i2c spi buses: enforce drivers to set default SPI/I2C bus frequency

Not a lot of drivers use the global default, which is somewhat arbitrary.

platforms/common/i2c_spi_buses.cpp

@@ -62,6 +62,10 @@ const char *BusCLIArguments::parseDefaultArguments(int argc, char *argv[])
 int BusCLIArguments::getopt(int argc, char *argv[], const char *options)
 {
 	if (_options[0] == 0) { // need to initialize
+		if (!validateConfiguration()) {
+			return EOF;
+		}
+
 		char *p = (char *)&_options;
 
 		if (_i2c_support) {
@@ -182,6 +186,23 @@ int BusCLIArguments::getopt(int argc, char *argv[], const char *options)
 	return ch;
 }
 
+bool BusCLIArguments::validateConfiguration()
+{
+	bool success = true;
+
+	if (_i2c_support && default_i2c_frequency == -1) {
+		PX4_ERR("Bug: driver %s does not set default_i2c_frequency", px4_get_taskname());
+		success = false;
+	}
+
+	if (_spi_support && default_spi_frequency == -1) {
+		PX4_ERR("Bug: driver %s does not set default_spi_frequency", px4_get_taskname());
+		success = false;
+	}
+
+	return success;
+}
+
 
 BusInstanceIterator::BusInstanceIterator(const char *module_name,
 		const BusCLIArguments &cli_arguments, uint16_t devid_driver_index)

platforms/common/include/px4_platform_common/i2c_spi_buses.h

@@ -117,10 +117,12 @@ public:
 	void *custom_data{nullptr}; ///< driver-specific custom argument
 
 	// driver defaults, if not specified via CLI
-	int default_spi_frequency{20 * 1000 * 1000}; ///< default spi bus frequency [Hz]
-	int default_i2c_frequency{400 * 1000}; ///< default i2c bus frequency [Hz]
+	int default_spi_frequency{-1}; ///< default spi bus frequency (driver needs to set this) [Hz]
+	int default_i2c_frequency{-1}; ///< default i2c bus frequency (driver needs to set this) [Hz]
 
 private:
+	bool validateConfiguration();
+
 	char _options[32] {};
 	int _optind{1};
 	const char *_optarg{nullptr};