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 17:22:08 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Andy Shevchenko <andy.shevchenko@...il.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 09/11/2020 18:15:30+0200, Andy Shevchenko wrote:
> > > > 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.

Exactly, that is what I'm telling to them.

> 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.
> 

This is the valid reason and as you can see, it has nothing to do with
userspace.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com