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

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Emil Renner Berthing <kernel@esmil.dk>
Cc: linux-riscv <linux-riscv@lists.infradead.org>,
	devicetree <devicetree@vger.kernel.org>,
	linux-clk <linux-clk@vger.kernel.org>,
	"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
	"open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Rob Herring <robh+dt@kernel.org>,
	Michael Turquette <mturquette@baylibre.com>,
	Stephen Boyd <sboyd@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Marc Zyngier <maz@kernel.org>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Jiri Slaby <jirislaby@kernel.org>,
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	Drew Fustini <drew@beagleboard.org>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Michael Zhu <michael.zhu@starfivetech.com>,
	Fu Wei <tekkamanninja@gmail.com>, Anup Patel <anup.patel@wdc.com>,
	Atish Patra <atish.patra@wdc.com>,
	Matteo Croce <mcroce@microsoft.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Huan Feng <huan.feng@starfivetech.com>
Subject: Re: [PATCH v3 12/16] pinctrl: starfive: Add pinctrl driver for StarFive SoCs
Date: Wed, 3 Nov 2021 16:13:58 +0200	[thread overview]
Message-ID: <YYKZJiv4SMQxrx7R@smile.fi.intel.com> (raw)
In-Reply-To: <CANBLGczTnf1UrRt=d-czaG-CE=Rwb1x6MV4c97ia+P3u5Mt8Jg@mail.gmail.com>

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@gmail.com> wrote:
> > On Tue, Nov 2, 2021 at 10:35 PM Emil Renner Berthing <kernel@esmil.dk> wrote:
> > > On Tue, 2 Nov 2021 at 21:02, Andy Shevchenko <andy.shevchenko@gmail.com> wrote:
> > > > On Tue, Nov 2, 2021 at 6:50 PM Emil Renner Berthing <kernel@esmil.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