## Physical Device Driver Reference

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### 1Ch - Remarks

Each device driver receives this packet twice for each device header. On entry of the START SHUTDOWN call, the function code is set to 0. On entry of the END SHUTDOWN call, the function code is set to 1. The reserved field is set to 0.

Note: Swapping is turned off prior to calling device drivers with the Shutdown command. Therefore, all device driver code that processes the Shutdown strategy command should reside in the device drivers resident segment or be in a swappable segment that is locked into memory before the Shutdown command is issued.

The physical device driver must perform the following actions:

Commit buffered data to the device.
Set the status WORD in the request header.

A device driver is called with the system SHUTDOWN request packet only if it is a level 2 device driver or if it is a level 3 device driver and has turned on the SHUTDOWN support flag of the Capabilities field found in the physical device driver header.