std.log provides 8 log levels and corresponding logging functions. It
allows the user to override the logging "backend" by defining root.log
and to override the default log level by defining root.log_level.
Logging functions accept a scope parameter which allows the implementer
of the logging "backend" to filter logging by library as well as level.
Using the standardized syslog [1] log levels ensures that std.log will
be flexible enough to work for as many use-cases as possible. If we were
to stick with only 3/4 log levels, std.log would be insufficient for
large and/or complex projects such as a kernel or display server.
[1]: https://tools.ietf.org/html/rfc5424#section-6.2.1
