Hi,
The recent introduction of heaps in the optee driver [1] made possible the creation of heaps as modules.
It's generally a good idea if possible, including for the already existing system and CMA heaps.
The system one is pretty trivial, the CMA one is a bit more involved, especially since we have a call from kernel/dma/contiguous.c to the CMA heap code. This was solved by turning the logic around and making the CMA heap call into the contiguous DMA code.
Let me know what you think, Maxime
1: https://lore.kernel.org/dri-devel/20250911135007.1275833-4-jens.wiklander@li...
Signed-off-by: Maxime Ripard mripard@kernel.org --- Changes in v4: - Fix compilation failure - Rework to take into account OF_RESERVED_MEM - Fix regression making the default CMA area disappear if not created through the DT - Added some documentation and comments - Link to v3: https://lore.kernel.org/r/20260303-dma-buf-heaps-as-modules-v3-0-24344812c70...
Changes in v3: - Squashed cma_get_name and cma_alloc/release patches - Fixed typo in Export dev_get_cma_area commit title - Fixed compilation failure with DMA_CMA but not OF_RESERVED_MEM - Link to v2: https://lore.kernel.org/r/20260227-dma-buf-heaps-as-modules-v2-0-454aee7e06c...
Changes in v2: - Collect tags - Don't export dma_contiguous_default_area anymore, but export dev_get_cma_area instead - Mentioned that heap modules can't be removed - Link to v1: https://lore.kernel.org/r/20260225-dma-buf-heaps-as-modules-v1-0-2109225a090...
--- Maxime Ripard (8): dma: contiguous: Turn heap registration logic around dma: contiguous: Make dev_get_cma_area() a proper function dma: contiguous: Make dma_contiguous_default_area static dma: contiguous: Export dev_get_cma_area() mm: cma: Export cma_alloc(), cma_release() and cma_get_name() dma-buf: heaps: Export mem_accounting parameter dma-buf: heaps: cma: Turn the heap into a module dma-buf: heaps: system: Turn the heap into a module
drivers/dma-buf/dma-heap.c | 1 + drivers/dma-buf/heaps/Kconfig | 4 +-- drivers/dma-buf/heaps/cma_heap.c | 22 +++---------- drivers/dma-buf/heaps/system_heap.c | 5 +++ include/linux/dma-buf/heaps/cma.h | 16 --------- include/linux/dma-map-ops.h | 14 ++++---- kernel/dma/contiguous.c | 66 +++++++++++++++++++++++++++++++++---- mm/cma.c | 3 ++ 8 files changed, 82 insertions(+), 49 deletions(-) --- base-commit: c081b71f11732ad2c443f170ab19c3ebe8a1a422 change-id: 20260225-dma-buf-heaps-as-modules-1034b3ec9f2a
Best regards,