Beagleboard:BeagleBone Debian Image Migration

Kernel

What changes were made to sysfs?

3.8 kernel sysfs entry	4.x kernel sysfs entry
/sys/devices/bone_capemgr.*	/sys/devices/platform/bone_capemgr
/sys/devices/ocp.*	/sys/devices/platform/ocp/
/sys/devices/ocp.*/helper.*/AIN*	/sys/bus/iio/devices/iio:device0

Device Tree

cape-universal

Help! My overlay won't load! There's just this weird cape in slot 4.

You've met cape-universal. It is meant to often make overlays unnecessary, but you can also just disable it by changing the following line in /boot/uEnv.txt:

  cmdline=coherent_pool=1M quiet cape_universal=enable

to

  cmdline=coherent_pool=1M quiet

cape-universal is also automatically disabled if bone_capemgr.enable_partno occurs in the kernel cmdline (even if its argument is blank) or any overlay is already applied via capemgr before cape-universal can be loaded.

Disabling eMMC or HDMI

HDMI and eMMC are now part of the main dtb instead of being virtual CAPEs, which means that to disable these you change the 'dtb' variable in /boot/uEnv.txt instead of using capemgr.disable_partno:

3.8 kernel cape_disable=capemgr.disable_partno=	4.x kernel dtb=
(blank)	am335x-boneblack.dtb
BB-BONELT-HDMI	?
BB-BONELT-HDMI,BB-BONELT-HDMIN	am335x-boneblack-emmc-overlay.dtb
BB-BONE-EMMC-2G	am335x-boneblack-hdmi-overlay.dtb
BB-BONE-EMMC-2G,BB-BONELT-HDMI	am335x-boneblack-nhdmi-overlay.dtb
BB-BONE-EMMC-2G,BB-BONELT-HDMI,BB-BONELT-HDMIN	am335x-boneblack-overlay.dtb

See also this survey of BeagleBone DTBs.

Enabling the ADC

This requires configuring the ADC via device tree, e.g. by loading the /lib/firmware/BB-ADC-00A0.dtbo overlay (source code) using capemgr:

  echo BB-ADC >/sys/devices/platform/bone_capemgr/slots