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Subject: Re: [Ksummit-discuss] [RFC PATCH 2/3] MAINTAINERS, Handbook:
 Subsystem Profile
To:     Dan Williams <dan.j.williams@intel.com>,
        linux-kernel@vger.kernel.org
Cc:     vishal.l.verma@intel.com,
        ksummit-discuss@lists.linuxfoundation.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-nvdimm@lists.01.org, Dmitry Vyukov <dvyukov@google.com>,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Steve French <stfrench@microsoft.com>,
        "Tobin C. Harding" <me@tobin.cc>
References: <154225759358.2499188.15268218778137905050.stgit@dwillia2-desk3.amr.corp.intel.com>
 <154225760492.2499188.14152986544451112930.stgit@dwillia2-desk3.amr.corp.intel.com>
From:   Frank Rowand <frowand.list@gmail.com>
Message-ID: <9f6aece0-da64-78b5-0eda-fe039fc1ad09@gmail.com>
Date:   Thu, 15 Nov 2018 16:11:59 -0800
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On 11/14/18 8:53 PM, Dan Williams wrote:
> As presented at the 2018 Linux Plumbers conference [1], the Subsystem
> Profile is proposed as a way to reduce friction between committers and
> maintainers and perhaps encourage conversations amongst maintainers
> about best practice policies.

Thanks for working on this.


> The profile contains short answers to some of the common policy
> questions a contributor might have, or that a maintainer might consider
> formalizing. The current list of maintenance policies is:
> 
> Overview: General introduction to maintaining the subsystem
> Core: List of source files considered core
> Leaf: List of source files that consume core functionality
> Patches or Pull requests: Simple statement of expected submission format
> Last -rc for new feature submissions: Expected lead time for submissions
> Last -rc to merge features: Deadline for merge decisions
> Non-author Ack / Review Tags Required: Patch review economics
> Test Suite: Pass this suite before requesting inclusion
> Resubmit Cadence: When to ping the maintainer
> Trusted Reviewers: Help for triaging patches
> Time Zone / Office Hours: When might a maintainer be available
> Checkpatch / Style Cleanups: Policy on pure cleanup patches
> Off-list review: Request for review gates
> TODO: Potential development tasks up for grabs, or active focus areas
> 
> The goal of the Subsystem Profile is to set expectations for
> contributors and interim or replacement maintainers for a subsystem.
> 
> See Documentation/maintainer/subsystem-profile.rst for more details, and
> a follow-on example profile for the libnvdimm subsystem.
> 
> [1]: https://linuxplumbersconf.org/event/2/contributions/59/
> 
> Cc: Jonathan Corbet <corbet@lwn.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
> Cc: Steve French <stfrench@microsoft.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Tobin C. Harding <me@tobin.cc>
> Cc: Olof Johansson <olof@lixom.net>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: Joe Perches <joe@perches.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  Documentation/maintainer/index.rst             |    1 
>  Documentation/maintainer/subsystem-profile.rst |  145 ++++++++++++++++++++++++
>  MAINTAINERS                                    |    4 +
>  3 files changed, 150 insertions(+)
>  create mode 100644 Documentation/maintainer/subsystem-profile.rst
> 
> diff --git a/Documentation/maintainer/index.rst b/Documentation/maintainer/index.rst
> index 2a14916930cb..1e6b1aaa6024 100644
> --- a/Documentation/maintainer/index.rst
> +++ b/Documentation/maintainer/index.rst
> @@ -11,4 +11,5 @@ additions to this manual.
>  
>     configure-git
>     pull-requests
> +   subsystem-profile
>  
> diff --git a/Documentation/maintainer/subsystem-profile.rst b/Documentation/maintainer/subsystem-profile.rst
> new file mode 100644
> index 000000000000..a74b624e0972
> --- /dev/null
> +++ b/Documentation/maintainer/subsystem-profile.rst
> @@ -0,0 +1,145 @@
> +.. _subsystemprofile:
> +
> +Subsystem Profile
> +=================
> +
> +The Subsystem Profile is a collection of policy positions that a
> +maintainer or maintainer team establishes for the their subsystem. While
> +there is a wide range of technical nuance on maintaining disparate
> +sections of the kernel, the Subsystem Profile documents a known set of
> +major process policies that vary between subsystems.  What follows is a
> +list of policy questions a maintainer can answer and include a document
> +in the kernel, or on an external website. It advertises to other
> +maintainers and contributors the local policy of the subsystem. Some
> +sections are optional like "Overview", "Off-list review", and "TODO".
> +The others are recommended for all subsystems to address, but no section
> +is mandatory. In addition there are no wrong answers, just document how
> +a subsystem typically operates. Note that the profile follows the
> +subsystem not the maintainer, i.e. there is no expectation that a
> +maintainer of multiple subsystems deploys the same policy across those
> +subsystems.
> +
> +
> +Overview
> +--------
> +In this optional section of the profile provide a free form overview of
> +the subsystem written as a hand-off document. In other words write a
> +note to someone that would receive the “keys to the castle” in the event
> +of extended or unexpected absence. “So, you have recently become the
> +maintainer of the XYZ subsystem, condolences, it is a thankless job,
> +here is the lay of the land.” Details to consider are the extended
> +details that are not included in MAINTAINERS, and not addressed by the
> +other profile questions below. For example details like, who has access
> +to the git tree, branches that are pulled into -next, relevant
> +specifications, issue trackers, and sensitive code areas. If available
> +the Overview should link to other subsystem documentation that may
> +clarify, re-iterate, emphasize / de-emphasize portions of the global
> +process documentation for contributors (CodingStyle, SubmittingPatches,
> +etc...).
> +
> +
> +Core
> +----
> +A list of F: tags (as described by MAINTAINERS) listing what the
> +maintainer considers to be core files. The review and lead time
> +constraints for 'core' code may be stricter given the increased
> +sensitivity and risk of change.
> +
> +
> +Patches or Pull requests
> +------------------------
> +Some subsystems allow contributors to send pull requests, most require
> +mailed patches. State “Patches only”, or “Pull requests accepted”.

This may create some confusion if only "Pull requests accepted" is the
contents of this section.  My understanding has been that all changes
should be available on a mail list for review before being accepted
by the maintainer, even if eventually the final version of the series
that is accepted is applied by the maintainer as a pull instead of
via applying patches.

Is my "must appear on a mail list" understanding correct?


> +
> +
> +Last -rc for new feature submissions
> +------------------------------------
> +New feature submissions targeting the next merge window should have
> +their first posting for consideration before this point. Patches that
> +are submitted after this point should be clear that they are targeting
> +the NEXT+1 merge window, or should come with sufficient justification
> +why they should be considered on an expedited schedule. A general
> +guideline is to set expectation with contributors that new feature
> +submissions should appear before -rc5. The answer may be different for
> +'Core:' files, include a second entry prefixed with 'Core:' if so.

I would expect the -rc to vary based on the patch series size, complexity,
risk, number of revisions that will occur, how controversial, number of
-rc releases before Linus chooses to release, etc.  You would need a
crystal ball to predict much of this.  I could see being able to provide
a good estimate of this value for a relatively simple patch.


> +
> +
> +Last -rc to merge features
> +--------------------------
> +Indicate to contributors the point at which an as yet un-applied patch
> +set will need to wait for the NEXT+1 merge window. Of course there is no
> +obligation to ever except any given patchset, but if the review has not
> +concluded by this point the expectation the contributor should wait and
> +resubmit for the following merge window. The answer may be different for
> +'Core:' files, include a second entry prefixed with 'Core:' if so.

Same comment as for the previous section, with the additional complexity
that each unique patch series should bake in -next.


> +
> +
> +Non-author Ack / Review Tags Required
> +-------------------------------------

The title of this section seems a bit different than the description
below.  A more aligned title would be something like "Maintainer
self-commit review requirements".


> +Let contributors and other maintainers know whether they can expect to
> +see the maintainer self-commit patches without 3rd-party review. Some
> +subsystem developer communities are so small as to make this requirement
> +impractical. Others may have been bootstrapped by a submission of
> +self-reviewed code at the outset, but have since moved to a
> +non-author review-required stance. This section sets expectations on the
> +code-review economics in the subsystem. For example, can a contributor
> +trade review of a maintainer's, or other contributor's patches in
> +exchange for consideration of their own.

Then another section (which is the one I expected when I slightly
mis-read the section title) would be: Review Tags Requirements",
which would discuss what type of review is expected, encouraged,
or required.


> +
> +
> +Test Suite
> +----------
> +Indicate the test suite all patches are expected to pass before being
> +submitted for inclusion consideration.
> +
> +
> +Resubmit Cadence
> +----------------
> +Define a rate at which a contributor should wait to resubmit a patchset
> +that has not yet received comments. A general guideline is to try to
> +meet a deadline of 1 - 2 weeks to acknowledge starting consideration for
> +a patch set.

Or ping instead of resubmitting?  If you resubmit the same series with
an unchanged version then comments could be split across multiple
email threads.  If you resubmit the same series with a new version
number, the same comment split can occur plus it can be confusing
that two versions have the same contents.  I suspect that there may be
some maintainers who do prefer a resubmit, but that is just wild
conjecture on my part.


> +
> +
> +Trusted Reviewers
> +-----------------
> +While a maintainer / maintainer-team is expected to be reviewer of last
> +resort the review load is less onerous when distributed amongst
> +contributors and or a trusted set of individuals.  This section is
> +distinct from the R: tag (Designated Reviewer). Whereas R: identifies
> +reviewers that should always be copied on a patch submission, the
> +trusted reviewers here are individuals contributors can reach out to if
> +a few 'Resubmit Cadence' intervals have gone by without maintainer
> +action, or to otherwise consult for advice.

This seems redundant with the MAINTAINERS reviewers list.  It seems like
the role specified in this section is more of an ombudsman or developer
advocate who can assist with the review and/or accept flow if the
maintainer is being slow to respond.


> +
> +
> +Time Zone / Office Hours
> +------------------------
> +Let contributors know the time of day when one or more maintainers are
> +usually actively monitoring the mailing list.

I would strike "actively monitoring the mailing list".  To me, it should
be what are the hours of the day that the maintainer might happen to poll
(or might receive an interrupt) from the appropriate communications
channels (could be IRC, could be email, etc).

For my area, I would want to say something like: I tend to be active
between 17:00 UTC (18:00 UTC when daylight savings) and 25:00 (26:00),
but often will check for urgent or brief items up until 07:00 (08:00).
I interact with email via a poll model.  I interact with IRC via a
pull model and often overlook IRC activity for multiple days).

-Frank


> +
> +
> +Checkpatch / Style Cleanups
> +---------------------------
> +For subsystems with long standing code bases it is reasonable to decline
> +to accept pure coding-style fixup patches. This is where you can let
> +contributors know “Standalone style-cleanups are welcome”,
> +“Style-cleanups to existing code only welcome with other feature
> +changes”, or “Standalone style-cleanups to existing code are not
> +welcome”.
> +
> +
> +Off-list review
> +---------------
> +A maintainer may optionally require that contributors seek prior review
> +of patches before initial submission for upstream. For example,
> +“Developers from organization X, please seek internal review before
> +requesting upstream review”. This policy identifies occasions where a
> +maintainer wants to reflect some of the review load back to an
> +organization.
> +
> +
> +TODO
> +----
> +In this optional section include a list of work items that might be
> +suitable for onboarding a new developer to the subsystem.
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 83b7b3943a12..bb4a83a7684d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -99,6 +99,10 @@ Descriptions of section entries:
>  	   Obsolete:	Old code. Something tagged obsolete generally means
>  			it has been replaced by a better system and you
>  			should be using that.
> +	P: Subsystem Profile document for the maintainer entry.  This
> +	   is either an in-tree file or a URI to a document.  The
> +	   contents of a Subsystem Profile are described in
> +	   Documentation/maintainer/subsystem-profile.rst.
>  	F: Files and directories with wildcard patterns.
>  	   A trailing slash includes all files and subdirectory files.
>  	   F:	drivers/net/	all files in and below drivers/net
> 
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