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    SubjectRe: [RFC PATCH 0/1] dt-bindings: arm: Add scmi_devid paramter for
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    On Tue, Feb 22, 2022 at 04:14:40PM +0000, Sudeep Holla wrote:
    > On Tue, Feb 22, 2022 at 09:06:25AM +0100, Krzysztof Kozlowski wrote:
    > > On 21/02/2022 22:39, Oleksii Moisieiev wrote:
    > > > Hi Krzysztof,
    > > >
    > > > On Mon, Feb 21, 2022 at 10:01:43PM +0100, Krzysztof Kozlowski wrote:
    > > >> On 21/02/2022 18:26, Oleksii Moisieiev wrote:
    > > >>> Introducing new parameter called scmi_devid to the device-tree bindings.
    > > >>> This parameter should be set for the device nodes, which has
    > > >>> clocks/power-domains/resets working through SCMI.
    > > >>> Given parameter should set the device_id, needed to set device
    > > >>> permissions in the Firmware. This feature will be extremely useful for
    > > >>> the virtualized systems, which has more that one Guests running on the
    > > >>> system at the same time or for the syestems, which require several
    > > >>> agents with different permissions. Trusted agent will use scmi_devid to
    > > >>> set the Device permissions for the Firmware (See Section 4.2.2.10 [0]
    > > >>> for details).
    > > >>> Agents concept is described in Section 4.2.1 [0].
    > > >>>
    > > >>> scmi_devid in Device-tree node example:
    > > >>> usb@e6590000
    > > >>> {
    > > >>> scmi_devid = <19>;
    > > >>> clocks = <&scmi_clock 3>, <&scmi_clock 2>;
    > > >>> resets = <&scmi_reset 10>, <&scmi_reset 9>;
    > > >>> power-domains = <&scmi_power 0>;
    > > >>> };
    > > >>
    > > >> And how do you prevent DT overlay adding such devid to any other node
    > > >> thus allowing any other device to send requests with given devid?
    > > >>
    > > > Thank you for the quick response.
    > > > scmi_devid value will be used only by Trusted Agent when the device
    > > > permissions are set. Non-trusted agents, which in our case are
    > > > represented as Guest OS are using scmi drivers, already present in linux
    > > > kernel, ignores scmi_devid and uses scmi_clocks, scmi_power, scmi_reset
    > > > nodes to access to SCMI protocol.
    > >
    > > Ah, ok.
    > >
    > > >
    > > >> Plus few technicalities:
    > > >> 1. Hyphen, not underscore in property name, so scmi-devid.
    > > >
    > > > Thanks for the tip, I will change that in v2.
    > >
    > > Few more thoughts:
    > > 1. This looks specific to ARM SCMI, so you also need vendor prefix, so
    > > something like:
    > > arm,scmi-devid
    > > arm,scmi-device-id
    > >
    >
    > Keeping the other discussion separate, I wanted to comment on this.
    > I agree with Krzysztof on having vendor specific prefix if we decide to add
    > this device id thing. However, I prefer not to use "arm,scmi-" here.
    > It can be "xen,scmi-" as we had plans to introduce some concepts in SCMI
    > spec that may use looks like this device-id. I would just like to avoid
    > conflicting with that in the future. It may happen to be same in the future
    > (i.e. this xen device-id matches 100% with definition of device-id we might
    > introduce in the spec, but I want to make assumption otherwise and leave
    > scope for divergence however small/little it can be). No issues even if
    > they converge and match 100% later in the far future.
    >

    xem,scmi- works for me. What do other thinks?
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