linux-kernel - Re: [PATCH 2/4] dt-bindings: display: ssd1307fb: Add entry for SINO WEALTH SH1106

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Date:   Mon, 4 Apr 2022 17:48:14 +0200
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     wens@...nel.org, Javier Martinez Canillas <javier@...hile0.org>
Cc:     Maxime Ripard <mripard@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH 2/4] dt-bindings: display: ssd1307fb: Add entry for SINO
 WEALTH SH1106

Hello Chen-Yu,

On 4/4/22 17:06, Chen-Yu Tsai wrote:

[snip]

>>>      enum:
>>> +      - sinowealth,sh1106-i2c
>>
>> I like that you didn't include a "fb" suffix for this, the existing
>> ones are cargo culting from the previous fbdev driver to make existing
>> DTBs compatible with the DRM driver.
>>
>> I've been thinking if I should post a patch to compatible strings
>> without the "fb" and mark the current ones as deprecated...
>>
>> Reviewed-by: Javier Martinez Canillas <javierm@...hat.com>
> 
> I also thought about dropping the "-i2c" suffix, but then thought
> there might be a case where someone wanted to search the device
> tree specifically for an I2C connected node using said compatible
> string.
> 
> What do you think?
> 
>

tl; dr: unfortunately we can't do it due how SPI and I2C report module
aliases. Otherwise module auto loading will not work. I wrote a much
longer explanation with some details not so long ago:

https://patchwork.kernel.org/project/dri-devel/patch/20220209091204.2513437-1-javierm@redhat.com/#24730793

BTW, I bought a SSD1306 SPI controller and go it working this weekend.

I plan to post the patches once yours land, to avoid in-flight series
that may conflict. And what I did is mark the -fb as deprecated, then
added "ssd130x-i2c" and "ssd130x-spi" compatibles strings.

The WIP patches can be found here in case you are interested:

https://github.com/martinezjavier/linux/tree/drm-ssd130x-spi

> ChenYu
> 

-- 
Best regards,

Javier Martinez Canillas
Linux Engineering
Red Hat