linux-kernel - [PATCH] powerpc: Check !irq instead of irq == NO_IRQ and remove NO

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Date:   Mon, 23 Jan 2023 13:26:46 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc: Check !irq instead of irq == NO_IRQ and remove NO_IRQ

NO_IRQ is a relic from the old days. It is not used anymore in core
functions. By the way, function irq_of_parse_and_map() returns value 0
on error.

In some drivers, NO_IRQ is erroneously used to check the return of
irq_of_parse_and_map().

It is not a real bug today because the only architectures using the
drivers being fixed by this patch define NO_IRQ as 0, but there are
architectures which define NO_IRQ as -1. If one day those
architectures start using the non fixed drivers, there will be a
problem.

Long time ago Linus advocated for not using NO_IRQ, see
https://lkml.org/lkml/2005/11/21/221 . He re-iterated the same view
recently in https://lkml.org/lkml/2022/10/12/622

So test !irq instead of tesing irq == NO_IRQ.

All other usage of NO_IRQ for powerpc were remove in previous cycle
so time has come to remove NO_IRQ completely for powerpc.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/irq.h    | 3 ---
 arch/powerpc/platforms/44x/fsp2.c | 2 +-
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/irq.h b/arch/powerpc/include/asm/irq.h
index 5c1516a5ba8f..deadd2149426 100644
--- a/arch/powerpc/include/asm/irq.h
+++ b/arch/powerpc/include/asm/irq.h
@@ -16,9 +16,6 @@

 extern atomic_t ppc_n_lost_interrupts;

-/* This number is used when no interrupt has been assigned */
-#define NO_IRQ			(0)
-
 /* Total number of virq in the platform */
 #define NR_IRQS		CONFIG_NR_IRQS

diff --git a/arch/powerpc/platforms/44x/fsp2.c b/arch/powerpc/platforms/44x/fsp2.c
index e2e4f6d8150d..56d91dbef577 100644
--- a/arch/powerpc/platforms/44x/fsp2.c
+++ b/arch/powerpc/platforms/44x/fsp2.c
@@ -205,7 +205,7 @@ static void __init node_irq_request(const char *compat, irq_handler_t errirq_han

 	for_each_compatible_node(np, NULL, compat) {
 		irq = irq_of_parse_and_map(np, 0);
-		if (irq == NO_IRQ) {
+		if (!irq) {
 			pr_err("device tree node %pOFn is missing a interrupt",
 			      np);
 			of_node_put(np);
-- 
2.38.1