linux-kernel - Re: [PATCH v3] iio: mma8452: support either of the available interrupt pins

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Date:	Thu, 15 Oct 2015 11:14:45 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Martin Kepplinger <martink@...teo.de>
Cc:	Lars-Peter Clausen <lars@...afoo.de>, robh+dt@...nel.org,
	pawel.moll@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, jic23@...nel.org, knaack.h@....de,
	pmeerw@...erw.net, mfuzzey@...keon.com, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	Martin Kepplinger <martin.kepplinger@...obroma-systems.com>
Subject: Re: [PATCH v3] iio: mma8452: support either of the available
 interrupt pins

On Thu, Oct 15, 2015 at 11:32:59AM +0200, Martin Kepplinger wrote:
> Am 2015-10-14 um 17:12 schrieb Lars-Peter Clausen:
> > On 10/14/2015 03:15 PM, Martin Kepplinger wrote:
> > [...]
> >> +			if (irq1 > 0)
> >> +				client->irq = irq1;
> > 
> > You must not overwrite client->irq, that field is manged by the I2C core and
> > is supposed to be read only for device drivers.
> >
> 
> I thought about it again and before I implement it, let me show you:
> 
> since interrupt-names would be "invented" anyways ("INT1", "INT2"),
> here's an idea for the bindings doc that would be a more long-term
> solution to implement:
> 
>   - interrupts: interrupt mapping for GPIO IRQ
> 
>         These devices have two interrupt pins called INT1 and INT2 they
>         can route their different interrupt sources to:

This being the case, the binding should only talk about INT1 and INT2.
The names might be "invented", but they describe the physical pins on
the device, and thus describe a physical property of the device.

>         IRQ Name        Interrupt Source        Wired Pin
>         --------        ----------------        ---------
>         DATA_READY_1    data ready              INT1
>         DATA_READY_2                            INT2
>         MOTION_1        motion events           INT1
>         MOTION_2                                INT2
>         INT1            all                     INT1
>         INT2                                    INT2
> 
>   - interrupt-names: should contain IRQ Names in the order in which they
>                      were supplied in the interrupts property.
> 
>                      Depending on how your chip is wired and what
>                      interrupt sources should be handled by the driver,
>                      choose one IRQ Name per Interrupt source, or
>                      INT1/INT2 for all sources to one pin here.

The configuration of logical interrupts to those physical pins is a
choice that can be made at runtime, and should not live in the DT. It is
not a property of the hardware.

Thanks,
Mark.
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