HelenOS sources

DP_CNTR1          341 uspace/drv/nic/ne2k/dp8390.c 	pio_read_8(ne2k->port + DP_CNTR1);
DP_CNTR1          604 uspace/drv/nic/ne2k/dp8390.c 		for (errors = pio_read_8(ne2k->port + DP_CNTR1); errors > 0; --errors)
HelenOS homepage, sources at GitHub