iokit/IOKit/IOService.h

165     @param messageType Type of the message - IOKit defined in IOKit/IOMessage.h or family specific.
167     @param messageArgument An argument for message, dependent on its type.
595     @discussion Registering an IOService object informs possible clients of its existance and instantiates drivers that may be used with it; <code>terminate</code> involves the opposite process of informing clients that an IOService object is no longer able to be used and will be destroyed. By default, if any client has the service open, <code>terminate</code> fails. If the <code>kIOServiceRequired</code> flag is passed however, <code>terminate</code> will be successful though further progress in the destruction of the IOService object will not proceed until the last client has closed it. The service will be made inactive immediately upon successful termination, and all its clients will be notified via their @link message message@/link method with a message of type <code>kIOMessageServiceIsTerminated</code>. Both these actions take place on the caller's thread. After the IOService object is made inactive, further matching or attach calls will fail on it. Each client has its @link stop stop@/link method called upon their close of an inactive IOService object , or on its termination if they do not have it open. After <code>stop</code>, @link detach detach@/link is called in each client. When all clients have been detached, the @link finalize finalize@/link method is called in the inactive service. The termination process is inherently asynchronous because it will be deferred until all clients have chosen to close.
1163 /*! @function message
1164     @abstract Receives a generic message delivered from an attached provider.
1165     @discussion A provider may deliver messages via the <code>message</code> method to its clients informing them of state changes, such as <code>kIOMessageServiceIsTerminated</code> or <code>kIOMessageServiceIsSuspended</code>. Certain messages are defined by the I/O Kit in <code>IOMessage.h</code> while others may be family dependent. This method is implemented in the client to receive messages.
1167     @param provider The provider from which the message originates.
1169     @result An IOReturn code defined by the message type. */
1171     virtual IOReturn message( UInt32 type, IOService * provider,
1175     @abstract Sends a generic message to an attached client.
1176     @discussion A provider may deliver messages via the @link message message@/link method to its clients informing them of state changes, such as <code>kIOMessageServiceIsTerminated</code> or <code>kIOMessageServiceIsSuspended</code>. Certain messages are defined by the I/O Kit in <code>IOMessage.h</code> while others may be family dependent. This method may be called in the provider to send a message to the specified client, which may be useful for overrides.
1178     @param client A client of the IOService to send the message.
1181     @result The return code from the client message call. */
1187     @abstract Sends a generic message to all attached clients.
1188     @discussion A provider may deliver messages via the @link message message@/link method to its clients informing them of state changes, such as <code>kIOMessageServiceIsTerminated</code> or <code>kIOMessageServiceIsSuspended</code>. Certain messages are defined by the I/O Kit in <code>IOMessage.h</code> while others may be family dependent. This method may be called in the provider to send a message to all the attached clients, via the @link messageClient messageClient@/link method.