Commit 2034134d authored by Maxime Ripard's avatar Maxime Ripard Committed by Sumit Semwal
Browse files

doc: dma-buf: List the heaps by name 



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: default avatarT.J. Mercier <tjmercier@google.com>
Signed-off-by: default avatarMaxime Ripard <mripard@kernel.org>
Signed-off-by: default avatarSumit 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
parent 7910d693

Documentation/userspace-api/dma-buf-heaps.rst

+12 −10
Original line number Diff line number Diff line
@@ -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

=================