I've been working on a new ARM port, and developed a serial driver for 
this platform, basing much of the code on existing ARM port serial 
drivers, most of which seem to have borrowed code from the dev/ic/com.c 
serial driver. In trying to understand better exactly what's going on in 
the interaction between the serial driver and tty layer, I came across a 
test that checks to see if the return value from the line discipline's 
l_rint( ) function equals -1. Comments in the serial driver suggest that 
this condition indicates that "the line discipline's buffer is out of 
space." However, the standard termios line discipline's l_rint( ) 
function is statically initialized to the ttyinput( ) function, and it 
looks like ttyinput( ) always returns 0. I know it's possible for  an 
alternative line discipline to be used, and perhaps that could return a 
non-zero value, but I guess my main question is:

--> are the required semantics of the functions in the line discipline 
linesw struct documented somewhere?

Particularly, the return value meanings?

Thanks,
  \
  Jon

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              Jonathan Sevy
  Geometric and Intelligent Computing Lab
            Drexel University
     http://gicl.cs.drexel.edu/sevy
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