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Message-id: <572C5DEE.3070307@samsung.com>
Date: Fri, 06 May 2016 11:03:42 +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
On 04/29/2016 09:20 AM, Jacek Anaszewski wrote:
> 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.
Since the merge window is imminent, I've addressed those issues by
myself and applied the patch set to the for-next branch
of linux-leds.git.
Thanks,
Jacek Anaszewski
> 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
>>
>
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