libcamera: log: De-duplicate _log() functions and LogMessage constructor

The _log() functions, as well as the LogMessage constructor, exist in
two versions, one that takes a log category, and one that doesn't. The
latter uses the default log category. This can be simplified by passing
a LogCategory pointer to _log(), which can then be null for the default
category, and moving the retrieval of the default log category from the
LogMessage constructor to the _log() function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Sebastian Fricke <sebastian.fricke@posteo.net>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/internal/log.h

@@ -55,8 +55,6 @@ const LogCategory &_LOG_CATEGORY(name)()				\
 class LogMessage
 {
 public:
-	LogMessage(const char *fileName, unsigned int line,
-		   LogSeverity severity);
 	LogMessage(const char *fileName, unsigned int line,
 		   const LogCategory &category, LogSeverity severity);
 
@@ -92,23 +90,20 @@ protected:
 	virtual std::string logPrefix() const = 0;
 
 	LogMessage _log(const char *file, unsigned int line,
-			LogSeverity severity) const;
+			const LogCategory *category,
-	LogMessage _log(const char *file, unsigned int line,
-			const LogCategory &category,
 			LogSeverity severity) const;
 };
 
-LogMessage _log(const char *file, unsigned int line, LogSeverity severity);
 LogMessage _log(const char *file, unsigned int line,
-		const LogCategory &category, LogSeverity severity);
+		const LogCategory *category, LogSeverity severity);
 
 #ifndef __DOXYGEN__
 #define _LOG_CATEGORY(name) logCategory##name
 
 #define _LOG1(severity) \
-	_log(__FILE__, __LINE__, Log##severity).stream()
+	_log(__FILE__, __LINE__, nullptr, Log##severity).stream()
 #define _LOG2(category, severity) \
-	_log(__FILE__, __LINE__, _LOG_CATEGORY(category)(), Log##severity).stream()
+	_log(__FILE__, __LINE__, &_LOG_CATEGORY(category)(), Log##severity).stream()
 
 /*
  * Expand the LOG() macro to _LOG1() or _LOG2() based on the number of

src/libcamera/log.cpp

@@ -763,24 +763,6 @@ const LogCategory &LogCategory::defaultCategory()
  * directly. Use the LOG() macro instead access the log infrastructure.
  */
 
-/**
- * \brief Construct a log message for the default category
- * \param[in] fileName The file name where the message is logged from
- * \param[in] line The line number where the message is logged from
- * \param[in] severity The log message severity, controlling how the message
- * will be displayed
- *
- * Create a log message pertaining to line \a line of file \a fileName. The
- * \a severity argument sets the message severity to control whether it will be
- * output or dropped.
- */
-LogMessage::LogMessage(const char *fileName, unsigned int line,
-		       LogSeverity severity)
-	: category_(LogCategory::defaultCategory()), severity_(severity)
-{
-	init(fileName, line);
-}
-
 /**
  * \brief Construct a log message for a given category
  * \param[in] fileName The file name where the message is logged from
@@ -913,26 +895,6 @@ Loggable::~Loggable()
  * \return A string to be prefixed to the log message
  */
 
-/**
- * \brief Create a temporary LogMessage object to log a message
- * \param[in] fileName The file name where the message is logged from
- * \param[in] line The line number where the message is logged from
- * \param[in] severity The log message severity
- *
- * This method is used as a backeng by the LOG() macro to create a log message
- * for locations inheriting from the Loggable class.
- *
- * \return A log message
- */
-LogMessage Loggable::_log(const char *fileName, unsigned int line,
-			  LogSeverity severity) const
-{
-	LogMessage msg(fileName, line, severity);
-
-	msg.stream() << logPrefix() << ": ";
-	return msg;
-}
-
 /**
  * \brief Create a temporary LogMessage object to log a message
  * \param[in] fileName The file name where the message is logged from
@@ -946,31 +908,17 @@ LogMessage Loggable::_log(const char *fileName, unsigned int line,
  * \return A log message
  */
 LogMessage Loggable::_log(const char *fileName, unsigned int line,
-			  const LogCategory &category,
+			  const LogCategory *category,
 			  LogSeverity severity) const
 {
-	LogMessage msg(fileName, line, category, severity);
+	LogMessage msg(fileName, line,
+		       category ? *category : LogCategory::defaultCategory(),
+		       severity);
 
 	msg.stream() << logPrefix() << ": ";
 	return msg;
 }
 
-/**
- * \brief Create a temporary LogMessage object to log a message
- * \param[in] fileName The file name where the message is logged from
- * \param[in] line The line number where the message is logged from
- * \param[in] severity The log message severity
- *
- * This function is used as a backeng by the LOG() macro to create a log
- * message for locations not inheriting from the Loggable class.
- *
- * \return A log message
- */
-LogMessage _log(const char *fileName, unsigned int line, LogSeverity severity)
-{
-	return LogMessage(fileName, line, severity);
-}
-
 /**
  * \brief Create a temporary LogMessage object to log a message
  * \param[in] fileName The file name where the message is logged from
@@ -984,9 +932,11 @@ LogMessage _log(const char *fileName, unsigned int line, LogSeverity severity)
  * \return A log message
  */
 LogMessage _log(const char *fileName, unsigned int line,
-		const LogCategory &category, LogSeverity severity)
+		const LogCategory *category, LogSeverity severity)
 {
-	return LogMessage(fileName, line, category, severity);
+	return LogMessage(fileName, line,
+			  category ? *category : LogCategory::defaultCategory(),
+			  severity);
 }
 
 /**