iokit/IOKit/IOEventSource.h

   1 /*
   2  * Copyright (c) 1998-2000, 2009 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
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  23  * Please see the License for the specific language governing rights and
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  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29 Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
  30 HISTORY
  31     1998-7-13   Godfrey van der Linden(gvdl)
  32         Created.
  33     1998-10-30  Godfrey van der Linden(gvdl)
  34         Converted to C++
  35 */
  36 #ifndef _IOKIT_IOEVENTSOURCE_H
  37 #define _IOKIT_IOEVENTSOURCE_H
  38
  39 #include <sys/cdefs.h>
  40
  41 #include <libkern/c++/OSObject.h>
  42
  43 #include <IOKit/IOLib.h>
  44 #include <IOKit/system.h>
  45 #include <IOKit/IOWorkLoop.h>
  46
  47 #if IOKITSTATS
  48 #include <IOKit/IOStatisticsPrivate.h>
  49 #endif
  50
  51 __BEGIN_DECLS
  52 #include <mach/clock_types.h>
  53 #include <kern/clock.h>
  54 __END_DECLS
  55
  56 /*!
  57     @class IOEventSource : public OSObject
  58     @abstract Abstract class for all work-loop event sources.
  59     @discussion The IOEventSource declares the abstract super class that all
  60 event sources must inherit from if an IOWorkLoop is to receive events from them.
  61 <br><br>
  62         An event source can represent any event that should cause the work-loop of a
  63 device to wake up and perform work.  Two examples of event sources are the
  64 IOInterruptEventSource which delivers interrupt notifications and IOCommandGate
  65 which delivers command requests.
  66 <br><br>
  67         A kernel module can always use the work-loop model for serialising access to
  68 anything at all.  The IOEventSource is used for communicating events to the
  69 work-loop, and the chain of event sources should be used to walk the possible
  70 event sources and demultipex them.  Note a particular instance of an event
  71 source may only be a member of 1 linked list chain.  If you need to move it
  72 between chains than make sure it is removed from the original chain before
  73 attempting to move it.
  74 <br><br>
  75         The IOEventSource makes no attempt to maintain the consistency of its internal data across multi-threading.  It is assumed that the user of these basic tools will protect the data that these objects represent in some sort of device wide instance lock.     For example the IOWorkLoop maintains the event chain by using an IOCommandGate and thus single threading access to its state.
  76 <br><br>
  77         All subclasses of IOEventSource that wish to perform work on the work-loop thread are expected to implement the checkForWork() member function. As of Mac OS X, 10.7 (Darwin 11), checkForWork is no longer pure virtual, and should not be overridden if there is no work to be done.
  78
  79 <br><br>
  80         checkForWork() is the key method in this class.  It is called by some work-loop when convienient and is expected to evaluate its internal state and determine if an event has occurred since the last call.  In the case of an event having occurred then the instance defined target(owner)/action will be called.      The action is stored as an ordinary C function pointer but the first parameter is always the owner.  This means that a C++ member function can be used as an action function though this depends on the ABI.
  81 <br><br>
  82         Although the eventChainNext variable contains a reference to the next event source in the chain this reference is not retained.  The list 'owner' i.e. the client that creates the event, not the work-loop, is expected to retain the source.
  83 */
  84 class IOEventSource : public OSObject
  85 {
  86     OSDeclareAbstractStructors(IOEventSource)
  87     friend class IOWorkLoop;
  88 #if IOKITSTATS
  89     friend class IOStatistics;
  90 #endif
  91
  92 public:
  93 /*!
  94     @typedef Action
  95     @discussion Placeholder type for C++ function overloading discrimination.
  96 As the all event sources require an action and it has to be stored somewhere
  97 and be of some type, this is that type.
  98     @param owner
  99         Target of the function, can be used as a refcon.  The owner is set
 100 during initialisation.   Note if a C++ function was specified this parameter
 101 is implicitly the first paramter in the target member function's parameter list.
 102 */
 103     typedef void (*Action)(OSObject *owner, ...);
 104
 105 /*! @defined IOEventSourceAction
 106     @discussion Backward compatibilty define for the old non-class scoped type definition.  See $link IOEventSource::Action */
 107  #define IOEventSourceAction IOEventSource::Action
 108
 109 protected:
 110 /*! @var eventChainNext
 111         The next event source in the event chain. nil at end of chain. */
 112     IOEventSource *eventChainNext;
 113
 114 /*! @var owner The owner object called when an event has been delivered. */
 115     OSObject *owner;
 116
 117 /*! @var action
 118         The action method called when an event has been delivered */
 119     Action action;
 120
 121 /*! @var enabled
 122         Is this event source enabled to deliver requests to the work-loop. */
 123     bool enabled;
 124
 125 #if XNU_KERNEL_PRIVATE
 126
 127     enum
 128     {
 129         kPassive = 0x0001,
 130         kActive  = 0x0002,
 131     };
 132     uint8_t  eventSourceReserved1[1];
 133     uint16_t flags;
 134 #if __LP64__
 135     uint8_t eventSourceReserved2[4];
 136 #endif /* __LP64__ */
 137
 138 #endif /* XNU_KERNEL_PRIVATE */
 139
 140 /*! @var workLoop What is the work-loop for this event source. */
 141     IOWorkLoop *workLoop;
 142
 143 /*! @var refcon What ever the client wants to do, see $link setRefcon. */
 144     void *refcon;
 145
 146 /*! @struct ExpansionData
 147     @discussion This structure will be used to expand the capablilties of the IOEventSource in the future.
 148     */
 149     struct ExpansionData {
 150 #if IOKITSTATS
 151             struct IOEventSourceCounter *counter;
 152 #else
 153             void *iokitstatsReserved;
 154 #endif
 155         };
 156
 157 /*! @var reserved
 158     Reserved for future use.  (Internal use only)  */
 159     ExpansionData *reserved;
 160
 161 /*! @function init
 162     @abstract Primary initialiser for the IOEventSource class.
 163     @param owner
 164         Owner of this instance of an event source.  Used as the first parameter
 165 of the action callout.  Owner must be an OSObject.
 166     @param action
 167         Pointer to C call out function.  Action is a pointer to a C function
 168 that gets called when this event source has outstanding work.  It will usually
 169 be called by the checkForWork member function.  The first parameter of the
 170 action call out will always be the owner, this allows C++ member functions to
 171 be used as actions.  Defaults to 0.
 172     @result true if the inherited classes and this instance initialise
 173 successfully.
 174 */
 175     virtual bool init(OSObject *owner, IOEventSource::Action action = 0);
 176
 177     virtual void free( void ) APPLE_KEXT_OVERRIDE;
 178
 179 /*! @function checkForWork
 180     @abstract Virtual member function used by IOWorkLoop for work
 181 scheduling.
 182     @discussion This function will be called to request a subclass to check
 183 its internal state for any work to do and then to call out the owner/action.
 184 If this event source never performs any work (e.g. IOCommandGate), this
 185 method should not be overridden. NOTE: This method is no longer declared pure
 186 virtual. A default implementation is provided in IOEventSource.
 187     @result Return true if this function needs to be called again before all its outstanding events have been processed.
 188         */
 189     virtual bool checkForWork();
 190
 191 /*! @function setWorkLoop
 192     @abstract Set'ter for $link workLoop variable.
 193     @param workLoop
 194         Target work-loop of this event source instance.  A subclass of
 195 IOWorkLoop that at least reacts to signalWorkAvailable() and onThread functions.
 196 */
 197     virtual void setWorkLoop(IOWorkLoop *workLoop);
 198
 199 /*! @function setNext
 200     @abstract Set'ter for $link eventChainNext variable.
 201     @param next
 202         Pointer to another IOEventSource instance.
 203 */
 204     virtual void setNext(IOEventSource *next);
 205
 206 /*! @function getNext
 207     @abstract Get'ter for $link eventChainNext variable.
 208     @result value of eventChainNext.
 209 */
 210     virtual IOEventSource *getNext() const;
 211
 212
 213 protected:
 214     // Methods to access the IOWorkLoop exported fields
 215     void signalWorkAvailable();
 216     void openGate();
 217     void closeGate();
 218     bool tryCloseGate();
 219     int sleepGate(void *event, UInt32 type);
 220         int sleepGate(void *event, AbsoluteTime deadline, UInt32 type);
 221     void wakeupGate(void *event, bool oneThread);
 222
 223 public:
 224 /*! @function setAction
 225     @abstract Set'ter for $link action variable.
 226     @param action Pointer to a C function of type IOEventSource::Action. */
 227     virtual void setAction(IOEventSource::Action action);
 228
 229 /*! @function getAction
 230     @abstract Get'ter for $link action variable.
 231     @result value of action. */
 232     virtual IOEventSource::Action getAction() const;
 233
 234 /*! @function enable
 235     @abstract Enable event source.
 236     @discussion A subclass implementation is expected to respect the enabled
 237 state when checkForWork is called.  Calling this function will cause the
 238 work-loop to be signalled so that a checkForWork is performed. */
 239     virtual void enable();
 240
 241 /*! @function disable
 242     @abstract Disable event source.
 243     @discussion A subclass implementation is expected to respect the enabled
 244 state when checkForWork is called. */
 245     virtual void disable();
 246
 247 /*! @function isEnabled
 248     @abstract Get'ter for $link enable variable.
 249     @result true if enabled. */
 250     virtual bool isEnabled() const;
 251
 252 /*! @function getWorkLoop
 253     @abstract Get'ter for $link workLoop variable.
 254     @result value of workLoop. */
 255     virtual IOWorkLoop *getWorkLoop() const;
 256
 257 /*! @function onThread
 258     @abstract Convenience function for workLoop->onThread.
 259     @result true if called on the work-loop thread.
 260 */
 261     virtual bool onThread() const;
 262
 263 private:
 264     OSMetaClassDeclareReservedUnused(IOEventSource, 0);
 265     OSMetaClassDeclareReservedUnused(IOEventSource, 1);
 266     OSMetaClassDeclareReservedUnused(IOEventSource, 2);
 267     OSMetaClassDeclareReservedUnused(IOEventSource, 3);
 268     OSMetaClassDeclareReservedUnused(IOEventSource, 4);
 269     OSMetaClassDeclareReservedUnused(IOEventSource, 5);
 270     OSMetaClassDeclareReservedUnused(IOEventSource, 6);
 271     OSMetaClassDeclareReservedUnused(IOEventSource, 7);
 272 };
 273
 274 #endif /* !_IOKIT_IOEVENTSOURCE_H */