Release bus after use

Dear all,
I have a problem with my BBB.
I use several buses such as GPMC, SPI…and I initialize the by a dtbo file in the /etc/rc.local
If I try to take a look in /sys/devices/bone_capemgr.10/slots I can clearly see them loaded and they work.
Now, at some point, after I used it, I would like to release them without to reboot the system; in particular I would like to have them as GPIO.
I tried to remove one bus by doing:
echo -n > /sys/devices/bone_capemgr.10/slots
(“n” is the number assigned to the bus)
and actually it is removed. If I try to do again:
cat /sys/devices/bone_capemgr.10/slots
I do no see it anymore.
However if I try to use them as gpio (by /sys/class/gpio etc…etc), I cannot control them:
they are loaded and I can change the software value but with the probe of the oscilloscope, I do not see it moving.
Do you have any idea?
Let me know if you need more informations.

my uname -a is
Linux arm 3.8.13-bone28 #1 SMP Thu Sep 12 23:22:35 UTC 2013 armv7l GNU/Linux