Re: [PATCH v2 3/4] dt-bindings: firmware: Add Qualcomm QSEECOM interface

[Rob Herring <robh@kernel.org>]

On Fri, Jan 27, 2023 at 07:46:49PM +0100, Maximilian Luz wrote:
> Add bindings for the Qualcomm Secure Execution Environment interface
> (QSEECOM).
> 
> Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
> ---
> 
> Changes in v2:
>  - Replaces uefisecapp bindings.
>  - Fix various dt-checker complaints.
> 
> ---
>  .../bindings/firmware/qcom,qseecom.yaml       | 49 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  2 files changed, 50 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,qseecom.yaml
> 
> diff --git a/Documentation/devicetree/bindings/firmware/qcom,qseecom.yaml b/Documentation/devicetree/bindings/firmware/qcom,qseecom.yaml
> new file mode 100644
> index 000000000000..540a604f81bc
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/firmware/qcom,qseecom.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/firmware/qcom,qseecom.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Qualcomm Secure Execution Environment Communication Interface
> +
> +maintainers:
> +  - Maximilian Luz <luzmaximilian@gmail.com>
> +
> +description: |
> +  QSEECOM provides an interface to Qualcomm's Secure Execution Environment
> +  (SEE) running in the Trust Zone via SCM calls. In particular, it allows

SCM is SMCCC or something else?

> +  communication with secure applications running therein.
> +
> +  Applications running in this environment can, for example, include
> +  'uefisecapp', which is required for accessing UEFI variables on certain
> +  systems as these cannot be accessed directly.
> +
> +properties:
> +  compatible:
> +    items:
> +      - enum:
> +          - qcom,qseecom-sc8280xp
> +      - const: qcom,qseecom
> +
> +  qcom,scm:
> +    $ref: '/schemas/types.yaml#/definitions/phandle'
> +    description:
> +      A phandle pointing to the QCOM SCM device (see ./qcom,scm.yaml).
> +
> +required:
> +  - compatible
> +  - qcom,scm
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    firmware {
> +        scm {
> +            compatible = "qcom,scm-sc8280xp", "qcom,scm";
> +        };
> +        qseecom {
> +            compatible = "qcom,qseecom-sc8280xp", "qcom,qseecom";
> +            qcom,scm = <&scm>;

Why do you need this in DT? If you already know you have a firmware 
interface (via "qcom,scm"), then query the firmware to see if the SEE is 
there.

Rob