HelenOS sources

CTRL_FRCDPLX      413 uspace/drv/nic/e1k/e1k.c 	ctrl |= CTRL_FRCDPLX;
CTRL_FRCDPLX      455 uspace/drv/nic/e1k/e1k.c 	ctrl &= ~(CTRL_FRCDPLX);
CTRL_FRCDPLX      483 uspace/drv/nic/e1k/e1k.c 	ctrl |= CTRL_FRCDPLX;
HelenOS homepage, sources at GitHub