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From:   Christophe Leroy <christophe.leroy@csgroup.eu>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc:     Christophe Leroy <christophe.leroy@csgroup.eu>,
        linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org
Subject: [PATCH v2] ata: sata_dwc_460ex: Check !irq instead of irq == NO_IRQ
Date:   Fri, 11 Nov 2022 09:30:46 +0100
Message-Id: <146506d93c96b842422d31a90b5d23c98b70a111.1668155425.git.christophe.leroy@csgroup.eu>
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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.

And remove the fallback definition of NO_IRQ at the top of the file.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v2: Also removed the #ifndef NO_IRQ #define NO_IRQ 0 at the top
---
 drivers/ata/sata_dwc_460ex.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c
index e3263e961045..7b7e1516dbdd 100644
--- a/drivers/ata/sata_dwc_460ex.c
+++ b/drivers/ata/sata_dwc_460ex.c
@@ -42,10 +42,6 @@
 #define sata_dwc_writel(a, v)	writel_relaxed(v, a)
 #define sata_dwc_readl(a)	readl_relaxed(a)
 
-#ifndef NO_IRQ
-#define NO_IRQ		0
-#endif
-
 #define AHB_DMA_BRST_DFLT	64	/* 16 data items burst length */
 
 enum {
@@ -242,7 +238,7 @@ 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 +1176,7 @@ 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