iio: light: add support for UVIS25 sensor

add support for STMicroelectronics UVIS25 uv sensor
http://www.st.com/resource/en/datasheet/uvis25.pdf

- continuos mode support
- i2c support
- spi support
- trigger mode support
- system PM support

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/light/st_uvis25_i2c.c

@@ -0,0 +1,69 @@
+/*
+ * STMicroelectronics uvis25 i2c driver
+ *
+ * Copyright 2017 STMicroelectronics Inc.
+ *
+ * Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
+ *
+ * Licensed under the GPL-2.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/acpi.h>
+#include <linux/i2c.h>
+#include <linux/slab.h>
+#include <linux/regmap.h>
+
+#include "st_uvis25.h"
+
+#define UVIS25_I2C_AUTO_INCREMENT	BIT(7)
+
+const struct regmap_config st_uvis25_i2c_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.write_flag_mask = UVIS25_I2C_AUTO_INCREMENT,
+	.read_flag_mask = UVIS25_I2C_AUTO_INCREMENT,
+};
+
+static int st_uvis25_i2c_probe(struct i2c_client *client,
+			       const struct i2c_device_id *id)
+{
+	struct regmap *regmap;
+
+	regmap = devm_regmap_init_i2c(client, &st_uvis25_i2c_regmap_config);
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "Failed to register i2c regmap %d\n",
+			(int)PTR_ERR(regmap));
+		return PTR_ERR(regmap);
+	}
+
+	return st_uvis25_probe(&client->dev, client->irq, regmap);
+}
+
+static const struct of_device_id st_uvis25_i2c_of_match[] = {
+	{ .compatible = "st,uvis25", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, st_uvis25_i2c_of_match);
+
+static const struct i2c_device_id st_uvis25_i2c_id_table[] = {
+	{ ST_UVIS25_DEV_NAME },
+	{},
+};
+MODULE_DEVICE_TABLE(i2c, st_uvis25_i2c_id_table);
+
+static struct i2c_driver st_uvis25_driver = {
+	.driver = {
+		.name = "st_uvis25_i2c",
+		.pm = &st_uvis25_pm_ops,
+		.of_match_table = of_match_ptr(st_uvis25_i2c_of_match),
+	},
+	.probe = st_uvis25_i2c_probe,
+	.id_table = st_uvis25_i2c_id_table,
+};
+module_i2c_driver(st_uvis25_driver);
+
+MODULE_AUTHOR("Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>");
+MODULE_DESCRIPTION("STMicroelectronics uvis25 i2c driver");
+MODULE_LICENSE("GPL v2");