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Subject[PATCH 09/12] irqdomain: Reserve IRQs for legacy domain
It is really important to make sure irqs used by the legacy domain are
still reserved in the irq_desc subsystem so they don't get allocated
for some other purpose. Without SPARSE_IRQ, this generally isn't a
problem because it is assumed that all irqs have static assignments
(which isn't actually true, and is part of the reason why SPARSE_IRQ
should really be turned on these days). However, when SPARSE_IRQs is
turned on, the irq range passed to irq_domain_add_legacy() is not
guaranteed to be reserved.

This patch fixes the problem by unconditionally reserving any irqs
passed into irq_domain_add_legacy(). The irqs may have already been
reserved, so the return code on irq_reserve_irqs() may report a
failure, but it should still be safe.

Signed-off-by: Grant Likely <>
kernel/irq/irqdomain.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index d6d0de0..c0a00de 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -151,6 +151,13 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
if (!domain)
return NULL;

+ /*
+ * Do our best to reserve the irq descs; but this overlaps with the nr_irqs setting
+ * from the platform code
+ */
+ if (irq_reserve_irqs(first_irq, size))
+ pr_info("IRQs %i..%i already reserved, overlapping with nr_irqs?\n",
+ first_irq, first_irq + size - 1);
WARN_ON(irq_domain_associate_many(domain, first_irq, first_hwirq, size));

return domain;

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