PnP Internal SIR Adapters
Infrared SIR devices that attach internally and that support Plug and Play functionality are exposed as infrared SIR Plug and Play devices through the system BIOS (PNP0510 or PNP0511). These devices appear to IrDA miniport drivers as conventional UARTs. These devices are supported by the combination of the IrDA miniport driver, that is supplied by the operating system, irsir.sys, and a serial driver. The serial driver can be the one that is supplied by the operating system, serial.sys, or a compatible third-party serial driver.
These devices do not appear in the Ports (COM & LPT) element in the list in Device Manager, a Control Panel application, because they are not exposed through the BIOS as serial devices. This means that the serial driver does not load automatically on this port, and these devices are otherwise invisible to users and application programs as conventional serial ports.
Once these devices are installed through Plug and Play, they appear to the user in the Infrared adapters element in the list in Device Manager. In addition, the system-supplied IrDA miniport driver is installed and it uses the resources that describe the underlying IrDA UART. To use IrDA UART resources, the system-supplied IrDA miniport driver loads the serial driver as a lower-filter driver.
The resources that the SIR IrDA UART requires must be exposed in the conventional Plug and Play manner through the system BIOS. Plug and Play attempts to locate a set of nonconflicting resources. To enable all system hardware to work together, built-in or OEM-bundled hardware must always supply suitable resource sets. The operating system does not allow interrupt sharing. Therefore, SIR UART hardware must be configurable to work on interrupts other than interrupts three and four, which are the traditional serial interrupts. The interrupt configuration must be exposed through the BIOS.
Note that in many cases, requiring that interrupts three and four be exposed for the SIR IrDA UART might not work.