FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/reserved-memory/shared-dma-pool.yaml

     # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
     %YAML 1.2
     ---
     $id: http://devicetree.org/schemas/reserved-memory/shared-dma-pool.yaml#
     $schema: http://devicetree.org/meta-schemas/core.yaml#
     
     title: /reserved-memory DMA pool node bindings
     
     maintainers:
      - devicetree-spec@vger.kernel.org
    
    allOf:
      - $ref: "reserved-memory.yaml"
    
    properties:
      compatible:
        oneOf:
          - const: shared-dma-pool
            description: >
              This indicates a region of memory meant to be used as a shared
              pool of DMA buffers for a set of devices. It can be used by an
              operating system to instantiate the necessary pool management
              subsystem if necessary.
    
          - const: restricted-dma-pool
            description: >
              This indicates a region of memory meant to be used as a pool
              of restricted DMA buffers for a set of devices. The memory
              region would be the only region accessible to those devices.
              When using this, the no-map and reusable properties must not
              be set, so the operating system can create a virtual mapping
              that will be used for synchronization. The main purpose for
              restricted DMA is to mitigate the lack of DMA access control
              on systems without an IOMMU, which could result in the DMA
              accessing the system memory at unexpected times and/or
              unexpected addresses, possibly leading to data leakage or
              corruption. The feature on its own provides a basic level of
              protection against the DMA overwriting buffer contents at
              unexpected times. However, to protect against general data
              leakage and system memory corruption, the system needs to
              provide way to lock down the memory access, e.g., MPU. Note
              that since coherent allocation needs remapping, one must set
              up another device coherent pool by shared-dma-pool and use
              dma_alloc_from_dev_coherent instead for atomic coherent
              allocation.
    
      linux,cma-default:
        type: boolean
        description: >
          If this property is present, then Linux will use the region for
          the default pool of the contiguous memory allocator.
    
      linux,dma-default:
        type: boolean
        description: >
          If this property is present, then Linux will use the region for
          the default pool of the consistent DMA allocator.
    
    if:
      properties:
        compatible:
          contains:
            const: restricted-dma-pool
    then:
      properties:
        no-map: false
        reusable: false
    
    unevaluatedProperties: false
    
    examples:
      - |
          reserved-memory {
              #address-cells = <1>;
              #size-cells = <1>;
              ranges;
    
              /* global autoconfigured region for contiguous allocations */
              linux,cma {
                  compatible = "shared-dma-pool";
                  reusable;
                  size = <0x4000000>;
                  alignment = <0x2000>;
                  linux,cma-default;
              };
    
              display_reserved: framebuffer@78000000 {
                  reg = <0x78000000 0x800000>;
              };
    
              restricted_dma_reserved: restricted-dma-pool@50000000 {
                  compatible = "restricted-dma-pool";
                  reg = <0x50000000 0x4000000>;
              };
          };
    
    ...

Cache object: bdba7ee1cfadc3f341c04b39b8d587c6