linux-kernel - Re: [PATCH v2 4/5] iio: trigger: add support for STM32 EXTI triggers

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Date:   Sat, 4 Feb 2017 21:03:14 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Fabrice Gasnier <fabrice.gasnier@...com>,
        Russell King <linux@...linux.org.uk>,
        Rob Herring <robh+dt@...nel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald <pmeerw@...erw.net>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v2 4/5] iio: trigger: add support for STM32 EXTI triggers

On Sat, Feb 4, 2017 at 12:39 PM, Jonathan Cameron <jic23@...nel.org> wrote:
> On 03/02/17 19:40, Linus Walleij wrote:

>>> +               if (ret) {
>>> +                       dev_err(&pdev->dev, "request IRQ %d failed\n", irq);
>>> +                       return ret;
>>> +               }
>>
>> Here you need some elaborate trigger edge handling.
>>
>> The flags that you define as "0" here, how do we say that we
>> want to handle rising or falling edges, for example?
>>
>> I think you might want to establish these DT properties for
>> GPIO triggers:
>>
>> gpio-trigger-rising-edge;
>> gpio-trigger-falling-edge;
>>
>> Then:
>>
>> int irq_flags = 0;
>>
>> if (of_property_read_bool(np, "gpio-trigger-rising-edge")
>>    irq_flags |= IRQF_TRIGGER_RISING;
>> else if (of_property_read_bool(np, "gpio-trigger-falling-edge")
>>    irq_flags |= IRQF_TRIGGER_FALLING;
>
> Should this not all be part of the interrupt specification rather
> than down here in the specific driver?

I might be thinking a bit too generic here actually.

I was thinking we need to support something that has
gpio-controller; so a consumer can get a GPIO line reference
but would not also be an interrupt-controller; so it can't
serve interrupts through the device tree bindings but
may still do so from the driver using gpiolibs .to_irq().

So the specifier would need to come in someplace else.

But I think that is maybe not at all realistic.

If there is an interrupt trigger, that can be used with
a gpio-controller that is also an interrupt-controller,
that should be fine, and then we can use the standard
DT bindings to specify the interrupt type.

Yours,
Linus Walleij