Hello List,
i hope i found the right addres for this small problem.
I have a userspace daemon which controls leds via sysfs API
"/sys/class/leds/Soft1/brightness". Each time i turn the LED off
by writing 0 to brightness the /proc/sys/kernel/hotplug deamon
is called with "ACTION:change SUBSYSTEM:leds DEVNAME:(null)
DEVPATH:/devices/...."
from led-class.c ----------------------------
if (state == LED_OFF)
led_trigger_remove(led_cdev);
__led_set_brightness(led_cdev, state);
But in fact there is no change of trigger because "none" was setup between
enabling LED and disabling it. So from my point of view there is no change
from "none" to "remove" which justifies a "kobject_uevent_env(&led_cdev->dev-
>kobj, KOBJ_CHANGE, envp)".
To solve this problem of unusefull waste of CPU-time i suggest the following
patch. Please consider the implementation which saved a lot of valuable CPU-
power in my case:
Index: drivers/leds/led-triggers.c
===================================================================
--- drivers/leds/led-triggers.c (Revision 14968)
+++ drivers/leds/led-triggers.c (Arbeitskopie)
@@ -106,10 +106,11 @@
const char *name;
name = trig ? trig->name : "none";
- event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
/* Remove any existing trigger */
if (led_cdev->trigger) {
+ event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
+
write_lock_irqsave(&led_cdev->trigger->leddev_list_lock,
flags);
list_del(&led_cdev->trig_list);
write_unlock_irqrestore(&led_cdev->trigger->leddev_list_lock,
@@ -122,6 +123,8 @@
led_set_brightness(led_cdev, LED_OFF);
}
if (trig) {
+ event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
+
write_lock_irqsave(&trig->leddev_list_lock, flags);
list_add_tail(&led_cdev->trig_list, &trig->led_cdevs);
write_unlock_irqrestore(&trig->leddev_list_lock, flags);
Thank you for your attention
--
i. A.
Jürgen Schindele
Softwareentwicklung
PSI Nentec GmbH
Greschbachstraße 12
76229 Karlsruhe
Deutschland
Telefon: +49 721 94249-51
Telefax: +49 721 94249-10
schindele@xxxxxxxxx
www.nentec.de
Geschäftsführung: Klaus Becker, Wolfgang Fischer
Sitz der Gesellschaft: Karlsruhe
Handelsregister: Amtsgericht Mannheim HRB 107658
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