linux-kernel - Re: [PATCH v5 04/11] pwm: max7360: Add MAX7360 PWM support

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Message-ID: <Z9vydaUguJiVaHtU@smile.fi.intel.com>
Date: Thu, 20 Mar 2025 12:48:21 +0200
From: Andy Shevchenko <andriy.shevchenko@...el.com>
To: Uwe Kleine-König <ukleinek@...nel.org>
Cc: mathieu.dubois-briand@...tlin.com, Lee Jones <lee@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Kamel Bouhara <kamel.bouhara@...tlin.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Michael Walle <mwalle@...nel.org>, Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Danilo Krummrich <dakr@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-input@...r.kernel.org, linux-pwm@...r.kernel.org,
	Grégory Clement <gregory.clement@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v5 04/11] pwm: max7360: Add MAX7360 PWM support

On Thu, Mar 20, 2025 at 08:50:00AM +0100, Uwe Kleine-König wrote:
> On Wed, Mar 19, 2025 at 01:18:50PM +0200, Andy Shevchenko wrote:
> > On Tue, Mar 18, 2025 at 05:26:20PM +0100, mathieu.dubois-briand@...tlin.com wrote:

...

> > > +	chip = devm_pwmchip_alloc(dev->parent, MAX7360_NUM_PWMS, 0);
> > 
> > This is quite worrying. The devm_ to parent makes a lot of assumptions that may
> > not be realised. If you really need this, it has to have a very good comment
> > explaining why and object lifetimes.
> 
> Pretty sure this is broken. This results for example in the device link
> being created on the parent. So if the pwm devices goes away a consumer
> might not notice (at least in the usual way). I guess this was done to
> ensure that #pwm-cells is parsed from the right dt node? If so, that
> needs a different adaption. That will probably involve calling
> device_set_of_node_from_dev().

It's an MFD based driver, and MFD core cares about propagating fwnode by
default. I believe it should just work if we drop that '->parent' part.

-- 
With Best Regards,
Andy Shevchenko