tty(4) buffer sizes

[Matthew Dillon]

: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 
:continue?

    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
    commit both.

: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.
:
:-- 
:Hasso

    If you want me to repo-copy something (to retain the cvs history),
    email me a list of files to rename.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>