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: 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

diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst
index a0979440d2a4258c0f76912cd3f160d183fa9aa1..5d68cab9ef131c4f8fd5f0562d7439705ce85a2e 100644 (file)
--- a/Documentation/userspace-api/dma-buf-heaps.rst
+++ b/Documentation/userspace-api/dma-buf-heaps.rst
@@ -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
 =================