> I wrote:
> > Jacek Anaszewski wrote:
> >
> > On 08/04/2015 05:56 AM, Craig McQueen wrote:
> > > I've written a udev rule to catch uevent "change" events, with the
> > > goal of
> > setting LED user/group/permissions whenever trigger settings are
> changed.
> > >
> > > http://unix.stackexchange.com/a/202870/34376
> > >
> > > However, I've noticed that a TRIGGER uevent "change" event is
> > > generated
> > every time an LED is turned off.
> > >
> > > E.g. in one terminal:
> > > udevadm monitor -p
> > >
> > > In another terminal:
> > > echo 0 > /sys/class/leds/beaglebone:green:usr3/brightness
> > >
> > > The first terminal shows:
> > >
> > > KERNEL[15446.374466] change
> > /devices/leds/leds/beaglebone:green:usr3 (leds)
> > > ACTION=change
> > > DEVPATH=/devices/leds/leds/beaglebone:green:usr3
> > > SEQNUM=39147
> > > SUBSYSTEM=leds
> > > TRIGGER=none
> > >
> > > This behaviour is not ideal, because I really only want this uevent
> > > if the
> > trigger really has changed.
> > >
> > > I presume this is due to these two lines in brightness_store() in led-
> class.c:
> > > if (state == LED_OFF)
> > > led_trigger_remove(led_cdev);
> > >
> > > What would be the recommended way to improve this, so a TRIGGER
> > uevent "change" event is only generated if the trigger is actually
> > reset to 'none' in this scenario?
> > >
> > > I've noticed this on kernel 3.14.48 running on BeagleBone Black.
> > >
> >
> > You can define your rule so that it would not be matched when
> > TRIGGER=none.
>
> I tried adding TRIGGER!="none" as in this rule:
>
> SUBSYSTEM=="leds", ACTION=="change", TRIGGER!="none",
> RUN+="/bin/chgrp -R leds /sys%p", RUN+="/bin/chmod -R g=u /sys%p"
>
> But the rule never seems to run. I can't figure out why not. Unless the older
> version of udev I'm using (182) doesn't support !=.
I figured it out. I need ENV{TRIGGER} and not just TRIGGER.
SUBSYSTEM=="leds", ACTION=="change", ENV{TRIGGER}!="none", RUN+="/bin/chgrp -R
leds /sys%p", RUN+="/bin/chmod -R g=u /sys%p"
--
Craig McQueen
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