There currently isn't any documentation for how to use the EC to set various functions, especially since usually these are things covered by the tp-smapi kernel modules which doesn't work under Coreboot/Libreboot.
For example, to fix the mute button and allow control from the OS one may run:
More useful might be the ability to set charge thresholds, where one has to set byte 0x03 to 0x44 for the max value (or 0x40 for the min value) and follow that by setting 0x24 to the desired value in the range 0x8a (10%) to 0xe4 (100%) as integer values.
The same can be done for Ultrabay batteries too by using 0x25 instead of 0x24.
Note: This has been confirmed to be working on my T400 running 20160907, both with a regular/main battery and an Ultrabay one.
But does this work on newer versions of libreboot?
'Testing' versions, that is.
This isn't strictly related to Libreboot or a version thereof.
The EC on these thinkpads is proprietary (AFAIK, the only device with a FOSS EC to ever have a stable Libreboot release was the asus C201).
ectool merely provides a way to interact with the EC, especially since that is usually handled by the SMAPI, which Coreboot (rightly) refuses to implement on grounds of it being a huge security hole.
Ok. Might still want to test in newer versions.
In case something changed inside coreboot