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Message-id: <57230B26.9010300@samsung.com>
Date: Fri, 29 Apr 2016 09:20:06 +0200
From: Jacek Anaszewski <j.anaszewski@...sung.com>
To: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc: linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
Richard Purdie <rpurdie@...ys.net>,
Kumar Gala <galak@...eaurora.org>,
Ian Campbell <ijc+devicetree@...lion.org.uk>,
Mark Rutland <mark.rutland@....com>,
Pawel Moll <pawel.moll@....com>,
Rob Herring <robh+dt@...nel.org>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v3 1/3] leds: triggers: Allow to switch the trigger to
"panic" on a kernel panic
Hi Ezequiel,
Thanks for the update. It's indeed reasonable to have all the
switching infrastructure in ledtrig-panic.c.
I've noticed two minor issues below.
On 04/29/2016 12:03 AM, Ezequiel Garcia wrote:
> This commit adds a new led_cdev flag LED_PANIC_INDICATOR, which
> allows to mark a specific LED to be switched to the "panic"
> trigger, on a kernel panic.
>
> This is useful to allow the user to assign a regular trigger
> to a given LED, and still blink that LED on a kernel panic.
>
> Signed-off-by: Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
> ---
> drivers/leds/led-triggers.c | 2 +-
> drivers/leds/leds.h | 1 +
> drivers/leds/trigger/Kconfig | 3 +++
> drivers/leds/trigger/ledtrig-panic.c | 47 ++++++++++++++++++++++++++++++++++++
> include/linux/leds.h | 1 +
> 5 files changed, 53 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 2181581795d3..55fa65e1ae03 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -26,7 +26,7 @@
> * Nests outside led_cdev->trigger_lock
> */
> static DECLARE_RWSEM(triggers_list_lock);
> -static LIST_HEAD(trigger_list);
> +LIST_HEAD(trigger_list);
>
> /* Used by LED Class */
>
> diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
> index db3f20da7221..7d38e6b9a740 100644
> --- a/drivers/leds/leds.h
> +++ b/drivers/leds/leds.h
> @@ -30,5 +30,6 @@ void led_set_brightness_nosleep(struct led_classdev *led_cdev,
>
> extern struct rw_semaphore leds_list_lock;
> extern struct list_head leds_list;
> +extern struct list_head trigger_list;
>
> #endif /* __LEDS_H_INCLUDED */
> diff --git a/drivers/leds/trigger/Kconfig b/drivers/leds/trigger/Kconfig
> index beac8c31c51b..4e4521c9072a 100644
> --- a/drivers/leds/trigger/Kconfig
> +++ b/drivers/leds/trigger/Kconfig
> @@ -121,6 +121,9 @@ config LEDS_TRIGGER_PANIC
> depends on LEDS_TRIGGERS
> help
> This allows LEDs to be configured to blink on a kernel panic.
> + Enabling this option will allow to mark certain LEDs as 'panic-indicators',
s/"panic-indicators"/panic indicators/
I understand that you referred here to the DT property name, but this
is not obvious at first glance, and it is an implementation detail.
> + allowing to blink them on a kernel panic, even if they are set to
> + a different trigger.
> If unsure, say Y.
>
> endif # LEDS_TRIGGERS
> diff --git a/drivers/leds/trigger/ b/drivers/leds/trigger/ledtrig-panic.c
> index 627b350c5ec3..3e447bd2064a 100644
> --- a/drivers/leds/trigger/ledtrig-panic.c
> +++ b/drivers/leds/trigger/ledtrig-panic.c
> @@ -11,10 +11,54 @@
>
> #include <linux/kernel.h>
> #include <linux/init.h>
> +#include <linux/notifier.h>
> #include <linux/leds.h>
> +#include "../leds.h"
>
> static struct led_trigger *trigger;
>
> +/*
> + * This is a called in a special context by the atomic panic
s/is a/is/
> + * notifier. This means the trigger can be changed without
> + * worrying about locking.
> + */
> +static void led_trigger_set_panic(struct led_classdev *led_cdev)
> +{
> + struct led_trigger *trig;
> +
> + list_for_each_entry(trig, &trigger_list, next_trig) {
> + if (strcmp("panic", trig->name))
> + continue;
> + if (led_cdev->trigger)
> + list_del(&led_cdev->trig_list);
> + list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
> +
> + /* Avoid the delayed blink path */
> + led_cdev->blink_delay_on = 0;
> + led_cdev->blink_delay_off = 0;
> +
> + led_cdev->trigger = trig;
> + if (trig->activate)
> + trig->activate(led_cdev);
> + break;
> + }
> +}
> +
> +static int led_trigger_panic_notifier(struct notifier_block *nb,
> + unsigned long code, void *unused)
> +{
> + struct led_classdev *led_cdev;
> +
> + list_for_each_entry(led_cdev, &leds_list, node)
> + if (led_cdev->flags & LED_PANIC_INDICATOR)
> + led_trigger_set_panic(led_cdev);
> + return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block led_trigger_panic_nb = {
> + .notifier_call = led_trigger_panic_notifier,
> +};
> +
> static long led_panic_blink(int state)
> {
> led_trigger_event(trigger, state ? LED_FULL : LED_OFF);
> @@ -23,6 +67,9 @@ static long led_panic_blink(int state)
>
> static int __init ledtrig_panic_init(void)
> {
> + atomic_notifier_chain_register(&panic_notifier_list,
> + &led_trigger_panic_nb);
> +
> led_trigger_register_simple("panic", &trigger);
> panic_blink = led_panic_blink;
> return 0;
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 19eb10278bea..7e9fb00e15e8 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -50,6 +50,7 @@ struct led_classdev {
> #define LED_SYSFS_DISABLE (1 << 22)
> #define LED_DEV_CAP_FLASH (1 << 23)
> #define LED_HW_PLUGGABLE (1 << 24)
> +#define LED_PANIC_INDICATOR (1 << 25)
>
> /* Set LED brightness level
> * Must not sleep. Use brightness_set_blocking for drivers
>
--
Best regards,
Jacek Anaszewski
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