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Merge branch 'fix/issue-18391-psram-default-docs_v6.0' into 'release/v6.0'

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docs: clarify PSRAM default allocation behavior (v6.0)

See merge request espressif/esp-idf!47053
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Marius Vikhammer
2026-04-29 11:22:07 +08:00
parent f91a82a15c d09e551417
commit 430b404637
5 changed files with 32 additions and 7 deletions
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docs/en/api-guides/external-ram.rst
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@@ -87,11 +87,13 @@ It is recommended to access the PSRAM by ESP-IDF heap memory allocator (see next
Add External RAM to the Capability Allocator
--------------------------------------------
Select this option by choosing ``Make RAM allocatable using heap_caps_malloc(..., MALLOC_CAP_SPIRAM)`` from :ref:`CONFIG_SPIRAM_USE`.
Select this option by choosing ``Add RAM to heap_caps allocator (malloc() stays internal by default)`` from :ref:`CONFIG_SPIRAM_USE`.
When enabled, memory is mapped to data virtual address space and also added to the :doc:`capabilities-based heap memory allocator </api-reference/system/mem_alloc>` using ``MALLOC_CAP_SPIRAM``.
When enabled, memory is mapped to data virtual address space and also added to the :doc:`capabilities-based heap memory allocator </api-reference/system/mem_alloc>` using ``MALLOC_CAP_SPIRAM``. Since this memory is also tagged with ``MALLOC_CAP_DEFAULT``, calls such as ``heap_caps_malloc(size, MALLOC_CAP_DEFAULT)`` can still return PSRAM pointers.
To allocate memory from external RAM, a program should call ``heap_caps_malloc(size, MALLOC_CAP_SPIRAM)``. After use, this memory can be freed by calling the normal ``free()`` function.
To explicitly allocate memory from external RAM, a program should call ``heap_caps_malloc(size, MALLOC_CAP_SPIRAM)``. After use, this memory can be freed by calling the normal ``free()`` function.
In this mode, standard ``malloc()`` does not allocate from external RAM by default because it uses a separate default allocation policy.
.. _external_ram_config_malloc: