Added 'How to contribute to Busybox' doc.

[oweals/busybox.git] / docs / contributing.txt

Contributing To Busybox
=======================

This document describes what you need to do to contribute to Busybox, where
you can help, guidelines on testing, and how to submit a well-formed patch
that is more likely to be accepted.

The Busybox home page is at: http://busybox.lineo.com



Pre-Contribution Checklist
--------------------------

So you want to contribute to Busybox, eh? Great, wonderful, glad you want to
help. However, before you dive in, headlong and hotfoot, there are some things
you need to do:


Checkout the Latest Code from CVS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is a necessary first step. Please do not try to work with the last
released version, as there is a good chance that somebody has already worked
on the area you had in mind and your patch might already be obsolete.

For information on how to check out Busybox from CVS, please look at the
following links:

        http://oss.lineo.com/cvs_anon.html
        http://oss.lineo.com/cvs_howto.html


Read the Mailing List
~~~~~~~~~~~~~~~~~~~~~

No one is required to read the entire archives of the mailing list, but you
should at least read up on what people have been talking about lately. If
you've recently discovered a problem, chances are somebody else has too. If
you're the first to discover a problem, post a message and let the rest of us
know.

Archives can be found here:

        http://opensource.lineo.com/lists/busybox/

If you have a serious interest in Busybox, i.e. you are using it day-to-day or
as part of an embedded project, it's a good idea to join the mailing list.

A web-based sign-up form can be found here:

        http://opensource.lineo.com/mailman/listinfo/busybox


Coordinate with the Applet Maintainer
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Some (not all) of the applets in Busybox are "owned" by a maintainer who has
put significant effort into it and is probably more familiar with it than
others. To find the maintainer of an applet, look at the top of the .c file
for a name following the word 'Copyright' or 'Written by'.

Before plunging ahead, it's a good idea to send a message to the mailing list
that says: "Hey, I was thinking about adding the 'transmogrify' feature to the
'foo' applet.  Would this be useful? Is anyone else working on it?" You might
want to CC the maintainer (if any) with your question.



Areas Where You Can Help
------------------------

Busybox can always use improvement! If you're looking for ways to help, there
there are a variety of areas where you could help.


What Busybox Doesn't Need
~~~~~~~~~~~~~~~~~~~~~~~~~

Before listing the areas where you _can_ help, it's worthwhile to mention the
areas where you shouldn't bother. While Busybox strives to be the "Swiss Army
Knife" of embedded Linux, there are some applets that will not be accepted:

 - Any filesystem manipulation tools: Busybox is filesystem independent and
   we do not want to start adding mkfs/fsck tools for every (or any)
   filesystem under the sun. (fsck_minix.c and mkfs_minix.c are living on
   borrowed time.)  There are far too many of these tools out there.  Use
   the upstream version.  Not everything has to be part of Busybox.

 - Any partitioning tools: Partitioning a device is typically done once and
   only once, and tools which do this generally do not need to reside on the
   target device (esp a flash device). If you need a partitioning tool, grab
   one (such as fdisk, sfdisk, or cfdisk from util-linux) and use that, but
   don't try to merge it into busybox. These are nasty and complex and we
   don't want to maintain them.

 - Any disk, device, or media-specific tools: Use the -utils or -tools package
   that was designed for your device; don't try to shoehorn them into Busybox.

 - Any architecture specific tools: Busybox is (or should be) architecture
   independent. Do not send us tools that cannot be used across multiple
   platforms / arches.


Bug Reporting
~~~~~~~~~~~~~

If you find a bug in Busybox, you can send a bug report to our bug tracking
system (homepage: http://bugs.lineo.com). Instructions on how to send a bug
report to the tracking system can be found at:

        http://bugs.lineo.com/Reporting.html
        
The README file that comes with Busybox also describes how to submit a bug.

A well-written bug report will include a transcript of a shell session that
demonstrates the bad behavior and enables anyone else to duplicate the bug on
their own machine.


Bug Triage
~~~~~~~~~~

Validating and confirming bugs is nearly as important as reporting them in the
first place. It is valuable to know if a bug can be duplicated on a different
machine, on a different filesystem, on a different architecture, with a
different C library, and so forth.

To see a listing of all the bugs currently filed against Busybox, look here:

        http://bugs.lineo.com/db/pa/lbusybox.html

If you have comments to add to a bug (can / can't duplicate, think a bug
should be closed / reopened), please send it to [bugnumber]@bugs.lineo.com.
The message you send will automatically be forwarded to the mailing list for
all to see.


Write Documentation
~~~~~~~~~~~~~~~~~~~

Chances are, documentation in Busybox is either missing or needs improvement.
Either way, help is welcome.

Work is being done to automatically generate documentation from sources,
especially from the usage.h file. If you want to correct the documentation,
please make changes to the pre-generation parts, rather than the generated
documentation. [More to come on this later...]

It is preferred that modifications to documentation be submitted in patch
format (more on this below), but we're a little more lenient when it comes to
docs. You could, for example, just say "after the listing of the mount
options, the following example would be helpful..."


Consult Existing Sources
~~~~~~~~~~~~~~~~~~~~~~~~

For a quick listing of "needs work" spots in the sources, cd into the Busybox
directory and run the following:

        for i in TODO FIXME XXX; do grep $i *.[ch]; done

This will show all of the trouble spots or 'questionable' code. Pick a spot,
any spot, these are all invitations for you to contribute.


Consult The Bug-Tracking System
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Head to: http://bugs.lineo.com/db/pa/lBusybox.html and look at the bugs on
there. Pick one you think you can fix, and fix it. If it's a wishlist item and
someone's requesting a new feature, take a stab at adding it. Everything
previously said about "reading the mailing list" and "coordinating with the
applet maintainer" still applies.


Add a New Applet
~~~~~~~~~~~~~~~~

If you want to add a new applet to Busybox, we'd love to see it. However,
before you write any code, please ask beforehand on the mailing list something
like "Do you think applet 'foo' would be useful in Busybox?" or "Would you
guys accept applet 'foo' into Busybox if I were to write it?" If the answer is
"no" by the folks on the mailing list, then you've saved yourself some time.
Conversely, you could get some positive responses from folks who might be
interested in helping you implement it, or can recommend the best approach.
Perhaps most importantly, this is your way of calling "dibs" on something and
avoiding duplication of effort.

Also, before you write a line of code, please read the 'new-applet-HOWTO.txt'
file in the docs/ directory.


Janitorial Work
~~~~~~~~~~~~~~~

These are dirty jobs, but somebody's gotta do 'em.

 - Security audits:
   http://www.securityfocus.com/frames/?content=/forums/secprog/secure-programming.html

 - Synthetic code removal: http://www.perl.com/pub/2000/06/commify.html - This
   is very Perl-specific, but the advice given in here applies equally well to
   C.

 - C library funciton use audits: Verifying that functions are being used
   properly (called with the right args), replacing unsafe library functions
   with safer versions, making sure return codes are being checked, etc.

 - Where appropriate, replace preprocessor defined macros and values with
   compile-time equivalents.

 - Makefile improvements:
   http://www.canb.auug.org.au/~millerp/rmch/recu-make-cons-harm.html
   (I think the recursive problems are pretty much taken care of at this point, non?)

 - "Ten Commandments" compliance: (this is a "maybe", certainly not as
   important as any of the previous items.)
    http://web.onetelnet.ch/~twolf/tw/c/ten_commandments.html

Other useful links:

 - the comp.lang.c FAQ: http://web.onetelnet.ch/~twolf/tw/c/index.html#Sources



Submitting Patches To Busybox
-----------------------------

Here are some guidelines on how to submit a patch to Busybox.


Making A Patch
~~~~~~~~~~~~~~

If you've got anonymous CVS access set up, making a patch is simple. Just make
sure you're in the busybox/ directory and type 'cvs diff -bwu > mychanges.patch'.
You can send the resulting .patch file to the mailing list with a description
of what it does. (But not before you test it! See the next section for some
guidelines.) It is preferred that patches be sent as attachments, but it is
not required.

Also, feel free to help test other people's patches and reply to them with
comments. You can apply a patch by saving it into your busybox/ directory and
typing 'patch < mychanges.patch'. Then you can recompile, see if it runs, test
if it works as advertised, and post your findings to the mailing list.

NOTE: Please do not include extraneous or irrelevant changes in your patches.
Please do not try to "bundle" two patches together into one. Make single,
discreet changes on a per-patch basis. Sometimes you need to make a patch that
touches code in many places, but these kind of patches are rare and should be
coordinated with a maintainer.


Testing Guidelines
~~~~~~~~~~~~~~~~~~

It's considered good form to test your new feature before you submit a patch
to the mailing list, and especially before you commit a change to CVS. Here
are some guidelines on how to test your changes.

 - Always test Busybox applets against GNU counterparts and make sure the
   behavior / output is identical between the two.

 - Try several different permutations and combinations of the features you're
   adding (i.e. different combinations of command-line switches) and make sure
   they all work; make sure one feature does not interfere with another.

 - Make sure you test compiling against the source both with the feature
   turned on and turned off in Config.h and make sure Busybox compiles cleanly
   both ways.

 - Run the multibuild.pl script in the tests directory and make sure
   everything checks out OK. (Do this from within the busybox/ directory by
   typing: 'tests/multibuild.pl'.)


Making Sure Your Patch Doesn't Get Lost
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

If you don't want your patch to be lost or forgotten, send it to the bug
tracking system (http://bugs.lineo.com). You do this by emailing your patch in
a message to submit@bugs.lineo.com with a subject line something like this:

        [PATCH] - Adds "transmogrify" feature to "foo"

In the body, you should have a pseudo-header that looks like the following:

    Package: busybox
    Version: v0.50pre (or whatever the current version is)
    Severity: wishlist

The remainder of the body should read along these lines:

        This patch adds the "transmogrify" feature to the "foo" applet. I have
        tested this on [arch] system(s) and it works. I have tested it against the
        GNU counterparts and the outputs are identical. I have run the scripts in
        the 'tests' directory and nothing breaks.

Detailed instructions on how to submit a bug to the tracking system are at:

        http://bugs.lineo.com/Reporting.html



Improving Your Chances of Patch Acceptance
------------------------------------------

Even after you send a brilliant patch to the mailing list, sometimes it can go
unnoticed, un-replied-to, and sometimes (sigh) even lost. This is an
unfortunate fact of life, but there are steps you can take to help your patch
get noticed and convince a maintainer that it should be added:


Be Succinct
~~~~~~~~~~~

A patch that includes small, isolated, obvious changes is more likely to be
accepted than a patch that touches code in lots of different places or makes
sweeping, dubious changes.


Back It Up
~~~~~~~~~~

Hard facts on why your patch is better than the existing code will go a long
way toward convincing maintainers that your patch should be included.
Specifically, patches are more likely to be accepted if they are provably more
correct, smaller, faster, simpler, or more maintainable than the existing
code.

Conversely, any patch that is supported with nothing more than "I think this
would be cool" or "this patch is good because I say it is and I've got a Phd
in Computer Science" will likely be ignored.


Follow The Style Guide
~~~~~~~~~~~~~~~~~~~~~~

It's considered good form to abide by the established coding style used in a
project; Busybox is no exception. We have gone so far as to delineate the
"elements of Busybox style" in the file docs/style-guide.txt. Please follow
them.


Work With Someone Else
~~~~~~~~~~~~~~~~~~~~~~

Working on a patch in isolation is less effective than working with someone
else for a variety of reasons. If another Busybox user is interested in what
you're doing, then it's two (or more) voices instead of one that can petition
for inclusion of the patch. You'll also have more people that can test your
changes, or even offer suggestions on better approaches you could take.

Getting other folks interested follows as a natural course if you've received
responses from queries to applet maintainer or positive responses from folks
on the mailing list.

We've made strident efforts to put a useful "collaboration" infrastructure in
place in the form of mailing lists, the bug tracking system, and CVS. Please
use these resources.


Be Polite
~~~~~~~~~

The old saying "You'll catch more flies with honey than you will with vinegar"
applies when submitting patches to the mailing list for approval. The way you
present your patch is sometimes just as important as the actual patch itself
(if not more so). Being rude to the maintainers is not an effective way to
convince them that your patch should be included; it will likely have the
opposite effect.



Final Words
-----------

If all of this seems complicated, don't panic, it's really not that tough. If
you're having difficulty following some of the steps outlined in this
document don't worry, the folks on the Busybox mailing list are a fairly
good-natured bunch and will work with you to help get your patches into shape
or help you make contributions.

If you submit several patches that demonstrate that you are a skilled and wise
coder, you may be invited to become a committer, thus enabling you to commit
changes directly to CVS.