Cordio MTU/ACL sizing confusion

I am trying to understand the basic Cordio stack (target: NRF52), and also adjust the default/desired MTU sizes.

Question 1
What components are actually used in the (default) setup of the Cordio stack on the nRF52 target. I see 3:

  • Cordio
  • Cordio-LL
  • Cordio-LL-nrf52840
    Each of these components has mbed_lib.json files with settings that seem to be duplicated, which leads to the 2nd question…

Question 2
I’d like to make use of a 256-byte user data payload for a given attribute. Looking at the lib.json(s), I have been able to track down 4 settings that related to this:

  1. cordio.desired-att-mtu
  2. cordio.rx-acl-buffer-size (which needs to be X bytes larger than desired-att-mtu)?
  3. cordio-ll.max-acl-size
  4. cordio-ll-nrf52840.max-acl-size

(3) and (4) of this list is where I started to become confused. Do these settings also need to be increased to match the cordio parent settings?

Any guidance on this would be much appreciated
thanks

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Is the Cordio team active in answering any of these questions?