The key concepts or models of Patchwork are outlined below.


Projects typically represent a software project or sub-project. A Patchwork server can host multiple projects. Each project can have multiple maintainers. Projects usually have a 1:1 mapping with a mailing list, though it’s also possible to have multiple projects in the same list using the subject as filter. Patches, cover letters, and series are all associated with a single project.


People are anyone who has submitted a patch, cover letter, or comment to a Patchwork instance.


Users are anyone who has created an account on a given Patchwork instance.

Standard Users

A standard user can associate multiple email addresses with their user account, create bundles and store TODO lists.


Maintainers are a special type of user that with permissions to do certain operations that regular Patchwork users can’t. Patchwork maintainers usually have a 1:1 mapping with a project’s code maintainers though this is not necessary.

The operations that a maintainer can invoke include:

  • Change the state of a patch

  • Archive a patch

  • Delegate a patch, or be delegated a patch


Patchwork captures three types of mail to mailing lists: patches, cover letters, and replies to either patches or cover letters, a.k.a. comments. Any mail that does not fit one of these categories is ignored.


Patches are the central object in Patchwork structure. A patch contains both a diff and some metadata, such as the name, the description, the author, the version of the patch etc. Patchwork stores not only the patch itself but also various metadata associated with the email that the patch was parsed from, such as the message headers or the date the message itself was received.

Cover Letters

Cover letters provide a way to offer a “big picture” overview of a series of patches. When using Git, these mails can be recognised by way of their 0/N subject prefix, e.g. [00/11] A sample series. Like patches, Patchwork stores not only the various aspects of the cover letter itself, such as the name and body of the cover letter, but also various metadata associated with the email that the cover letter was parsed from.


Comments are replies to a submission - either a patch or a cover letter. Unlike a Mail User Agent (MUA) like Gmail, Patchwork does not thread comments. Instead, every comment is associated with either a patch or a cover letter, and organized by date.

Patch Metadata

Patchwork allows users to store various metadata against patches. This metadata is only configurable by a maintainer.


States track the state of patch in its lifecycle. States vary from project to project, but generally a minimum subset of “new”, “rejected” and “accepted” will exist.


Delegates are Patchwork users who are responsible for both reviewing a patch and setting its eventual state in Patchwork. This makes them akin to reviewers in other tools. Delegation works particularly well for larger projects where various subsystems, each with their own maintainer(s), can be identified. Only one delegate can be assigned to a patch.


Patchwork supports automatic delegation of patches. Refer to Autodelegation for more information.


Tags are specially formatted metadata appended to the foot the body of a patch or a comment on a patch. Patchwork extracts these tags at parse time and associates them with the patch. You add extra tags to an email by replying to the email. The following tags are available on a standard Patchwork install:


For example:

Acked-by: Stephen Finucane <stephen@that.guru>

For example:

Tested-by: Stephen Finucane <stephen@that.guru>

For example:

Reviewed-by: Stephen Finucane <stephen@that.guru>

The available tags, along with the significance of said tags, varies from project to project and Patchwork instance to Patchwork instance. The kernel project documentation provides an overview of the supported tags for the Linux kernel project.


Checks store the results of any tests executed (or executing) for a given patch. This is useful, for example, when using a continuous integration (CI) system to test patches. Checks have a number of fields associated with them:


A label to discern check from the checks of other testing systems


A brief, optional description of the check

Target URL

A target URL where a user can find information related to this check, such as test logs.


The state of the check. One of: pending, success, warning, fail


The user creating the check


Checks can only be created through the Patchwork APIs. Refer to ../api for more information.

Comment Metadata

Like patches, Patchwork allows users to store various bits of metadata against comments.

Action required

New in version 3.1.0.

Patchwork allows users to set an “action required” flag on patch and cover letter comments. This flag can be set by maintainers or by the users submitting the cover letters. Once the submitter has provided the required information, either the submitter or a maintainer can mark the comment as “addressed”. This provides a more granular way of tracking work items than patch states.


Users can indicate that a comment requires an action using a custom mail header. For more information, refer to Hint Headers.


Patchwork provides a number of ways to store groups of patches. Some of these are automatically generated, while others are user-defined.


Series are groups of patches, along with an optional cover letter. Series are mostly dumb containers, though they also contain some metadata themselves such as a version (which is inherited by the patches and cover letter) and a count of the number of patches found in the series.


Bundles are custom, user-defined groups of patches. Bundles can be used to keep patch lists, preserving order, for future inclusion in a tree. There’s no restriction of number of patches and they don’t even need to be in the same project. A single patch also can be part of multiple bundles at the same time. An example of Bundle usage would be keeping track of the Patches that are ready for merge to the tree.

To-do Lists

Patchwork users can store a to-do list of patches.


Events are raised whenever patches are created or modified.

All events have a number of common properties, along with some event-specific properties:


The type of event


The project this event belongs to


When this event was created


The user, if any, that caused/created this event


Additional information

Cover Letter Created



Sent when a cover letter is created.


Created cover letter

Patch Created



Sent when a patch is created.


Created patch

Patch Completed



Sent when a patch in a series has its dependencies met, or when a patch that is not in a series is created (since that patch has no dependencies).


Completed patch


Series from which patch dependencies were extracted, if any

Patch Delegated



Sent when a patch’s delegate is changed.


Updated patch


Previous delegate, if any


Current delegate, if any

Patch State Changed



Sent when a patch’s state is changed.


Updated patch


Previous state


Current state

Check Created



Sent when a patch check is created.


Created check

Series Created



Sent when a series is created.


Created series

Series Completed



Sent when a series is completed.


Completed series

What’s Not Exposed

  • Bundles

    We don’t expose an “added to bundle” event as it’s unlikely that this will be useful to either users or CI setters.

  • Comments

    Like Bundles, there likely isn’t much value in exposing these via the API.