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doc: dma-buf: List the heaps by name

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Since we're going to introduce multiple instances of the CMA heap
driver, there's no single CMA heap anymore.

Let's use the heap name instead to differentiate between all the heaps
available in the system.

While we're at it, let's also rework the backward compatibility part to
make it easier to amend later on.

Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
  [sumits: rebased to latest Doc]
Link: https://lore.kernel.org/r/20251013-dma-buf-ecc-heap-v8-1-04ce150ea3d9@kernel.org
This commit is contained in:
Maxime Ripard
2025-10-13 10:35:16 +02:00
committed by Sumit Semwal
parent 7910d69376
commit 2034134de6
1 changed files with 12 additions and 10 deletions
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22
Documentation/userspace-api/dma-buf-heaps.rst
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@@ -16,16 +16,18 @@ 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. The heap's name in devtmpfs is
``default_cma_region``. For backwards compatibility, when the
``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option is set, a duplicate node is
created following legacy naming conventions; the legacy name might be
``reserved``, ``linux,cma``, or ``default-pool``.
- The ``default_cma_region`` 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. Prior
to Linux 6.17, its name wasn't stable and could be called
``reserved``, ``linux,cma``, or ``default-pool``, depending on the
platform. From Linux 6.17 onwards, the creation of these heaps is
controlled through the ``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option for
backwards compatibility.
Naming Convention
=================