ucom/uftdi dropping bytes, with debug logs

[M. Warner Losh]

In message: <e6vcnn$um$1 at sea.gmane.org>
            Geoffrey Mainland <mainland at apeiron.net> writes:
: I've been trying to debug a problem with a ftdi-based serial device
: where bytes are being dropped. The device is a Moteiv tmote sky with a
: 8U232BM chip. Reprogramming this device always fails due to dropped
: bytes. I eventually set up a VMWare image (under Windows) to make
: debugging a bit easier, as I was crashing my machine often, and lo and
: behold the problem went away! It looks like VMWare's USB interface is
: buffering the data, so the FreeBSD driver works just fine under VMWare!
: 
: I turned on debugging in the ucom and uftdi drivers. Logs of the
: transfers under both VMWare and a native environment are posted at:
: 
: http://www.apeiron.net/~mainland/uftdi/vmware-log.txt.gz
: 
: and
: 
: http://www.apeiron.net/~mainland/uftdi/native-log.txt.gz
: 
: This is under a recent 6.1 stable (for both "machines").
: 
: As you can see, the VMWare transfer manages to read a lot more data...
: 
: How do I go about finding the real problem and fixing it? I know nothing
: about the FreeBSD USB stack...

I have similar problems with FTDI, but every time that I think I've
found one, I discover that I have a second 'tip' running that's eating
some characters :-(  Are you sure that this isn't happening?  I know
it is a "rookie" mistake, but I recently wasted a day on it, and I'm
no rookie :-).

Anyway, I've also seen other weird behavior with my ftdi dongle, but
I've never been able to reproduce it well enough to try to fix the
problem...

Warner