linux-kernel - Re: [PATCH 02/25] ACPI: irq: Add IRQ affinity reporting interface

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Message-ID: <CAJZ5v0hSJ6yMnfZgYDSZRqL_KMLc6f4kcY06dWGSPCFYjdcbfg@mail.gmail.com>
Date: Mon, 8 Sep 2025 19:20:15 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Marc Zyngier <maz@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
	linux-acpi@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, 
	Mark Rutland <mark.rutland@....com>, Will Deacon <will@...nel.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Rob Herring <robh@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Sven Peter <sven@...nel.org>, Janne Grunau <j@...nau.net>, 
	Suzuki K Poulose <suzuki.poulose@....com>, James Clark <james.clark@...aro.org>
Subject: Re: [PATCH 02/25] ACPI: irq: Add IRQ affinity reporting interface

On Mon, Sep 8, 2025 at 6:31 PM Marc Zyngier <maz@...nel.org> wrote:
>
> Plug the irq_populate_fwspec_info() helper into the ACPI layer
> to offer an IRQ affinity reporting function. This is currently
> only supported for the CONFIG_ACPI_GENERIC_GSI configurations,
> but could later be extended to legacy architectures if necessary.
>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/acpi/irq.c   | 15 +++++++++++++++
>  include/linux/acpi.h |  7 +++++++
>  2 files changed, 22 insertions(+)
>
> diff --git a/drivers/acpi/irq.c b/drivers/acpi/irq.c
> index 76a856c32c4d0..22f93fe23ddce 100644
> --- a/drivers/acpi/irq.c
> +++ b/drivers/acpi/irq.c
> @@ -300,6 +300,21 @@ int acpi_irq_get(acpi_handle handle, unsigned int index, struct resource *res)
>  }
>  EXPORT_SYMBOL_GPL(acpi_irq_get);
>
> +const struct cpumask *acpi_irq_get_affinity(acpi_handle handle,
> +                                           unsigned int index)
> +{
> +       struct irq_fwspec_info info;
> +       unsigned long flags;
> +
> +       if (!acpi_irq_parse_one(handle, index, &info.fwspec, &flags)) {
> +               if (!irq_populate_fwspec_info(&info) &&
> +                   info.flags & IRQ_FWSPEC_INFO_AFFINITY_VALID)
> +                       return info.affinity;
> +       }

I would prefer fewer logical negations to be used in this, for instance:

if (acpi_irq_parse_one(handle, index, &info.fwspec, &flags))
      return NULL;

if (irq_populate_fwspec_info(&info))
       return NULL;

if (info.flags & IRQ_FWSPEC_INFO_AFFINITY_VALID)
       return info.affinity;

return NULL;

> +
> +       return NULL;
> +}
> +
>  /**
>   * acpi_set_irq_model - Setup the GSI irqdomain information
>   * @model: the value assigned to acpi_irq_model
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 1c5bb1e887cd1..c506ae4bacc86 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -1509,12 +1509,19 @@ static inline int acpi_parse_spcr(bool enable_earlycon, bool enable_console)
>
>  #if IS_ENABLED(CONFIG_ACPI_GENERIC_GSI)
>  int acpi_irq_get(acpi_handle handle, unsigned int index, struct resource *res);
> +const struct cpumask *acpi_irq_get_affinity(acpi_handle handle,
> +                                           unsigned int index);
>  #else
>  static inline
>  int acpi_irq_get(acpi_handle handle, unsigned int index, struct resource *res)
>  {
>         return -EINVAL;
>  }
> +static inline const struct cpumask *acpi_irq_get_affinity(acpi_handle handle,
> +                                                         unsigned int index)
> +{
> +       return NULL;
> +}
>  #endif
>
>  #ifdef CONFIG_ACPI_LPIT
> --