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    SubjectRe: [PATCH V2 5/7] dt-bindings: Add xen,dev-domid property description for xen-grant DMA ops
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    On 17.05.22 03:27, Rob Herring wrote:

    Hello Rob, all


    > On Sat, May 07, 2022 at 09:19:06PM +0300, Oleksandr Tyshchenko wrote:
    >> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
    >>
    >> Introduce Xen specific binding for the virtualized device (e.g. virtio)
    >> to be used by Xen grant DMA-mapping layer in the subsequent commit.
    >>
    >> This binding indicates that Xen grant mappings scheme needs to be
    >> enabled for the device which DT node contains that property and specifies
    >> the ID of Xen domain where the corresponding backend resides. The ID
    >> (domid) is used as an argument to the grant mapping APIs.
    >>
    >> This is needed for the option to restrict memory access using Xen grant
    >> mappings to work which primary goal is to enable using virtio devices
    >> in Xen guests.
    >>
    >> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
    >> ---
    >> Changes RFC -> V1:
    >> - update commit subject/description and text in description
    >> - move to devicetree/bindings/arm/
    >>
    >> Changes V1 -> V2:
    >> - update text in description
    >> - change the maintainer of the binding
    >> - fix validation issue
    >> - reference xen,dev-domid.yaml schema from virtio/mmio.yaml
    >> ---
    >> .../devicetree/bindings/arm/xen,dev-domid.yaml | 37 ++++++++++++++++++++++
    >> Documentation/devicetree/bindings/virtio/mmio.yaml | 7 ++++
    >> 2 files changed, 44 insertions(+)
    >> create mode 100644 Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
    >>
    >> diff --git a/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
    >> new file mode 100644
    >> index 00000000..750e89e
    >> --- /dev/null
    >> +++ b/Documentation/devicetree/bindings/arm/xen,dev-domid.yaml
    >> @@ -0,0 +1,37 @@
    >> +# SPDX-License-Identifier: (GPL-2.0-only or BSD-2-Clause)
    >> +%YAML 1.2
    >> +---
    >> +$id: http://devicetree.org/schemas/arm/xen,dev-domid.yaml#
    >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
    >> +
    >> +title: Xen specific binding for virtualized devices (e.g. virtio)
    >> +
    >> +maintainers:
    >> + - Stefano Stabellini <sstabellini@kernel.org>
    >> +
    >> +select: true
    > Omit. No need to apply this on every single node.

    ok, will do


    >
    >> +
    >> +description:
    >> + This binding indicates that Xen grant mappings need to be enabled for
    >> + the device, and it specifies the ID of the domain where the corresponding
    >> + device (backend) resides. The property is required to restrict memory
    >> + access using Xen grant mappings.
    >> +
    >> +properties:
    >> + xen,dev-domid:
    > I kind of think 'dev' is redundant. Is there another kind of domid
    > possible?


    In general, yes. It is driver(frontend) domid. But, at least for now, I
    don't see why we will need an additional property for that.


    > Maybe xen,backend-domid or just xen,domid? I don't know Xen
    > too well, so ultimately up to you all.

    xen,domid sounds ambiguous to me.

    xen,backend-domid sounds perfectly fine to me, I even think it fits better.



    Stefano, Juergen, would you be happy with new xen,backend-domid name?

    If yes, Stefano could you please clarify, would you be OK if I retained
    your R-b tags (for all patches in current series which touch that
    property) after doing such renaming?




    >
    >> + $ref: /schemas/types.yaml#/definitions/uint32
    >> + description:
    >> + The domid (domain ID) of the domain where the device (backend) is running.
    >> +
    >> +additionalProperties: true
    >> +
    >> +examples:
    >> + - |
    >> + virtio@3000 {
    >> + compatible = "virtio,mmio";
    >> + reg = <0x3000 0x100>;
    >> + interrupts = <41>;
    >> +
    >> + /* The device is located in Xen domain with ID 1 */
    >> + xen,dev-domid = <1>;
    >> + };
    >> diff --git a/Documentation/devicetree/bindings/virtio/mmio.yaml b/Documentation/devicetree/bindings/virtio/mmio.yaml
    >> index 10c22b5..29a0932 100644
    >> --- a/Documentation/devicetree/bindings/virtio/mmio.yaml
    >> +++ b/Documentation/devicetree/bindings/virtio/mmio.yaml
    >> @@ -13,6 +13,9 @@ description:
    >> See https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=virtio for
    >> more details.
    >>
    >> +allOf:
    >> + - $ref: /schemas/arm/xen,dev-domid.yaml#
    >> +
    >> properties:
    >> compatible:
    >> const: virtio,mmio
    >> @@ -33,6 +36,10 @@ properties:
    >> description: Required for devices making accesses thru an IOMMU.
    >> maxItems: 1
    >>
    >> + xen,dev-domid:
    >> + description: Required when Xen grant mappings need to be enabled for device.
    >> + $ref: /schemas/types.yaml#/definitions/uint32
    > No need to define the type again nor describe it again.
    >
    > Instead, just change additionalProperties to unevaluateProperties in
    > this doc. The diff is the latter takes $ref's into account.

    ok, will do. Could you please clarify, shall I use?

    unevaluatedProperties: false

    or

    unevaluatedProperties:

    type: object


    I am not too familiar with this stuff. Both variants seem to pass
    validation.


    Thank you.


    >
    >> +
    >> required:
    >> - compatible
    >> - reg
    >> --
    >> 2.7.4
    >>
    >>
    --
    Regards,

    Oleksandr Tyshchenko

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