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Date: Wed, 29 Mar 2017 16:17:38 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Andrey Smirnov <andrew.smirnov@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernel/reboot: add devm_register_reboot_notifier
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On Mon, 20 Mar 2017 10:17:53 -0700 Andrey Smirnov <andrew.smirnov@gmail.com> wrote:

> Add devm_* wrapper around register_reboot_notifier to simplify device
> specific reboot notifier registration/unregistration.
> 
> --- a/kernel/reboot.c
> +++ b/kernel/reboot.c
> @@ -104,6 +104,33 @@ int unregister_reboot_notifier(struct notifier_block *nb)
>  }
>  EXPORT_SYMBOL(unregister_reboot_notifier);
>  
> +static void devm_unregister_reboot_notifier(struct device *dev, void *res)
> +{
> +	WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
> +}
> +
> +int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
> +{
> +	struct notifier_block **rcnb;
> +	int ret;
> +
> +	rcnb = devres_alloc(devm_unregister_reboot_notifier,
> +			    sizeof(*rcnb), GFP_KERNEL);
> +	if (!rcnb)
> +		return -ENOMEM;
> +
> +	ret = register_reboot_notifier(nb);
> +	if (!ret) {
> +		*rcnb = nb;
> +		devres_add(dev, rcnb);
> +	} else {
> +		devres_free(rcnb);
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL(devm_register_reboot_notifier);

Seems reasonable.  Can we please have some patches which actually use
this?