linux-kernel - Re: [PATCH] pinctrl: lochnagar: select GPIOLIB

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Date:   Tue, 7 Jan 2020 13:38:50 +0100
From:   Arnd Bergmann <arnd@...db.de>
To:     Richard Fitzgerald <rf@...nsource.cirrus.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Charles Keepax <ckeepax@...nsource.cirrus.com>,
        "moderated list:SOUND - SOC LAYER / DYNAMIC AUDIO POWER MANAGEM..." 
        <alsa-devel@...a-project.org>, patches@...nsource.cirrus.com,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pinctrl: lochnagar: select GPIOLIB

On Tue, Jan 7, 2020 at 12:58 PM Richard Fitzgerald
<rf@...nsource.cirrus.com> wrote:
> On 07/01/2020 10:39, Arnd Bergmann wrote:
> > On Tue, Jan 7, 2020 at 10:45 AM Linus Walleij <linus.walleij@...aro.org> wrote:
> >> On Wed, Dec 18, 2019 at 5:37 PM Arnd Bergmann <arnd@...db.de> wrote:
> >>> I wonder if GPIOLIB should just become mandatory when enabling the pinctrl
> >>> subsystem, or if there are still good reasons for leaving it disabled
> >>> on any machine that uses CONFIG_PINCTRL.
> >>
> >> Hm that is a tricky question, they almost always come in pair but are
> >> technically speaking separate subsystems.
> >
> > I think there are a number of use cases for GPIOLIB drivers without PINCTRL, but
> > are there any examples of the reverse?
>
> You could have muxable pins that aren't gpios. For example muxing
> between i2c/spi signals. So a pinctrl driver doesn't imply gpio.

I understand that this is the case in theory, but what I was wondering about
is whether there are any such users, or at least any that also want to
save a few kilobytes of kernel size for gpiolib.

          Arnd