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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Tue, 12 Feb 2019 11:37:45 +0100
Message-ID: <CAMpxmJWyxhjWrUVCePeg=g6uA=LEEbVBHGXTMQJ95jav4Zhyvg@mail.gmail.com>
Subject: Re: [PATCH v2 3/9] irq/irq_sim: provide irq_sim_fire_type()
To:     Marc Zyngier <marc.zyngier@arm.com>
Cc:     Bartosz Golaszewski <brgl@bgdev.pl>,
        Linus Walleij <linus.walleij@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>,
        linux-gpio <linux-gpio@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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wt., 12 lut 2019 o 11:27 Marc Zyngier <marc.zyngier@arm.com> napisa=C5=82(a=
):
>
> On 12/02/2019 09:19, Bartosz Golaszewski wrote:
> > wt., 12 lut 2019 o 10:10 Marc Zyngier <marc.zyngier@arm.com> napisa=C5=
=82(a):
> >>
> >> On 29/01/2019 08:44, Bartosz Golaszewski wrote:
> >>> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >>>
> >>> Provide a more specialized variant of irq_sim_fire() that allows to
> >>> specify the type of the fired interrupt. The type is stored in the
> >>> dummy irq context struct via the set_type callback.
> >>>
> >>> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >>> ---
> >>>  include/linux/irq_sim.h |  9 ++++++++-
> >>>  kernel/irq/irq_sim.c    | 26 ++++++++++++++++++++++----
> >>>  2 files changed, 30 insertions(+), 5 deletions(-)
> >>>
> >>> diff --git a/include/linux/irq_sim.h b/include/linux/irq_sim.h
> >>> index b96c2f752320..647a6c8ffb31 100644
> >>> --- a/include/linux/irq_sim.h
> >>> +++ b/include/linux/irq_sim.h
> >>> @@ -23,6 +23,7 @@ struct irq_sim_work_ctx {
> >>>
> >>>  struct irq_sim_irq_ctx {
> >>>       bool                    enabled;
> >>> +     unsigned int            type;
> >>>  };
> >>>
> >>>  struct irq_sim {
> >>> @@ -37,7 +38,13 @@ int irq_sim_init(struct irq_sim *sim, unsigned int=
 num_irqs);
> >>>  int devm_irq_sim_init(struct device *dev, struct irq_sim *sim,
> >>>                     unsigned int num_irqs);
> >>>  void irq_sim_fini(struct irq_sim *sim);
> >>> -void irq_sim_fire(struct irq_sim *sim, unsigned int offset);
> >>> +void irq_sim_fire_type(struct irq_sim *sim,
> >>> +                    unsigned int offset, unsigned int type);
> >>>  int irq_sim_irqnum(struct irq_sim *sim, unsigned int offset);
> >>>
> >>> +static inline void irq_sim_fire(struct irq_sim *sim, unsigned int of=
fset)
> >>> +{
> >>> +     irq_sim_fire_type(sim, offset, IRQ_TYPE_DEFAULT);
> >>> +}
> >>> +
> >>>  #endif /* _LINUX_IRQ_SIM_H */
> >>> diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
> >>> index 2bcdbab1bc5a..e3160b5e59b8 100644
> >>> --- a/kernel/irq/irq_sim.c
> >>> +++ b/kernel/irq/irq_sim.c
> >>> @@ -25,6 +25,15 @@ static void irq_sim_irqunmask(struct irq_data *dat=
a)
> >>>       irq_ctx->enabled =3D true;
> >>>  }
> >>>
> >>> +static int irq_sim_set_type(struct irq_data *data, unsigned int type=
)
> >>> +{
> >>> +     struct irq_sim_irq_ctx *irq_ctx =3D irq_data_get_irq_chip_data(=
data);
> >>> +
> >>> +     irq_ctx->type =3D type;
> >>> +
> >>> +     return 0;
> >>> +}
> >>> +
> >>>  static void irq_sim_handle_irq(struct irq_work *work)
> >>>  {
> >>>       struct irq_sim_work_ctx *work_ctx;
> >>> @@ -107,6 +116,7 @@ int irq_sim_init(struct irq_sim *sim, unsigned in=
t num_irqs)
> >>>       sim->chip.name =3D "irq_sim";
> >>>       sim->chip.irq_mask =3D irq_sim_irqmask;
> >>>       sim->chip.irq_unmask =3D irq_sim_irqunmask;
> >>> +     sim->chip.irq_set_type =3D irq_sim_set_type;
> >>>
> >>>       sim->work_ctx.pending =3D bitmap_zalloc(num_irqs, GFP_KERNEL);
> >>>       if (!sim->work_ctx.pending) {
> >>> @@ -192,21 +202,29 @@ irq_sim_get_ctx(struct irq_sim *sim, unsigned i=
nt offset)
> >>>  }
> >>>
> >>>  /**
> >>> - * irq_sim_fire - Enqueue an interrupt.
> >>> + * irq_sim_fire_type - Enqueue an interrupt.
> >>>   *
> >>>   * @sim:        The interrupt simulator object.
> >>>   * @offset:     Offset of the simulated interrupt which should be fi=
red.
> >>> + * @type:    Type of the fired interrupt. Must be one of the followi=
ng:
> >>> + *           IRQ_TYPE_EDGE_RISING, IRQ_TYPE_EDGE_FALLING,
> >>> + *           IRQ_TYPE_EDGE_BOTH, IRQ_TYPE_LEVEL_HIGH,
> >>> + *           IRQ_TYPE_LEVEL_LOW, IRQ_TYPE_DEFAULT
> >>>   */
> >>> -void irq_sim_fire(struct irq_sim *sim, unsigned int offset)
> >>> +void irq_sim_fire_type(struct irq_sim *sim,
> >>> +                    unsigned int offset, unsigned int type)
> >>>  {
> >>>       struct irq_sim_irq_ctx *ctx =3D irq_sim_get_ctx(sim, offset);
> >>>
> >>> -     if (ctx->enabled) {
> >>> +     /* Only care about relevant flags. */
> >>> +     type &=3D IRQ_TYPE_SENSE_MASK;
> >>> +
> >>> +     if (ctx->enabled && (ctx->type & type)) {
> >>
> >> I wonder how realistic this is, given that you do not track the releas=
e
> >> of a level. In short, mo matter what the type is, you treat everything
> >> as edge.
> >>
> >> What is the point of this?
> >>
> >
> > When userspace wants to monitor GPIO line interrupts, the GPIO
> > framework requests a threaded interrupt with IRQF_TRIGGER_FALLING,
> > IRQF_TRIGGER_RISING or both. The testing module tries to act like real
> > hardware and so if we pass only one of the *_TRIGGER_* flags, we want
> > the simulated interrupt of corresponding type to be fired.
>
> Well, that's not how HW works.
>
> >
> > Another solution - if you don't like this one -  would be to have more
> > specialized functions: irq_sim_fire_rising() and
> > irq_sim_fire_falling(). How about that?
>
> I think you're missing the point. So far, your API has been "an
> interrupt has fired", no matter what the trigger is, and that's fine.
> That's just modeling the output of an abstract interrupt controller into
> whatever the irqsim is simulating.
>
> Now, what you're exposing is "this is how the line changed". Which is an
> entirely different business, as you're now exposing the device output
> line. Yes, you can model it with raising/falling, but you need at least
> resampling for level interrupts, and actual edge detection (raising
> followed by raising only generates a single interrupt, while
> raising-falling-raising generates two).
>

This logic is later taken care of in the gpio-mockup driver in this
series. It checks the line state changes and decides if the interrupt
should be fired.

Bart

> At the moment, I don't see any of that so I seriously doubt the validity
> of the approach.
>