linux-kernel - [PATCH] genirq: Don't return error on missing optional irq_request

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Date:   Thu, 12 May 2022 18:05:44 +0200
From:   Antonio Borneo <antonio.borneo@...s.st.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, <linux-kernel@...r.kernel.org>
CC:     Antonio Borneo <antonio.borneo@...s.st.com>,
        <linux-stm32@...md-mailman.stormreply.com>
Subject: [PATCH] genirq: Don't return error on missing optional irq_request_resources()

Function irq_chip::irq_request_resources() is reported as optional
in the declaration of struct irq_chip.
If the parent irq_chip does not implement it, we should ignore it
and return.

Don't return error if the functions is missing.

Signed-off-by: Antonio Borneo <antonio.borneo@...s.st.com>
---

As follow-up of discussion in
https://lore.kernel.org/lkml/875ymd6xdu.wl-maz@kernel.org/
here is a proposal for changing the returned value.

A similar issue is present for the optional function
irq_set_vcpu_affinity(), to be covered separately, if needed.

---
 kernel/irq/chip.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 54af0deb239b..eb921485930f 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -1513,7 +1513,8 @@ int irq_chip_request_resources_parent(struct irq_data *data)
 	if (data->chip->irq_request_resources)
 		return data->chip->irq_request_resources(data);

-	return -ENOSYS;
+	/* no error on missing optional irq_chip::irq_request_resources */
+	return 0;
 }
 EXPORT_SYMBOL_GPL(irq_chip_request_resources_parent);

base-commit: c5eb0a61238dd6faf37f58c9ce61c9980aaffd7a
-- 
2.36.0