Re: [PATCH 4/4] dma-heap: Devicetree binding for chunk heap
From: John Stultz <hidden>
Date: 2020-11-18 03:01:28
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On Tue, Nov 17, 2020 at 10:19 AM Minchan Kim [off-list ref] wrote:
quoted hunk ↗ jump to hunk
From: Hyesoo Yu <redacted> Document devicetree binding for chunk heap on dma heap framework Signed-off-by: Hyesoo Yu <redacted> Signed-off-by: Minchan Kim <minchan@kernel.org> --- .../bindings/dma-buf/chunk_heap.yaml | 52 +++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 Documentation/devicetree/bindings/dma-buf/chunk_heap.yamldiff --git a/Documentation/devicetree/bindings/dma-buf/chunk_heap.yaml b/Documentation/devicetree/bindings/dma-buf/chunk_heap.yaml new file mode 100644 index 000000000000..f382bee02778 --- /dev/null +++ b/Documentation/devicetree/bindings/dma-buf/chunk_heap.yaml@@ -0,0 +1,52 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/dma-buf/chunk_heap.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: Device tree binding for chunk heap on DMA HEAP FRAMEWORK + +maintainers: + - Sumit Semwal <sumit.semwal@linaro.org> + +description: | + The chunk heap is backed by the Contiguous Memory Allocator (CMA) and + allocates the buffers that are made up to a list of fixed size chunks + taken from CMA. Chunk sizes are configurated when the heaps are created. + +properties: + compatible: + enum: + - dma_heap,chunk + + memory-region: + maxItems: 1 + + alignment: + maxItems: 1 + +required: + - compatible + - memory-region + - alignment + +additionalProperties: false + +examples: + - | + reserved-memory { + #address-cells = <2>; + #size-cells = <1>; + + chunk_memory: chunk_memory { + compatible = "shared-dma-pool"; + reusable; + size = <0x10000000>; + }; + }; + + chunk_default_heap: chunk_default_heap { + compatible = "dma_heap,chunk"; + memory-region = <&chunk_memory>; + alignment = <0x10000>; + };
So I suspect Rob will push back on this as he has for other dt bindings related to ion/dmabuf heaps (I tried to push a similar solution to exporting multiple CMA areas via dmabuf heaps). The proposal he seemed to like best was having an in-kernel function that a driver would call to initialize the heap (associated with the CMA region the driver is interested in). Similar to Kunihiko Hayashi's patch here: - https://lore.kernel.org/lkml/1594948208-4739-1-git-send-email-hayashi.kunihiko@socionext.com/ (local) The one sticking point for that patch (which I think is a good one), is that we don't have any in-tree users, so it couldn't be merged yet. A similar approach might be good here, but again we probably need to have at least one in-tree user which could call such a registration function. thanks -john