linux-kernel - Re: [PATCH next] perf: arm-ni: Fix an NULL vs IS

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Message-ID: <948daae7-8d94-4d44-93e7-1764f6500be6@arm.com>
Date: Wed, 11 Sep 2024 13:13:44 +0100
From: Robin Murphy <robin.murphy@....com>
To: Dan Carpenter <dan.carpenter@...aro.org>
Cc: Will Deacon <will@...nel.org>, Mark Rutland <mark.rutland@....com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 kernel-janitors@...r.kernel.org
Subject: Re: [PATCH next] perf: arm-ni: Fix an NULL vs IS_ERR() bug

On 2024-09-11 8:39 am, Dan Carpenter wrote:
> The devm_ioremap() function never returns error pointers, it returns a
> NULL pointer if there is an error.

Ah, this code went through a few evolutions, and apparently I missed 
that devm_ioremap() and devm_ioremap_resource() helpfully have different 
behaviour, urgh. Thanks Dan!

Reviewed-by: Robin Murphy <robin.murphy@....com>

> Fixes: 4d5a7680f2b4 ("perf: Add driver for Arm NI-700 interconnect PMU")
> Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> ---
>   drivers/perf/arm-ni.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/arm-ni.c b/drivers/perf/arm-ni.c
> index b72df3aea93e..90fcfe693439 100644
> --- a/drivers/perf/arm-ni.c
> +++ b/drivers/perf/arm-ni.c
> @@ -603,8 +603,8 @@ static int arm_ni_probe(struct platform_device *pdev)
>   	 */
>   	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>   	base = devm_ioremap(&pdev->dev, res->start, resource_size(res));
> -	if (IS_ERR(base))
> -		return PTR_ERR(base);
> +	if (!base)
> +		return -ENOMEM;
>   
>   	arm_ni_probe_domain(base, &cfg);
>   	if (cfg.type != NI_GLOBAL)