Re: Conceptual USB doc?

> You are wanting to talk to a "USB device". You need specs about what
> the device does.  Until then, it's sort of like "I have this device
> that you talk to via ethernet".

That much I did know.  I didn't go into details here because it's only
tangentially relevant; I'd rather *understand* it, with making it work
following naturally from that, rather than just making it work by
invoking ununderstood magic.

> ugen is a kernel driver for doing reads/writes to endpoints from user
> space.  For many odd devices that attach via USB, that's useful.

That might be suitable.

The device is a Teracube 2e, an open smartphone (supposedly open, at
least; I haven't gotten close enough to it to know just how open it
actually is - on the maker's webpages I did not manage to find pointers
to anything useful for building my own software for it, only the
digital version of end-user-targeted four-colour glossies).  The
software that's on it at present is of negative value to me - it
appears to be a variant of Android which, among other things refuses to
complete its initial setup without making me agree to a ToS even though
I told it to disable all the things which might be a basis for needing
that ToS.  I did manage to find the nerve pinch to get it to drop into
ROM code on powerup.  But the bootloader just says "connect to host and
run fastboot", with a webpage pointer which indicates that fastboot is
a fragment of an Android dev environment, and I want to have as little
to do with Android as I can manage here.

I did find a _little_ doc on the protocol fastboot speaks over USB, but
it assumes knowledge of concepts I don't have, saying things like

	Basic Requirements</h2><ul><li><p>USB</p><ul><li>Two bulk
	endpoints (in, out) are required</li><li>Max packet size must
	be 64 bytes for full-speed, 512 bytes for high-speed and 1024
	bytes for Super Speed USB.</li><li>The protocol is entirely
	host-driven and synchronous [...].

Setting up "two bulk endpoints", even with the help of something like
libusb atop ugen, requires knowing enough about what that means to find
and make the appropriate calls.  (If I can even find a libusb that
works on the host I want to use; there is usually some level of
bludgeoning required to make others' software work on my machines.)

Also, I've found that, even when working at higher levels, knowledge of
the lower levels always becomes important eventually.  Hence my asking
for documentation instead of just "how do I do this?".

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