leds: triggers: Allow to switch the trigger to "panic" on a kernel panic

[linux.git] / drivers / leds / trigger / ledtrig-panic.c

diff --git a/drivers/leds/trigger/ledtrig-panic.c b/drivers/leds/trigger/ledtrig-panic.c
index 627b350c5ec3155b5d8e2879f083d45e44b136d4..d735526b9db4f79c3e80f220f019994f13dcf35c 100644 (file)
--- 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 called in a special context by the atomic panic
+ * 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;