linux-kernel - Re: [PATCH v3 7/9] driver core: Correct parameter check for API device_for_each_child_reverse

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Message-ID: <20241216152310.0000166a@huawei.com>
Date: Mon, 16 Dec 2024 15:23:10 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Zijun Hu <zijun_hu@...oud.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
	<rafael@...nel.org>, Tejun Heo <tj@...nel.org>, Josef Bacik
	<josef@...icpanda.com>, Jens Axboe <axboe@...nel.dk>, Boris Burkov
	<boris@....io>, Davidlohr Bueso <dave@...olabs.net>, Dave Jiang
	<dave.jiang@...el.com>, Alison Schofield <alison.schofield@...el.com>, Vishal
 Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>, Dan
 Williams <dan.j.williams@...el.com>, <linux-kernel@...r.kernel.org>,
	<cgroups@...r.kernel.org>, <linux-block@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, Zijun Hu <quic_zijuhu@...cinc.com>
Subject: Re: [PATCH v3 7/9] driver core: Correct parameter check for API
 device_for_each_child_reverse_from()

On Thu, 12 Dec 2024 21:38:43 +0800
Zijun Hu <zijun_hu@...oud.com> wrote:

> From: Zijun Hu <quic_zijuhu@...cinc.com>
> 
> device_for_each_child_reverse_from() checks (!parent->p) for its
> parameter @parent, and that is not consistent with other APIs of
> its cluster as shown below:
> 
> device_for_each_child_reverse_from() // check (!parent->p)
> device_for_each_child_reverse()      // check (!parent || !parent->p)
> device_for_each_child()              // same above
> device_find_child()                  // same above
> 
> Correct the API's parameter @parent check by (!parent || !parent->p).
> 
> Signed-off-by: Zijun Hu <quic_zijuhu@...cinc.com>
Given that 'from' implies continuation of an iteration I can see why
it might not ever be relevant to check parent.  It's harmless, but to
my mind unnecessary.

Jonathan

> ---
>  drivers/base/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index 69bb6bf4bd12395226ee3c99e2f63d15c7e342a5..34fb13f914b3db47e6a047fdabf3c9b18ecc08cc 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -4050,7 +4050,7 @@ int device_for_each_child_reverse_from(struct device *parent,
>  	struct device *child;
>  	int error = 0;
>  
> -	if (!parent->p)
> +	if (!parent || !parent->p)
>  		return 0;
>  
>  	klist_iter_init_node(&parent->p->klist_children, &i,
>