On 5 April 2016 at 18:36, Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx> wrote:
> Hi Ezequiel,
>
>
> On 04/04/2016 10:22 PM, Ezequiel Garcia wrote:
>>
>> Now that we can mark any LED (even those in use by delayed blink
>> triggers) to trigger on a kernel panic, let's introduce a nosleep
>> led_trigger_event API.
>>
>> This API is needed to skip the delayed blink path on
>> led_trigger_event. LEDs that are switched on a kernel panic,
>> might be in use by a delayed blink trigger.
>>
>> This will be used by the panic LED trigger.
>>
>> Signed-off-by: Ezequiel Garcia <ezequiel@xxxxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/leds/led-triggers.c | 26 ++++++++++++++++++++++----
>> include/linux/leds.h | 4 ++++
>> 2 files changed, 26 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
>> index f5c9d7c4d181..00b9d8497777 100644
>> --- a/drivers/leds/led-triggers.c
>> +++ b/drivers/leds/led-triggers.c
>> @@ -307,8 +307,9 @@ EXPORT_SYMBOL_GPL(devm_led_trigger_register);
>>
>> /* Simple LED Tigger Interface */
>>
>> -void led_trigger_event(struct led_trigger *trig,
>> - enum led_brightness brightness)
>> +static void do_led_trigger_event(struct led_trigger *trig,
>> + enum led_brightness brightness,
>> + bool nosleep)
>> {
>> struct led_classdev *led_cdev;
>>
>> @@ -316,12 +317,29 @@ void led_trigger_event(struct led_trigger *trig,
>> return;
>>
>> read_lock(&trig->leddev_list_lock);
>> - list_for_each_entry(led_cdev, &trig->led_cdevs, trig_list)
>> - led_set_brightness(led_cdev, brightness);
>
>
> led_set_brightness() can gently disable blinking if passed 0 in the
> brightness argument. IMHO this patch is not needed then.
>
>
Yes, but the blinking disable is deferred, and so might never
run (e.g. I'd say it won't run on a non-preemptible kernel).
I think we need this API, or otherwise some way of circumventing
the deferred path on led_set_brightness. For instance, we
could turn off delay_on and delay_off in the panic atomic notifier.
I'm not strongly convinced by any approach, but this API seemed
slightly cleaner.
--
Ezequiel García, VanguardiaSur
www.vanguardiasur.com.ar
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