35 lines
1.3 KiB
ReStructuredText
35 lines
1.3 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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==============================
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Allocating dma-buf using heaps
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==============================
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Dma-buf Heaps are a way for userspace to allocate dma-buf objects. They are
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typically used to allocate buffers from a specific allocation pool, or to share
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buffers across frameworks.
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Heaps
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=====
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A heap represents a specific allocator. The Linux kernel currently supports the
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following heaps:
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- The ``system`` heap allocates virtually contiguous, cacheable, buffers.
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- The ``default_cma_region`` heap allocates physically contiguous,
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cacheable, buffers. Only present if a CMA region is present. Such a
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region is usually created either through the kernel commandline
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through the ``cma`` parameter, a memory region Device-Tree node with
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the ``linux,cma-default`` property set, or through the
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``CMA_SIZE_MBYTES`` or ``CMA_SIZE_PERCENTAGE`` Kconfig options. Prior
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to Linux 6.17, its name wasn't stable and could be called
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``reserved``, ``linux,cma``, or ``default-pool``, depending on the
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platform.
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- A heap will be created for each reusable region in the device tree
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with the ``shared-dma-pool`` compatible, using the full device tree
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node name as its name. The buffer semantics are identical to
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``default-cma-region``.
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Naming Convention
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