B.5.6 How lines are divided into types

The lines in devices are distinguished in the following manner:

1. Leading white space is removed.
2. If the resulting line begins with the exact string define, followed by one or more white space characters, the line is processed as a macro definition.
3. Otherwise, the line is scanned for the first instance of a colon (:) or an equals sign (=).
4. If a colon is encountered first, the line is processed as a driver definition.
5. Otherwise, if an equals sign is encountered, the line is processed as a macro definition.
6. Otherwise, the line is ill-formed.