Книга: Microsoft Windows Embedded CE 6.0 Exam Preparation Kit

Communication between Drivers and the OAL

Communication between Drivers and the OAL

In addition to the standard set of IOCTLs required by the kernel, drivers can communicate with the OAL through custom IOCTLs implemented in OEMIoControl. Kernel-mode drivers call OEMIoControl indirectly through KernelIoControl, passing in the custom IOCTL. The kernel does no processing, other than passing the parameters straight through to OEMIoControl. However, user-mode drivers cannot directly call custom OAL IOCTLs by default. The KernelIOControl calls from user-mode drivers or processes are passed to OEMIoControl through a kernel-mode component (Oalioctl.dll), which maintains a list of user-accessible OAL IOCTL codes. The call is rejected if the requested IOCTL code is not listed in this module, but you can customize this list by modifying the Oalioctl.cpp file that is located in the %_WINCEROOT%PublicCommonOakOalioctl folder.

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