linux-kernel - Dropped characters in serial connection without flow control

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 28 Oct 2009 18:59:37 +0100
From:	Peter Stuge <peter@...ge.se>
To:	linux-kernel@...r.kernel.org
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <greg@...ah.com>
Subject: Dropped characters in serial connection without flow control

Peter Stuge wrote:
> I'm writing a line discipline for a serial port multiplexing
> hardware

There is no(!) support for flow control in the hardware.

Is there anything I can do to reduce serial port interrupt latency or
otherwise try to mitigate this in my ldisc or in Linux in general? I
realize that it will never be quite reliable without any flow
control.

Baud rate is currently 115200 but could become 57600.

Is there something in particular that I can do wrong or right in
the ldisc?

Might it be a good idea to add a circ_buf in the receiver path and
move out any and all attempts at parsing incoming data? Currently
it has a simple message buffer and a state machine in there.

Characters are dropped both going out and coming in. Nothing to do
about the out direction, but maybe input can be made reliable?

I don't expect it, but maybe you know a trick?

//Peter
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/