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The -D 's are necessary to give your driver the kernel's view of the header files and to get the Linux version in those cases where alternatives exist. Driver Prefix Choose a short prefix to put on the front of all your identifier names and routine names. The role of this prefix is to allow the LiS configuration process to build some tables that reference certain symbols within your driver. It is important that you get the declaration of your driver open routine correct. There was a different prototype for the open routine in SVR 3 versus SVR 4.