linux-kernel - Re: [PATCH v17] pwm: opencores: Add PWM driver support

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Message-ID: <a4qprb2s7kqzhgewf54oxelrr4inuka5ozsadqybnft3moe6xy@kigsy6zevieq>
Date: Tue, 18 Mar 2025 10:58:40 +0100
From: Uwe Kleine-König <ukleinek@...nel.org>
To: Maud Spierings <maud_spierings@...mail.com>
Cc: william.qiu@...rfivetech.com, hal.feng@...rfivetech.com, 
	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org, p.zabel@...gutronix.de
Subject: Re: [PATCH v17] pwm: opencores: Add PWM driver support

Hello Maud,

On Tue, Jan 07, 2025 at 07:37:13AM +0100, Maud Spierings wrote:
> I did some more digging, took a look at the pwm-backlight driver in the
> vendor kernel, and it seems there are some tweaks there [1] (all the way at
> the bottom). And it explains some things, first off why it didn't error
> before without the inverted polarity, because it sets this value in the
> pwm-backlight driver in that kernel.
> 
> but the interesting line is this one:
> |brightness = (u8)~brightness;

Huh, that confirms my prejudice that vendor trees are bad. Even in
combination with

	state.polarity = PWM_POLARITY_INVERSED;

in the probe function this is horrible. This effectively renders your
testing useless.

Best regards
Uwe

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