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From:   Bartosz Golaszewski <brgl@bgdev.pl>
Date:   Fri, 3 Dec 2021 15:58:13 +0100
Message-ID: <CAMRc=Mdw1pEUntRkJRYcuQH9ZhWc9=psPDe7bXwkj=RCYQKO=g@mail.gmail.com>
Subject: Re: [PATCH resend] gpio: aggregator: Add interrupt support
To:     Geert Uytterhoeven <geert+renesas@glider.be>
Cc:     Linus Walleij <linus.walleij@linaro.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Enrico Weigelt metux IT consult <info@metux.net>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Arnd Bergmann <arnd@kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
        Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        virtualization@lists.linux-foundation.org,
        stratos-dev@op-lists.linaro.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, Dec 3, 2021 at 3:56 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
>
> On Fri, Dec 3, 2021 at 3:06 PM Geert Uytterhoeven
> <geert+renesas@glider.be> wrote:
> >
> > Currently the GPIO Aggregator does not support interrupts.  This means
> > that kernel drivers going from a GPIO to an IRQ using gpiod_to_irq(),
> > and userspace applications using line events do not work.
> >
> > Add interrupt support by providing a gpio_chip.to_irq() callback, which
> > just calls into the parent GPIO controller.
> >
> > Note that this does not implement full interrupt controller (irq_chip)
> > support, so using e.g. gpio-keys with "interrupts" instead of "gpios"
> > still does not work.
> >
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
> > ---
> > I would prefer to avoid implementing irq_chip support, until there is a
> > real use case for this.
> >
> > This has been tested with gpio-keys and gpiomon on the Koelsch
> > development board:
> >
> >   - gpio-keys, using a DT overlay[1]:
> >
> >         $ overlay add r8a7791-koelsch-keyboard-controlled-led
> >         $ echo gpio-aggregator > /sys/devices/platform/frobnicator/driver_override
> >         $ echo frobnicator > /sys/bus/platform/drivers/gpio-aggregator/bind
> >
> >         $ gpioinfo frobnicator
> >         gpiochip12 - 3 lines:
> >                 line   0:      "light"      "light"  output  active-high [used]
> >                 line   1:         "on"         "On"   input   active-low [used]
> >                 line   2:        "off"        "Off"   input   active-low [used]
> >
> >         $ echo 255 > /sys/class/leds/light/brightness
> >         $ echo 0 > /sys/class/leds/light/brightness
> >
> >         $ evtest /dev/input/event0
> >
> >   - gpiomon, using the GPIO sysfs API:
> >
> >         $ echo keyboard > /sys/bus/platform/drivers/gpio-keys/unbind
> >         $ echo e6055800.gpio 2,6 > /sys/bus/platform/drivers/gpio-aggregator/new_device
> >         $ gpiomon gpiochip12 0 1
> >
> > [1] "ARM: dts: koelsch: Add overlay for keyboard-controlled LED"
> >     https://git.kernel.org/pub/scm/linux/kernel/git/geert/renesas-drivers.git/commit/?h=topic/renesas-overlays&id=c78d817869e63a3485bb4ab98aeea6ce368a396e
> > ---
> >  drivers/gpio/gpio-aggregator.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/gpio-aggregator.c b/drivers/gpio/gpio-aggregator.c
> > index e9671d1660ef4b40..869dc952cf45218b 100644
> > --- a/drivers/gpio/gpio-aggregator.c
> > +++ b/drivers/gpio/gpio-aggregator.c
> > @@ -371,6 +371,13 @@ static int gpio_fwd_set_config(struct gpio_chip *chip, unsigned int offset,
> >         return gpiod_set_config(fwd->descs[offset], config);
> >  }
> >
> > +static int gpio_fwd_to_irq(struct gpio_chip *chip, unsigned int offset)
> > +{
> > +       struct gpiochip_fwd *fwd = gpiochip_get_data(chip);
> > +
> > +       return gpiod_to_irq(fwd->descs[offset]);
> > +}
> > +
> >  /**
> >   * gpiochip_fwd_create() - Create a new GPIO forwarder
> >   * @dev: Parent device pointer
> > @@ -411,7 +418,8 @@ static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
> >         for (i = 0; i < ngpios; i++) {
> >                 struct gpio_chip *parent = gpiod_to_chip(descs[i]);
> >
> > -               dev_dbg(dev, "%u => gpio-%d\n", i, desc_to_gpio(descs[i]));
> > +               dev_dbg(dev, "%u => gpio %d irq %d\n", i,
> > +                       desc_to_gpio(descs[i]), gpiod_to_irq(descs[i]));
> >
> >                 if (gpiod_cansleep(descs[i]))
> >                         chip->can_sleep = true;
> > @@ -429,6 +437,7 @@ static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
> >         chip->get_multiple = gpio_fwd_get_multiple_locked;
> >         chip->set = gpio_fwd_set;
> >         chip->set_multiple = gpio_fwd_set_multiple_locked;
> > +       chip->to_irq = gpio_fwd_to_irq;
> >         chip->base = -1;
> >         chip->ngpio = ngpios;
> >         fwd->descs = descs;
> > --
> > 2.25.1
> >
>
> Applied, thanks!
>
> Bart

Eek, missed the explanation.

I think this is fine. For user-space eventual switch to a real
irq_chip won't break anything so let's take it.

Bart