tty(4) buffer sizes
dillon at apollo.backplane.com
Mon Jan 14 09:23:12 PST 2008
:I have tested briefly some UMTS/HSDPA modems with idea to obtain one, but
:couldn't get them work reliably in DragonFly. All of them were using the
:umsm(4) driver and using HSDPA (3.6Mbit/s).
:The problem is that tty(4) buffers are too small. With current code I
:couldn't get single MTU size packets through, dmesg was full of "kernel:
:ucom0: lost 374 chars" messages. Devices started to work for me without
:the messages if I increased umsm(4) buffers (UMSMBUFSZ) to 4096 and
:applied this oneliner to the sys/kern/tty.c:
:I'm not familiar with tty(4) code in general, so I'm not able to evaluate
:whether it's safe or not and what other things should be changed etc.
:Comment seems to say that it should apply to old devices only, but
:clearly ucom(4) doesn't know anything about t_ispeedwat. Should it?
:umsm(4) doesn't know anything of line speed either :). How should I
It's fine. The tty code is very old and the defaults are designed
for an era of VAX 780's with tiny amounts of memory. Go ahead and
:As as sidenote, I think that we should rename umsm(4) to ugensa(4) like it
:is NetBSD. There is nothing Qualcomm MSM chip specific in the driver.
If you want me to repo-copy something (to retain the cvs history),
email me a list of files to rename.
<dillon at backplane.com>
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