netdev - RE: [PATCH net-next] net: x25_asy: Delete the x25

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Date:   Thu, 5 Nov 2020 22:35:23 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Xie He' <xie.he.0141@...il.com>
CC:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>
Subject: RE: [PATCH net-next] net: x25_asy: Delete the x25_asy driver

From: Xie He
> Sent: 05 November 2020 19:35
> 
> On Thu, Nov 5, 2020 at 1:10 AM David Laight <David.Laight@...lab.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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