iio: imu: add BNO055 I2C driver

This path adds an I2C driver for communicating to a BNO055 IMU via I2C bus
and it enables the BNO055 core driver to work in this scenario.

Signed-off-by: Andrea Merello <andrea.merello@iit.it>

drivers/iio/imu/bno055/Kconfig

@@ -7,3 +7,9 @@ config BOSH_BNO055_SERIAL
 	tristate "Bosh BNO055 attached via serial bus"
 	depends on SERIAL_DEV_BUS
 	select BOSH_BNO055_IIO
+
+config BOSH_BNO055_I2C
+	tristate "Bosh BNO055 attached via I2C bus"
+	depends on I2C
+	select REGMAP_I2C
+	select BOSH_BNO055_IIO

drivers/iio/imu/bno055/Makefile

@@ -2,3 +2,4 @@
 
 obj-$(CONFIG_BOSH_BNO055_IIO) += bno055.o
 obj-$(CONFIG_BOSH_BNO055_SERIAL) += bno055_sl.o
+obj-$(CONFIG_BOSH_BNO055_I2C) += bno055_i2c.o

drivers/iio/imu/bno055/bno055_i2c.c

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * I2C interface for Bosh BNO055 IMU.
+ * This file implements I2C communication up to the register read/write
+ * level.
+ *
+ * Copyright (C) 2021 Istituto Italiano di Tecnologia
+ * Electronic Design Laboratory
+ * Written by Andrea Merello <andrea.merello@iit.it>
+ */
+
+#include <linux/i2c.h>
+#include <linux/regmap.h>
+#include <linux/module.h>
+
+#include "bno055.h"
+
+#define BNO055_I2C_XFER_BURST_BREAK_THRESHOLD 3 /* FIXME */
+
+static int bno055_i2c_probe(struct i2c_client *client,
+			    const struct i2c_device_id *id)
+{
+	struct regmap *regmap =
+		devm_regmap_init_i2c(client, &bno055_regmap_config);
+
+	if (IS_ERR(regmap)) {
+		dev_err(&client->dev, "Unable to init register map");
+		return PTR_ERR(regmap);
+	}
+
+	return bno055_probe(&client->dev, regmap,
+			    BNO055_I2C_XFER_BURST_BREAK_THRESHOLD);
+
+	return 0;
+}
+
+static const struct i2c_device_id bno055_i2c_id[] = {
+	{"bno055", 0},
+	{ },
+};
+MODULE_DEVICE_TABLE(i2c, bno055_i2c_id);
+
+static struct i2c_driver bno055_driver = {
+	.driver = {
+		.name = "bno055-i2c",
+	},
+	.probe = bno055_i2c_probe,
+	.id_table = bno055_i2c_id
+};
+module_i2c_driver(bno055_driver);
+
+MODULE_AUTHOR("Andrea Merello");
+MODULE_DESCRIPTION("Bosch BNO055 I2C interface");
+MODULE_LICENSE("GPL v2");