linux-kernel - Re: [PATCH v9 1/1] gpio: add sloppy logic analyzer using polling

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Message-ID: <CAMRc=McpRjQO8mUrOA4bU_YqO8Tc9-Ujytfy1fcjGUEgH9NW0A@mail.gmail.com>
Date: Thu, 13 Jun 2024 11:43:12 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Arnd Bergmann <arnd@...db.de>
Cc: Linus Walleij <linus.walleij@...aro.org>, 
	Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>, Jonathan Corbet <corbet@....net>, 
	Kent Gibson <warthog618@...il.com>, linux-doc@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	"open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v9 1/1] gpio: add sloppy logic analyzer using polling

On Thu, Jun 13, 2024 at 10:50 AM Arnd Bergmann <arnd@...db.de> wrote:
>
> On Thu, Jun 13, 2024, at 10:27, Linus Walleij wrote:
> > On Thu, Jun 13, 2024 at 10:17 AM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> >
> >> On second thought
> >> though: are you sure drivers/gpio/ is the right place for it?
> >
> > Actually that is something I requested.
> >
> > I think it fits in drivers/gpio as it is such a clear cut usage of GPIO
> > lines, and it doesn't really fit into any other subsystem.
> >
> >> May I suggest moving it over to drivers/misc/?
> >
> > Misc is a bit...
> > messy. I remember Arnd being very sceptical about putting stuff there
> > rather than creating new subsystems, so since I've tried to avoid it,
> > albeit recently more and more stuff gets merged there again :/
>
> Right, and that is mostly to avoid having code in there because
> there is no other place for it. Some parts of drivers/misc should
> have been a separate subsystem, some should have use an existing
> subsystem, and other parts should have never been merged.
>
> The parts of drivers/misc that make the most sense to me are
> those that expose a one-of-a-kind piece of hardware as a
> single character device.
>
> This one would probably fit into drivers/misc/ better than
> some other drivers we have in there, but leaving it in
> drivers/gpio/ also seems fine.
>

This is my point. This really is a one-of-a-kind module that also
doesn't register with any particular subsystem. If anything fits into
drivers/misc/ then it's this.

To prove this point, I even moved the gpio-virtuser driver I'm working
on to drivers/misc/ too as it isn't a GPIO provider either and merely
a GPIO consumer with a one-shot user-space interface not conforming to
any standards.

> I could also imagine the functionality being exposed
> through drivers/iio/ in a way that is similar to an
> adc, but I don't know if that would work in practice or
> how much of a rewrite that would be.
>

I could see it using configfs instead of DT for configuration and iio
for presenting the output but - from what Wolfram said - insisting on
this will simply result in this development being dropped entirely.

Bart