Re: [PATCH v4 8/8] irqchip/al-fic: add irq_set_affinity callback

[Thomas Gleixner <tglx@kernel.org>]

On Thu, Oct 08 2026 at 09:00, Eliav Farber wrote:
> The FIC aggregates up to 32 interrupt sources into a single parent GIC
> SPI and has no per-child affinity control; affinity is determined by the
> parent GIC SPI routing.
>
> irq_set_affinity() fails with -EINVAL when the target irqchip has no
> irq_set_affinity callback, which prevents drivers that call it from
> probing when their interrupt is routed through a FIC instance. Add an
> irq_set_affinity callback that returns IRQ_SET_MASK_OK_DONE
> unconditionally.
>
> Affinity requests cannot be forwarded to the parent GIC SPI, because it
> may be shared by several FIC instances and changing its affinity for one
> child would silently move all the others. A pr_warn_once() is emitted
> when the requested affinity differs from the parent's current affinity,
> giving visibility without failing the caller.

No. That's a horrible hack and just pretends to solve a problem.

We have the interrupt redirection infrastructure to handle that
correctly. See fcc1d0dabd and subsequent commits.

Thanks,

        tglx