linux-kernel - Re: [PATCH v6 2/2] dt-bindings: cros-ec: Add ChromeOS fingerprint binding

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Message-ID: <CAD=FV=UU-AENyChCvVAKH709E4hFtgo4Txa8zFDY=JM1UifA0g@mail.gmail.com>
Date:   Tue, 14 Jun 2022 15:41:25 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Benson Leung <bleung@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, patches@...ts.linux.dev,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, chrome-platform@...ts.linux.dev,
        Guenter Roeck <groeck@...omium.org>,
        Craig Hesling <hesling@...omium.org>,
        Tom Hughes <tomhughes@...omium.org>,
        Alexandru M Stan <amstan@...omium.org>,
        Tzung-Bi Shih <tzungbi@...nel.org>,
        Matthias Kaehlcke <mka@...omium.org>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH v6 2/2] dt-bindings: cros-ec: Add ChromeOS fingerprint binding

Hi,

On Tue, Jun 14, 2022 at 12:51 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Add a binding to describe the fingerprint processor found on Chromebooks
> with a fingerprint sensor. Previously we've been describing this with
> the google,cros-ec-spi binding but it lacks gpio and regulator control
> used during firmware flashing.
>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>
> Cc: <devicetree@...r.kernel.org>
> Cc: <chrome-platform@...ts.linux.dev>
> Cc: Guenter Roeck <groeck@...omium.org>
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Craig Hesling <hesling@...omium.org>
> Cc: Tom Hughes <tomhughes@...omium.org>
> Cc: Alexandru M Stan <amstan@...omium.org>
> Cc: Tzung-Bi Shih <tzungbi@...nel.org>
> Cc: Matthias Kaehlcke <mka@...omium.org>
> Cc: Benson Leung <bleung@...omium.org>
> Cc: Lee Jones <lee.jones@...aro.org>
> Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  .../bindings/chrome/google,cros-ec-fp.yaml    | 97 +++++++++++++++++++
>  .../bindings/mfd/google,cros-ec.yaml          |  9 ++
>  2 files changed, 106 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/chrome/google,cros-ec-fp.yaml
>
> diff --git a/Documentation/devicetree/bindings/chrome/google,cros-ec-fp.yaml b/Documentation/devicetree/bindings/chrome/google,cros-ec-fp.yaml
> new file mode 100644
> index 000000000000..48c02bd4585c
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/chrome/google,cros-ec-fp.yaml
> @@ -0,0 +1,97 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/chrome/google,cros-ec-fp.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: ChromeOS Embedded Fingerprint Controller
> +
> +description:
> +  Google's ChromeOS embedded fingerprint controller is a device which
> +  implements fingerprint functionality such as unlocking a Chromebook
> +  without typing a password.
> +
> +maintainers:
> +  - Tom Hughes <tomhughes@...omium.org>
> +
> +select:
> +  properties:
> +    compatible:
> +      contains:
> +        const: google,cros-ec-spi
> +  required:
> +    - compatible
> +    - boot0-gpios

I've never personally used "select" before and I'm not sure where it's
documented. Without knowing anything, it seems weird to me that in
this file we're matching against a compatible that's not
google,cros-ec-fp. Randomly grabbing some other example that's similar
(panel-lvds.yaml) looks more like what I would have expected. AKA in
this file:

select:
  properties:
    compatible:
      contains:
        const: google,cros-ec-fp
  required:
    - compatible

...and then in the other file:

select:
  properties:
    compatible:
      contains:
        const: google,cros-ec-spi
  not:
    properties:
      compatible:
        contains:
          const: google,cros-ec-fp
  required:
    - compatible


Of course, if one of the dt maintainers gives different advice then
listen to them. ;-)

-Doug