This driver acts as a shim to connect PCI serial and parallel ports to the sio(4) and ppc(4) driver.
The list of supported devices is in sys/dev/puc/pucdata.c. Support for new cards should be added there.
If the PUC_FASTINTR option is used, the driver will try to use fast interrupts. This should lower the interrupt latency and should be used if the sio(4) driver reports "silo overflow" errors. It cannot be used if the interrupt is shared.