linux-kernel - [PATCH 3/5] genirq: Provide an IRQ affinity mask in non-SMP configs

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Date:   Sun,  8 May 2022 22:43:31 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>
Cc:     Samuel Holland <samuel@...lland.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Guo Ren <guoren@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Wei Xu <xuwei5@...ilicon.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: [PATCH 3/5] genirq: Provide an IRQ affinity mask in non-SMP configs

IRQ affinity masks are not allocated in uniprocessor configurations.
This requires special case non-SMP code in drivers for irqchips which
have per-CPU enable or mask registers.

Since IRQ affinity is always the same in a uniprocessor configuration,
we can still provide the correct affinity mask without allocating one
per IRQ. We can reuse the system-wide cpu_possible_mask.

By returning a real cpumask from irq_data_get_affinity_mask even when
SMP is disabled, irqchip drivers which iterate over that mask will
automatically do the right thing.

Signed-off-by: Samuel Holland <samuel@...lland.org>
---

 include/linux/irq.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 48ac33ca3703..d716e882c020 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -151,7 +151,9 @@ struct irq_common_data {
 #endif
 	void			*handler_data;
 	struct msi_desc		*msi_desc;
+#ifdef CONFIG_SMP
 	cpumask_var_t		affinity;
+#endif
 #ifdef CONFIG_GENERIC_IRQ_EFFECTIVE_AFF_MASK
 	cpumask_var_t		effective_affinity;
 #endif
@@ -879,7 +881,11 @@ static inline int irq_data_get_node(struct irq_data *d)
 
 static inline struct cpumask *irq_data_get_affinity_mask(struct irq_data *d)
 {
+#ifdef CONFIG_SMP
 	return d->common->affinity;
+#else
+	return &__cpu_possible_mask;
+#endif
 }
 
 static inline struct cpumask *irq_get_affinity_mask(int irq)
-- 
2.35.1