Question: Device Tree Overlay, Capemanager

Hi there,

I´m pretty new to Linux and the BBB. I´m using Debian Jessie and struggling with the DTO. I think I have an little idea now how it works. I try to export a dtbo to the slots.

this is what i get when i cat the slotsfile:

debian@beaglebone:/lib/firmware$ cat /sys/devices/platform/bone_capemgr/slots
0: PF---- -1
1: PF---- -1
2: PF---- -1
3: PF---- -1
4: P-O-L- 0 Override Board Name,00A0,Override Manuf,univ-emmc

but if I try to export a .dtbo from (for example the UART2 overlay) to the slotsfile it says:

debian@beaglebone:/lib/firmware$ sudo echo “BB-UART2-00A0.dtbo” > /sys/devices/platform/bone_capemgr/slots
-bash: /sys/devices/platform/bone_capemgr/slots: Permission denied

Why is the permission denied? I cant even unexport the slot #4:

debian@beaglebone:/lib/firmware$ sudo echo -4 > /sys/devices/platform/bone_capemgr/slots
-bash: /sys/devices/platform/bone_capemgr/slots: Permission denied

Any ideas?

Your command is failing because the command is essentially two parts. Or,
more correctly you're piping the output of one command, into a file. Both
operations require elevated permissions, but the sudo command is only
working for the first half. So if you run this command as root, it should
work fine. Or you can run it thus.

sudo sh -C "echo 'BB-UART2-00A0.dtbo' > /sys/devices/platform/bone_
capemgr/slots"

You should be aware that sudo is not a direct replacement for being root,
and as such some situations will work differently, or not at all in a few
cases.