Nicolas Besson - Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

Developing Bus-Agnostic Drivers<\/p> <\/div>

Similar to settings for installable ISRs, memory-mapped windows, and PCI device instance information, you can maintain any GPIO numbers or timing configurations in the registry and achieve in this way a bus-agnostic driver design. The underlying idea of a bus-agnostic driver is the support of multiple bus implementations for the same hardware chipset, such as PCI or PCMCIA, without requiring code modifications.<\/p>

To implement a bus-agnostic driver, use the following approach:<\/p>

1. Maintain all necessary configuration parameters in the driver's registry subkey, and use the Windows Embedded CE registry helper functions DDKReg_GetIsrInfo, DDKReg_GetWindowInfo, and DDKReg_GetPciInfo to retrieve these settings during driver initialization.<\/p>

2. Call HalTranslateBusAddress to translate bus-specific addresses to system physical addresses and then call MmMapIoSpace to map the physical addresses to virtual addresses.<\/p>

3. Reset the hardware, mask the interrupt, and load an installable ISR by calling the LoadIntChainHandler function with information obtained from DDKReg_GetIsrInfo.<\/p>

4. Load any initialization settings for the installable ISR from the registry by using RegQueryValueEx and pass the values to the installable ISR in a call to KernelLibIoControl with a user-defined IOCTL. For example, the Generic Installable Interrupt Service Routine (GIISR) included in Windows Embedded CE uses an IOCTL_GIISR_INFO handler to initialize instance information that enables GIISR to recognize when the device's interrupt bit is set and return the corresponding SYSINTR value. You can find the source code in the C:\Wince600\Public\Common\Oak\Drivers\Giisr folder.<\/p>

5. Begin the IST by calling the CreateThread function and unmask the interrupt.<\/p>