Hi all!

Today I tried to get bluetooth working on the PRiW0, which led me down a different rabbithole in the lands of "devuan vs. raspbian". First the findings:

Devuan:
- /dev/ttyACM0 appears always, either accessable on GPIO14/15 or via something unknown (should be bt).
- /dev/ttyS0 apperars only, when the "pi3-miniuart-bt" overlay is loaded. ttyS0 is then on gpio14/15, ttyACM0 is visible but connected to someting unknown (should be bt).
- Whatever device shoud be connected to bt, it is not: htcattach always times out.
- "enable_uart=1" crashes the bootloader (not the kernel - that is not even loaded at that point). In fact, anything "enable=XXX" crashes the bootloder.

Raspbian:
- both devices work as documented by the raspbianpi foundation either on gpio14/15 or bt.
- hciattach initializes bluetooth.
- "enable_uart=1" prevents the diappearance of "/dev/ttyS0" (which is renamed to serial0 by systemd)

Both systems run the same kernel, the same firmware (updated with "rpi-update" and firmware tree copied over from raspbien).

The only differences in the system layout (apart from systemd vs. sysv) I found were these:
- Raspbian has an extra file /boot/LICENSE.oracle
- Raspbian FAT partition starts at block 8192, while Devuan starts at 2048. But only the first block is used, all other are zero.

Running out of ideas I copied all files from the devuan root partition over to the raspbian root partition and booted the system. Guess what: The boot process without systemd is 10 seconds faster AND bluetooth is working!

But this fishy: all binary files in /boot are identical (devuan/rasbian), so the bootloader and kernel sould have shown the same behaviour, i.e. either crash or work on both systems when "enable_uart=1". And ttyS0 and ttyAMA0 sould behave identical, but they don't. Why? Where's the difference that matters?

And the more pressing question: As now devuan is installed over the cops of raspbian, who can I figure out what files are used on startup? The bluetooth init probram is definitly a resurrected part of raspbian, but what else?


Nik




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