linux-kernel - Re: [PATCH v2 1/3] dt-bindings: eeprom: Add ST M24LR control interface

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Message-ID: <be95cc2d-f548-4c71-a57b-8107009b8776@kernel.org>
Date: Sun, 1 Jun 2025 17:42:41 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Abd-Alrhman Masalkhi <abd.masalkhi@...il.com>,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc: arnd@...db.de, gregkh@...uxfoundation.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org
Subject: Re: [PATCH v2 1/3] dt-bindings: eeprom: Add ST M24LR control
 interface

On 01/06/2025 17:30, Abd-Alrhman Masalkhi wrote:
> Add support for the control interface of STMicroelectronics M24LR
> RFID/NFC EEPROM chips.
> 
> Signed-off-by: Abd-Alrhman Masalkhi <abd.masalkhi@...il.com>
> ---
>  .../devicetree/bindings/eeprom/st,m24lr.yaml  | 72 +++++++++++++++++++

Do not send next version while the discussion is still happening.

>  1 file changed, 72 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/eeprom/st,m24lr.yaml

I still do not understand what is this device exactly. You said this is
not EEPROM, so my advice of putting this in eeprom seems not correct.

> 
> diff --git a/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml b/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml
> new file mode 100644
> index 000000000000..6d72325865d6
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/eeprom/st,m24lr.yaml
> @@ -0,0 +1,72 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/eeprom/st,m24lr.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: STMicroelectronics M24LR Series NFC/RFID EEPROM Control Interface
> +
> +maintainers:
> +  - Abd-Alrhman Masalkhi <abd.masalkhi@...il.com>
> +
> +description: |

Do not need '|' unless you need to preserve formatting.

> +  STMicroelectronics M24LR series are dual-interface (RF + I2C)
> +  EEPROM chips. These devices support I2C-based access to both
> +  memory and a system area that controls authentication and configuration.
> +  They expose two I2C addresses: one for EEPROM memory and one for the
> +  system control area (e.g., UID, password management).

e.g., -> e.g.

> +
> +allOf:
> +  - $ref: ../i2c/i2c-mux.yaml#

Full path, so /schemas/i2c/i2c-mux.... but this is not an i2c mux, at
least not in your description, so something feels incomplete or incorrect.

> +
> +properties:
> +  compatible:
> +    enum:
> +      - st,m24lr04e-r
> +      - st,m24lr16e-r
> +      - st,m24lr64e-r

What does "r" stand for?

> +
> +  reg:
> +    maxItems: 1
> +
> +  pagesize:
> +    enum: [1, 4, 8, 16, 32, 64, 128, 256]
> +    default: 1
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: >

Do not need '>' unless you need to preserve formatting.

> +      Maximum number of bytes that can be written in one I2C transaction.
> +      the default is 1.

Don't repeat constraints in free form text. I already asked for this.


> +
> +required:
> +  - compatible
> +  - reg
> +
> +unevaluatedProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      i2cmux@57 {

Nothing in commit msg or binding description explained why this is
i2c-mux.  i2c-mux is not an eeprom. Exposing two I2C addresses also does
not mean it is mux - we already have such devices and they were never
called mux.

> +        compatible = "st,m24lr04e-r";
> +        reg = <0x57>;

Where is the second address? It is supposed to be here.

> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        i2c@0 {
> +          reg = <0x0>;
> +          #address-cells = <1>;
> +          #size-cells = <0>;
> +
> +          eeprom@53 {
> +            compatible = "atmel,24c04";


And even if there was a mux here, then where is the second device?

> +            reg = <0x53>;
> +            address-width = <16>;
> +            pagesize = <4>;
> +          };
> +        };
> +      };
> +    };
> +...


Best regards,
Krzysztof