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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Mon, 25 Sep 2023 16:24:20 +0200
Message-ID: <CAMRc=McuKNg5r7m6OPtwYc3er7i6JB2JN=H6QVJU_G9BVtnuAA@mail.gmail.com>
Subject: Re: [PATCH] gpiolib: extend the critical sections of lookup tables
To:     Linus Walleij <linus.walleij@linaro.org>
Cc:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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On Wed, Sep 20, 2023 at 2:51=E2=80=AFPM Bartosz Golaszewski <brgl@bgdev.pl>=
 wrote:
>
> On Wed, 20 Sep 2023 12:58:58 +0200, Linus Walleij <linus.walleij@linaro.o=
rg> said:
> > On Wed, Sep 20, 2023 at 11:33=E2=80=AFAM Bartosz Golaszewski <brgl@bgde=
v.pl> wrote:
> >> On Wed, 20 Sep 2023 11:12:58 +0200, Linus Walleij
> >> <linus.walleij@linaro.org> said:
> >> > On Wed, Sep 20, 2023 at 10:56=E2=80=AFAM Bartosz Golaszewski <brgl@b=
gdev.pl> wrote:
> >
> >> > Can we rename this function gpiod_find_lookup_table_locked()
> >> > as per precedents in the kernel, to indicate that it needs to be
> >> > called with a lock held?
> >> >
> >>
> >> I think you mean gpiod_find_lookup_table_unlocked() as with this chang=
e it
> >> will no longer take the lock?
> >
> > I think the pattern is the one I indicated: *_locked() means the functi=
on
> > is to be called with the appropriate lock held, cf
> > arch/arm64/kvm/hyp/nvhe/mm.c
> >
> > pkvm_create_mappings() takes a lock and then calls
> > pkvm_create_mappings_locked() which even asserts that
> > the lock is held.
> >
>
> Ha! I always though the pattern is to call the functions that *DON'T* tak=
e
> the lock _unlocked(). This is what I used in gpiolib-cdev.c or gpio-sim.c=
.
>
> I guess both conventions make sense in some way.
>
> Bart

I don't think I will be doing it just now. We don't use this
convention elsewhere in drivers/gpio/ and we'll have a lot of locking
reworked soon anyway. We may get to it when that is done.

Bart