Bluetooth: possible bug and question

(I trust tech-net is suitable for bluetooth matters.  If not, I'll be
happy to move this elsewhere; just tell me where.)

The possible bug:

In general, HCI_CMD_foo and HCI_OCF_foo have the same low octet.  But
when foo is SNIFF_SUBRATING, they don't.  This makes
HCI_CMD_SNIFF_SUBRATING collide with HCI_CMD_FLOW_SPECIFICATION.

This has been so since, at least, 5.2, and I checked cvsweb from a work
machine today (I have the 10.1 source trickling over, but that will
take time; while I think I understand why it's done, it _is_ broken for
access from my own machines), which makes me think it's so in -current
as well.

Is this a bug, or am I missing something?

The question:

I'm trying to implement some bluetooth code (on 5.2).  What I'm trying
to implement at the moment is the ability to play audio through a
bluetooth speaker, but that's just a first task; I'd like to implement
other things.

I'm running into trouble, and I suspect much of the trouble arises
because I'm missing some important concents and how they relate to one
another.  (As one simple example, it is not clear to me how HCI, L2CAP,
RFCOMM, and SCO relate to one another, and, except for what I can infer
from manpages like btsco(4), it's unclear when I'd want which one.)  Is
there a reference anyone would recommend?  I found bluetooth.com, but
their PDFs specifically deny the right to use them to anyone not one of
their members - even though their webserver cheerfully hands them out
to anyone who cares to bother fetching them.  (Or, more precisely, this
is true of at least one of their PDFs, their core document, the first
one I tried to look at.  I didn't bother checking others.)

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