Re: [PATCH v2] leds: heartbeat: stop on shutdown

Shuah Khan
2012-04-24T15:24:37Z

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@ahsoftware.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@linux-foundation.org>

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