor
+
+Example:
+
+isl29501@57 {
+	compatible = "renesas,isl29501";
+	reg = <0x57>;
+};

drivers/iio/proximity/Kconfig

@@ -20,6 +20,19 @@ endmenu
 
 menu "Proximity and distance sensors"
 
+config ISL29501
+	tristate "Intersil ISL29501 Time Of Flight sensor"
+	depends on I2C
+	select IIO_BUFFER
+	select IIO_TRIGGERED_BUFFER
+	select IIO_KFIFO_BUF
+	help
+	  Say Y here if you want to build a driver for the Intersil ISL29501
+	  Time of Flight sensor.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called isl29501.
+
 config LIDAR_LITE_V2
 	tristate "PulsedLight LIDAR sensor"
 	select IIO_BUFFER

drivers/iio/proximity/Makefile

@@ -5,6 +5,7 @@
 
 # When adding new entries keep the list in alphabetical order
 obj-$(CONFIG_AS3935)		+= as3935.o
+obj-$(CONFIG_ISL29501)		+= isl29501.o
 obj-$(CONFIG_LIDAR_LITE_V2)	+= pulsedlight-lidar-lite-v2.o
 obj-$(CONFIG_RFD77402)		+= rfd77402.o
 obj-$(CONFIG_SRF04)		+= srf04.o