Re: [PATCH 2/8] dt-bindings: connector: Add MikorBUS connector

[Ayush Singh]

On 9/11/24 22:56, Rob Herring wrote:

> On Wed, Sep 11, 2024 at 07:57:19PM +0530, Ayush Singh wrote:
> > Add DT bindings for mikroBUS interface. MikroBUS [0] is an open standard
> > developed by MikroElektronika for connecting add-on boards to
> > microcontrollers or microprocessors.
> Typo in the subject...
>
> Isn't this v6? Where's the revision history?

Well, at this point, it almost has nothing in common with [0] (the 
previous patch series was about making mikroBUS a Linux bus) and is more 
of a continuation of [1]. So I thought it would be better to treat it as 
a new patch series.

> > MikroBUS connector node will optionally act as nexus nodes for routing
> > GPIOs and PWM.
> >
> > For GPIOs, the following pin numbering should be followed:
> >
> >    0: PWM
> >    1: INT
> >    2: RX
> >    3: TX
> >    4: SCL
> >    5: SDA
> >    6: MOSI
> >    7: MISO
> >    8: SCK
> >    9: CS
> >    10: RST
> >    11: AN
> >
> > For PWM, the PWM pin should be on channel 0.
> >
> > I am not quite sure how to deal with the nexus node properties
> > (#gpio-cells, gpio-map, gpio-map-mask, gpio-map-pass-thru) since they
> > seem to conflict with upstream gpio schema (gpio-controller is a
> > dependency of #gpio-cells).
> >
> > [0]: https://www.mikroe.com/
> >
> > Signed-off-by: Ayush Singh <ayush@xxxxxxxxxxxxxxx>
> > ---
> >   .../bindings/connector/mikrobus-connector.yaml     | 40 ++++++++++++++++++++++
> >   MAINTAINERS                                        |  5 +++
> >   2 files changed, 45 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/connector/mikrobus-connector.yaml b/Documentation/devicetree/bindings/connector/mikrobus-connector.yaml
> > new file mode 100644
> > index 000000000000..603e4627076c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/connector/mikrobus-connector.yaml
> > @@ -0,0 +1,40 @@
> > +# SPDX-License-Identifier: GPL-2.0 OR BSD-2-Clause
> > +#
> > +# Copyright (c) Ayush Singh <ayush@xxxxxxxxxxxxxxx>
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/connector/mikrobus-connector.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: mikroBUS add-on board socket
> > +
> > +maintainers:
> > +  - Ayush Singh <ayush@xxxxxxxxxxxxxxx>
> > +
> > +properties:
> > +  compatible:
> > +    const: mikrobus-connector
> > +
> > +required:
> > +  - compatible
> > +
> > +additionalProperties: true
> Cannot be true. You're schema must be complete. I don't understand what
> happened to everything else in the binding.


So the current dtschema makes `gpio-controller` dependency of 
`#gpio-cells` which should not hold true for nexus node [2]. I also 
wanted to understand if the nexus node schema should go in upstream 
dtschema or be in kernel tree.

I will try to figure out how nexus node properties should look by taking 
interrupt nexus node bindings as a starting point.


[0]: 
https://lore.kernel.org/linux-arm-kernel/20240627-mikrobus-scratch-spi-v5-0-9e6c148bf5f0@xxxxxxxxxxxxxxx/

[1]: 
https://lore.kernel.org/linux-arm-kernel/20240702164403.29067-1-afd@xxxxxx/

[2]: 
https://devicetree-specification.readthedocs.io/en/v0.3/devicetree-basics.html#nexus-nodes-and-specifier-mapping


Ayush Singh