disablement and enablement of a computer serial port.

if Bios has control of it, it simply flips a bit in a device manager chip on the board..

From that point, the OS does not see that serial port. Which also means, there is no IRQ assigned to it or port addresses etc.. in otherwords, no resources assigned to it.

USB serial ports are a different story..

Jamie

OK, that would be in evidence when the Bios interface allows disabling.

There must be a customary way for the OS to read the state of the bit. Otherwise communication software would have to allow for obscure hardware variations. Can software flip the bit? Ie. can a port can be enabled and disabled when the system is running?

Fortunately I'm only interested in RS-232 style serial ports, for now at least.

Thanks! ... Peter E.

Depends what you mean by software. The ancient vt1211 superi/o chip does its configuration via port writes. You may need to be in kernel context to be allowed to do that(or ioperm()). You may have to browse datasheets, to find out if others are similar or if there's a de-facto standard. Having a look at intels LPC bus specs may be necessary, too. (they're available online)

any Web pages cover the software topics but I've found nothing explaining h ow a BIOS disables a port. Is is done by clearing any interrupt assignment to the port? Is the power to the UART shut off? Other ways? Probably mo re than one technique has been used but not a large number.

What exactly are you tring to do? If you are using Windows, you should be a ble to disable it using the device manager.