dma-buf.rst

Buffer Sharing and Synchronization

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 as finished access, and (3) reservation, which manages the shared or exclusive fence(s) associated with the buffer.

Shared DMA Buffers

.. kernel-doc:: drivers/dma-buf/dma-buf.c
   :export:

.. kernel-doc:: include/linux/dma-buf.h
   :internal:

Reservation Objects

.. kernel-doc:: drivers/dma-buf/reservation.c
   :doc: Reservation Object Overview

.. kernel-doc:: drivers/dma-buf/reservation.c
   :export:

.. kernel-doc:: include/linux/reservation.h
   :internal:

DMA Fences

.. kernel-doc:: drivers/dma-buf/dma-fence.c
   :export:

.. kernel-doc:: include/linux/dma-fence.h
   :internal:

Seqno Hardware Fences

.. kernel-doc:: drivers/dma-buf/seqno-fence.c
   :export:

.. kernel-doc:: include/linux/seqno-fence.h
   :internal:

DMA Fence Array

.. kernel-doc:: drivers/dma-buf/dma-fence-array.c
   :export:

.. kernel-doc:: include/linux/dma-fence-array.h
   :internal:

DMA Fence uABI/Sync File

.. kernel-doc:: drivers/dma-buf/sync_file.c
   :export:

.. kernel-doc:: include/linux/sync_file.h
   :internal: