Kernel-Mode Drivers (Compact 7)
3/12/2014
Windows Embedded Compact 7 runs device drivers in kernel mode, by default. Kernel-mode drivers have direct access to user memory buffers; therefore, kernel-mode drivers incur less overhead than user-mode drivers in moving data to and from the device. User-mode drivers require additional resource overhead for marshaling user data across process boundaries. For more information about data marshaling, see Marshal Data Between Memory Buffers.
Because kernel-mode drivers have direct access to both kernel memory and user memory, a low-quality kernel-mode driver can result in overall system instability. Therefore, kernel-mode drivers must be robust. A kernel-mode driver error can cause a kernel error, which results in system failure. If you are developing a kernel-mode driver, you must check and handle all inputs to driver functions carefully, and you must assume that these inputs come from untrusted sources.
When to Create a Kernel-Mode Driver
The kernel-mode driver model is a good choice for a new device driver implementation if any one of the following is true:
- Your device driver is a network driver, a file system driver, or it interfaces with the GWES. These subsystems only work with kernel-mode device drivers.
- Your device driver is a native driver. Only stream drivers can run in user-mode.
- The efficiency of your device driver is more important than possible system instability due to a driver error.
- You require access to internal kernel structures or kernel APIs in order to control your device.
- You require direct, synchronous access to user memory buffers.
For More Information About Kernel-Mode Drivers
To learn more about kernel-mode drivers, see the Windows Embedded Compact 7 topics described in the following table.
| Topic | Description |
|---|---|
Describes functions that are used by drivers for handling bus address translations, allocating and mapping device memory, setting up direct memory access (DMA) buffers, and performing I/O operations. |
|
Describes functions for allocating physical memory, mapping between virtual and physical memory addresses, forwarding device I/O controls, interrupt handler registration, and interrupt masking. |