Make it a little bit more clear what's going on and fix some formatting. Signed-off-by: Daniel Stone <daniels@xxxxxxxxxxxxx> --- Documentation/driver-api/dma-buf.rst | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) v2: New. diff --git a/Documentation/driver-api/dma-buf.rst b/Documentation/driver-api/dma-buf.rst index f92a32d095d9..862dbc2759d0 100644 --- a/Documentation/driver-api/dma-buf.rst +++ b/Documentation/driver-api/dma-buf.rst @@ -5,14 +5,22 @@ The dma-buf subsystem provides the framework for sharing buffers for hardware (DMA) access across multiple device drivers and subsystems, and for synchronizing asynchronous hardware access. -This is used, for example, by drm "prime" multi-GPU support, but is of -course not limited to GPU use cases. - -The three main components of this are: (1) dma-buf, representing a -sg_table and exposed to userspace as a file descriptor to allow passing -between devices, (2) fence, which provides a mechanism to signal when -one device has finished access, and (3) reservation, which manages the -shared or exclusive fence(s) associated with the buffer. +As an example, it is used extensively by the DRM subsystem to exchange +buffers between processes, contexts, library APIs within the same +process, and also to exchange buffers with other subsystems such as +V4L2. + +This document describes the way in which kernel subsystems can use and +interact with the three main primitives offered by dma-buf: + + - dma-buf, representing a sg_table and exposed to userspace as a file + descriptor to allow passing between processes, subsystems, devices, + etc; + - dma-fence, providing a mechanism to signal when an asynchronous + hardware operation has completed; and + - dma-resv, which manages a set of dma-fences for a particular dma-buf + allowing implicit (kernel-ordered) synchronization of work to + preserve the illusion of coherent access Shared DMA Buffers ------------------ -- 2.41.0
