linux-kernel - Re: [PATCH v2 1/6] of: add infra for finding CPU id from phandle

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Message-ID: <20250504-eminent-sepia-cuscus-fc7f7e@kuoka>
Date: Sun, 4 May 2025 19:48:11 +0200
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Alireza Sanaee <alireza.sanaee@...wei.com>
Cc: devicetree@...r.kernel.org, robh@...nel.org, 
	jonathan.cameron@...wei.com, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linuxarm@...wei.com, mark.rutland@....com, 
	shameerali.kolothum.thodi@...wei.com
Subject: Re: [PATCH v2 1/6] of: add infra for finding CPU id from phandle

On Fri, May 02, 2025 at 05:12:55PM GMT, Alireza Sanaee wrote:
> Get CPU id from phandle. Many drivers get do this by getting hold of CPU
> node first through a phandle and then find the CPU ID using the relevant
> function. This commit encapsulates cpu node finding and improves
> readability.
> 
> The API interface requires two parameters, 1) node, 2) pointer to CPU
> node. API sets the pointer to the CPU node and allows the driver to play
> with the CPU itself, for logging purposes for instance.

Run checkpatch - missing SoB.

> ---
>  drivers/of/cpu.c   | 24 ++++++++++++++++++++++++
>  include/linux/of.h |  8 ++++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/of/cpu.c b/drivers/of/cpu.c
> index 5214dc3d05ae..1e8d1fa04d3c 100644
> --- a/drivers/of/cpu.c
> +++ b/drivers/of/cpu.c
> @@ -173,6 +173,30 @@ int of_cpu_node_to_id(struct device_node *cpu_node)
>  }
>  EXPORT_SYMBOL(of_cpu_node_to_id);
>  
> +/**
> + * of_cpu_phandle_to_id: Get the logical CPU number for a given device_node
> + *
> + * @node: Pointer to the device_node containing CPU phandle.
> + * @cpu_np: Pointer to the device_node for CPU.
> + *
> + * Return: The logical CPU number of the given CPU device_node or -ENODEV if
> + * the CPU is not found. If the property is not found, it returns -1. On
> + * success, cpu_np will always point to the retrieved CPU device_node.
> + */
> +int of_cpu_phandle_to_id(const struct device_node *node,
> +			 struct device_node **cpu_np)
> +{
> +	if (!node)
> +		return -1;
> +
> +	*cpu_np = of_parse_phandle(node, "cpu", 0);
> +	if (!cpu_np)
> +		return -ENODEV;
> +
> +	return of_cpu_node_to_id(*cpu_np);

You leak the node... or intention was to return it to the caller, but
then you need to document that caller must drop the ref.

Best regards,
Krzysztof