linux-kernel - Re: [PATCH] gpiolib: Avoid side effects in gpio_is

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Date:   Wed, 17 May 2023 17:10:02 +0800
From:   Kent Gibson <warthog618@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
        Linus Walleij <linus.walleij@...aro.org>,
        "brgl@...ev.pl" <brgl@...ev.pl>,
        "johan@...nel.org" <johan@...nel.org>,
        "maz@...nel.org" <maz@...nel.org>,
        Ben Brown <Ben.Brown@...iedtelesis.co.nz>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpiolib: Avoid side effects in gpio_is_visible()

On Wed, May 17, 2023 at 11:54:58AM +0300, Andy Shevchenko wrote:
> On Wed, May 17, 2023 at 2:50 AM Chris Packham
> <Chris.Packham@...iedtelesis.co.nz> wrote:
> > On 17/05/23 10:47, Kent Gibson wrote:
> 
> ...
> 
> > I'm sure both of these applications could be re-written around libgpiod
> > but that would incur a significant amount of regression testing on
> > existing platforms. And I still consider dealing with GPIO chips an
> > extra headache that the applications don't need (particularly with the
> > sheer number of them the SFP case).
> 
> It seems to me that having no in-kernel driver for your stuff is the
> main point of all headache here. But I might be mistaken.
> 

Yeah, that is probably a fair call.
I tend to have GPIO blinkers on and try to solve things from userspace,
but this application is probably moving outside the bounds that the uAPI
(or the much accursed sysfs) is intended for - if you want industrial
grade reliability go in-kernel.

Cheers,
Kent.
ps Sorry if I jumped in on this thread uninvited, but with the TZ
differences involved I thought it useful.