Bug 58812

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User-Agent: Mozilla/4.51 [en] (WinNT; I)

Description of problem:
We  use a  usb  modem as  a  tty character  device  with N_TTY  line
discipline.  For that terminal ONLCR flag is on, so opost() function
from n_tty.c tries to output \n character as a pair \r + \n.
 
To do  that it calls  tty->driver.put_char(tty, c) which  points to 
acm_tty_write() two times, once for each character.                 
 
First call  for \r  goes through  fine, but the  second call  for \n
returns  0  because  of  acm->writeurb.status  ==  -EINPROGRESS  and
doesn't send that \n character.
 
opost() function  doesn't check a return value from put_char(), doesn't
detect dropped characters, and always returns 0 (OK).
write_chan() gets that OK from opost() and doesn't know that it needs to
re-send a character. 
 
The same problem occurs on several different hardware platforms, with
two different Linux kernels (2.2 and 2.4),
and with different usb-modems.


Version-Release number of selected component (if applicable):


How reproducible:
Always

Steps to Reproduce:
1.use mgetty to answer incoming calls on a usb modem
2.use another machine to dail in (we used cu program to do that)
3. login

	

Actual Results:  All output from the remote site goes into one line 


Additional info: