@@ -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
------------------
Make it a little bit more clear what's going on and fix some formatting. Signed-off-by: Daniel Stone <daniels@collabora.com> --- Documentation/driver-api/dma-buf.rst | 24 ++++++++++++++++-------- 1 file changed, 16 insertions(+), 8 deletions(-) v2: New.