linux-kernel - Re: [PATCH v2 1/2] dt-bindings: hwmon: pmbus: add lt3074

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Message-ID: <dbd9cc84-a0b6-4323-b343-6e80aaaf2d14@roeck-us.net>
Date: Thu, 27 Feb 2025 08:32:58 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Rob Herring <robh@...nel.org>,
	Cedric Encarnacion <cedricjustine.encarnacion@...log.com>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
	Delphine CC Chiu <Delphine_CC_Chiu@...ynn.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: hwmon: pmbus: add lt3074

On Thu, Feb 27, 2025 at 09:50:23AM +0100, Krzysztof Kozlowski wrote:
> > > > 
> > > > hwmon code might need some changes, but that's not really relevant for
> > > > proper hardware description.
> > > 
> > > Normally, I would agree, but it seems generic pmbus code expects this
> > > structure. This just came up with changing another binding maintained by
> > > 'Not Me' to follow this structure. We're stuck with the existing way, so
> > > I don't know that it is worth supporting 2 ways forever. OTOH, is it
> > > guaranteed that these devices will only ever be pmbus devices or that
> > > other regulator devices which are not handled as pmbus devices currently
> > > will be in the future. If so, more flexibility in the bindings will be
> > > needed.
> > > 
> > 
> > I would appreciate if someone would explain to me what the problems with
> > the current PMBus code actually are. I have seen several comments claiming
> 
> Not exactly a problem but missing feature. pmbus code (at least one of
> macros I looked at) expects regulator node and some sort of child of it
> (vout), while such simple devices should be:
> 
> regulator {
> 	compatible = "adi,lt3074";
> 	regulator-name = "vout";
> 	regulator-min-microvolt = "100000";
> 	regulator-max-microvolt = "100000";
> };
> 
> so without any of regulators and regulators/vout subnodes.
> 
> > that the code should be changed, but I have no idea what the expected changes
> > actually are or, in other words, what the PMBus code should be doing
> > differently.
> 
> I did not investigate much into pmbus code, but this might be as simple
> as accepting arguments for .of_match and .regulators_node and then
> accepting NULLs as them as well. Or a new macro which assigns NULLs
> there.
> 

Unless I am missing something, the following should do the trick.

diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index ddb19c9726d6..289767e5d599 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -512,7 +512,6 @@ int pmbus_regulator_init_cb(struct regulator_dev *rdev,
 	{							\
 		.name = (_name),				\
 		.of_match = of_match_ptr(_name),		\
-		.regulators_node = of_match_ptr("regulators"),	\
 		.ops = &pmbus_regulator_ops,			\
 		.type = REGULATOR_VOLTAGE,			\
 		.owner = THIS_MODULE,				\

Maybe someone can check if that works.

Thanks,
Guenter