fxos8701cq + fxas21002c: add support for I2C

src/drivers/magnetometer/ak09916/ak09916.cpp

@@ -170,11 +170,11 @@ AK09916::check_id()
 	return (AK09916_DEVICE_ID_A == deviceid);
 }
 
-void
+int
 AK09916::write_reg(uint8_t reg, uint8_t value)
 {
 	const uint8_t cmd[2] = { reg, value};
-	transfer(cmd, 2, nullptr, 0);
+	return transfer(cmd, 2, nullptr, 0);
 }
 
 int

src/drivers/magnetometer/ak09916/ak09916.hpp

@@ -105,7 +105,7 @@ protected:
 
 	uint8_t read_reg(uint8_t reg);
 	void read_block(uint8_t reg, uint8_t *val, uint8_t count);
-	void write_reg(uint8_t reg, uint8_t value);
+	int write_reg(uint8_t reg, uint8_t value);
 
 private:
 

src/drivers/magnetometer/lsm303agr/LSM303AGR.cpp

@@ -233,13 +233,13 @@ uint8_t LSM303AGR::read_reg(unsigned reg)
 	return cmd[1];
 }
 
-void LSM303AGR::write_reg(unsigned reg, uint8_t value)
+int LSM303AGR::write_reg(unsigned reg, uint8_t value)
 {
 	uint8_t	cmd[2];
 	cmd[0] = reg | DIR_WRITE;
 	cmd[1] = value;
 
-	transfer(cmd, nullptr, sizeof(cmd));
+	return transfer(cmd, nullptr, sizeof(cmd));
 }
 
 void LSM303AGR::start()

src/drivers/magnetometer/lsm303agr/LSM303AGR.hpp

@@ -152,13 +152,14 @@ private:
 	 * @param		The register to read.
 	 * @return		The value that was read.
 	 */
-	uint8_t			read_reg(unsigned reg);
+	uint8_t			read_reg(unsigned reg) override;
 
 	/**
 	 * Write a register in the LSM303AGR
 	 *
 	 * @param reg		The register to write.
 	 * @param value		The new value to write.
+	 * @return		OK on success, negative errno otherwise.
 	 */
-	void			write_reg(unsigned reg, uint8_t value);
+	int			write_reg(unsigned reg, uint8_t value) override;
 };