Device Driver Tutorial

Defining the Module Initialization Entry Point

The _init(9E) routine returns type int and takes no arguments. The _init(9E) routine must call the mod_install(9F) function and return the success or failure value that is returned by mod_install(9F).

The mod_install(9F) function takes an argument that is a modlinkage(9S) structure. See Defining the Module Linkage Structures for information about the modlinkage(9S) structure.

This driver is supposed to write a message each time an entry point is entered. Use the cmn_err(9F) function to write a message to a system log. The cmn_err(9F) function usually is used to report an error condition. The cmn_err(9F) function also is useful for debugging in the same way that you might use print statements in a user program. Be sure to remove cmn_err() calls that are used for development or debugging before you compile your production version driver. You might want to use cmn_err() calls in a production driver to write error messages that would be useful to a system administrator.

The cmn_err(9F) function requires you to include the cmn_err.h header file, the ddi.h header file, and the sunddi.h header file. The cmn_err(9F) function takes two arguments. The first argument is a constant that indicates the severity of the error message. The message written by this driver is not an error message but is simply a test message. Use CE_NOTE for the value of this severity constant. The second argument the cmn_err(9F) function takes is a string message.

The following code is the _init(9E) routine that you should enter into your dummy.c file. The ml structure is the modlinkage(9S) structure that is discussed in Defining the Module Linkage Structures.

    cmn_err(CE_NOTE, "Inside _init");