Concept question: what is PDM driver?

[Oscarh]

I can understand PDM device is for device emulation. What's exactly PDM drivers (registered with VBoxDriversRegister)?

Thanks
-Oscar

[fth0]

VirtualBox uses (PDM) devices to provide virtual hardware to the guest OS, and (PDM) drivers to access the physical hardware on the host. For example, the guest OS uses its keyboard driver to access the virtual keyboard provided by VirtualBox, and VirtualBox uses its keyboard driver to access the physical keyboard of the PC.

[Oscarh]

It's clear to me now. Many thanks, fth0.

Thanks
-Oscar