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.. SPDX-License-Identifier: GPL-2.0
==============================
Allocating dma-buf using heaps
==============================
Dma-buf Heaps are a way for userspace to allocate dma-buf objects. They are
typically used to allocate buffers from a specific allocation pool, or to share
buffers across frameworks.
Heaps
=====
A heap represents a specific allocator. The Linux kernel currently supports the
following heaps:
- The ``system`` heap allocates virtually contiguous, cacheable, buffers.
- The ``cma`` heap allocates physically contiguous, cacheable,
buffers. Only present if a CMA region is present. Such a region is
usually created either through the kernel commandline through the
`cma` parameter, a memory region Device-Tree node with the
`linux,cma-default` property set, or through the `CMA_SIZE_MBYTES` or
`CMA_SIZE_PERCENTAGE` Kconfig options. Depending on the platform, it
might be called ``reserved``, ``linux,cma``, or ``default-pool``.
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