USB, select/poll for ucom

M. Warner Losh imp at
Wed Jun 25 09:16:00 PDT 2003

In message: <E19VCk7-000254-00 at>
            Danny Braniss <danny at> writes:
: > I'm able to use ppp with umodem/ucom.  My brother uses ulpcom/ucom for
: > his ppp needs.  I'm pretty sure that select is involved. :-)
: > 
: > >From what I can see in the code, I'd expect that it would work because
: > the ttypoll routine is specified for the poll routine.  Why do you
: > think it wouldn't work?
: well, for one, my program doesn't work :-), it works with the RS232 version.
: so i started to poke around, and did some reading, and as far as i could tell,
: the read(2) has to be initiated by the host, but my knowledge of usb is close
: to zero - it was zero 2 days ago, but still looking for some better docs, and
: polish my english - as far as i remember interrupt is not polling, but the
: ohci docs imply that :-)

have fun.  the mindshare book is good.  however, it took me a long
time to get a usb 'aha' moment and understand its twisty maze was
really a workable design obscured by standardese...  I suspect it is a
problem in the usb chipset driver for the com part.  ttypoll just says
'you have data in the buffer' so for some reason the data isn't making
into the tty buffer.


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