linux-kernel - Re: [PATCH v2] leds: heartbeat: stop on shutdown

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Message-ID: <1335281074.2347.4.camel@lorien2>
Date:	Tue, 24 Apr 2012 09:24:34 -0600
From:	Shuah Khan <shuahkhan@...il.com>
To:	Alexander Holler <holler@...oftware.de>
Cc:	shuahkhan@...il.com, linux-kernel@...r.kernel.org,
	Richard Purdie <rpurdie@...ys.net>
Subject: Re: [PATCH v2] leds: heartbeat: stop on shutdown

On Tue, 2012-04-24 at 17:07 +0200, Alexander Holler wrote:
> A halted kernel should not show a heartbeat.
> 
> Signed-off-by: Alexander Holler <holler@...oftware.de>
> ---
>  drivers/leds/ledtrig-heartbeat.c |   18 +++++++++++++++++-
>  1 files changed, 17 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/leds/ledtrig-heartbeat.c b/drivers/leds/ledtrig-heartbeat.c
> index 759c0bb..1c05bd9 100644
> --- a/drivers/leds/ledtrig-heartbeat.c
> +++ b/drivers/leds/ledtrig-heartbeat.c
> @@ -18,6 +18,7 @@
>  #include <linux/timer.h>
>  #include <linux/sched.h>
>  #include <linux/leds.h>
> +#include <linux/reboot.h>
>  #include "leds.h"
>  
>  struct heartbeat_trig_data {
> @@ -101,13 +102,28 @@ static struct led_trigger heartbeat_led_trigger = {
>  	.deactivate = heartbeat_trig_deactivate,
>  };
>  
> +static int heartbeat_reboot_notifier(struct notifier_block *nb,
> +				     unsigned long code, void *unused)
> +{
> +	led_trigger_unregister(&heartbeat_led_trigger);
> +	return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block heartbeat_reboot_nb = {
> +	.notifier_call = heartbeat_reboot_notifier,
> +};
> +
>  static int __init heartbeat_trig_init(void)
>  {
> -	return led_trigger_register(&heartbeat_led_trigger);
> +	int rc = led_trigger_register(&heartbeat_led_trigger);
> +	if( ! rc )
> +		register_reboot_notifier(&heartbeat_reboot_nb);

Do you need to check return value here? I see return value being checked
in some places in the kernel and not in others. Not checking is fine for
now since register_reboot_notifier() always returns 0. 

Maybe adding return handling might not be a bad idea to be consistent
with other places that do check.

FYI - Andrew Morton is handling led patches these days. You might want
to send include him  <akpm@...ux-foundation.org>

> +	return rc;
>  }
>  
>  static void __exit heartbeat_trig_exit(void)
>  {
> +	unregister_reboot_notifier(&heartbeat_reboot_nb);
>  	led_trigger_unregister(&heartbeat_led_trigger);
>  }
>  


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