1.. SPDX-License-Identifier: GPL-2.0 2 3============================== 4Feature and driver maintainers 5============================== 6 7The term "maintainer" spans a very wide range of levels of engagement 8from people handling patches and pull requests as almost a full time job 9to people responsible for a small feature or a driver. 10 11Unlike most of the chapter, this section is meant for the latter (more 12populous) group. It provides tips and describes the expectations and 13responsibilities of maintainers of a small(ish) section of the code. 14 15Drivers and alike most often do not have their own mailing lists and 16git trees but instead send and review patches on the list of a larger 17subsystem. 18 19Responsibilities 20================ 21 22The amount of maintenance work is usually proportional to the size 23and popularity of the code base. Small features and drivers should 24require relatively small amount of care and feeding. Nonetheless 25when the work does arrive (in form of patches which need review, 26user bug reports etc.) it has to be acted upon promptly. 27Even when a particular driver only sees one patch a month, or a quarter, 28a subsystem could well have a hundred such drivers. Subsystem 29maintainers cannot afford to wait a long time to hear from reviewers. 30 31The exact expectations on the response time will vary by subsystem. 32The patch review SLA the subsystem had set for itself can sometimes 33be found in the subsystem documentation. Failing that as a rule of thumb 34reviewers should try to respond quicker than what is the usual patch 35review delay of the subsystem maintainer. The resulting expectations 36may range from two working days for fast-paced subsystems (e.g. networking) 37to as long as a few weeks in slower moving parts of the kernel. 38 39Mailing list participation 40-------------------------- 41 42Linux kernel uses mailing lists as the primary form of communication. 43Maintainers must be subscribed and follow the appropriate subsystem-wide 44mailing list. Either by subscribing to the whole list or using more 45modern, selective setup like 46`lei <https://people.kernel.org/monsieuricon/lore-lei-part-1-getting-started>`_. 47 48Maintainers must know how to communicate on the list (plain text, no invasive 49legal footers, no top posting, etc.) 50 51Reviews 52------- 53 54Maintainers must review *all* patches touching exclusively their drivers, 55no matter how trivial. If the patch is a tree wide change and modifies 56multiple drivers - whether to provide a review is left to the maintainer. 57 58When there are multiple maintainers for a piece of code an ``Acked-by`` 59or ``Reviewed-by`` tag (or review comments) from a single maintainer is 60enough to satisfy this requirement. 61 62If the review process or validation for a particular change will take longer 63than the expected review timeline for the subsystem, maintainer should 64reply to the submission indicating that the work is being done, and when 65to expect full results. 66 67Refactoring and core changes 68---------------------------- 69 70Occasionally core code needs to be changed to improve the maintainability 71of the kernel as a whole. Maintainers are expected to be present and 72help guide and test changes to their code to fit the new infrastructure. 73 74Bug reports 75----------- 76 77Maintainers must ensure severe problems in their code reported to them 78are resolved in a timely manner: regressions, kernel crashes, kernel warnings, 79compilation errors, lockups, data loss, and other bugs of similar scope. 80 81Maintainers furthermore should respond to reports about other kinds of 82bugs as well, if the report is of reasonable quality or indicates a 83problem that might be severe -- especially if they have *Supported* 84status of the codebase in the MAINTAINERS file. 85 86Open development 87---------------- 88 89Discussions about user reported issues, and development of new code 90should be conducted in a manner typical for the larger subsystem. 91It is common for development within a single company to be conducted 92behind closed doors. However, development and discussions initiated 93by community members must not be redirected from public to closed forums 94or to private email conversations. Reasonable exceptions to this guidance 95include discussions about security related issues. 96 97Selecting the maintainer 98======================== 99 100The previous section described the expectations of the maintainer, 101this section provides guidance on selecting one and describes common 102misconceptions. 103 104The author 105---------- 106 107Most natural and common choice of a maintainer is the author of the code. 108The author is intimately familiar with the code, so it is the best person 109to take care of it on an ongoing basis. 110 111That said, being a maintainer is an active role. The MAINTAINERS file 112is not a list of credits (in fact a separate CREDITS file exists), 113it is a list of those who will actively help with the code. 114If the author does not have the time, interest or ability to maintain 115the code, a different maintainer must be selected. 116 117Multiple maintainers 118-------------------- 119 120Modern best practices dictate that there should be at least two maintainers 121for any piece of code, no matter how trivial. It spreads the burden, helps 122people take vacations and prevents burnout, trains new members of 123the community etc. etc. Even when there is clearly one perfect candidate, 124another maintainer should be found. 125 126Maintainers must be human, therefore, it is not acceptable to add a mailing 127list or a group email as a maintainer. Trust and understanding are the 128foundation of kernel maintenance and one cannot build trust with a mailing 129list. Having a mailing list *in addition* to humans is perfectly fine. 130 131Corporate structures 132-------------------- 133 134To an outsider the Linux kernel may resemble a hierarchical organization 135with Linus as the CEO. While the code flows in a hierarchical fashion, 136the corporate template does not apply here. Linux is an anarchy held 137together by (rarely expressed) mutual respect, trust and convenience. 138 139All that is to say that managers almost never make good maintainers. 140The maintainer position more closely matches an on-call rotation 141than a position of power. 142 143The following characteristics of a person selected as a maintainer 144are clear red flags: 145 146 - unknown to the community, never sent an email to the list before 147 - did not author any of the code 148 - (when development is contracted) works for a company which paid 149 for the development rather than the company which did the work 150 151Non compliance 152============== 153 154Subsystem maintainers may remove inactive maintainers from the MAINTAINERS 155file. If the maintainer was a significant author or played an important 156role in the development of the code, they should be moved to the CREDITS file. 157 158Removing an inactive maintainer should not be seen as a punitive action. 159Having an inactive maintainer has a real cost as all developers have 160to remember to include the maintainers in discussions and subsystem 161maintainers spend brain power figuring out how to solicit feedback. 162 163Subsystem maintainers may remove code for lacking maintenance. 164 165Subsystem maintainers may refuse accepting code from companies 166which repeatedly neglected their maintainership duties. 167