linux-kernel - Re: [PATCH v4 02/19] dt-bindings: auxdisplay: ht16k33: Document Adafruit segment displays

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Message-ID: <YQhYIZTlQ/LhjHht@robh.at.kernel.org>
Date:   Mon, 2 Aug 2021 14:40:01 -0600
From:   Rob Herring <robh@...nel.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Miguel Ojeda <ojeda@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mips@...r.kernel.org, Pavel Machek <pavel@....cz>,
        Paul Burton <paulburton@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Marek Behun <marek.behun@....cz>, devicetree@...r.kernel.org,
        Robin van der Gracht <robin@...tonic.nl>
Subject: Re: [PATCH v4 02/19] dt-bindings: auxdisplay: ht16k33: Document
 Adafruit segment displays

On Tue, 27 Jul 2021 16:04:42 +0200, Geert Uytterhoeven wrote:
> The Holtek HT16K33 LED controller is not only used for driving
> dot-matrix displays, but also for driving segment displays.
> 
> Document compatible values for the Adafruit 7-segment[1] and
> 14-segment[2] FeatherWing expansion boards with red displays.  According
> to the schematics, all other Adafruit 7-segment and 14-segment display
> backpack and FeatherWing expansion boards (including bare boards and
> boards fitted with displays) are compatible with these two boards.
> 
> [1] https://www.adafruit.com/product/3108
> [2] https://www.adafruit.com/product/3130
> 
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> v4:
>   - Combine compatible values for 7/14 segment displays into an enum,
> 
> v3:
>   - Drop color property,
> 
> v2:
>   - Fix type of color to uint32,
>   - "refresh-rate-hz" is still required for dot-matrix displays.
> 
> Alternatives I considered:
>   1. Document the attached display type in a child node.
>      I.e. specify segment type, number of characters, and wiring.
>      Especially the latter would become really complex, due to the sheer
>      amount of possible wiring combinations.
>      Using this method, you also loose the ability to just connect a
>      display to an i2c bus, and instantiate the device from sysfs,
>      without using DT:
> 
> 	echo adafruit,3130 0x70 > /sys/class/i2c/i2c-adapter/.../new_device
> 
>   2. Document all Adafruit 7-segment and 14-segment display backpack and
>      FeatherWing expansion boards.
>      This would lead to a myriad of compatible values:
> 
>       - items:
> 	  - enum:
> 	      - adafruit,878      # 0.56" 4-Digit 7-Segment Display Backpack (Red)
> 	      - adafruit,879      # 0.56" 4-Digit 7-Segment Display Backpack (Yellow)
> 	      - adafruit,880      # 0.56" 4-Digit 7-Segment Display Backpack (Green)
> 	      - adafruit,881      # 0.56" 4-Digit 7-Segment Display Backpack (Blue)
> 	      - adafruit,1002     # 0.56" 4-Digit 7-Segment Display Backpack (White)
> 	  - const: adafruit,877   # 0.56" 4-Digit 7-Segment Backpack
> 	  - const: holtek,ht16k33
> 
>       - items:
> 	  - enum:
> 	      - adafruit,1268     # 1.2" 4-Digit 7-Segment Display Backpack (Green)
> 	      - adafruit,1269     # 1.2" 4-Digit 7-Segment Display Backpack (Yellow)
> 	      - adafruit,1270     # 1.2" 4-Digit 7-Segment Display Backpack (Red)
> 	  - const: adafruit,1271  # 1.2" 4-Digit 7-Segment Backpack
> 	  - const: holtek,ht16k33
> 
>       - items:
> 	  - enum:
> 	      - adafruit,1911     # 0.54" Quad Alphanumeric Display Backpack (Red)
> 	      - adafruit,1912     # 0.54" Quad Alphanumeric Display Backpack (Blue)
> 	      - adafruit,2157     # 0.54" Quad Alphanumeric Display Backpack (White)
> 	      - adafruit,2158     # 0.54" Quad Alphanumeric Display Backpack (Yellow)
> 	      - adafruit,2159     # 0.54" Quad Alphanumeric Display Backpack (Yellow-Green)
> 	      - adafruit,2160     # 0.54" Quad Alphanumeric Display Backpack (Green)
> 	  - const: adafruit,1910  # 0.54" Quad 14-segment Alphanumeric Backpack
> 	  - const: holtek,ht16k33
> 
>       - items:
> 	  - enum:
> 	      - adafruit,3106     # 0.56" 4-Digit 7-Segment FeatherWing Display (Blue)
> 	      - adafruit,3107     # 0.56" 4-Digit 7-Segment FeatherWing Display (Green)
> 	      - adafruit,3108     # 0.56" 4-Digit 7-Segment FeatherWing Display (Red)
> 	      - adafruit,3109     # 0.56" 4-Digit 7-Segment FeatherWing Display (White)
> 	      - adafruit,3110     # 0.56" 4-Digit 7-Segment FeatherWing Display (Yellow)
> 	  - const: adafruit,3088  # 0.56" 4-Digit 7-Segment FeatherWing
> 	  - const: holtek,ht16k33
> 
>       - items:
> 	  - enum:
> 	      - adafruit,3127     # 0.54" Quad Alphanumeric FeatherWing Display (White)
> 	      - adafruit,3128     # 0.54" Quad Alphanumeric FeatherWing Display (Blue)
> 	      - adafruit,3129     # 0.54" Quad Alphanumeric FeatherWing Display (Green)
> 	      - adafruit,3130     # 0.54" Quad Alphanumeric FeatherWing Display (Red)
> 	      - adafruit,3131     # 0.54" Quad Alphanumeric FeatherWing Display (Yellow)
> 	      - adafruit,3132     # 0.54" Quad Alphanumeric FeatherWing Display (Yellow-Green)
> 	  - const: adafruit,3089  # 0.54" Quad 14-segment Alphanumeric FeatherWing
> 	  - const: holtek,ht16k33
> ---
>  .../bindings/auxdisplay/holtek,ht16k33.yaml   | 20 ++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 

Reviewed-by: Rob Herring <robh@...nel.org>