linux-kernel - Re: [PATCH 1/2] dt-bindings: display: Add Sharp Memory LCD bindings

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Message-ID: <c7bf08aa-e7a0-4b60-b9fe-b43215ce3fb9@kernel.org>
Date: Thu, 25 Jul 2024 08:17:01 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Alex Lanzano <lanzano.alex@...il.com>, mehdi.djait@...tlin.com,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: display: Add Sharp Memory LCD bindings

On 25/07/2024 02:47, Alex Lanzano wrote:
> Add device tree bindings for the monochrome Sharp Memory LCD
> 
> Signed-off-by: Alex Lanzano <lanzano.alex@...il.com>
> ---
>  .../bindings/display/sharp,sharp-memory.yaml  | 97 +++++++++++++++++++
>  include/dt-bindings/display/sharp-memory.h    |  9 ++
>  2 files changed, 106 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/sharp,sharp-memory.yaml
>  create mode 100644 include/dt-bindings/display/sharp-memory.h
> 
> diff --git a/Documentation/devicetree/bindings/display/sharp,sharp-memory.yaml b/Documentation/devicetree/bindings/display/sharp,sharp-memory.yaml
> new file mode 100644
> index 000000000000..a79edd97c857
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/sharp,sharp-memory.yaml

Filename based on compatible, so e.g. sharp,ls010b7dh04.yaml.

> @@ -0,0 +1,97 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/display/sharp,sharp-memory.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Sharp Memory LCD panels
> +
> +maintainers:
> +  - Alex Lanzano <lanzano.alex@...il.com>
> +
> +description:
> +  This binding is for the Sharp Memory LCD monochrome displays.

Do not say that binding is a binding... instead describe hardware.

> +
> +properties:
> +  compatible:
> +    enum:
> +      - sharp,ls010b7dh04
> +      - sharp,ls011b7dh03
> +      - sharp,ls012b7dd01
> +      - sharp,ls013b7dh03
> +      - sharp,ls013b7dh05
> +      - sharp,ls018b7dh02
> +      - sharp,ls027b7dh01
> +      - sharp,ls027b7dh01a
> +      - sharp,ls032b7dd02
> +      - sharp,ls044q7dh01
> +
> +  reg:
> +    maxItems: 1
> +
> +  spi-cs-high: true

You can drop it.

> +
> +  spi-max-frequency:
> +    maximum: 2000000
> +
> +  vcom-mode:

Missing vendor prefix.

> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: |
> +      VCOM is a signal that prevents DC bias from being built up in
> +      the panel resulting in pixels being forever stuck in one state.
> +      vcom-mode can be set to one of three modes
> +
> +      SHARP_MEMORY_SOFTWARE_VCOM - This method uses a kthread to periodically send a
> +      "maintain display" message to the display, toggling the vcom
> +      bit on and off with each message

You described Linux, this is not suitable for bindings.

> +
> +      SHARP_MEMORY_EXTERNAL_VCOM - This method relies on an external clock to generate
> +      the signal on the EXTCOMM pin
> +
> +      SHARP_MEMORY_PWM_VCOM - This method uses a pwm device to generate the signal
> +      on the EXTCOMM pin

I don't see why do you even need this property. Just choose the best
option based on available connections/pins.

> +
> +    enum: [ 0, 1, 2 ]

Here 0/1/2 but above something entirely else. Just use strings.

> +
> +  enable-gpios:
> +    maxItems: 1
> +    description: Enables display

Drop description and maxItems. :true is enough

> +
> +  pwms:
> +    maxItems: 1
> +    description: External VCOM signal
> +
> +required:
> +  - compatible
> +  - reg
> +  - spi-cs-high
> +  - vcom-mode
> +

allOf:

and missing ref to spi peripheral props

> +if:
> +  properties:
> +    vcom-mode:
> +      # SHARP_MEMORY_PWM_VCOM
> +      enum: [2]
> +then:
> +  required:
> +    - pwms
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    #include <dt-bindings/display/sharp-memory.h>
> +
> +    spi {
> +            #address-cells = <1>;
> +            #size-cells = <0>;

Mess indentation.

Use 4 spaces for example indentation.

> +
> +            display@0{
> +                    compatible = "sharp,ls013b7dh03";
> +                    reg = <0>;
> +                    spi-cs-high;
> +                    spi-max-frequency = <1000000>;
> +                    vcom-mode = <SHARP_MEMORY_SOFTWARE_VCOM>;
> +            };
> +    };
> +...
> diff --git a/include/dt-bindings/display/sharp-memory.h b/include/dt-bindings/display/sharp-memory.h
> new file mode 100644
> index 000000000000..dea14c7bd7ec
> --- /dev/null
> +++ b/include/dt-bindings/display/sharp-memory.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) */
> +#ifndef _DT_BINDINGS_SHARP_MEMORY
> +#define _DT_BINDINGS_SHARP_MEMORY
> +
> +#define SHARP_MEMORY_SOFTWARE_VCOM	0
> +#define SHARP_MEMORY_EXTERNAL_VCOM	1
> +#define SHARP_MEMORY_PWM_VCOM		2

Nope, drop the binding.


Best regards,
Krzysztof