linux-kernel - Re: [PATCH v12 04/10] pwm: max7360: Add MAX7360 PWM support

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Message-Id: <DBVF5EWK7WRF.3Q0CRECYQOER0@bootlin.com>
Date: Wed, 06 Aug 2025 16:36:32 +0200
From: "Mathieu Dubois-Briand" <mathieu.dubois-briand@...tlin.com>
To: Uwe Kleine-König <ukleinek@...nel.org>
Cc: "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>, <andriy.shevchenko@...el.com>,
 Grégory Clement <gregory.clement@...tlin.com>, "Thomas
 Petazzoni" <thomas.petazzoni@...tlin.com>, "Andy Shevchenko"
 <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v12 04/10] pwm: max7360: Add MAX7360 PWM support

On Wed Aug 6, 2025 at 4:02 PM CEST, Uwe Kleine-König wrote:
> On Wed, Aug 06, 2025 at 02:07:15PM +0200, Mathieu Dubois-Briand wrote:
>> > I think the right thing to do here is:
>> >
>> > 	if (wf->period_length_ns > MAX7360_PWM_PERIOD_NS)
>> > 		return 1;
>> > 	else
>> > 		return 0;
>> 
>> I can definitely do that, but now I'm a bit confused by the meaning of
>> this return value: is it 0 on success, 1 if some rounding was made,
>> -errno on error? So I believe I should only return 0 if
>> wf->period_length_ns == MAX7360_PWM_PERIOD_NS, no?
>> 
>> Or reading this comment on pwm_round_waveform_might_sleep(), maybe we
>> only have to return 1 if some value is rounded UP. So I believe the test
>> should be (wf->period_length_ns < MAX7360_PWM_PERIOD_NS).
>
> Right,
>
> 	if (wf->period_length_ns < MAX7360_PWM_PERIOD_NS)
> 		return 1;
> 	else
> 		return 0;
>
> So 0 = request could be matched by only rounding down, 1 = request could
> be matched but rounding up was needed, negative value = error.
>

Ok, thanks for the explanation.

I will fix the return value, and a new version should come soon.

Best regards,
Mathieu

-- 
Mathieu Dubois-Briand, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com