NAME
        PRD_READPREFS - read the current driver preferences in a buffer (V44)

   FUNCTION
        This is a non standard read command that reads the driver
        preferences.

   IO REQUEST
        io_Message      mn_ReplyPort set if quick I/O is not possible
        io_Command      PRD_READPREFS
        io_Flags        IOB_QUICK set if quick I/O is possible
        io_Length       the size of the buffer in io_Data
        io_Data         a buffer
        io_Actual       the number of bytes copied to the buffer.

        If the read fails because the buffer is too small you should double
        the size of the buffer and try it again.

        Never interpret the contents of the buffer. You are allowed to save
        it to file (as one block of data) and of course to write it back to
        the driver (PRD_WRITEPREFS).

        If you close the printer device between prd_editprefs and the
        actual printing (CMD_WRITE or PRD_DUMPRPORTTAGS) you must read
        the prefs after prd_editprefs and write it back before printing
        or the driver may forget the user changes.