Re: [PATCH v3 1/5] iio: proximity: sx9500: Assign interrupt from GpioIo()

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 6 Nov 2017 11:35:56 +0200
Mika Westerberg <mika.westerberg@linux.intel.com> wrote:

> On Sat, Nov 04, 2017 at 03:11:19AM +0000, Jonathan Cameron wrote:
> > On Fri, 3 Nov 2017 15:03:36 +0200
> > Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
> >   
> > > The commit 0f0796509c07
> > > 
> > > ("iio: remove gpio interrupt probing from drivers that use a single
> > > interrupt")
> > > 
> > > removed custom IRQ assignment for the drivers which are enumerated via
> > > ACPI or OF. Unfortunately, some ACPI tables have IRQ line defined as
> > > GpioIo() resource and thus automatic IRQ allocation will fail.  
> > 
> > I'll ask the obvious question - is this allowed under the ACPI spec?  
> 
> Yes, it is perfectly fine.

I'm unconvinced...

> 
> > > Partially revert the commit 0f0796509c07 to restore original
> > > behaviour.
> > > 
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>  
> > 
> > I really don't like scattering fixes for broken ACPI tables through
> > drivers...  Is there really no better solution to this?  
> 
> This is not about broken ACPI tables. We just currently have
> "convenience" stuff in the kernel that translates trivial things like a
> single ACPI GpioInt() resource directly to a device interrupt. If the
> table has multiple GpioInt()s or uses GpioIo() then it is up to the
> driver to handle device specific details.

I agree on the multiple cases needing hanlding. 
What bothers me is that there is no guarantee at all that a GpioIo
can even do an interrupt.

(table 6.2.17 in the 6.1 spec for example makes it clear that we are
in a mess)  If it is a gpioio lots of the interrupt specific stuff
cannot be supplied (all the stuff in byte 7)

So as I read the ACPI specification any interrupt specified as GpioIO
is simply broken.

> 
> > On patches like this best to pull in ACPI and GPIO on the cc list.
> > 
> > Also cc'd Mika who made the original change to support gpioint.  
> 
> The patch looks fine to me,
> 
> Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>

I'll probably take it anyway to support the platforms doing this particular
piece of fun as doubtlessly the chance of fixing the firmware is next
to nothing...

Jonathan
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