Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _WINSTA_H

// The WinStation (session) driver configuration.
typedef struct _WDCONFIG
    WDNAME WdName; // The descriptive name of the WinStation driver.
    DLLNAME WdDLL; // The driver's image name.
    DLLNAME WsxDLL; // Used by the Terminal Services service to communicate with the WinStation driver.
    ULONG WdFlag; // Driver flags.
    ULONG WdInputBufferLength; // Length, in bytes, of the input buffer used by the driver. Defaults to 2048.
    DLLNAME CfgDLL; // Configuration DLL used by Terminal Services administrative tools for configuring the driver.
    WDPREFIX WdPrefix; // Used as the prefix of the WinStation name generated for the connected sessions with this WinStation driver.


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This type is documented in the [MS-TSTS] specification.