POS events
This section describes the events that are passed from the device driver to the Point of Service (POS) API layer by using ReadFile. When an application successfully claims a device through the POS API, the runtime will maintain a continuous read operation against the device driver to receive events. The I/O is message-based. ReadFile needs to pass in a buffer sufficiently large enough to read in the current event. The driver retains the message until a read request with a sufficient output buffer to read the entire message is made.