# Re: \[PATCH RFC 2/3\] genirq: Honor existing IRQ affinities when setting affinity hints

- From: Jakub Kicinski \<kuba@kernel.org\>
- Date: 2026-08-20 16:42:10 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/08/17440382
- Thread: https://ratatoskr.run/netdev/2026/08/17434340/t.md

```text
On Wed, 19 Aug 2026 16:30:31 +0200 Florian Bezdeka wrote:
> Some device drivers implement an IRQ balancing / spreading mechanism
> based on cpumask_local_spread() and irq_set_affinity_hint() (deprecated)
> or irq_set_affinity_and_hint().

Not an expert on IRQs, but this may make the API even more confusing.
irq_set_affinity_and_hint() not setting the affinity seems odd.

I'd go the other way and either have irq_update_affinity_hint() apply
the affinity if it's safe to do so, or create a new function for
"defaults".

Really, the drivers are dumb here, they are just trying to pass to 
the core a hint which is: This is Nth of X IRQs, please spread them on
the NUMA node where the device is attached. Ideally this (Nth of X)
should even be part of request_irq() args. IRQ core already knows the
device/NUMA node. Drivers juggling multiple flavors of uAPI-shaped API
is... not very scalable. People rarely get this right.
```