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Subject: Re: [PATCH] iio: dummy: evgen: use irq_sim
To: Bartosz Golaszewski <brgl@bgdev.pl>
Cc: Jonathan Cameron <jic23@kernel.org>, Hartmut Knaack <knaack.h@gmx.de>,
        Peter Meerwald-Stadler <pmeerw@pmeerw.net>, linux-iio@vger.kernel.org,
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References: <20170926164910.31137-1-brgl@bgdev.pl>
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 <CAMRc=Mc26u0n6tCXajnK3vhJ6N4acGgZp2atS0otGLZNSNhxpA@mail.gmail.com>
From: Lars-Peter Clausen <lars@metafoo.de>
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Date: Thu, 28 Sep 2017 10:04:03 +0200
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On 09/27/2017 09:23 PM, Bartosz Golaszewski wrote:
>>>               return ret;
>>> -     }
>>> -     iio_evgen->chip.name = iio_evgen_name;
>>> -     iio_evgen->chip.irq_mask = &iio_dummy_event_irqmask;
>>> -     iio_evgen->chip.irq_unmask = &iio_dummy_event_irqunmask;
>>> -     for (i = 0; i < IIO_EVENTGEN_NO; i++) {
>>> -             irq_set_chip(iio_evgen->base + i, &iio_evgen->chip);
>>> -             irq_set_handler(iio_evgen->base + i, &handle_simple_irq);
>>> -             irq_modify_status(iio_evgen->base + i,
>>> -                               IRQ_NOREQUEST | IRQ_NOAUTOEN,
>>> -                               IRQ_NOPROBE);
>>> -     }
>>> -     init_irq_work(&iio_evgen->handler.work, iio_dummy_work_handler);
>>> +
>>> +     iio_evgen->base = irq_sim_irqnum(&iio_evgen->irq_sim, 0);
>> I saw you introduced irq_sim_baseirq(), to get rid of ->base. But as far as
>> I can see the only remaining places where we need the base is to do the
>> reverse lookup from IRQ to index. It would be nice if the irq_sim had a
>> function for that, then we wouldn't have to know about the base at all.
>>
> 
> I'm not sure I understand. Irq sim doesn't know anything about iio
> data structures, so how would such a reverse lookup work in this case?

Reverse lookup in the sense of translating IRQ number to offset. All we ever
do with the base in the IIO code is `irq - base` to get the offset. I'd hide
that calculation in a helper in the irq_sim code. This nicely splits
functionality and implementation, the IIO code doesn't have to know how to
get offset from the IRQ.