linux-kernel - Re: [PATCH v3] dmaengine: moxart: handle irq_of_parse_and

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Message-Id: <68f613a0-64c8-4c3c-915c-ce6e76eee317@app.fastmail.com>
Date: Sun, 18 Aug 2024 14:27:56 +0200
From: "Arnd Bergmann" <arnd@...db.de>
To: "Ma Ke" <make24@...as.ac.cn>, "Vinod Koul" <vkoul@...nel.org>,
 "Andrew Morton" <akpm@...ux-foundation.org>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v3] dmaengine: moxart: handle irq_of_parse_and_map() errors

On Sun, Aug 18, 2024, at 09:17, Ma Ke wrote:
> Zero and negative number is not a valid IRQ for in-kernel code and the
> irq_of_parse_and_map() function returns zero on error.  So this check for
> valid IRQs should only accept values > 0.
>
> Cc: stable@...r.kernel.org
> Fixes: 2d9e31b9412c ("dmaengine: moxart: remove NO_IRQ")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>
> ---

This makes no sense to me, you explain why the current code is
correct and then change it to something wrong?

> diff --git a/drivers/dma/moxart-dma.c b/drivers/dma/moxart-dma.c
> index 66dc6d31b603..16dd3c5aba4d 100644
> --- a/drivers/dma/moxart-dma.c
> +++ b/drivers/dma/moxart-dma.c
> @@ -568,7 +568,7 @@ static int moxart_probe(struct platform_device *pdev)
>  		return -ENOMEM;
> 
>  	irq = irq_of_parse_and_map(node, 0);
> -	if (!irq) {
> +	if (irq <= 0) {
>  		dev_err(dev, "no IRQ resource\n");
>  		return -EINVAL;

The "if (!irq)" is clearly the intended check, as you explain
irq_of_parse_and_map() returns 0 on error.

      Arnd