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There are two ways to load stream interface drivers. One involves the Device Manager, while the other is specific to applications.
The first type of loading occurs at startup. When a Windows CE–based platform starts up, it starts the Device Manager. In turn, the Device Manager reads the contents of the HKEY_LOCAL_MACHINE\Drivers\Builtinkey and loads any stream interface drivers listed there. For example, on many Windows CE–based platforms, the Device Manager loads the driver for built-in serial ports (Serial.dll) through this mechanism.
The third type of loading occurs when the Device Manager cannot automatically detect the connection of a peripheral to a platform. Unrecognized devices are often serial devices because there is no automatic way for Windows CE to detect the connection of a serial device to a serial port. If the Device Manager cannot automatically recognize a peripheral, the application that needs to use the peripheral must load the peripheral's driver. The following is the standard sequence of actions for this type of loading:
PC Card device drivers are handled as a special case when a user connects a PC Card to a Windows CE-based platform. In this situation, the PC Card socket driver detects the card insertion event and notifies the Device Manager that it needs to load a PC Card device driver. The Device Manager uses the PC Card's Plug and Play identifier to locate the correct device driver for the PC Card. The Device Manager then checks the HKEY_LOCAL_MACHINE\Drivers\PCMCIA\key for a subkey matching the Plug and Play identifier. If one exists, it loads the driver listed within that key. If there is no match, the Device Manager calls all of the detection functions that are listed within the HKEY_LOCAL_MACHINE\Drivers\PCMCIA\Detectkey. If one of the detection functions returns a value indicating that it can handle the PC Card, the Device Manager loads and initializes that stream interface driver.
Whenever the Device Manager loads a device driver — either at system boot time or due to a PC Card insertion — the Device Manager calls the ActivateDevicefunction for the stream interface driver and creates a numbered subkey within the HKEY_LOCAL_MACHINE\Drivers\Active\key to track the driver. ActivateDevicealso locks the stream interface driver into working RAM. This prevents the driver from being swapped out and prevents any paging activity that would slow driver operation when servicing interrupts.
Last updated on Tuesday, July 13, 2004