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

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Message-ID: <20250506112627.00004a7f.alireza.sanaee@huawei.com>
Date: Tue, 6 May 2025 11:26:27 +0100
From: Alireza Sanaee <alireza.sanaee@...wei.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
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 Sun, 4 May 2025 19:48:11 +0200
Krzysztof Kozlowski <krzk@...nel.org> wrote:

> 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.
Shoot! I guess I know what happened! Will use the script.
> 
> > ---
> >  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.
That's fair, I include documentation for that.
> 
> Best regards,
> Krzysztof
> 
>