linux-kernel - Re: [PATCH 3/3] irq/irq_sim: implement irq_sim

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Message-ID: <CAMRc=MfTrrg3_WUoabZxrQZr4aM_UOGvmoGrqR3yFmPmhNB-6Q@mail.gmail.com>
Date:   Wed, 18 Oct 2017 14:49:07 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] irq/irq_sim: implement irq_sim_irq2offset()

2017-10-18 12:13 GMT+02:00 Marc Zyngier <marc.zyngier@....com>:
>

[snip!]

> It looks to me that this is all because the irq_sim creation is a bit awkward.
> You end-up with all kind of exotic interfaces because you don't know the base
> of the irq range at creation time.
>
> How about something like this:
>
> diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
> index 24caabf1a0f7..484c3544c0d1 100644
> --- a/kernel/irq/irq_sim.c
> +++ b/kernel/irq/irq_sim.c
> @@ -49,7 +49,8 @@ static void irq_sim_handle_irq(struct irq_work *work)
>   * @sim:        The interrupt simulator object to initialize.
>   * @num_irqs:   Number of interrupts to allocate
>   *
> - * Returns 0 on success and a negative error number on failure.
> + * Returns the interrupt base on success and a negative error number
> + * on failure.
>   */
>  int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
>  {
> @@ -78,7 +79,7 @@ int irq_sim_init(struct irq_sim *sim, unsigned int num_irqs)
>         init_irq_work(&sim->work_ctx.work, irq_sim_handle_irq);
>         sim->irq_count = num_irqs;
>
> -       return 0;
> +       return sim->irq_base;
>  }
>  EXPORT_SYMBOL_GPL(irq_sim_init);
>
> You can then deal with the offset directly in your driver, as you're
> guaranteed a 1:1 mapping.
>

This is what we have now in next for iio. The thing is we want to get
rid of irq_base from the iio driver and store it (and relevant logic)
in irq_sim to have less code in the caller. Otherwise we duplicate
this info.

Thanks,
Bartosz