linux-kernel - Re: [PATCH 10/21] leds: gpio: make legacy gpiolib interface optional

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Message-Id: <9fb37e55-0c86-4ac6-acd3-b8c1bc722b3f@app.fastmail.com>
Date: Wed, 20 Aug 2025 14:00:56 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Lee Jones" <lee@...nel.org>
Cc: "Arnd Bergmann" <arnd@...nel.org>, "Bartosz Golaszewski" <brgl@...ev.pl>,
 "Linus Walleij" <linus.walleij@...aro.org>,
 "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
 "Pavel Machek" <pavel@...nel.org>,
 "Javier Carrasco" <javier.carrasco.cruz@...il.com>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
 "Kees Cook" <kees@...nel.org>, "Anish Kumar" <yesanishhere@...il.com>,
 "Mukesh Ojha" <quic_mojha@...cinc.com>,
 "Thomas Zimmermann" <tzimmermann@...e.de>,
 "Dmitry Rokosov" <ddrokosov@...utedevices.com>, linux-leds@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 10/21] leds: gpio: make legacy gpiolib interface optional

On Wed, Aug 20, 2025, at 09:16, Lee Jones wrote:
> On Tue, 19 Aug 2025, Arnd Bergmann wrote:
>
> Sounds like we're between a rock and a hard place with this.

I don't think either variant is that bad to be honest, as it
gets us a long way towards removing the legacy interface from
default builds without having to update or remove the holdouts
immediately. It's mainly led-gpio and gpio-keys that need
a change like this.

Splitting out the entire gpio_led_platform_data handling
into a single #ifdef function block would be a little cleaner,
but that would in turn require changing over a couple of
files that got converted from legacy gpio numbers to passing
gpio descriptors or lookup tables (ppc44x/warp, x86/sel3350,
arm/omap1), making them use device properties instead.

> Will the legacy parts be removed at some point or do you foresee us
> supporting this forever?

It's hard to predict an timeline here, there is certainly a lot of
interest in minimizing the legacy users as much as possible and
patches are getting written for x86 and arm, but I don't see much
movement on the mips and sh platforms. These are also the ones
that have been holdouts for CONFIG_LEGACY_CLK for years, and I
hope we can eventually drop support for those boards.

That said, I first need to get my own act together and refresh
my patches to drop the old arm board files so we can merge that.

      Arnd