[RFC v2 PATCH 0/2] Introduce irqchip and VIRQ layer prototypes

[Anup Patel]

On Mon, Feb 2, 2026 at 8:32 PM Raymond Mao <raymondmaoca at gmail.com> wrote:
>
> From: Raymond Mao <raymond.mao at riscstar.com>
>
> This RFC introduces irqchip abstraction and VIRQ layers for APLIC
> wired interrupt support in OpenSBI.
>
> In the current OpenSBI implementation, APLIC support primarily focuses
> on initialization and delegation, while external interrupt handling
> for wired interrupts remains largely stubbed. As a result:
> - There is no generic mechanism for OpenSBI drivers or platforms to
>   register handlers for wired interrupt lines.
> - Interrupt dispatch remains tightly coupled to specific irqchip
>   implementations.
>
> The goal is to introduce a small, extensible abstraction for irqchip
> to hide the HW details and provide abstract operations like interrupt
> provider registration, claim/complete/mask/unmask operations.

We don't need claim() and complete() callbacks instead single eoi()
callback is sufficient because the APLIC driver will have to anyway
read the CLAIM register to get the hardware irq number.

>
> VIRQ (Virtual IRQ) layer is on top of INTC, providing IRQ state
> management via per-(domain,hart) IRQ pending queue, with courier
> dispatching and interface to enqueue/pop/complete an IRQ and map hwirq
> to virtual IRQ number to avoid exposure of hwirq.

Thinking about this more, a separate VIRQ layer will consume
quite a bit of memory for managing the virtual IRQ space.

Instead of a VIRQ layer, each irqchip having its own HWIRQ space
is much more flexible and scalable. I spent past 2 days trying to
come-up with this abstraction which I will post in a few minutes.

I hope this will save time in reviews.

>
> Raymond Mao (2):
>   lib: sbi: introduce abstraction for wired interrupt handling
>   lib: sbi: Add VIRQ interrupt abstraction
>
> Changes in v2:
> - Move INTC to irqchip
> - Move hwirq mapping to VIRQ
> - Remove get_caps and pass in max_src during provider registration
> - All irqchip interface use hwirq as parameter
>
>  include/sbi/sbi_irqchip.h | 52 ++++++++++++++++++++++
>  include/sbi/sbi_virq.h    | 90 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 142 insertions(+)
>  create mode 100644 include/sbi/sbi_virq.h
>
> --
> 2.25.1
>
>
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Regards,
Anup