From: Xie He
Sent: 05 November 2020 19:35
On Thu, Nov 5, 2020 at 1:10 AM David Laight [off-list ref] wrote:
quoted
quoted
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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