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SubjectRe: [PATCH V3 5/8] dt-bindings: Add xen,grant-dma IOMMU description for xen-grant DMA ops
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On 30/05/2022 23:00, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>

Thank you for your patch. There is something to discuss/improve.

> diff --git a/Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml b/Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml
> new file mode 100644
> index 00000000..ab5765c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iommu/xen,grant-dma.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iommu/xen,grant-dma.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Xen specific IOMMU for virtualized devices (e.g. virtio)
> +
> +maintainers:
> + - Stefano Stabellini <sstabellini@kernel.org>
> +
> +description:
> + The reference to Xen specific IOMMU node using "iommus" property indicates
> + that Xen grant mappings need to be enabled for the device, and it specifies
> + the ID of the domain where the corresponding backend resides.
> + The binding is required to restrict memory access using Xen grant mappings.
> +
> +properties:
> + compatible:
> + const: xen,grant-dma
> +
> + '#iommu-cells':
> + const: 1
> + description:
> + Xen specific IOMMU is multiple-master IOMMU device.
> + The single cell describes the domid (domain ID) of the domain where
> + the backend is running.
> +
> +required:
> + - compatible
> + - "#iommu-cells"
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + xen_iommu {

No underscores in node names, generic node names, so this looks like
"iommu".

> + compatible = "xen,grant-dma";
> + #iommu-cells = <1>;
> + };
> +
> + virtio@3000 {
> + compatible = "virtio,mmio";
> + reg = <0x3000 0x100>;
> + interrupts = <41>;
> +
> + /* The backend is located in Xen domain with ID 1 */
> + iommus = <&xen_iommu 1>;

There is no need usually to give consumer examples in provider binding.
If there is nothing specific here (looks exactly like every IOMMU
consumer in Linux kernel), drop the consumer.

> + };


Best regards,
Krzysztof

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