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

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Date:   Fri, 11 Nov 2022 17:18:18 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Christophe Leroy <christophe.leroy@...roup.eu>
Cc:     linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org
Subject: Re: [PATCH] ata: sata_dwc_460ex: Check !irq instead of irq == NO_IRQ

On 11/11/22 03:50, Christophe Leroy wrote:
> 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;
>  	}

You can also remove the:

#ifndef NO_IRQ

#define NO_IRQ          0

#endif

at the top of the file.

-- 
Damien Le Moal
Western Digital Research