PNI RM3100 magnetometer driver (#10302)

* tested on SPI (px4fmu-v4pro)
 * WIP I2C support

src/drivers/magnetometer/rm3100/rm3100_i2c.cpp

@@ -0,0 +1,165 @@
+/****************************************************************************
+ *
+ *   Copyright (c) 2018 PX4 Development Team. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name PX4 nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/**
+ * @file rm3100_i2c.cpp
+ *
+ * I2C interface for RM3100
+ */
+
+#include <px4_config.h>
+
+#include <assert.h>
+#include <debug.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <arch/board/board.h>
+
+#include <drivers/device/i2c.h>
+#include <drivers/drv_mag.h>
+#include <drivers/drv_device.h>
+
+#include "board_config.h"
+#include "rm3100.h"
+
+#if defined(PX4_I2C_BUS_ONBOARD) || defined(PX4_I2C_BUS_EXPANSION)
+
+#define RM3100_ADDRESS		0x20
+
+#define DIR_READ		(1<<7)
+#define DIR_WRITE		(0<<7)
+
+class RM3100_I2C : public device::I2C
+{
+public:
+	RM3100_I2C(int bus);
+	virtual ~RM3100_I2C() = default;
+
+	virtual int     init();
+	virtual int     ioctl(unsigned operation, unsigned &arg);
+	virtual int     read(unsigned address, void *data, unsigned count);
+	virtual int     write(unsigned address, void *data, unsigned count);
+
+protected:
+	virtual int     probe();
+
+};
+
+device::Device *
+RM3100_I2C_interface(int bus);
+
+device::Device *
+RM3100_I2C_interface(int bus)
+{
+	return new RM3100_I2C(bus);
+}
+
+RM3100_I2C::RM3100_I2C(int bus) :
+	I2C("RM300_I2C", nullptr, bus, RM3100_ADDRESS, 400000)
+{
+	_device_id.devid_s.devtype = DRV_MAG_DEVTYPE_RM3100;
+}
+
+int
+RM3100_I2C::init()
+{
+	/* this will call probe() */
+	return I2C::init();
+}
+
+int
+RM3100_I2C::ioctl(unsigned operation, unsigned &arg)
+{
+	switch (operation) {
+
+	case MAGIOCGEXTERNAL:
+		return external();
+
+	case DEVIOCGDEVICEID:
+		return CDev::ioctl(nullptr, operation, arg);
+
+	default:
+		return  -EINVAL;
+	}
+}
+
+int
+RM3100_I2C::probe()
+{
+	uint8_t data = 0;
+
+	_retries = 10;
+
+	if (read(ADDR_REVID, &data, 1)) {
+		DEVICE_DEBUG("RM3100 read_reg fail");
+		return -EIO;
+	}
+
+	_retries = 2;
+
+	if (data != RM3100_REVID) {
+		DEVICE_DEBUG("RM3100 bad ID: %02x", data);
+		return -EIO;
+	}
+
+	return OK;
+}
+
+int
+RM3100_I2C::read(unsigned address, void *data, unsigned count)
+{
+	uint8_t cmd = address | DIR_READ;
+	return transfer(&cmd, 1, (uint8_t *)data, count);
+}
+
+int
+RM3100_I2C::write(unsigned address, void *data, unsigned count)
+{
+	uint8_t buf[32];
+
+	if (sizeof(buf) < (count + 1)) {
+		return -EIO;
+	}
+
+	buf[0] = address | DIR_WRITE;
+	memcpy(&buf[1], data, count);
+
+	return transfer(&buf[0], count + 1, nullptr, 0);
+}
+
+#endif /* PX4_I2C_OBDEV_RM3100 */