[RFC] HOWTO do Linux kernel development

[Greg KH]

Over time, I get a lot of the same kind of emails from developers.
Messages asking how to do this or that, or how this process works. I
also see a lot of new developers make the same mistakes (wrong patch
format, no signed-off-by:, not sent to the proper developer, wrong
coding style, etc.)

Along with these requests, I have heard a lot of complaints over time,
about how there is no single place to go to to figure out how to do
Linux kernel development, and where to point other people to.

So, I've been working on a document for the past week or so to help
alleviate a lot of these problems. If nothing else, it should be a place
where anyone can point someone to when they ask the common questions, or
do something in the not-correct way. I'd like to add this to the Linux
kernel source tree, so it will be kept up to date over time, as things
change (like the development process.) Ideally I'd like to put it in
the main directory as HOWTO, but I don't know how others feel about
this.

Anyway, I'd like to get comments on what has been produced so far. I
know the section about the development process is still not complete (it
has a <TODO> mark), and if anyone wants to fill that in, I'd really
appreciate it.

I would like to thank Pat Mochel, Hanna Linder, Randy Dunlap, Kay
Sievers, Vojtech Pavlik, and Jan Kara for their review and comments on
early drafts of this document.

thanks,

greg k-h

------------------------------

HOWTO do Linux kernel development
---------------------------------

This is the be-all, end-all document on this topic. It contains
instructions on how to become a Linux kernel developer and how to learn
to work with the Linux kernel development community.

If anything in this document becomes out of date, please send in patches
to the maintainer of this file, who is listed at the bottom of the
document.

Intro
-----

So, you want to learn how to become a Linux kernel developer? Or you
have been told by your manager, "Go write a Linux driver for this
device." This document's goal is to teach you everything you need to
know to achieve this by describing the process you need to go through,
and hints on how to work with the community. It will also try to
explain some of the reasons why the community works like it does.

The kernel is written mostly in C, with some architectural-dependent
parts written in assembly. A good understanding of C is required to
kernel development. Assembly (any architecture) is not required unless
you plan to do low-level development for that architecture. Though they
are not a good substitute for a solid C education and/or years of
experience, the following books are good, if anything for reference:

"The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
"Practical C Programming" by Steve Oualline [O'Reilly]
"Programming the 80386" by Crawford and Gelsinger [Sybek]
"UNIX Systems for Modern Architectures" by Curt Schimmel [Addison Wesley]

The kernel is written using GNU C and the GNU toolchain. While it
adheres to the ISO C99 (??) standard, it uses a number of extensions
that are not featured in the standard. It can sometimes be difficult to
understand the assumptions the kernel has on the toolchain and the
extensions that it uses, and unfortunately there is no definitive
reference for them. Please check the gcc info pages (`info gcc`) for
some information on them.

Please remember that you are trying to learn how to work with the
existing development community. It is a very diverse group of people,
with very high standards for coding, style and procedure. These
procedures have been created over time based on what they have found to
work best for such a large and geographically dispersed team. Try to
learn as much as possible about these procedures ahead of time, as they
are well documented, and not expect people to adapt to you, or your
company's way of doing things.

Legal Issues
------------

The Linux kernel source code is released under the GPL. Please see the
file, COPYING, in the main directory of the source tree, for details on
the license. If you have further questions about the license, please
contact a lawyer, and do not ask on the Linux kernel mailing list. The
people on the mailing lists are not lawyers, and you should not rely on
their statements on legal matters.

Documentation
------------

The Linux kernel source tree has a large range of documents that are
invaluable in learning how to interact with the kernel community. When
new features are added to the kernel, it is recommended that new
documentation files are also added, that explain how to use the feature.
Here is a list of files that are in the kernel source tree that are
required reading:
Documetation/CodingStyle
This describes the Linux kernel coding style, and some of the
rationale behind it. All new code is expected to follow the
guidelines in this document. Most maintainers will only accept
patches if these rules are followed, and many people will only
review code if it is in the proper style.

Documentation/SubmittingPatches
Documentation/SubmittingDrivers
These files describe in explicit detail how to successfully create
and send a patch, including (but not limited to):
- Email contents
- Email format
- Who to send it to
Following these rules will not guarantee success (as all patches are
subject to scrutiny of content and style), but not following them
will almost always prevent it.

Other excellent descriptions of how to create patches properly are:
"The Perfect Patch"
http://www.zip.com.au/~akpm/linux/patches/stuff/tpp.txt
"Linux kernel patch submission format"
http://linux.yyz.us/patch-format.html

Documentation/stable_api_nonsense.txt
This file describes the rationale behind the conscious decision to
not have a stable API within the kernel, including for things like:
- Subsystem shim-layers (for compatibility?)
- Driver portability between Operating Systems.
- Mitigating rapid change within the kernel source tree (or
preventing rapid change)
This document is crucial for understand the Linux development
philosophy and is very important for people moving to Linux from
development on other Operating Systems.

Documentation/SecurityBugs
If you feel you have found a security problem in the Linux kernel,
please follow the steps in this document to help notify the kernel
developers, and help solve the issue.

Documentation/ManagementStyle
This document describes how Linux kernel maintainers operate and the
shared ethos behind their methodologies. This is important reading
for anyone new to kernel development (or anyone simply curious about
it), as it resolves a lot of common misconceptions and confusion
about the unique behavior of kernel maintainers.

Documentation/stable_kernel_rules.txt
This file describes the rules on how the stable kernel releases
happen, and what to do if you want to get a change into one of these
releases.

Documentation/kernel-docs.txt
A list of external documentation that pertains to kernel
development. Please consult this list, if you do not find what you
are looking for within the in-kernel documentation.

The kernel also has a large number of documents that can be
automatically generated from the source code itself. This includes a
full description of the in-kernel api, and rules on how to handle
locking properly. The documents will be created in the
Documentation/DocBook/ directory and can be generated as PDF,
Postscript, HTML, and man pages by running:
make pdfdocs
make psdocs
make htmldocs
make mandocs
respectively from the main kernel source directory.

Becoming A Kernel Developer
---------------------------

If you do not know anything about Linux kernel development, you should
look at the Linux KernelNewbies project:
http://kernelnewbies.org
It consists of a helpful mailing list, where you can ask almost any type
of basic kernel development question (make sure to search the archives
first, before asking something that has already been answered in the
past.) It also has a IRC channel that you can use to ask questions in
real-time, and a lot of helpful documentation that is useful for
learning about Linux kernel development.

The website has basic information about code organization, subsystems,
and current projects (both in-tree and out-of-tree). It also basic
logistical information, like compiling a kernel and applying a patch.

If you do not know where you want to start, but you want to look for
some task to start doing to join into the kernel development community,
go to the Linux Kernel Janitor's project:
http://janitor.kernelnewbies.org/
It is a great place to start. It describes a list of relatively simple
tasks that need to be cleaned up and fixed within the Linux kernel
source tree. Working with the developers in charge of this project, you
will learn the basics of getting your patch into the Linux kernel tree,
and possibly point you in the direction of what to go work on next, if
you do not already have an idea.

If you already have a chunk of code that you want to have go into the
kernel tree, but need some help getting it in the proper form, the
kernel-mentors project was created to help you out with this. It is a
mailing list, and can be found at:
http://selenic.com/mailman/listinfo/kernel-mentors

The development process
-----------------------

<TODO>

Mailing lists
-------------

As some of the above documents describe, the majority of the core kernel
developers participate on the Linux Kernel Mailing list. Details on how
to subscribe and unsubscribe from the list, can be found at:
http://vger.kernel.org/vger-lists.html#linux-kernel
There are archives of the mailing list on the web in many different
places. Use a search engine to find these archives. It is highly
recommended that you search the archives about the topic you want to bring
up, before you post it to the list. A lot of things are already discussed
in detail and are only recorded at the mailing list archives.

Most of the individual kernel subsystems also have their own separate
mailing list where they do their development efforts. See the
MAINTAINERS file for a list of what these lists are, for the different
groups.

Many of the lists are hosted on kernel.org. Information on them can be
found here:
http://vger.kernel.org/vger-lists.html

Please remember to follow good behavioral habits when using the lists.
Though a bit cheesy, the following URL has some simple guidelines for
interacting with the list (or any list):
http://www.albion.com/netiquette/

If multiple people respond to your mail, the CC: list of recipients may
get pretty large. Don't remove anybody from the CC: list without a good
reason, or don't reply only to the list address. Get used to receive the
mail twice, one from the sender and the one from the list and don't try
to tune that by adding fancy mail-headers, people will not like it.

Remember to keep the context and the attribution of your replies intact,
keep the "John Kernelhacker wrote ...:" lines at the top of you reply and
add your statements between the individual quoted sections instead of
writing at the top of the mail.

If you add patches to your mail, make sure they are plain readable text
as stated in Documentation/SubmittingPatches. Kernel developers don't
want to deal with attachments or compressed patches, they may want
to comment individual lines of your patch, which works only that way.
Make sure you use a mail program that does not mangle spaces and tab
characters. A good first test is to send the mail to yourself and try
to apply your own patch by yourself. If that doesn't work, get your
mail program fixed or change it until it works.

Above all, please remember to show respect to other subscribers.

Working with the community
--------------------------

The kernel community works differently than most traditional corporate
development environments. Here are a list of things that you can try to
do to try to avoid problems:
Good things to say regarding your proposed changes:
- "This solves multiple problems."
- "This deletes 2000 lines of code."
- "Here is a patch that explains what I am trying to describe."
- "I tested it on 5 different architectures..."
- "Here is a series of small patches that..."
- "This increases performance on typical machines..."

Bad things you should avoid saying:
- "We did it this way in AIX/ptx/Solaris, so therefore it must be
good..."
- "I've being doing this for 20 years, so..."
- "It makes this proprietary benchmark go faster"
- "This is required for my company to make money"
- "This is for our Enterprise product line."
- "Here is my 1000 page design document that describes my idea"
- "I've been working on this for 6 months..."
- "Here's a 5000 line patch that..."
- "I rewrote all of the current mess, and here it is..."
- "I have a deadline, and this patch needs to be applied now."

Another way the kernel community is different than most traditional
software engineering work environments is the faceless nature of
interaction. One benefit of using email and irc as the primary forms of
communication is the lack of discrimination based on gender or race.
The Linux kernel work environment is accepting of women and minorities
because all you are is an email address. The international aspect also
helps to level the playing field because you can't guess gender based on
a person's name. A man may be named Andrea and a woman may be named Pat.
Most women who have worked in the Linux kernel and have expressed an
opinion have had positive experiences. Here is a group that is a good
starting point for women interested in contributing to Linux:
http://www.linuxchix.org/

The language barrier can be present for some people who are not
comfortable with English. A good grasp of the language can be needed in
order to get ideas across properly on mailing lists, so it is
recommended that you check your emails to make sure they make sense in
English before sending them.

Break your changes up
---------------------

The Linux kernel community does not gladly accept large chunks of code
dropped on it all at once. The changes need to be properly introduced,
discussed, and broken up into tiny, individual portions. This is almost
exactly opposite of what companies are used to doing. Your proposal
should also be introduced very early in the development process, so that
you can receive feedback on what you are doing. It also lets the
community feel that you are working with them, and not simply using them
as a dumping ground for your feature. However, don't send 50 emails at
one time to a mailing list, your patch series should be smaller than
that almost all of the time.

The reasons for breaking things up are the following:

1) Small patches increase the likelihood that your patches will be
applied, since they don't take much time or effort to verify for
correctness. A 5 line patch can be applied by a maintainer with
barely a second glance. But, a 500 line patch may take hours to
review for correctness (the time it takes is exponentially
proportional to the size of the patch, or something).

Small patches also make it very easy to debug when something goes
wrong. It's much easier to back out patches one by one, than it is
to dissect a very large patch after it's been applied (and broken
something).

2) It's important not only to send small patches, but also to rewrite
and simplify (or simply re-order) patches before submitting them.

Here is an analogy from kernel developer Al Viro:
"Think of a teacher grading homework from a math student. The
teacher does not want to see the student's trials and errors
before they came up with the solution. They want to see the
cleanest, most elegant answer. A good student knows this, and
would never submit her intermediate work before the final
solution."

The same is true of kernel development. The maintainers and
reviewers do not want to see the thought process behind the
solution to the problem one is solving. They want to see a
simple and elegant solution."

That may be challenging to keep the balance between presenting an elegant
solution and working together with the community and discuss your
unfinished work. Therefore it is good to get early in the process to
get feedback to improve your work, but also keep your changes in small
chunks that they may get already accepted, even when your whole task is
not ready for inclusion now.

Also realize that it is not acceptable to send patches for inclusion
that are unfinished and will be "fixed up later."

Justify your change
-------------------

Along with breaking up your patches, it is very important for you to let
the Linux community know why they should add this change. New features
must be justified as being needed and useful.

All of these things are sometimes very hard to do. It can take years to
perfect these practices (if at all). It's a continuous process of
improvement that requires a lot of patience and determination. But,
don't give up. It's possible. Many have done it before, and each had to
start exactly where you are now.

----------
Thanks to Randy Dunlap and Gerrit Huizenga for the list of things you
should and should not say. Also thanks to Pat Mochel, Hanna Linder,
Randy Dunlap, Kay Sievers, Vojtech Pavlik, and Jan Kara for their review
and comments on early drafts of this document.

Maintainer: Greg Kroah-Hartman <gr...@kroah.com>

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majo...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

[Greg KH]

On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> So, I've been working on a document for the past week or so to help
> alleviate a lot of these problems.

Oh, the latest version can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
as I'm keeping it in my git patch tree.

thanks,

greg k-h

[Jeffrey V. Merkey]

Greg KH wrote:

I'd like to add some sections to the doc.

APPENDIX E.

Chapter 1. How to get rich on IPO's and how to get people to give you IP
for free and work like slaves simply for attribution.
Chapter 2. How to setup a kernel development rat maze with no cheese in
the maze (only the smell of cheese).
Chapter 3. Rat Races. How to get the rats to run the maze and keep the
maze clean.

NOTE: This email is a parody (joke) and should not be taken seriously.

:-)

Jeff

[Kalin KOZHUHAROV]

Greg KH wrote:
> On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
>
>>So, I've been working on a document for the past week or so to help
>>alleviate a lot of these problems.
>
>
> Oh, the latest version can be found at:
> http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> as I'm keeping it in my git patch tree.

As far as the development proces is in TODO state, what about adding Paolo Ciarrocchi's (CCed) doc
there?
http://linux.tar.bz/articles/2.6-development_process

NB: I just host the artice (with Paolo's permission), and actualy from a few hours ago :-)

Kalin.
--
|[ ~~~~~~~~~~~~~~~~~~~~~~ ]|
+-> http://ThinRope.net/ <-+
|[ ______________________ ]|

[Randy.Dunlap]

On Tue, 15 Nov 2005, Kalin KOZHUHAROV wrote:

> Greg KH wrote:
> > On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> >
> >>So, I've been working on a document for the past week or so to help
> >>alleviate a lot of these problems.
> >
> >
> > Oh, the latest version can be found at:
> > http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> > as I'm keeping it in my git patch tree.
>
> As far as the development proces is in TODO state, what about adding Paolo Ciarrocchi's (CCed) doc
> there?
> http://linux.tar.bz/articles/2.6-development_process
>
> NB: I just host the artice (with Paolo's permission), and actualy from a few hours ago :-)
>
> Kalin.

As good as that article is, it only mentions "review" for
-stable patches -- nothing about how new functionality or
other fixes are reviewed and added to Linux, which is a
big oversight IMO... although not at all easy to write/describe.

--
~Randy

[Josh Boyer]

On 11/14/05, Greg KH <gre...@suse.de> wrote:
> On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> > So, I've been working on a document for the past week or so to help
> > alleviate a lot of these problems.
>
> Oh, the latest version can be found at:
> http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> as I'm keeping it in my git patch tree.

I don't know if this should go in the <TODO> section of the
development process or somewhere else within "Working with the
community", but I think something along the lines of this might be
helpful:

Leave your ego at home
---------------------------------

The goal of the kernel community is to provide the best possible
kernel there is. When you submit a patch for acceptance, it will be
reviewed on it's technical merits and those alone. So, what should
you be expecting?

- criticism,
- comments
- requests for change
- requests justification.

Remember, this is part of getting your patch into the kernel. You
have to be able to take criticism and comments about your patches,
evaluate them at a technical level and either rework your patches or
provide clear and concise reasoning as to why those changes should not
be made.

What should you not do?

- expect your patch to be accepted without question
- become defensive
- ignore comments and resubmit the patch without making any changes
- explain how your project is funded by XYZ and therefore must be
awesome as it is

In a community that is looking for the best technical solution
possible, there is no place for ego. You have to be cooperative,
polite, and willing to adapt your idea to fit within the kernel.
Remember, being wrong is ok as long as you are willing to work toward
a solution that is right.

josh

[Coywolf Qi Hunt]

2005/11/15, Greg KH <gre...@suse.de>:

> Over time, I get a lot of the same kind of emails from developers.
> Messages asking how to do this or that, or how this process works. I
> also see a lot of new developers make the same mistakes (wrong patch
> format, no signed-off-by:, not sent to the proper developer, wrong
> coding style, etc.)
>
> Along with these requests, I have heard a lot of complaints over time,
> about how there is no single place to go to to figure out how to do
> Linux kernel development, and where to point other people to.
>
> So, I've been working on a document for the past week or so to help
> alleviate a lot of these problems. If nothing else, it should be a place
> where anyone can point someone to when they ask the common questions, or
> do something in the not-correct way. I'd like to add this to the Linux
> kernel source tree, so it will be kept up to date over time, as things
> change (like the development process.) Ideally I'd like to put it in
> the main directory as HOWTO, but I don't know how others feel about

You put it in the top directory to draw the most attention? Compare to
source trees of other kernel projects, Linux source tree looks clean.
Please don't spoil that. What's wrong with Documentation/ ?

> this.
>
> Anyway, I'd like to get comments on what has been produced so far. I
> know the section about the development process is still not complete (it
> has a <TODO> mark), and if anyone wants to fill that in, I'd really
> appreciate it.
>
> I would like to thank Pat Mochel, Hanna Linder, Randy Dunlap, Kay
> Sievers, Vojtech Pavlik, and Jan Kara for their review and comments on
> early drafts of this document.
>

--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/

[Paul Jackson]

Josh wrote:
> In a community that is looking for the best technical solution
> possible, there is no place for ego.

No, there is a place for ego, an essential place. Some of the best
hackers on lkml have no shortage of ego. They just don't get their ego
too closely attached to any particular piece of code or technical
position. Rather they take pride in their willingness and ability to
find better answers (even in their own work, done five minutes ago ;).

I don't normally quote Colin Powell (a recent U.S. Secretary of State),
but this one time he said it well:

Avoid having your ego so close to your position that
when your position falls, your ego goes with it.

-- Colin Powell

Ego deficient pansies risk wilting on lkml.

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <p...@sgi.com> 1.925.600.0401

[Randy.Dunlap]

On Mon, 14 Nov 2005, Paul Jackson wrote:

> Josh wrote:
> > In a community that is looking for the best technical solution
> > possible, there is no place for ego.
>
> No, there is a place for ego, an essential place. Some of the best
> hackers on lkml have no shortage of ego. They just don't get their ego
> too closely attached to any particular piece of code or technical
> position. Rather they take pride in their willingness and ability to
> find better answers (even in their own work, done five minutes ago ;).
>
> I don't normally quote Colin Powell (a recent U.S. Secretary of State),
> but this one time he said it well:
>
>
> Avoid having your ego so close to your position that
> when your position falls, your ego goes with it.
>
> -- Colin Powell

Nice advice. I (too often) see people who are working on the
<technology du jour> to be so tied up with it that they
think it's the greatest thing around.

> Ego deficient pansies risk wilting on lkml.

--
~Randy

[Josh Boyer]

On 11/14/05, Paul Jackson <p...@sgi.com> wrote:
> Josh wrote:
> > In a community that is looking for the best technical solution
> > possible, there is no place for ego.
>
> No, there is a place for ego, an essential place. Some of the best
> hackers on lkml have no shortage of ego. They just don't get their ego
> too closely attached to any particular piece of code or technical
> position. Rather they take pride in their willingness and ability to
> find better answers (even in their own work, done five minutes ago ;).

Ok, fair enough. All I was really trying to say is "don't be an ass
and assume that you know everything" in a polite way. Apparently that
isn't my forte.

> Ego deficient pansies risk wilting on lkml.

Did you just call me a pansy? I prefer idiot thank you very much ;)

josh

[Paul Jackson]

> Apparently that isn't my forte.

It may well be your forte. I was commenting on your post, not on you.

> Did you just call me a pansy? I prefer idiot thank you very much ;)

At least you are not wilting ;).

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <p...@sgi.com> 1.925.600.0401

[Josh Boyer]

On 11/14/05, Paul Jackson <p...@sgi.com> wrote:

> > Apparently that isn't my forte.
>
> It may well be your forte. I was commenting on your post, not on you.

How about this:

The goal of the kernel community is to provide the best possible
kernel there is. When you submit a patch for acceptance, it will be
reviewed on it's technical merits and those alone. So, what should
you be expecting?

- criticism,
- comments
- requests for change
- requests justification.

Remember, this is part of getting your patch into the kernel. You
have to be able to take criticism and comments about your patches,
evaluate them at a technical level and either rework your patches or
provide clear and concise reasoning as to why those changes should not
be made.

What should you not do?

- expect your patch to be accepted without question
- become defensive
- ignore comments and resubmit the patch without making any changes
- explain how your project is funded by XYZ and therefore must be
awesome as it is

In a community that is looking for the best technical solution
possible, there will always be differing opinions on how beneficial a
patch is. You have to be cooperative, and
willing to adapt your idea to fit within the kernel. Or at least be
willing to prove your idea is worth it. Remember, being wrong is ok

as long as you are willing to work toward a solution that is right.

josh

[Paul Jackson]

Josh wrote:
> How about this:

Good.

I'd add to the list of "what should you be expecting"

- silence (Some lkml posts are ignored. Improve it and try again.)

--
I won't rest till it's the best ...
Programmer, Linux Scalability
Paul Jackson <p...@sgi.com> 1.925.600.0401

[Greg KH]

On Tue, Nov 15, 2005 at 09:18:35AM +0900, Kalin KOZHUHAROV wrote:
> Greg KH wrote:
> > On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> >
> >>So, I've been working on a document for the past week or so to help
> >>alleviate a lot of these problems.
> >
> >
> > Oh, the latest version can be found at:
> > http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> > as I'm keeping it in my git patch tree.
>
> As far as the development proces is in TODO state, what about adding
> Paolo Ciarrocchi's (CCed) doc there?
> http://linux.tar.bz/articles/2.6-development_process

Ah, a very nice summary.

Paolo, can I use this document as a base for this section in the HOWTO
file (with proper attribution of course.)

thanks,

greg k-h

[Greg KH]

On Mon, Nov 14, 2005 at 07:01:50PM -0800, Paul Jackson wrote:
> Josh wrote:
> > How about this:
>
> Good.
>
> I'd add to the list of "what should you be expecting"
>
> - silence (Some lkml posts are ignored. Improve it and try again.)

Very important to add, thanks for pointing it out.

greg k-h

[Greg KH]

On Tue, Nov 15, 2005 at 09:08:30AM +0800, Coywolf Qi Hunt wrote:
> 2005/11/15, Greg KH <gre...@suse.de>:

> > So, I've been working on a document for the past week or so to help
> > alleviate a lot of these problems. If nothing else, it should be a place
> > where anyone can point someone to when they ask the common questions, or
> > do something in the not-correct way. I'd like to add this to the Linux
> > kernel source tree, so it will be kept up to date over time, as things
> > change (like the development process.) Ideally I'd like to put it in
> > the main directory as HOWTO, but I don't know how others feel about
>
> You put it in the top directory to draw the most attention? Compare to
> source trees of other kernel projects, Linux source tree looks clean.
> Please don't spoil that. What's wrong with Documentation/ ?

People do not seem to even realize Documentation/ is there :(

Now if those same people would notice anything in the root directory
either, is another story...

It's just a suggestion.

thanks,

greg k-h

[Greg KH]

On Mon, Nov 14, 2005 at 08:52:55PM -0600, Josh Boyer wrote:
> On 11/14/05, Paul Jackson <p...@sgi.com> wrote:
> > > Apparently that isn't my forte.
> >
> > It may well be your forte. I was commenting on your post, not on you.
>
> How about this:

<snip>

Very nice, thanks. I've incorporated your comments, making them pretty
much the whole "Working with the community" section.

thanks again.

greg k-h

[Coywolf Qi Hunt]

2005/11/15, Greg KH <gr...@kroah.com>:

> On Tue, Nov 15, 2005 at 09:08:30AM +0800, Coywolf Qi Hunt wrote:
> > 2005/11/15, Greg KH <gre...@suse.de>:
> > > So, I've been working on a document for the past week or so to help
> > > alleviate a lot of these problems. If nothing else, it should be a place
> > > where anyone can point someone to when they ask the common questions, or
> > > do something in the not-correct way. I'd like to add this to the Linux
> > > kernel source tree, so it will be kept up to date over time, as things
> > > change (like the development process.) Ideally I'd like to put it in
> > > the main directory as HOWTO, but I don't know how others feel about
> >
> > You put it in the top directory to draw the most attention? Compare to
> > source trees of other kernel projects, Linux source tree looks clean.
> > Please don't spoil that. What's wrong with Documentation/ ?
>
> People do not seem to even realize Documentation/ is there :(

Those who don't notice Documentation, don't deserve it, and are not
likely/willingly to be the audience,

>
> Now if those same people would notice anything in the root directory
> either, is another story...

That is rather like top-posting or CAPITALIZATION, or spamming.

>
> It's just a suggestion.
>

We are unlikely to relocate files. So if it gets there, it'll stay
there all along.

--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/

[Greg KH]

On Tue, Nov 15, 2005 at 01:51:44PM +0800, Coywolf Qi Hunt wrote:
> 2005/11/15, Greg KH <gr...@kroah.com>:
> > On Tue, Nov 15, 2005 at 09:08:30AM +0800, Coywolf Qi Hunt wrote:
> > > 2005/11/15, Greg KH <gre...@suse.de>:
> > > > So, I've been working on a document for the past week or so to help
> > > > alleviate a lot of these problems. If nothing else, it should be a place
> > > > where anyone can point someone to when they ask the common questions, or
> > > > do something in the not-correct way. I'd like to add this to the Linux
> > > > kernel source tree, so it will be kept up to date over time, as things
> > > > change (like the development process.) Ideally I'd like to put it in
> > > > the main directory as HOWTO, but I don't know how others feel about
> > >
> > > You put it in the top directory to draw the most attention? Compare to
> > > source trees of other kernel projects, Linux source tree looks clean.
> > > Please don't spoil that. What's wrong with Documentation/ ?
> >
> > People do not seem to even realize Documentation/ is there :(
>
> Those who don't notice Documentation, don't deserve it, and are not
> likely/willingly to be the audience,

Actually this is exactly the audience this is for, people who do not
know where to look for the stuff they are trying to find.

Now getting people to realize that this is the file they really want to
look at is a different task, but not impossible.

> > Now if those same people would notice anything in the root directory
> > either, is another story...
>
> That is rather like top-posting or CAPITALIZATION, or spamming.

Cool, I'm a top-poster, SPAMMER for creating a HOWTO file in the root
directory of the kernel tree. And here I thought I had been called
every bad name in the book before :)

> > It's just a suggestion.
>
> We are unlikely to relocate files. So if it gets there, it'll stay
> there all along.

git makes it trivial to move files, so this is not true at all.

thanks,

greg k-h

[Coywolf Qi Hunt]

2005/11/15, Greg KH <gr...@kroah.com>:
> On Tue, Nov 15, 2005 at 01:51:44PM +0800, Coywolf Qi Hunt wrote:
> > 2005/11/15, Greg KH <gr...@kroah.com>:
> > > On Tue, Nov 15, 2005 at 09:08:30AM +0800, Coywolf Qi Hunt wrote:
> > > > 2005/11/15, Greg KH <gre...@suse.de>:
> > > > > So, I've been working on a document for the past week or so to help
> > > > > alleviate a lot of these problems. If nothing else, it should be a place
> > > > > where anyone can point someone to when they ask the common questions, or
> > > > > do something in the not-correct way. I'd like to add this to the Linux
> > > > > kernel source tree, so it will be kept up to date over time, as things
> > > > > change (like the development process.) Ideally I'd like to put it in
> > > > > the main directory as HOWTO, but I don't know how others feel about
> > > >
> > > > You put it in the top directory to draw the most attention? Compare to
> > > > source trees of other kernel projects, Linux source tree looks clean.
> > > > Please don't spoil that. What's wrong with Documentation/ ?
> > >
> > > People do not seem to even realize Documentation/ is there :(
> >
> > Those who don't notice Documentation, don't deserve it, and are not
> > likely/willingly to be the audience,
>
> Actually this is exactly the audience this is for, people who do not
> know where to look for the stuff they are trying to find.
>
> Now getting people to realize that this is the file they really want to
> look at is a different task, but not impossible.

Seriously doubt it. Or even they find the howto in top directory, they
aren't going to persevere in finishing reading it. So please keep it
as short as possible to full achieve your goal.

>
> > > Now if those same people would notice anything in the root directory
> > > either, is another story...
> >
> > That is rather like top-posting or CAPITALIZATION, or spamming.
>
> Cool, I'm a top-poster, SPAMMER for creating a HOWTO file in the root
> directory of the kernel tree. And here I thought I had been called
> every bad name in the book before :)

np then, I've done my job as a reminder.
btw, also remember to add there a
tutorial-for-dummies-step-by-step-in-ten-days and the like.

>
> > > It's just a suggestion.
> >
> > We are unlikely to relocate files. So if it gets there, it'll stay
> > there all along.
>
> git makes it trivial to move files, so this is not true at all.

I mean we are unlikely/lazy to do relocation. So it's a
once-wrong-always-wrong thing.

--
Coywolf Qi Hunt
http://sosdg.org/~coywolf/

[Paolo Ciarrocchi]

On 11/15/05, Greg KH <gr...@kroah.com> wrote:
> On Tue, Nov 15, 2005 at 09:18:35AM +0900, Kalin KOZHUHAROV wrote:
> > Greg KH wrote:
> > > On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> > >
> > >>So, I've been working on a document for the past week or so to help
> > >>alleviate a lot of these problems.
> > >
> > >
> > > Oh, the latest version can be found at:
> > > http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> > > as I'm keeping it in my git patch tree.
> >
> > As far as the development proces is in TODO state, what about adding
> > Paolo Ciarrocchi's (CCed) doc there?
> > http://linux.tar.bz/articles/2.6-development_process
>
> Ah, a very nice summary.
>
> Paolo, can I use this document as a base for this section in the HOWTO
> file (with proper attribution of course.)

Yup!
Of course you can.

--
Paolo

[Andi Kleen]

Greg KH <gre...@suse.de> writes:

> The kernel is written using GNU C and the GNU toolchain. While it
> adheres to the ISO C99 (??) standard, it uses a number of extensions

C89 - The few left over gcc 2.95 users are blocking modern C constructs.
Even without that it would be a C99 subset, e.g. arbitary long long divisions
or floating point are not supported.

Also the kernel is a freestanding C environment, so parts are not supported.

> Also realize that it is not acceptable to send patches for inclusion
> that are unfinished and will be "fixed up later."

I'm not sure I fully agree on that. I conflicts with the "merge early, merge
often" imperative. IMHO it's ok to submit patches that are not perfect,
but improve something or make a incremental cleanup step, as long as the
problems are not severe and the patch by itself is a clear improvement. Of course
this is handled on a case by case basis.

>
> Justify your change
> -------------------
>
> Along with breaking up your patches, it is very important for you to let
> the Linux community know why they should add this change. New features
> must be justified as being needed and useful.

My request is that each patch should carry a meaningful changelog.
That should tell why and a rough (doesn't need to be detailed) overview how
the change is done.

-Andi

[Greg KH]

On Tue, Nov 15, 2005 at 03:42:44PM +0100, Andi Kleen wrote:
> Greg KH <gre...@suse.de> writes:
>
> > The kernel is written using GNU C and the GNU toolchain. While it
> > adheres to the ISO C99 (??) standard, it uses a number of extensions
>
> C89 - The few left over gcc 2.95 users are blocking modern C constructs.
> Even without that it would be a C99 subset, e.g. arbitary long long divisions
> or floating point are not supported.
>
> Also the kernel is a freestanding C environment, so parts are not supported.

Thanks, I've modified it to mention this.

> > Also realize that it is not acceptable to send patches for inclusion
> > that are unfinished and will be "fixed up later."
>
> I'm not sure I fully agree on that. I conflicts with the "merge early, merge
> often" imperative. IMHO it's ok to submit patches that are not perfect,
> but improve something or make a incremental cleanup step, as long as the
> problems are not severe and the patch by itself is a clear improvement. Of course
> this is handled on a case by case basis.

Yeah, it is a case-by-case, but generally we want to know up front what
the final result is going to be.

> > Justify your change
> > -------------------
> >
> > Along with breaking up your patches, it is very important for you to let
> > the Linux community know why they should add this change. New features
> > must be justified as being needed and useful.
>
> My request is that each patch should carry a meaningful changelog.
> That should tell why and a rough (doesn't need to be detailed) overview how
> the change is done.

Others privately commented on this too, and I've added a section
describing it.

Thanks for the comments.

greg k-h

[Greg KH]

On Tue, Nov 15, 2005 at 09:37:58AM +0100, Paolo Ciarrocchi wrote:
> On 11/15/05, Greg KH <gr...@kroah.com> wrote:
> > On Tue, Nov 15, 2005 at 09:18:35AM +0900, Kalin KOZHUHAROV wrote:
> > > Greg KH wrote:
> > > > On Mon, Nov 14, 2005 at 02:07:09PM -0800, Greg KH wrote:
> > > >
> > > >>So, I've been working on a document for the past week or so to help
> > > >>alleviate a lot of these problems.
> > > >
> > > >
> > > > Oh, the latest version can be found at:
> > > > http://www.kernel.org/git/?p=linux/kernel/git/gregkh/patches.git;a=blob;f=HOWTO
> > > > as I'm keeping it in my git patch tree.
> > >
> > > As far as the development proces is in TODO state, what about adding
> > > Paolo Ciarrocchi's (CCed) doc there?
> > > http://linux.tar.bz/articles/2.6-development_process
> >
> > Ah, a very nice summary.
> >
> > Paolo, can I use this document as a base for this section in the HOWTO
> > file (with proper attribution of course.)
>
> Yup!
> Of course you can.

Great, thanks for letting me borrow from you.

I'll have an update based on all of the feedback, and Paolo's article
soon.

greg k-h

[Luca]

Greg KH <gre...@suse.de> ha scritto:
> Intro
> -----
[...]

> Though they
> are not a good substitute for a solid C education and/or years of
> experience, the following books are good, if anything for reference:
>
> "The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
> "Practical C Programming" by Steve Oualline [O'Reilly]
> "Programming the 80386" by Crawford and Gelsinger [Sybek]
> "UNIX Systems for Modern Architectures" by Curt Schimmel [Addison Wesley]

Hi Greg,
you may want to add:

"Linux Kernel Development, 2nd ed." by Robert Love [Novell Press]
and
"Linux Device Drivers, 3rd ed." by J. Corbet, A. Rubini and G. Kroah-Hartman [O'Reilly]

IMHO the first one is a must-have for beginners who want to have an
overall picture of the kernel and LDD is very helpful when you start doing
some real work :)

Luca
--
Home: http://kronoz.cjb.net
Al termine di un pranzo di nozze mi hanno dato un
amaro alle erbe cosi' schifoso che perfino sull'etichetta
c'era un frate che vomitava.

[Josh Boyer]

On 11/15/05, Luca <kro...@kronoz.cjb.net> wrote:
> Greg KH <gre...@suse.de> ha scritto:
> > Intro
> > -----
> [...]
> > Though they
> > are not a good substitute for a solid C education and/or years of
> > experience, the following books are good, if anything for reference:
> >
> > "The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
> > "Practical C Programming" by Steve Oualline [O'Reilly]
> > "Programming the 80386" by Crawford and Gelsinger [Sybek]
> > "UNIX Systems for Modern Architectures" by Curt Schimmel [Addison Wesley]
>
> Hi Greg,
> you may want to add:
>
> "Linux Kernel Development, 2nd ed." by Robert Love [Novell Press]
> and
> "Linux Device Drivers, 3rd ed." by J. Corbet, A. Rubini and G. Kroah-Hartman [O'Reilly]
>
> IMHO the first one is a must-have for beginners who want to have an
> overall picture of the kernel and LDD is very helpful when you start doing
> some real work :)

I'll second that.

josh

[Greg KH]

On Tue, Nov 15, 2005 at 09:10:51PM +0100, Luca wrote:
> Greg KH <gre...@suse.de> ha scritto:
> > Intro
> > -----
> [...]
> > Though they
> > are not a good substitute for a solid C education and/or years of
> > experience, the following books are good, if anything for reference:
> >
> > "The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
> > "Practical C Programming" by Steve Oualline [O'Reilly]
> > "Programming the 80386" by Crawford and Gelsinger [Sybek]
> > "UNIX Systems for Modern Architectures" by Curt Schimmel [Addison Wesley]
>
> Hi Greg,
> you may want to add:
>
> "Linux Kernel Development, 2nd ed." by Robert Love [Novell Press]
> and
> "Linux Device Drivers, 3rd ed." by J. Corbet, A. Rubini and G. Kroah-Hartman [O'Reilly]
>
> IMHO the first one is a must-have for beginners who want to have an
> overall picture of the kernel and LDD is very helpful when you start doing
> some real work :)

Those books are good, but this section is just for where to get the
basics of C and Unix. The file Documentation/kernel-docs.txt should
have a pointer to these two books, and this HOWTO does point to that
file.

thanks,

greg k-h

[sitexec]

On Nov 15, 2005, at 12:10 PM, Luca wrote:

> Greg KH <gre...@suse.de> ha scritto:
>> Intro
>> -----
> [...]
>> Though they
>> are not a good substitute for a solid C education and/or years of
>> experience, the following books are good, if anything for reference:
>>
>> "The C Programming Language" by Kernighan and Ritchie [Prentice Hall]
>> "Practical C Programming" by Steve Oualline [O'Reilly]
>> "Programming the 80386" by Crawford and Gelsinger [Sybek]
>> "UNIX Systems for Modern Architectures" by Curt Schimmel [Addison
>> Wesley]
>
> Hi Greg,
> you may want to add:
>
> "Linux Kernel Development, 2nd ed." by Robert Love [Novell Press]
> and
> "Linux Device Drivers, 3rd ed." by J. Corbet, A. Rubini and G.
> Kroah-Hartman [O'Reilly]
>
> IMHO the first one is a must-have for beginners who want to have an
> overall picture of the kernel and LDD is very helpful when you
> start doing
> some real work :

just wanted to let anyone who wants the two books (linux kernel
development & linux device drivers) mentioned you can get them for 56
$ together on amazon which is a pretty good deal

-site

[Randy.Dunlap]

and as I told Greg a few days ago, there are lots of bad URLs (links)
in that file (and in Documentation/ in general), so feel free to send
corrections for them. I have some corrections, but not yet in patch
format.

---
~Randy

[Michael Kerrisk]

Greg,

Under 'Documentation', there is the text:

When new features are added to the kernel, it is recommended
that new documentation files are also added which explain how
to use the feature.

Could you also add something like:

When a new feature changes the interface that the kernel
exposes to userland, it is recommended that you send
information or a man-pages patch explaining the change
to the manual pages maintainer at mtk-ma...@gmx.net.

Thanks,

Michael

--
10 GB Mailbox, 100 FreeSMS/Monat http://www.gmx.net/de/go/topmail
+++ GMX - die erste Adresse für Mail, Message, More +++

[li...@horizon.com]

> What should you not do?
>
> - expect your patch to be accepted without question
> - become defensive
> - ignore comments and resubmit the patch without making any changes
> - explain how your project is funded by XYZ and therefore must be
> awesome as it is
>
> In a community that is looking for the best technical solution
> possible, there will always be differing opinions on how beneficial a
> patch is. You have to be cooperative, and
> willing to adapt your idea to fit within the kernel. Or at least be
> willing to prove your idea is worth it. Remember, being wrong is ok
> as long as you are willing to work toward a solution that is right.

One thing to add is that you do NOT have to be a crowd-pleasing politican
and make every change that some random person on lkml suggests.

Indeed, because you're getting comments from a large group of individuals
and not a single entity, you may get flat-out contradictory feedback.

Obviously, comments from the maintainers of subsystems you're touching
should be accorded significant weight, but you can disagree with Linus
if you have a good enough reason. What you should do is think about the
comments and, if you disagree, explain why your way is better.

[Greg KH]

On Wed, Nov 16, 2005 at 09:12:50AM +0100, Michael Kerrisk wrote:
> Greg,
>
> Under 'Documentation', there is the text:
>
> When new features are added to the kernel, it is recommended
> that new documentation files are also added which explain how
> to use the feature.
>
> Could you also add something like:
>
> When a new feature changes the interface that the kernel
> exposes to userland, it is recommended that you send
> information or a man-pages patch explaining the change
> to the manual pages maintainer at mtk-ma...@gmx.net.

Do you want to start documenting the sysfs tree interface? Do you have
man pages for all of the kernel syscalls now?

Anyway, I'll add it, as it is better to error on the side of caution
here.

thanks,

greg k-h

[Michael Kerrisk]

Greg,

> > Under 'Documentation', there is the text:
> >
> > When new features are added to the kernel, it is recommended
> > that new documentation files are also added which explain how
> > to use the feature.
> >
> > Could you also add something like:
> >
> > When a new feature changes the interface that the kernel
> > exposes to userland, it is recommended that you send
> > information or a man-pages patch explaining the change
> > to the manual pages maintainer at mtk-ma...@gmx.net.
>
> Do you want to start documenting the sysfs tree interface?

There should be a sysfs(5) man page. Unfortunately there is
not one yet. If someone wants to start one off...

> Do you have
> man pages for all of the kernel syscalls now?

All, no. Most, yes.

> Anyway, I'll add it, as it is better to error on the side of caution
> here.

Thanks.

Michael

--
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7

Want to help with man page maintenance? Grab the latest
tarball at ftp://ftp.win.tue.nl/pub/linux-local/manpages/
and grep the source files for 'FIXME'.

[Pavel Machek]

Hi!

> > Those who don't notice Documentation, don't deserve it, and are not
> > likely/willingly to be the audience,
>
> Actually this is exactly the audience this is for, people who do not
> know where to look for the stuff they are trying to find.
>
> Now getting people to realize that this is the file they really want to
> look at is a different task, but not impossible.
>
> > > Now if those same people would notice anything in the root directory
> > > either, is another story...
> >
> > That is rather like top-posting or CAPITALIZATION, or spamming.
>
> Cool, I'm a top-poster, SPAMMER for creating a HOWTO file in the root
> directory of the kernel tree. And here I thought I had been called
> every bad name in the book before :)

HOWTO is really wrong name for it. I'd expect "how to compile kernel" there.
Plus, some people actually needing advice will miss it because they'll only
search Doc*/

--
64 bytes from 195.113.31.123: icmp_seq=28 ttl=51 time=448769.1 ms