linux-kernel - Re: [PATCH v2 1/2] device property: Add fwnode_irq_get

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Date:   Wed, 10 Nov 2021 22:34:43 +0530
From:   Puranjay Mohan <puranjay12@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, rafael@...nel.org,
        heikki.krogerus@...ux.intel.com, kuba@...nel.org,
        saravanak@...gle.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        linux-iio <linux-iio@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] device property: Add fwnode_irq_get_byname()

On Wed, Nov 10, 2021 at 2:23 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Wed, Nov 10, 2021 at 01:38:39AM +0530, Puranjay Mohan wrote:
> > The fwnode framework did not have means to obtain the IRQ number from
> > the name of a node.
> > Add that now, in form of the fwnode_irq_get_byname() function.
>
> ...
>
> > +int fwnode_irq_get_byname(struct fwnode_handle *fwnode, const char *name)
> > +{
> > +     int index;
> > +
> > +     if (unlikely(!name))
> > +             return -EINVAL;
>
> > +     index = fwnode_property_match_string(fwnode, "interrupt-names", name);
> > +     if (index < 0)
> > +             return index;
>
> It won't work like this. The ACPI table quite likely won't have this in them.
> Also it doesn't cover the GPIO interrupts in ACPI case.
>
> > +     return fwnode_irq_get(fwnode, index);
>
> Neither this covers GPIO IRQs.
>
> > +}
> > +EXPORT_SYMBOL(fwnode_irq_get_byname);
>
> So, first you need to provide a design for this how ACPI cases can be handled.
>
> Imagine these cases (at least) for _CRS method in ACPI:
>   1/ Single GSI
>
>         Interrupt()
>
>   2/ Single GPIO IRQ
>
>         GpioInt()
>
>   3/ Both in different orders
>     a)
>         Interrupt()
>         GpioInt()
>
>     b)
>         GpioInt()
>         Interrupt()
>
>   4/ Mixed (complicated cases)
>
>         Interrupt()
>         Interrupt()
>         GpioInt()
>         Interrupt()
>         GpioInt()
>
> Obvious question, what does the index mean in all these cases?
>
> Next one is, how can we quirk out the platforms with the old ACPI tables
> where no properties are provided? For GPIO there is struct acpi_gpio_params
> which goes deep into ACPI glue layer.
>
> Luckily, the GPIO IRQ case has already available APIs for indexing and naming
> match: acpi_dev_gpio_irq_get_by().
>
> Hence, the main task is to define index in cases like 4 and see what can be
> done for the GSI cases.
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Hi Andy,
I wrote this function keeping the device tree in mind. I will have to
look into ACPI and see how the cases you mentioned can be implemented.
Let's see how far I can get with understanding the ACPI.

-- 
Thanks and Regards

Yours Truly,

Puranjay Mohan