linux-kernel - Re: uses of irq_to_gpio() in drivers/staging/iio

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Date:	Tue, 02 Aug 2011 18:03:45 +0100
From:	Jonathan Cameron <jic23@....ac.uk>
To:	Ben Dooks <bjdooks@...glemail.com>
CC:	linux-iio@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: uses of irq_to_gpio() in drivers/staging/iio

On 08/02/11 17:43, Ben Dooks wrote:
> Whilst looking in drivers/staging/iio/accel/lis3l02dq_core.c, I
> came across the following lines of code
> 
>    708          if (spi->irq && gpio_is_valid(irq_to_gpio(spi->irq)) > 0) {
>    709                  ret = request_threaded_irq(st->us->irq,
>    710                                             &lis3l02dq_th,
>    711 &lis3l02dq_event_handler,
>    712                                             IRQF_TRIGGER_RISING,
>    713                                             "lis3l02dq",
>    714                                             indio_dev);
> 
> Which gives rise to the following questions:
> 
> 1) IRQ0 and GPIO0 are often valid numbers for GPIOs.
Good point - should fix that one.  Any suggestions for a neat way
to do it?
> 
> 2) Not all interrupts are necessarily GPIO interrupts. What happens
>    if the device is attached to a hardware interrupt line which is
>    not a GPIO?
> 
Easy. It doesn't work.  Stupid hardware doesn't necessarily drop
the interrupt line on a read. Hence it sticks high. If one only has
edge triggered interrupt lines that's a pain. Is there an easy way
around this?  When I wrote the relevant code a long time ago I couldn't
get anything else to work.

There may well be a better way but I haven't revisited this recently.
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