Re: [RFC PATCH v2 03/17] dt-bindings: mailbox: Add bindings for RISC-V SBI MPXY extension

[Rob Herring <robh@kernel.org>]

On Mon, Feb 03, 2025 at 02:18:52PM +0530, Anup Patel wrote:
> Add device tree bindings for the RISC-V SBI Message Proxy (MPXY)
> extension as a mailbox controller.
> 
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> ---
>  .../bindings/mailbox/riscv,sbi-mpxy-mbox.yaml | 54 +++++++++++++++++++
>  1 file changed, 54 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml b/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> new file mode 100644
> index 000000000000..8a05e089b710
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mailbox/riscv,sbi-mpxy-mbox.yaml
> @@ -0,0 +1,54 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mailbox/riscv,sbi-mpxy-mbox.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: RISC-V SBI Message Proxy (MPXY) extension based mailbox
> +
> +maintainers:
> +  - Anup Patel <anup@brainfault.org>
> +
> +description: |
> +  The RISC-V SBI Message Proxy (MPXY) extension [1] allows supervisor
> +  software to send messages through the SBI implementation (M-mode
> +  firmware or HS-mode hypervisor). The underlying message protocol
> +  and message format used by the supervisor software could be some
> +  other standard protocol compatible with the SBI MPXY extension
> +  (such as RISC-V Platform Management Interface (RPMI) [2]).
> +
> +  ===========================================
> +  References
> +  ===========================================
> +
> +  [1] RISC-V Supervisor Binary Interface (SBI)
> +      https://github.com/riscv-non-isa/riscv-sbi-doc/releases
> +
> +  [2] RISC-V Platform Management Interface (RPMI)
> +      https://github.com/riscv-non-isa/riscv-rpmi/releases
> +
> +properties:
> +  $nodename:
> +    const: sbi-mpxy-mbox

'mailbox' is the defined name for mailbox providers.

> +
> +  compatible:
> +    const: riscv,sbi-mpxy-mbox
> +
> +  "#mbox-cells":
> +    const: 2
> +    description:
> +      The first cell specifies channel_id of the SBI MPXY channel,
> +      the second cell specifies MSG_PROT_ID of the SBI MPXY channel
> +
> +required:
> +  - compatible
> +  - "#mbox-cells"
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    sbi-mpxy-mbox {
> +          compatible = "riscv,sbi-mpxy-mbox";
> +          #mbox-cells = <2>;

Is there an SBI node? #mbox-cells could just be part of that along with 
anything else that SBI is a provider for. And we already have the PMU 
SBI binding. It's all one thing, so there should be one SBI node. Then 
we can debate about child nodes of it.

Rob