linux-kernel - Re: trivial-devices with vdd-supply: true

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Message-ID: <7856f1b7-e12a-4530-82c5-416ec66e1885@linaro.org>
Date: Sat, 9 Mar 2024 16:00:24 +0100
From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To: Javier Carrasco <javier.carrasco.cruz@...il.com>,
 Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>
Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: trivial-devices with vdd-supply: true

On 09/03/2024 13:22, Javier Carrasco wrote:
> Hi,
> 
> I am trying to figure out the current policy to add trivial devices
> (I2C/SPI devices with at most one interrupt) to trivial-devices.yaml or
> include a dedicated file.
> 
> Apparently, bindings for the same sort of devices where "vdd-supply" is
> provided require their own file, and I wonder why there is no
> "vdd/supplied/whatever-trivial-devices.yaml".
> 
> Instead, files with trivial bindings + "vdd-supply: true" are added on a
> regular basis. That property is not saying anything specific about the

Anything needing supply is not really trivial anymore, because we want
the supply name to match more or less what's in datasheet.

Solution is sometimes to allow generic "power-supply", like panels have,
AFAIR. If you have new device, just add new binding for it or add the
device to existing binding with very, very similar device.

See also:
https://lore.kernel.org/all/YUz+psAILnF5L5GH@robh.at.kernel.org/
https://lore.kernel.org/all/20210921131804.GC1864238@roeck-us.net/
https://lore.kernel.org/all/CAL_JsqKJgvK8g+zbzLCBxnKbgAioBcdHWNAvqe4Z9BzkNMwPpA@mail.gmail.com/


> device beyond that it needs a supply, which is very common. Is that
> intended and no more generic bindings are desired?
> 
> On the other hand, trivial-devices.yaml includes several devices that do
> require a single supply (e.g. several sensors), but it is not explicitly
> documented. Did the requirement of providing vdd-supply arise after
> those devices were added to trivial-devices? I think that some devices

You would need to analyze the history... requirement of providing
supplies was kind of always. Just like trivial devices were.

> that were added to trivial-devices in the last months could have also
> had a vdd-supply property, so I am not sure about the rules to choose
> one way or another.

https://lore.kernel.org/all/20230505204810.GB3506915-robh@kernel.org/

Best regards,
Krzysztof