linux-kernel - Re: [PATCH] driver core: Remove double assignment

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Date:   Tue, 29 Sep 2020 14:25:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     poeschel@...onage.de
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] driver core: Remove double assignment

On Tue, Sep 29, 2020 at 01:58:08PM +0200, poeschel@...onage.de wrote:
> From: Lars Poeschel <poeschel@...onage.de>
> 
> This removes an assignment in device_add. It assigned the parent
> kobject to the kobject of the  new device. This is not necessary,
> because the call to kobject_add a few lines later also does this same
> assignment.
> 
> Signed-off-by: Lars Poeschel <poeschel@...onage.de>
> ---
>  drivers/base/core.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/base/core.c b/drivers/base/core.c
> index bb5806a2bd4c..03b5396cd192 100644
> --- a/drivers/base/core.c
> +++ b/drivers/base/core.c
> @@ -2847,8 +2847,6 @@ int device_add(struct device *dev)
>  		error = PTR_ERR(kobj);
>  		goto parent_error;
>  	}
> -	if (kobj)
> -		dev->kobj.parent = kobj;
>  
>  	/* use parent numa_node */
>  	if (parent && (dev_to_node(dev) == NUMA_NO_NODE))
> @@ -2856,7 +2854,7 @@ int device_add(struct device *dev)
>  
>  	/* first, register with generic layer. */
>  	/* we require the name to be set before, and pass NULL */
> -	error = kobject_add(&dev->kobj, dev->kobj.parent, NULL);
> +	error = kobject_add(&dev->kobj, kobj, NULL);

That's very subtle, and might not really be correct for all users, have
you checked?

Anyway, I'd rather leave this as-is if possible, as we know this works
correctly, and it is not going to save any time/energy to remove that
assignment, right?

thanks,

greg k-h