Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!rice!sun-spots-request
From: auspex!guy@uunet.uu.net (Guy Harris)
Newsgroups: comp.sys.sun
Subject: Re: Serial Line Buffer
Keywords: Miscellaneous
Message-ID: <5580@brazos.Rice.edu>
Date: 8 Mar 90 19:00:04 GMT
Sender: root@rice.edu
Organization: Sun-Spots
Lines: 25
Approved: Sun-Spots@rice.edu
X-Refs:  Original: v9n72
X-Sun-Spots-Digest: Volume 9, Issue 72, message 14

>The first suggestion, and probably the best (if you have source license),
>is to edit zs_asynch.c and change the value, remake your kernel and
>reboot.

Actually, there's more to it than that, since the code that maintains the
serial line buffer keeps indices to it in an "unsigned char", and thus
doesn't have to do any work to have the index go from 255 to 0; if you
change the size, you'll have to modify it to explicitly check for the
maximum size and wrap around.

>The second suggestion is to use the /etc/remote file like tip does.  It
>turns out that there is a capability called fs (frame size) which tip uses
>to buffer between file system writes when receiving files.  You`d probably
>need the tip source to see how it does the buffering (I assume that it is
>relatively fast) so that you don't take CPU cycles from your application.

Uh, that doesn't change the size of the serial line buffer, so I assume
the question "how do I increase the size of the serial line buffer" really
should have been "how do I achieve XXX", with an implicit (and possibly
incorrect) assumption that increasing the size of the serial line buffer
is the way to achieve XXX.  So, what is the XXX here?

(BTW, a quick scan of the "tip" source seems to indicate that it doesn't
use "fs" for *anything*; it dutifully gets the value from the
"/etc/remote" file, or defaults it to BUFSIZ, and then doesn't use it.)