README: Begin documenting development style rules

The first rule enforces the use of stdout/stderr for logging. Rationale
is provided in the README.

Change-Id: Ibb5b62ea1341aa951fd42b15e9cd14a836842032
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
1 file changed
tree: d8dabd29cc69097aaef27926406872fa08af4883
  1. Documentation/
  2. m4/
  3. test/
  4. xyz/
  5. .gitignore
  6. bootstrap.sh
  7. common.c
  8. common.h
  9. configure.ac
  10. dbus.h
  11. LICENSE
  12. Makefile.am
  13. mbox.h
  14. mboxctl.c
  15. mboxd.c
  16. mboxd_dbus.c
  17. mboxd_dbus.h
  18. mboxd_flash.h
  19. mboxd_flash_physical.c
  20. mboxd_flash_virtual.cpp
  21. mboxd_lpc.c
  22. mboxd_lpc.h
  23. mboxd_lpc_physical.c
  24. mboxd_lpc_virtual.cpp
  25. mboxd_msg.c
  26. mboxd_msg.h
  27. mboxd_pnor_partition_table.cpp
  28. mboxd_pnor_partition_table.h
  29. mboxd_windows.c
  30. mboxd_windows.h
  31. mtd.c
  32. pnor_partition.cpp
  33. pnor_partition.hpp
  34. pnor_partition_defs.h
  35. pnor_partition_table.cpp
  36. pnor_partition_table.hpp
  37. README.md
README.md

Copyright 2017 IBM

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

MBOX

This repo contains the protocol definition for the host to BMC mailbox communication specification which can be found in Documentation/mbox_procotol.md.

There is also a reference implementation of a BMC mailbox daemon, the details of which can be found in Documentation/mboxd.md.

Finally there is also an implementation of a mailbox daemon control program, the details of which can be found in Documentation/mboxctl.md.

Style Guide

Preamble

This codebase is a mix of C (due to its heritage) and C++. This is an ugly split: message logging and error handling can be vastly different inside the same codebase. The aim is to remove the split one way or the other over time and have consistent approaches to solving problems.

phosphor-mboxd is developed as part of the OpenBMC project, which also leads to integration of frameworks such as phosphor-logging. Specifically on phosphor-logging, it's noted that without care we can achieve absurd duplication or irritating splits in where errors are reported, as the C code is not capable of making use of the interfaces provided.

Rules

  1. Message logging MUST be done to stdout or stderr, and MUST NOT be done directly via journal APIs or wrappers of the journal APIs.

    Rationale:

    We have two scenarios where we care about output, with the important restriction that the method must be consistent between C and C++:

    1. Running in-context on an OpenBMC-based system
    2. Running the test suite

    In the first case it is desirable that the messages appear in the system journal. To this end, systemd will by default capture stdout and stderr of the launched binary and redirect it to the journal.

    In the second case it is desirable that messages be captured by the test runner (make check) for test failure analysis, and it is undesirable for messages to appear in the system journal (as these are tests, not issues affecting the health of the system they are being executed on).

    Therefore direct calls to the journal MUST be avoided for the purpose of message logging.

    Note: This section specifically targets the use of phosphor-logging's log<T>(). It does not prevent the use of elog<T>().