This chapter presented two distinct methods of dealing with time within a driver. Typically, a driver needs to keep track of time either to ensure the device is working normally or to poll for further device interaction. The I/O Timer mechanism is simple but crude, generating callbacks at fixed one-second intervals. CustomTimerDpc routines are used primarily for efficient polling of devices in lieu of device interrupts. The next chapter deals with DMA operations within the device and its associated driver.
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