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diff --git a/Documentation/gpu/introduction.rst b/Documentation/gpu/introduction.rst new file mode 100644 index 000000000000..1903595b5310 --- /dev/null +++ b/Documentation/gpu/introduction.rst @@ -0,0 +1,51 @@ +============ +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, &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 please use ->vfunc(). Note that kerneldoc does not +support referencing struct members directly, so please add a reference +to the vtable struct somewhere in the same paragraph or at least +section. + +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. |