mirror of https://gitee.com/openkylin/linux.git
115 lines
5.3 KiB
ReStructuredText
115 lines
5.3 KiB
ReStructuredText
============
|
|
Introduction
|
|
============
|
|
|
|
The Linux DRM layer contains code intended to support the needs of
|
|
complex graphics devices, usually containing programmable pipelines well
|
|
suited to 3D graphics acceleration. Graphics drivers in the kernel may
|
|
make use of DRM functions to make tasks like memory management,
|
|
interrupt handling and DMA easier, and provide a uniform interface to
|
|
applications.
|
|
|
|
A note on versions: this guide covers features found in the DRM tree,
|
|
including the TTM memory manager, output configuration and mode setting,
|
|
and the new vblank internals, in addition to all the regular features
|
|
found in current kernels.
|
|
|
|
[Insert diagram of typical DRM stack here]
|
|
|
|
Style Guidelines
|
|
================
|
|
|
|
For consistency this documentation uses American English. Abbreviations
|
|
are written as all-uppercase, for example: DRM, KMS, IOCTL, CRTC, and so
|
|
on. To aid in reading, documentations make full use of the markup
|
|
characters kerneldoc provides: @parameter for function parameters,
|
|
@member for structure members (within the same structure), &struct structure to
|
|
reference structures and function() for functions. These all get automatically
|
|
hyperlinked if kerneldoc for the referenced objects exists. When referencing
|
|
entries in function vtables (and structure members in general) please use
|
|
&vtable_name.vfunc. Unfortunately this does not yet yield a direct link to the
|
|
member, only the structure.
|
|
|
|
Except in special situations (to separate locked from unlocked variants)
|
|
locking requirements for functions aren't documented in the kerneldoc.
|
|
Instead locking should be check at runtime using e.g.
|
|
``WARN_ON(!mutex_is_locked(...));``. Since it's much easier to ignore
|
|
documentation than runtime noise this provides more value. And on top of
|
|
that runtime checks do need to be updated when the locking rules change,
|
|
increasing the chances that they're correct. Within the documentation
|
|
the locking rules should be explained in the relevant structures: Either
|
|
in the comment for the lock explaining what it protects, or data fields
|
|
need a note about which lock protects them, or both.
|
|
|
|
Functions which have a non-\ ``void`` return value should have a section
|
|
called "Returns" explaining the expected return values in different
|
|
cases and their meanings. Currently there's no consensus whether that
|
|
section name should be all upper-case or not, and whether it should end
|
|
in a colon or not. Go with the file-local style. Other common section
|
|
names are "Notes" with information for dangerous or tricky corner cases,
|
|
and "FIXME" where the interface could be cleaned up.
|
|
|
|
Also read the :ref:`guidelines for the kernel documentation at large <doc_guide>`.
|
|
|
|
Documentation Requirements for kAPI
|
|
-----------------------------------
|
|
|
|
All kernel APIs exported to other modules must be documented, including their
|
|
datastructures and at least a short introductory section explaining the overall
|
|
concepts. Documentation should be put into the code itself as kerneldoc comments
|
|
as much as reasonable.
|
|
|
|
Do not blindly document everything, but document only what's relevant for driver
|
|
authors: Internal functions of drm.ko and definitely static functions should not
|
|
have formal kerneldoc comments. Use normal C comments if you feel like a comment
|
|
is warranted. You may use kerneldoc syntax in the comment, but it shall not
|
|
start with a /** kerneldoc marker. Similar for data structures, annotate
|
|
anything entirely private with ``/* private: */`` comments as per the
|
|
documentation guide.
|
|
|
|
Getting Started
|
|
===============
|
|
|
|
Developers interested in helping out with the DRM subsystem are very welcome.
|
|
Often people will resort to sending in patches for various issues reported by
|
|
checkpatch or sparse. We welcome such contributions.
|
|
|
|
Anyone looking to kick it up a notch can find a list of janitorial tasks on
|
|
the :ref:`TODO list <todo>`.
|
|
|
|
Contribution Process
|
|
====================
|
|
|
|
Mostly the DRM subsystem works like any other kernel subsystem, see :ref:`the
|
|
main process guidelines and documentation <process_index>` for how things work.
|
|
Here we just document some of the specialities of the GPU subsystem.
|
|
|
|
Feature Merge Deadlines
|
|
-----------------------
|
|
|
|
All feature work must be in the linux-next tree by the -rc6 release of the
|
|
current release cycle, otherwise they must be postponed and can't reach the next
|
|
merge window. All patches must have landed in the drm-next tree by latest -rc7,
|
|
but if your branch is not in linux-next then this must have happened by -rc6
|
|
already.
|
|
|
|
After that point only bugfixes (like after the upstream merge window has closed
|
|
with the -rc1 release) are allowed. No new platform enabling or new drivers are
|
|
allowed.
|
|
|
|
This means that there's a blackout-period of about one month where feature work
|
|
can't be merged. The recommended way to deal with that is having a -next tree
|
|
that's always open, but making sure to not feed it into linux-next during the
|
|
blackout period. As an example, drm-misc works like that.
|
|
|
|
Code of Conduct
|
|
---------------
|
|
|
|
As a freedesktop.org project, dri-devel, and the DRM community, follows the
|
|
Contributor Covenant, found at: https://www.freedesktop.org/wiki/CodeOfConduct
|
|
|
|
Please conduct yourself in a respectful and civilised manner when
|
|
interacting with community members on mailing lists, IRC, or bug
|
|
trackers. The community represents the project as a whole, and abusive
|
|
or bullying behaviour is not tolerated by the project.
|