Re: [PATCH v5 01/11] dt-bindings: document generic access controller

[Gatien CHEVALLIER]

Hi Rob,

On 10/2/23 19:30, Rob Herring wrote:
> On Fri, Sep 29, 2023 at 04:28:42PM +0200, Gatien Chevallier wrote:
> > From: Oleksii Moisieiev <Oleksii_Moisieiev@xxxxxxxx>
> >
> > Introducing of the generic access controller bindings for the
> > access controller provider and consumer devices. Those bindings are
> > intended to allow a better handling of accesses to resources in a
> > hardware architecture supporting several compartments.
> >
> > This patch is based on [1]. It is integrated in this patchset as it
> > provides a use-case for it.
> >
> > Diffs with [1]:
> > 	- Rename feature-domain* properties to access-control* to narrow
> > 	  down the scope of the binding
> > 	- YAML errors and typos corrected.
> > 	- Example updated
> > 	- Some rephrasing in the binding description
> >
> > [1]: https://lore.kernel.org/lkml/0c0a82bb-18ae-d057-562b
> >
> > Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@xxxxxxxx>
> > Signed-off-by: Gatien Chevallier <gatien.chevallier@xxxxxxxxxxx>
> >
> > ---
> > Changes in V5:
> > 	- Diffs with [1]
> > 	- Discarded the [IGNORE] tag as the patch is now part of the
> > 	  patchset
> >
> >   .../access-controllers/access-controller.yaml | 90 +++++++++++++++++++
> >   1 file changed, 90 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/access-controllers/access-controller.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/access-controllers/access-controller.yaml b/Documentation/devicetree/bindings/access-controllers/access-controller.yaml
> > new file mode 100644
> > index 000000000000..9d305fccc333
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/access-controllers/access-controller.yaml
> > @@ -0,0 +1,90 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/access-controllers/access-controller.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Generic Domain Access Controller
> > +
> > +maintainers:
> > +  - Oleksii Moisieiev <oleksii_moisieiev@xxxxxxxx>
> > +
> > +description: |+
> > +  Common access controllers properties
> > +
> > +  Access controllers are in charge of stating which of the hardware blocks under
> > +  their responsibility (their domain) can be accesssed by which compartment. A
> > +  compartment can be a cluster of CPUs (or coprocessors), a range of addresses
> > +  or a group of hardware blocks. An access controller's domain is the set of
> > +  resources covered by the access controller.
> > +
> > +  This device tree bindings can be used to bind devices to their access
> > +  controller provided by access-controller property. In this case, the device is
> > +  a consumer and the access controller is the provider.
> > +
> > +  An access controller can be represented by any node in the device tree and
> > +  can provide one or more configuration parameters, needed to control parameters
> > +  of the consumer device. A consumer node can refer to the provider by phandle
> > +  and a set of phandle arguments, specified by '#access-controller-cells'
> > +  property in the access controller node.
> > +
> > +  Access controllers are typically used to set/read the permissions of a
> > +  hardware block and grant access to it. Any of which depends on the access
> > +  controller. The capabilities of each access controller are defined by the
> > +  binding of the access controller device.
> > +
> > +  Each node can be a consumer for the several access controllers.
> > +
> > +# always select the core schema
> > +select: true
> > +
> > +properties:
> > +  "#access-controller-cells":
> > +    $ref: /schemas/types.yaml#/definitions/uint32
>
> Drop. "#.*-cells" already defines the type.

Ok, I will drop it for V6

> > +    description:
> > +      Number of cells in a access-controller specifier;
> > +      Can be any value as specified by device tree binding documentation
> > +      of a particular provider.
> > +
> > +  access-control-provider:
> > +    description:
> > +      Indicates that the node is an access controller.
>
> Drop. The presence of "#access-controller-cells" is enough to do that.

Ok, I wasn't sure. I'll will drop it for V6

> > +
> > +  access-controller-names:
> > +    $ref: /schemas/types.yaml#/definitions/string-array
> > +    description:
> > +      A list of access-controller names, sorted in the same order as
> > +      access-controller entries. Consumer drivers will use
> > +      access-controller-names to match with existing access-controller entries.
> > +
> > +  access-controller:
>
> For consistency with other provider bindings: access-controllers

Ack

> > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > +    description:
> > +      A list of access controller specifiers, as defined by the
> > +      bindings of the access-controller provider.
> > +
> > +additionalProperties: true
> > +
> > +examples:
> > +  - |
> > +    uart_controller: access-controller@50000 {
> > +        reg = <0x50000 0x10>;
> > +        access-control-provider;
> > +        #access-controller-cells = <2>;
> > +    };
> > +
> > +    bus_controller: bus@60000 {
> > +        reg = <0x60000 0x10000>;
> > +        #address-cells = <1>;
> > +        #size-cells = <1>;
> > +        ranges;
> > +        access-control-provider;
> > +        #access-controller-cells = <3>;
> > +
> > +        uart4: serial@60100 {
> > +            reg = <0x60100 0x400>;
> > +            access-controller = <&uart_controller 1 2>,
> > +                                <&bus_controller 1 3 5>;
> > +            access-controller-names = "controller", "bus-controller";
>
> Not great names. It should indicate what access is being controlled
> locally. Perhaps "reg" for register access, "dma" or "bus" for bus
> master access. (Not sure what your uart_controller is controlling access
> to.)
>
> Rob

Yes, I agree it's poor naming. I'll come up with something more
adequate. Thank you for the input.

Best regards,
Gatien