From: Xie He
> Sent: 05 November 2020 19:35
>
> On Thu, Nov 5, 2020 at 1:10 AM David Laight <david.lai...@aculab.com> wrote:
> >
> > > This driver transports LAPB (X.25 link layer) frames over TTY links.
> >
> > I don't remember any requests to run LAPB over anything other
> > than synchronous links when I was writing LAPB implementation(s)
> > back in the mid 1980's.
> >
> > If you need to run 'comms over async uart links' there
> > are better options.
> >
> > I wonder what the actual use case was?
>
> I think this driver was just for experimental purposes. According to
> the author's comment at the beginning of x25_asy.c, this driver didn't
> implement FCS (frame check sequence), which was required by CCITT's
> standard. So I think this driver was not suitable for real-world use
> anyway.
Yes, you could get transparency by sending 0x7f bytes twice
(a bit like bisync) but you'd want the CRC to check for lost bytes.
I bet this was only ever used by the author and only to talk to itself.
David
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