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

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Date:   Tue, 7 Jan 2020 14:01:16 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Richard Fitzgerald <rf@...nsource.cirrus.com>,
        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 1:39 PM Arnd Bergmann <arnd@...db.de> wrote:
> 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.

I don't think so. In any case what we need to do at all times is
put gpiolib on lowcarb diet as it gets compiled into pretty much
everything (at least everything embedded), so I am working a bit on that.

Yours,
Linus Walleij