Looking for a way to trigger error on network adapter

[Francois Romieu]

Hello,

Context:
HDLC PCI adapter + line at 2 Mb/s + external traffic generator that fills 
the line with 5 to x1000 bytes frame.

I want to see how my code bahaves during rare (?) events: an overflow of 
the RX fifo (256 bytes) and a TX underrun. It's my understanding that if the 
adapter pains at DMAing, those errors should be triggered.
Could I/O at a inocuous location (a well-choosen PCI register ?) be enough 
for that ?

-- 
Ueimor