[PATCH] kernel/reboot: add devm_register_reboot_notifier

[PATCH] kernel/reboot: add devm_register_reboot_notifier

[Andrey Smirnov]

Add devm_* wrapper around register_reboot_notifier to simplify device
specific reboot notifier registration/unregistration.

Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
---
 include/linux/reboot.h |  3 +++
 kernel/reboot.c        | 27 +++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/linux/reboot.h b/include/linux/reboot.h
index a7ff409..0ca2541 100644
--- a/include/linux/reboot.h
+++ b/include/linux/reboot.h
@@ -38,6 +38,9 @@ extern int reboot_force;
 extern int register_reboot_notifier(struct notifier_block *);
 extern int unregister_reboot_notifier(struct notifier_block *);
 
+struct device;
+extern int devm_register_reboot_notifier(struct device *, struct notifier_block *);
+
 extern int register_restart_handler(struct notifier_block *);
 extern int unregister_restart_handler(struct notifier_block *);
 extern void do_kernel_restart(char *cmd);
diff --git a/kernel/reboot.c b/kernel/reboot.c
index bd30a97..e4ced88 100644
--- 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);
+
 /*
  *	Notifier list for kernel code which wants to be called
  *	to restart the system.
-- 
2.9.3

Re: [PATCH] kernel/reboot: add devm_register_reboot_notifier

[Andrew Morton]

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?

Re: [PATCH] kernel/reboot: add devm_register_reboot_notifier

[Andrey Smirnov]

On Wed, Mar 29, 2017 at 4:17 PM, Andrew Morton
<akpm@linux-foundation.org> wrote:
> 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?

I will be submitting a serdev/watchdog driver in next couple of weeks,
I can CC you on that thread.

Thanks,
Andrey Smirnov

Re: [PATCH] kernel/reboot: add devm_register_reboot_notifier

[Andrew Morton]

On Thu, 30 Mar 2017 15:55:43 -0700 Andrey Smirnov <andrew.smirnov@gmail.com> wrote:

> On Wed, Mar 29, 2017 at 4:17 PM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
> > 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?
> 
> I will be submitting a serdev/watchdog driver in next couple of weeks,
> I can CC you on that thread.

It would be nice to convert some other call sites as well, please - at
least to get additional test coverage and to demonstrate the usefulness
of the new interface.