linux-kernel - [PATCH] ata: sata_dwc_460ex: Check !irq instead of irq == NO

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Date:   Thu, 10 Nov 2022 19:50:33 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Damien Le Moal <damien.lemoal@...nsource.wdc.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Subject: [PATCH] ata: sata_dwc_460ex: Check !irq instead of irq == 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.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 drivers/ata/sata_dwc_460ex.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index e3263e961045..5fb80ccde65b 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -242,7 +242,7 @@ static int sata_dwc_dma_init_old(struct platform_device *pdev,

 	/* Get SATA DMA interrupt number */
 	hsdev->dma->irq = irq_of_parse_and_map(np, 1);
-	if (hsdev->dma->irq == NO_IRQ) {
+	if (!hsdev->dma->irq) {
 		dev_err(dev, "no SATA DMA irq\n");
 		return -ENODEV;
 	}
@@ -1180,7 +1180,7 @@ static int sata_dwc_probe(struct platform_device *ofdev)

 	/* Get SATA interrupt number */
 	irq = irq_of_parse_and_map(np, 0);
-	if (irq == NO_IRQ) {
+	if (!irq) {
 		dev_err(dev, "no SATA DMA irq\n");
 		return -ENODEV;
 	}
-- 
2.37.1