linux-kernel - Re: [PATCH v4 8/8] gpiolib: notify user-space about in-kernel line state changes

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Message-ID: <CAMRc=McjCinBEFNoHSTyFH7zU=JuyRfu1cfrOxkq=OjciKQkvQ@mail.gmail.com>
Date: Thu, 17 Oct 2024 16:14:24 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Kent Gibson <warthog618@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4 8/8] gpiolib: notify user-space about in-kernel line
 state changes

On Thu, Oct 17, 2024 at 2:53 PM Kent Gibson <warthog618@...il.com> wrote:
>
> On Thu, Oct 17, 2024 at 10:14:16AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > @@ -1447,8 +1450,6 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
> >               }
> >
> >               WRITE_ONCE(line->edflags, edflags);
> > -
> > -             gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
> >       }
> >       return 0;
> >  }
>
> I still get errors from this when reconfiguring lines with debounce.
> You should leave this notify in place and use _nonotify when setting the
> direction.
> i.e.
>
> @@ -1436,11 +1432,11 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
>                         int val = gpio_v2_line_config_output_value(&lc, i);
>
>                         edge_detector_stop(line);
> -                       ret = gpiod_direction_output(desc, val);
> +                       ret = gpiod_direction_output_nonotify(desc, val);
>                         if (ret)
>                                 return ret;
>                 } else {
> -                       ret = gpiod_direction_input(desc);
> +                       ret = gpiod_direction_input_nonotify(desc);
>                         if (ret)
>                                 return ret;
>
> @@ -1450,6 +1446,8 @@ static long linereq_set_config(struct linereq *lr, void __user *ip)
>                 }
>
>                 WRITE_ONCE(line->edflags, edflags);
> +
> +               gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
>         }
>         return 0;
>  }
>
> Given that, all my current tests are passing.
>

That looks good - after all we no longer notify from any place in
gpiolib-cdev.c anymore - but I'd like to learn what's wrong exactly.
Are you getting more events with debounce? Are you not getting any?

Bart