The very helpful write-up on how to use the cape manager (http://elinux.org/BeagleBone_and_the_3.8_Kernel#Cape_Manager_and_Device_Tree_Overlays) suggests that one can disable a cape by echoing the cape number to the cape mgr like so:
cat /sys/devices/bone_capemgr.9/slots
0: 54:PF—
1: 55:PF—
2: 56:PF—
3: 57:PF—
4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
5: ff:P-O-L Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
echo -5 >/sys/devices/bone_capemgr.9/slots
I did this after a “sudo -s” and oddly found myself back in my user shell instead of the root shell. I then wanted to check the situation and tried:
cat /sys/devices/bone_capemgr.9/slots
but that locks up and is unkillable (the process is stuck in a device driver, i.e. “D” state in ps). The only remedy I’ve found is a hard reset (/sbin/reboot doesn’t work). Is this a known issue?