0001: The SEED Process#

Status: Open for Comments Last Call Accepted Rejected

Proposal Date: 2022-10-31

Summary#

SEEDs are the process through which substantial changes to Pigweed are proposed, reviewed, and decided by community stakeholders to collaboratively drive the project in a favorable direction.

This document outlines the SEED process at a high level. Details about how SEEDs should be written and structured are described in 0002: SEED Template.

Motivation#

As Pigweed and its community grow, it becomes important to ensure that the Pigweed team, Pigweed users, and other community stakeholders align on the future of the project. To date, development of Pigweed has primarily been driven by the core team, and community feedback has been mostly informal and undocumented.

SEEDs are a formalized process for authoring, reviewing, and ratifying proposed changes to Pigweed.

The SEED process has several goals.

Increase the visibility of proposed changes to Pigweed early on and allow interested parties to engage in their design.
Maintain a public record of design decisions rendered during Pigweed’s development and the rationales behind them.
Ensure consistent API design across Pigweed modules through a formal team-wide review process.

Active SEEDs are discussed by the community through Gerrit code review comments as well as a SEEDs chatroom in Pigweed’s Discord server. Decisions are ultimately rendered by a review committee of Pigweed team members.

When is a SEED required?#

SEEDs should be written by any developer wishing to make a “substantial” change to Pigweed. Whether or not a change is considered “substantial” varies depending on what parts of Pigweed it touches and may change over time as the project evolves. Some general guidelines are established below.

Examples of changes considered “substantial” include, but are not limited to:

Adding a new top-level module.
Modifying a widely-used public API.
A breaking update to typical Pigweed user workflows (bootstrap, build setup, pw commands, etc.).
Changing any data interchange or storage protocol or format (e.g. transport protocols, flash layout), unless the change is small and backwards compatible (e.g. adding a field to an exchanged Protobuf message).
Changes to Pigweed’s code policy, style guides, or other project-level guidelines.
Whenever a Pigweed team member asks you to write a SEED.

Conversely, the following changes would likely not require a SEED:

Fixing typos.
Refactoring internal module code without public API changes.
Adding minor parallel operations to existing APIs (e.g. Read(ConstByteSpan) vs Read(const byte*, size_t)).

If you’re unsure whether a change you wish to make requires a SEED, it’s worth asking the Pigweed team in our Discord server prior to writing any code.

Process#

Suppose you’d like to propose a new Pigweed RPC Over Smoke Signals protocol.

If you haven’t already, clone the Pigweed repository and set it up locally, following the Getting Started guide.
Claim a number for your SEED. This should be the next sequential number listed within the SEED index’s toctree table. (We will use 5309 for our example.)

Create a new RST file for your SEED. Name the file with the number of your SEED followed by the lowercase title of the proposal, with words separated by hyphens.

touch seed/5309-pw_rpc-over-smoke-signals.rst

Include your document in the GN build by modifying seed/BUILD.gn:

# Insert your dependency to the doc group at the top of the file.
pw_doc_group("docs") {
  group_deps = [
    ":0001",
    ...
    ":5308",
    ":5309",
  ]
}

# Define a doc group target for your SEED.
pw_doc_group("5309") {
  sources = [ "5309-pw_rpc-over-smoke-signals.rst" ]
}

Push up your document to Gerrit, marking it as a Work-In-Progress change, following the Contributing guide.

Update the toctree in the SEED index adding a row for your SEED. The entry should be labeled with the title of your SEED and link to your work in progress change.

.. toctree::

   0001-the-seed-process
   ...
   5308-some-other-seed
   5309: pw_rpc Over Smoke Signals<https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/116577>

Commit your change to the index (and nothing else) with the commit message SEED-xxxx: Claim SEED number.
```
git add seed/0000-index.rst
git commit -m "SEED-5309: Claim SEED number"
```
Push a separate change to Gerrit with your SEED index modification and add GWSQ as a reviewer. Set Pigweed-Auto-Submit to +1.
Fill out your proposal document, using the SEED template as a guide.

If your SEED requires additional resources such as images, place them within a subdirectory named identically to your document without the .rst extension. These should be listed as inputs in your SEED’s GN doc group target.
```
seed/
  ...
  5309-pw_rpc-over-smoke-signals.rst
  5309-pw_rpc-over-smoke-signals/
    state-diagram.svg
```
When you feel you have enough substantive content in your proposal to be reviewed, push it up to Gerrit and switch the change from WIP to Active. This will begin the open comments period.
Create a thread for your SEED in the #seed channel of Pigweed’s Discord server.
Engage with reviewers to iterate on your proposal through its comment period.
When a tentative decision has been reached, a Pigweed team member will comment on your proposal with a summary of the discussion and reasoning, moving it into its Last Call phase (as described in the Lifecycle section).
Following the conclusion of the Last Call period, a Pigweed team member will sign off on the CL with a +2 vote, allowing it to be submitted. Update the reference in the SEED index with the link to your document and submit the CL.
```
.. toctree::

   0001-the-seed-process
   ...
   5308-some-other-seed
   5309-pw_rpc-over-smoke-signals
```

SEED documents#

SEEDs are written as ReST documents integrated with the rest of Pigweed’s documentation. They live directly within the core Pigweed repository, under a top-level seed/ subdirectory.

The structure of SEED documents themselves, their format, required sections, and other considerations are outlined in 0002: SEED Template.

The first 100 SEEDs (0000-0100) are Meta-SEEDs. These are reserved for internal Pigweed usage and generally detail SEED-related processes. Unlike regular SEEDs, Meta-SEEDs are living documents which may be revised over time.

The lifecycle of a SEED#

A SEED proposal undergoes several phases between first being published and a final decision.

Draft The SEED is a work-in-progress and not yet ready for comments.

The SEED exists in Gerrit as a Work-In-Progress (WIP) change.
Has an assigned SEED number and exists in the index.
Not yet ready to receive feedback.

Open for Comments The SEED is soliciting feedback.

The SEED has sufficient substance to be reviewed, as determined by its author.
A thread for the SEED is created in Discord to promote the proposal and open discussion.
Interested parties comment on the SEED to evaluate the proposal, raise questions and concerns, and express support or opposition.
Back and forth discussion between the author and reviewers, resulting in modifications to the document.
The SEED remains open for as long as necessary. Internally, Pigweed’s review committee will regularly meet to consider active SEEDs and determine when to advance to them the next stage.
Open SEEDs are assigned owners in the core Pigweed team, who are primarily responsible for engaging with the author to move the SEED through its review process.

Last Call A tentative decision has been reached, but commenters may raise final objections.

A tentative decision on the SEED has been made. The decision is issued at the best judgement of the SEED’s owner within the Pigweed team when they feel there has been sufficient discussion on the tradeoffs of the proposal to do so.
Transition is triggered manually by its owner, with a comment on the likely outcome of the SEED (acceptance / rejection).
On entering Last Call, the visibility of the SEED is widely boosted through Pigweed’s communication channels (Discord, mailing list, Pigweed Live, etc.) to solicit any strong objections from stakeholders.
Typically, Last Call lasts for a set period of 7 calendar days, after which the final decision is formalized.
If any substantial new arguments are raised during Last Call, the review committee may decide to re-open the discussion, returning the SEED to a commenting phase.

Accepted The proposal is ratified and ready for implementation.

The SEED is submitted into the Pigweed repository.
A tracking bug is created for the implementation, if applicable.
The SEED may no longer be modified (except minor changes such as typos). Follow-up discussions on the same topic require a new SEED.

Rejected The proposal has been turned down.

The SEED is submitted into the Pigweed repository to provide a permanent record of the considerations made for future reference.
The SEED may no longer be modified.

Deprecated The proposal was originally accepted and implemented but later removed.

The proposal was once implemented but later undone.
The SEED’s changelog contains justification for the deprecation.

Superseded The proposal was originally accepted and implemented but significant portions were later overruled by a different SEED.

A newer SEED proposal revisits the same topic and proposal and redesigns significant parts of the original.
The SEED is marked as superseded with a reference to the newer proposal.

Rationale#

Document format#

Three different documentation formats are considered for SEEDs:

ReST: Used for Pigweed’s existing documentation, making it a natural option.
Google Docs: The traditional way of writing SEED-like investigation and design documents.
Markdown: Ubiquitous across open-source projects, with extensive tooling available.

Summary#

Based on the evaluated criteria, ReST documents provide the best overall SEED experience. The primary issues with ReST exist around contributor tooling, which may be mitigated with additional investment from the Pigweed team.

The table below details the main criteria evaluated for each format, with more detailed explanations following.

Criterion	ReST	Markdown	Google Docs
Straightforward integration with existing docs	✅	❌	❌
Indexable on pigweed.dev	✅	✅	❌
Auditable through source control	✅	✅	❌
Archive of review comments and changes	✅	✅	❌
Accessible to contributors	❌	✅	✅
Extensive styling and formatting options	✅	❌	✅
Easy sharing between Google and external contributors	✅	✅	❌

Integration#

Goal

SEED documents should seamlessly integrate with the rest of Pigweed’s docs.

As all of Pigweed’s documentation is written using ReST, it becomes a natural choice for SEEDs. The use of other formats requires additional scaffolding and may not provide as seamless of an experience.

Indexability#

Goal

Design decisions in SEEDs should be readily available for Pigweed users.

pigweed.dev has a search function allowing users to search the site for Pigweed-related keywords. As SEEDs contain design discussion and rationales, having them appear in these searches offers useful information to users.

The search function is provided by Pigweed’s Sphinx build, so only documents which exist as part of that (ReST / Markdown) are indexed.

Auditability#

Goal

Changes to SEED documents should be reviewed and recorded.

ReST and Markdown documents exist directly within Pigweed’s source repository after being submitted, requiring any further changes to go through a code review process.

Conversely, Google Docs may be edited by anyone with access, making them prone to unintentional modification.

Archive of discussions#

Goal

Discussions during the review of a SEED should be well-archived for future reference.

ReST and Markdown documentation are submitted through Gerrit and follow the standard code review process. Review comments on the changes are saved in Gerrit and are easily revisited. Incremental updates to the SEED during the review process are saved as patch sets.

Comments in Google Docs are more difficult to find once they are resolved, and document changes do not exist as clearly-defined snapshots, making the history of a SEED harder to follow.

Accessibility#

Goal

SEEDs should be easy for contributors to write.

Both Markdown and Google Docs are easy to write, familiar to many, and have extensive tooling available. SEED documents can be written outside of the Pigweed ecosystem using authors’ preferred tools.

ReST, on the other hand, is an unfamiliar and occasionally strange format, and its usage for SEEDs is heavily tied to Pigweed’s documentation build. Authors are required to set up and constantly re-run this build, slowing iteration.

Format and styling#

Goal

SEED authors should have options for formatting various kinds of information and data in their proposals.

Markdown intentionally only offers limited control over document formatting, whereas ReST has a wide selection of directives and Google Docs functions as a traditional WYSIWYG editor, making them far more flexible.

0001: The SEED Process#

Summary#

Motivation#

When is a SEED required?#

Process#

SEED documents#

The lifecycle of a SEED#

Rationale#

Document format#

Summary#

Integration#

Indexability#

Auditability#

Archive of discussions#

Accessibility#

Format and styling#

Sharing between Google and non-Google#