linux-kernel - Re: [PATCH v3 12/16] pinctrl: starfive: Add pinctrl driver for StarFive SoCs

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Message-ID: <YYKZJiv4SMQxrx7R@smile.fi.intel.com>
Date:   Wed, 3 Nov 2021 16:13:58 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Emil Renner Berthing <kernel@...il.dk>
Cc:     linux-riscv <linux-riscv@...ts.infradead.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "open list:SERIAL DRIVERS" <linux-serial@...r.kernel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Maximilian Luz <luzmaximilian@...il.com>,
        Sagar Kadam <sagar.kadam@...ive.com>,
        Drew Fustini <drew@...gleboard.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Michael Zhu <michael.zhu@...rfivetech.com>,
        Fu Wei <tekkamanninja@...il.com>,
        Anup Patel <anup.patel@....com>,
        Atish Patra <atish.patra@....com>,
        Matteo Croce <mcroce@...rosoft.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Huan Feng <huan.feng@...rfivetech.com>
Subject: Re: [PATCH v3 12/16] pinctrl: starfive: Add pinctrl driver for
 StarFive SoCs

On Wed, Nov 03, 2021 at 01:35:23PM +0100, Emil Renner Berthing wrote:
> On Wed, 3 Nov 2021 at 10:13, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > On Tue, Nov 2, 2021 at 10:35 PM Emil Renner Berthing <kernel@...il.dk> wrote:
> > > On Tue, 2 Nov 2021 at 21:02, Andy Shevchenko <andy.shevchenko@...il.com> wrote:
> > > > On Tue, Nov 2, 2021 at 6:50 PM Emil Renner Berthing <kernel@...il.dk> wrote:

...

> > > > > +               irq_set_handler_locked(d, handle_bad_irq);
> > > >
> > > > Why? You have it already in ->probe(), what's the point?
> > >
> > > So last time you asked about this, I explained a situation where
> > > userspace first grabs a GPIO, set the interrupt to edge triggered, and
> > > then later loads a driver that requests an unsupported IRQ type.
> >
> > I didn't get this scenario. Is it real?
> 
> No, it's totally made up, but I mean we even have tools like fuzzing
> to help us find bugs that would never happen in real use cases.
> 
> > > Then
> > > I'd like to set the handler back to handle_bad_irq so we don't get
> > > weird interrupts, but maybe now you know a reason why that doesn't
> > > matter or can't happen?
> >
> > In ->probe() you set _default_ handler to bad(), what do you mean by
> > 'set the handler back to bad()'? How is it otherwise if you free an
> > interrupt?
> 
> It might not be, but when not sure I thought it better to error on the
> safe side.

With a dead code?

I do not believe there is an issue since. like I said, there are plenty drivers
that don't do what you are suggesting here --> 99.99% you added a dead code.

> > So, please elaborate with call traces what the scenario / use case you
> > are talking about. If it's true what you are saying, we have a
> > situation (plenty of GPIO drivers don't do what you are suggesting
> > here).

-- 
With Best Regards,
Andy Shevchenko