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Re: [bluetooth-dev] RE: Documentation ??



On Wed, 15 Nov 2000, Gordon McNutt wrote:
> If and only if (I think) you implement a tty interface then PPP can use you.
> I'm not sure PPP will work over a plain character device interface. Can anyone
> confirm?

Right,

even though the kernel-part of PPP is separated from the interface
(nowadays) in ppp_generic.c - the line discipline interface is in
ppp_async.c - the problem of directly interfacing the PPP kernel-part with
a char device is that there is no clean way of doing that in the kernel
(the kernel cannot just connect together PPP and JoeChardriver, it needs a
context to do it in, a filedescriptor for JoeChardriver etc). The line
discipline works best because it is a mechanism where the user opens a
file descriptor to a device and then through the line discipline change
command switches in PPP on that device (a tty). In effect it becomes like
a "/dev/ppp".

OTOH, it is trivial to setup a user-mode pipe using a pty/tty pair and the
plain character device you want to talk to, so that ppp-kernel hooks into
the tty line discipline and you keep shuffling data to/from the device you
want and into the pty. pppd can do this for you even.

-BW

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