linux-kernel - Re: [PATCH v5 1/7] irq/irq_sim: add irq_set

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Date:   Tue, 19 Feb 2019 16:33:49 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v5 1/7] irq/irq_sim: add irq_set_type() callback

wt., 19 lut 2019 o 14:40 Marc Zyngier <marc.zyngier@....com> napisał(a):
>
> On Tue, 19 Feb 2019 14:20:03 +0100
> Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> > wt., 19 lut 2019 o 13:25 Marc Zyngier <marc.zyngier@....com> napisał(a):
> > >
> > > On Mon, 18 Feb 2019 17:41:32 +0100
> > > Bartosz Golaszewski <brgl@...ev.pl> wrote:
> > >
> > > > From: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > > >
> > > > Implement the irq_set_type() callback and call irqd_set_trigger_type()
> > > > internally so that users interested in the configured trigger type can
> > > > later retrieve it using irqd_get_trigger_type().
> > > >
> > > > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > > > ---
> > > >  kernel/irq/irq_sim.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
> > > > index 98a20e1594ce..83ecc65d8be2 100644
> > > > --- a/kernel/irq/irq_sim.c
> > > > +++ b/kernel/irq/irq_sim.c
> > > > @@ -25,10 +25,18 @@ static void irq_sim_irqunmask(struct irq_data *data)
> > > >       irq_ctx->enabled = true;
> > > >  }
> > > >
> > > > +static int irq_sim_set_type(struct irq_data *data, unsigned int type)
> > > > +{
> > > > +     irqd_set_trigger_type(data, type);
> > > > +
> > > > +     return 0;
> > >
> > > You keep ignoring the requirement for sanitization of the trigger type.
> > > Frankly, I'm getting tired of fighting over 3 lines of incorrect code.
> > >
> >
> > It used to be there in previous versions, but I removed it on purpose
> > in v5. I understand why we needed that earlier, but if we now moved
> > *all* the logic behind the trigger type to the users of this API and
> > we're now simply storing any config we get, then why would we impose
> > any limits on it here? We don't do this now and this patch doesn't
> > change the current behavior. I really don't understand how not
> > rejecting certain trigger types makes this patch incorrect.
>
> You expose a new set_type callback. Only a set of valid values can be
> handled by the users of this interface. At least your mockup gpio only
> handles a narrow set of configuration. Not rejecting erroneous values
> is a bug. This isn't a new requirement; this is how the irqchip API
> works, as drivers do expect such a failure if requiring an invalid
> type.
>
> > > I guess that despite all the noise, you don't really want this code in
> > > after all.
> > >
> >
> > I do want and need this, but I really can't figure out from your
> > reviews how you imagine the correct solution. You said previously that
> > the irq_set_type callback should push the configuration to wherever
> > it's needed.
>
> Yes. But it doesn't mean it should accept something that cannot be
> handled by the irqchip. If you push it to the code that does the
> handling, it still has to return an error if the backing code decides
> that this is not a supported configuration.
>
> At the end of the day, where you store it is irrelevant for the problem
> at hand. There is an API, and you need to implement it correctly.
>
> > I believe the above patch does this. Should we then limit
> > the supported trigger types? That would mean that irq_sim would need
> > to know what users support. It seems inverted to me, but if you think
> > it's right, then my question is: will accepting only IRQ_TYPE_NONE,
> > IRQ_TYPE_EDGE_RISING and IRQ_TYPE_EDGE_FALLING in the above function
> > be enough for you to accept it? Is the rest fine?
>
> IRQ_TYPE_NONE doesn't mean anything, apart from "whatever defaults were
> there because I have no clue". In your case, I really don't see the
> point. The EDGE settings are what you handle, and are the only values
> that should be accepted.
>

Right, irq_set_type() isn't even called if there's no trigger set.

> As for the rest of the patches, I haven't looked at them, and probably
> won't (if only because I'm on holiday and would like to do something
> else...). All I'm asking from you is to give me a correct patch #1.
> Once I see that, I'll gladly ack it.
>

Thanks,
Bartosz