linux-kernel - Re: [PATCH v2] driver: platform: Support parsing GpioInt 0 in platform_get

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Date:   Sun, 24 Feb 2019 20:34:45 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Enrico Granata <egranata@...omium.org>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Dmitry Torokhov <dtor@...omium.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Gwendal Grignou <gwendal@...omium.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Brian Norris <briannorris@...omium.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Enrico Granata <egranata@...gle.com>
Subject: Re: [PATCH v2] driver: platform: Support parsing GpioInt 0 in platform_get_irq()

On Mon, Feb 11, 2019 at 8:01 PM <egranata@...omium.org> wrote:
>
> From: Enrico Granata <egranata@...omium.org>
>
> ACPI 5 added support for GpioInt resources as a way to provide
> information about interrupts mediated via a GPIO controller.
>
> Several device buses (e.g. SPI, I2C) have support for retrieving
> an IRQ specified via this type of resource, and providing it
> directly to the driver as an IRQ number.
>
> This is not currently done for the platform drivers, as platform_get_irq()
> does not try to parse GpioInt() resources. This requires drivers to
> either have to support only one possible IRQ resource, or to have code
> in place to try both as a failsafe.
>
> While there is a possibility of ambiguity for devices that exposes
> multiple IRQs, it is easy and feasible to support the common case
> of devices that only expose one IRQ which would be of either type
> depending on the underlying system's architecture.
>
> This commit adds support for parsing a GpioInt resource in order
> to fulfill a request for the index 0 IRQ for a platform device.
>
> Signed-off-by: Enrico Granata <egranata@...omium.org>

Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

> ---
> Changes in v2:
>  - only support IRQ index 0
>
>  drivers/base/platform.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/platform.c b/drivers/base/platform.c
> index 1c958eb33ef4d..0d3611cd1b3bc 100644
> --- a/drivers/base/platform.c
> +++ b/drivers/base/platform.c
> @@ -127,7 +127,20 @@ int platform_get_irq(struct platform_device *dev, unsigned int num)
>                 irqd_set_trigger_type(irqd, r->flags & IORESOURCE_BITS);
>         }
>
> -       return r ? r->start : -ENXIO;
> +       if (r)
> +               return r->start;
> +
> +       /*
> +        * For the index 0 interrupt, allow falling back to GpioInt
> +        * resources. While a device could have both Interrupt and GpioInt
> +        * resources, making this fallback ambiguous, in many common cases
> +        * the device will only expose one IRQ, and this fallback
> +        * allows a common code path across either kind of resource.
> +        */
> +       if (num == 0 && has_acpi_companion(&dev->dev))
> +               return acpi_dev_gpio_irq_get(ACPI_COMPANION(&dev->dev), num);
> +
> +       return -ENXIO;
>  #endif
>  }
>  EXPORT_SYMBOL_GPL(platform_get_irq);
> --
> 2.20.1.791.gb4d0f1c61a-goog
>