linux-kernel - Re: [RFC 4/4] iio: trigger: add GPIO trigger

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Date:   Sat, 25 Feb 2017 16:21:22 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Fabrice Gasnier <fabrice.gasnier@...com>,
        Lars-Peter Clausen <lars@...afoo.de>, linux@...linux.org.uk,
        robh+dt@...nel.org, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     linux-iio@...r.kernel.org, mark.rutland@....com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com,
        knaack.h@....de, pmeerw@...erw.net, benjamin.gaignard@...aro.org,
        benjamin.gaignard@...com, linus.walleij@...aro.org,
        Gregor Boirie <gregor.boirie@...rot.com>
Subject: Re: [RFC 4/4] iio: trigger: add GPIO trigger

On 20/02/17 16:24, Fabrice Gasnier wrote:
> On 02/18/2017 08:19 PM, Jonathan Cameron wrote:
>> On 17/02/17 16:16, Lars-Peter Clausen wrote:
>>> On 02/17/2017 05:03 PM, Fabrice Gasnier wrote:
>>>> GPIOs can be used to generate triggers for any IIO device.
>>>> Introduce generic GPIO trigger driver. It offers some options
>>>> to tune polarity (e.g. rising/falling edge), and label so trigger
>>>> name may be customized.
>>>> By default, gpio triggers will be named gpiotrigX, where X is gpio
>>>> number as returned by desc_to_gpio() call.
>>>> Rising edge is selected if polarity isn't set.
>>>
>>> If you want to use the GPIO only as an interrupt, just use it as an
>>> interrupt directly, no need to go the route via the GPIO.
>> Absolutely.  The majority of the bindings will then just become standard
>> interrupt bindings and will be effectively handled for you.
>>
>> Please work to extend the existing interrupt trigger driver rather than adding
>> this new one.  That one actually started as a gpio trigger then got
>> generalised into a interrupt trigger later so lets not do that again ;)
> 
> Hi Lars, Jonathan
> 
> Ok, got it.
> I'll drop this and focus on interrupt trigger, if this is worth having DT for it (e.g. patch 1 & 2 of this RFC).
> 
> BTW, I figured out there has been this patch a year ago, on interrupt trigger, to add device tree support:
> http://www.spinics.net/lists/linux-iio/msg23126.html
> Any reason why it hasn't found its way in ?
Gregor being very busy I suspect and not having time to address the reviews.

I 'think' the conclusion then was we needed some representative device that
could exist in devicetree to allow us to specify that a particular interrupt
could be used to trigger sensor capture.

Not a big issue, but probably still needs implementing unless Gregor has had
a chance to look at this.

Jonathan


> 
> Thanks for reviewing,
> Best Regards,
> Fabrice
> 
>>
>> Jonathan
>>
> -- 
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