linux-kernel - Re: [PATCH v2 1/2] dt-bindings: trivial-devices: add ltp8800

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Message-ID: <20241106-splurge-slaw-b4f1d33e4b09@spud>
Date: Wed, 6 Nov 2024 16:54:17 +0000
From: Conor Dooley <conor@...nel.org>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Cedric Encarnacion <cedricjustine.encarnacion@...log.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-hwmon@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
	Jonathan Corbet <corbet@....net>,
	Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Peter Yin <peteryin.openbmc@...il.com>,
	Noah Wang <noahwang.wang@...look.com>, Marek Vasut <marex@...x.de>,
	Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH v2 1/2] dt-bindings: trivial-devices: add ltp8800

On Wed, Nov 06, 2024 at 08:43:54AM -0800, Guenter Roeck wrote:
> On 11/6/24 08:11, Conor Dooley wrote:
> > On Wed, Nov 06, 2024 at 04:06:02PM +0000, Conor Dooley wrote:
> > > On Tue, Nov 05, 2024 at 08:34:01PM -0800, Guenter Roeck wrote:
> > > > On 11/5/24 19:09, Cedric Encarnacion wrote:
> > > > > Add Analog Devices LTP8800-1A, LTP8800-2, and LTP8800-4A DC/DC μModule
> > > > > regulator.
> > > 
> > > A single compatible for 3 devices is highly suspect. What is
> > > different between these devices?
> > 
> > Additionally, looking at one of the datasheets, this has several inputs
> > that could be controlled by a GPIO, a clock input and several supply
> > inputs. It also has a regulator output. I don't think it is suitable for
> > trivial-devices.yaml.
> > 
> 
> All PMBus devices are by definition regulators with input and output voltages.
> After all, PMBus stands for "Power Management Bus". Some of them are listed
> in trivial devices, some are not. Is that a general guidance, or in other
> words should I (we) automatically reject patches adding PMBus devices
> to the trivial devices file ?

Personally I like what Jonathan does for iio devices, where he requires
input supplies to be documented, which in turns means they can't go into
trivial-devices.yaml. I wanted to add an input supply option to
trivial-devices.yaml but ?Rob? was not a fan.
In this case it would need a dedicated binding to document the regulator
child node and permit things like regulator-always-on or for any
consumers of the regulator to exist. I suppose that probably applies to
all pmbus bindings?
In this case, there seems to be an input "sync" clock that may need to
be enabled, which is another nail in the coffin for
trivial-devices.yaml.

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