linux-kernel - Re: [PATCH v8 2/3] pinctrl: pinctrl-microchip-sgpio: Add pinctrl driver for Microsemi Serial GPIO

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Date:   Mon, 9 Nov 2020 18:15:30 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Lars Povlsen <lars.povlsen@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        devicetree <devicetree@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 2/3] pinctrl: pinctrl-microchip-sgpio: Add pinctrl
 driver for Microsemi Serial GPIO

On Mon, Nov 9, 2020 at 5:27 PM Alexandre Belloni
<alexandre.belloni@...tlin.com> wrote:
> On 09/11/2020 17:16:49+0200, Andy Shevchenko wrote:
> > On Mon, Nov 9, 2020 at 4:32 PM Alexandre Belloni
> > <alexandre.belloni@...tlin.com> wrote:
> > > On 09/11/2020 16:17:40+0200, Andy Shevchenko wrote:

...

> > > > > +               dev_err(pctldev->dev, "Pin %d direction as %s is not possible\n",
> > > > > +                       pin, input ? "input" : "output");
> > > >
> > > > Do we need this noise? Isn't user space getting a proper error code as
> > > > per doc and can handle this?
> > >
> > > Why would userspace get the error code?
> >
> > Huh?! Why it shouldn't. How will users know if they are doing something wrong?
> >
> > > Userspace should never have to
> > > handle gpios directly or you are doing something wrong.
> >
> > This is true, but check how error codes are propagated to the user space.
> >
>
> your point is to remove an error message because the error may be
> propagated to userspace. My point is that userspace should never use
> gpios and the kernel has to be the consumer.

Tell this to plenty of users of old sysfs interface and to libgpiod ones.
If what you are saying had been true, we would have never had the new
ABI for GPIOs.

> I don't see how your answer
> is relevant here.

I have an opposite opinion.

> Did you already check all the call sites from the
> kernel too?

If you think we have to print a message on each possible error case
(but not always the one) we will get lost in the messages disaster and
dmesg overflow.
It is consumer who should decide if the setting is critical or not to
be printed to user.

-- 
With Best Regards,
Andy Shevchenko