Am Montag, 10. April 2017, 20:42:23 schrieben Sie:
Hello Jacek,
that is a good hint. Yes the effect is the same and it works great too
for me. I was not looking to the most recent kernel sorry.
Thank you for your help
> Hi Juergen.
>
> On 04/10/2017 04:29 PM, Juergen Schindele wrote:
> > 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_lo
> > ck,
> >
> > @@ -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
>
> In 4.9 we have the following patch that should fix your problem,
> please let us know if it works for you:
>
> commit fbfa197afddd13f9bdca1c822f5d5730b50639eb
> Author: Jacek Anaszewski <jacek.anaszewski@xxxxxxxxx>
> Date: Sun Sep 18 20:24:29 2016 +0200
>
> leds: triggers: Return from led_trigger_set() if there is nothing to do
>
> If led_trigger_set() is called with "trig" argument set to NULL, and
> there
> is no trigger to remove then the function should return immediately so
> as to avoid doing unnecessary allocation and sending uevent.
>
> Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
> Reported-by: Daniel Romell <daro@xxxxxx>
> Acked-by Daniel Romell <daro@xxxxxx>
>
> diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
> index 59d6a3e..c7a38d4 100644
> --- a/drivers/leds/led-triggers.c
> +++ b/drivers/leds/led-triggers.c
> @@ -110,6 +110,9 @@ void led_trigger_set(struct led_classdev *led_cdev,
> struct led_trigger *trig)
> char *envp[2];
> const char *name;
>
> + if (!led_cdev->trigger && !trig)
> + return;
> +
> name = trig ? trig->name : "none";
> event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
--
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
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Sitz der Gesellschaft: Karlsruhe
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