Subject: Re: umodem
To: Jason Thorpe <email@example.com>
From: Lennart Augustsson <firstname.lastname@example.org>
Date: 01/26/2000 01:26:07
Jason Thorpe wrote:
> On Tue, 25 Jan 2000 13:17:57 -0800
> "Aaron J. Grier" <email@example.com> wrote:
> > don't you hook a modem to a communications port, and not the other way
> > around? IE
> > ucom* at uhub?
> > umodem* at ucom?
> > Does having only 'umodem* at uhub?' make sense? (IE can you use the
> > modem without having a ucom device associated with it?) Or is this just
> > the weird backwards way USB works?
> It's not really backwards if you understand the abstractions...
> `umodem' attaches to a specific class of USB device. `ucom' presents
> the TTY layer for that device. I expect that a forthcoming `userial'
> will also have a `ucom' child at some point, as well.
You are absolutely right, Jason. Except it will not be a single userial since
there is no standard, so each kind of serial adapter will have its own driver,
but they will all share the ucom part.
It does not make sense to have umodem without ucom, because then
you cannot access it in any way. The reason for having ucom be present in
the config file even when it is mandatory is to be able to nail down device
minor numbers for different devices. (Much as the audio device is required
to attach to all audio drivers, for the same reason.)