iokit/IOKit/IOWorkLoop.h

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * The contents of this file constitute Original Code as defined in and
   7  * are subject to the Apple Public Source License Version 1.1 (the
   8  * "License").  You may not use this file except in compliance with the
   9  * License.  Please obtain a copy of the License at
  10  * http://www.apple.com/publicsource and read it before using this file.
  11  *
  12  * This Original Code and all software distributed under the License are
  13  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  14  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  15  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
  17  * License for the specific language governing rights and limitations
  18  * under the License.
  19  *
  20  * @APPLE_LICENSE_HEADER_END@
  21  */
  22 /*
  23 Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
  24 HISTORY
  25     1998-7-13   Godfrey van der Linden(gvdl)
  26         Created.
  27     1998-10-30  Godfrey van der Linden(gvdl)
  28         Converted to C++
  29 */
  30
  31 #ifndef __IOKIT_IOWORKLOOP_H
  32 #define __IOKIT_IOWORKLOOP_H
  33
  34 #include <libkern/c++/OSObject.h>
  35 #include <IOKit/IOReturn.h>
  36 #include <IOKit/IOLib.h>
  37 #include <IOKit/IOLocks.h>
  38
  39 #include <IOKit/system.h>
  40
  41 class IOEventSource;
  42 class IOTimerEventSource;
  43 class IOCommandGate;
  44
  45 /*! @class IOWorkLoop
  46     @discussion An IOWorkLoop is a thread of control that is intended to be used to provide single threaded access to hardware.  This class has no knowledge of the nature and type of the events that it marshals and forwards.  When a device driver successfully starts (see IOService::start), it is expected to create the event sources it will need to receive events.  Then a work loop is initialized and the events are added to the work loop for monitoring.  In general this set up will be automated by the family superclass of the specific device.
  47 <br><br>
  48         The thread main method walks the event source linked list and messages each one requesting a work check.  At this point each event source is expected to notify its registered owner that the event has occurred.  After each event has been walked and each indicates that another loop isn't required (by setting the 'more' flag to false) the thread will go to sleep on a signaling semaphore.
  49 <br><br>
  50         When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop.
  51 */
  52 class IOWorkLoop : public OSObject
  53 {
  54     OSDeclareDefaultStructors(IOWorkLoop)
  55
  56 public:
  57 /*!
  58     @typedef Action
  59     @discussion Type and arguments of callout C function that is used when
  60 a runCommand is executed by a client.  Cast to this type when you want a C++
  61 member function to be used.  Note the arg1 - arg3 parameters are straight pass
  62 through from the runCommand to the action callout.
  63     @param target
  64         Target of the function, can be used as a refcon.  Note if a C++ function
  65 was specified, this parameter is implicitly the first parameter in the target
  66 member function's parameter list.
  67     @param arg0 Argument to action from run operation.
  68     @param arg1 Argument to action from run operation.
  69     @param arg2 Argument to action from run operation.
  70     @param arg3 Argument to action from run operation.
  71 */
  72     typedef IOReturn (*Action)(OSObject *target,
  73                                void *arg0, void *arg1,
  74                                void *arg2, void *arg3);
  75
  76 private:
  77 /*! @function threadMainContinuation
  78     @abstract Static function that calls the threadMain function.
  79 */
  80     static void threadMainContinuation(IOWorkLoop *self);
  81
  82 protected:
  83
  84 /*! @typedef maintCommandEnum
  85     @discussion Enumeration of commands that _maintCommand can deal with.
  86     @constant mAddEvent Used to tag a Remove event source command.
  87     @constant mRemoveEvent Used to tag a Remove event source command.
  88 */
  89     typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum;
  90
  91 /*! @var gateLock
  92     Mutual exclusion lock that is used by close and open Gate functions.
  93 */
  94     IORecursiveLock *gateLock;
  95
  96 /*! @var eventChain
  97     Pointer to first event source in linked list.
  98 */
  99     IOEventSource *eventChain;
 100
 101 /*! @var controlG
 102     Internal control gate to maintain event system.
 103 */
 104     IOCommandGate *controlG;
 105
 106 /*! @var workSpinLock
 107     The spin lock that is used to guard the 'workToDo' variable.
 108 */
 109     IOSimpleLock *workToDoLock;
 110
 111 /*! @var workThread
 112     Work loop thread.
 113 */
 114     IOThread workThread;
 115
 116 /*! @var workToDo
 117     Used to to indicate that an interrupt has fired and needs to be processed.
 118 */
 119     volatile bool workToDo;
 120
 121 /*! @var loopRestart
 122     Set if an event chain has been changed and the system has to be rechecked from start.  (Internal use only)
 123 */
 124     bool loopRestart;
 125
 126 /*! @struct ExpansionData
 127     @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
 128 */
 129     struct ExpansionData { };
 130
 131 /*! @var reserved
 132     Reserved for future use.  (Internal use only)
 133 */
 134     ExpansionData *reserved;
 135
 136 /*! @function _maintRequest
 137     @abstract Synchronous implementation of addEventSource and removeEventSource functions.
 138     @discussion This function implements the commands as defined in the maintCommandEnum.  It can be subclassed but it isn't an external API in the usual sense.  A subclass implementation of _maintRequest would be called synchronously with respect to the work loop and it should be implemented in the usual way that an ioctl would be.
 139     @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise.
 140 */
 141     virtual IOReturn _maintRequest(void *command, void *data, void *, void *);
 142
 143 /*! @function free
 144     @discussion Mandatory free of the object independent of the current retain count.  If the work loop is running, this method will not return until the thread has successfully terminated.  Each event source in the chain will be released and the working semaphore will be destroyed.
 145 <br><br>
 146         If the client has some outstanding requests on an event they will never be informed of completion.  If an external thread is blocked on any of the event sources they will be awakened with a KERN_INTERUPTED status.
 147 */
 148     virtual void free();
 149
 150 /*! @function threadMain
 151     @discussion Work loop threads main function.  This function consists of 3 loops: the outermost loop is the semaphore clear and wait loop, the middle loop terminates when there is no more work, and the inside loop walks the event list calling the checkForWork method in each event source.  If an event source has more work to do, it can set the more flag and the middle loop will repeat.  When no more work is outstanding the outermost will sleep until an event is signalled or the least wakeupTime, whichever occurs first.  If the event source does not require the semaphore wait to time out, it must set the provided wakeupTime parameter to zero.
 152 */
 153     virtual void threadMain();
 154
 155 public:
 156
 157 /*! @function workLoop
 158     @abstract Factory member function to constuct and intialize a work loop.
 159     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 160 */
 161     static IOWorkLoop *workLoop();
 162
 163 /*! @function init
 164     @discussion Initializes an instance of the workloop.  This method creates and initialses the signaling semaphore and forks the thread that will continue executing.
 165     @result Returns true if initialized successfully, false otherwise.
 166 */
 167     virtual bool init();
 168
 169 /*! @function getThread
 170     @abstract Gets the workThread.
 171     @result Returns workThread.
 172 */
 173     virtual IOThread getThread() const;
 174
 175 /*! @function onThread
 176     @abstract Is the current execution context on the work thread?
 177     @result Returns true if IOThreadSelf() == workThread.
 178 */
 179     virtual bool onThread() const;
 180
 181 /*! @function inGate
 182     @abstract Is the current execution context holding the work-loop's gate?
 183     @result Returns true if IOThreadSelf() is gate holder.
 184 */
 185     virtual bool inGate() const;
 186
 187 /*! @function addEventSource
 188     @discussion Add an event source to be monitored by the work loop.  This function does not return until the work loop has acknowledged the arrival of the new event source.  When a new event has been added the threadMain will always restart its loop and check all outstanding events.  The event source is retained by the work loop.
 189     @param newEvent Pointer to IOEventSource subclass to add.
 190     @result Always returns kIOReturnSuccess.
 191 */
 192     virtual IOReturn addEventSource(IOEventSource *newEvent);
 193
 194 /*! @function removeEventSource
 195     @discussion Remove an event source from the work loop.  This function does not return until the work loop has acknowledged the removal of the event source.  When an event has been removed the threadMain will always restart its loop and check all outstanding events.  The event source will be released before return.
 196     @param toRemove Pointer to IOEventSource subclass to remove.
 197     @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found.
 198 */
 199     virtual IOReturn removeEventSource(IOEventSource *toRemove);
 200
 201 /*! @function enableAllEventSources
 202     @abstract Calls enable() in all event sources.
 203     @discussion For all event sources in eventChain, call enable() function.  See IOEventSource::enable().
 204 */
 205     virtual void enableAllEventSources() const;
 206
 207 /*! @function disableAllEventSources
 208     @abstract Calls disable() in all event sources.
 209     @discussion For all event sources in eventChain, call disable() function.  See IOEventSource::disable().
 210 */
 211     virtual void disableAllEventSources() const;
 212
 213 /*! @function enableAllInterrupts
 214     @abstract Calls enable() in all interrupt event sources.
 215     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function.  See IOEventSource::enable().
 216 */
 217     virtual void enableAllInterrupts() const;
 218
 219 /*! @function disableAllInterrupts
 220     @abstract Calls disable() in all interrupt event sources.
 221     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid,  in eventChain call disable() function.  See IOEventSource::disable().
 222 */
 223     virtual void disableAllInterrupts() const;
 224
 225
 226 protected:
 227     // Internal APIs used by event sources to control the thread
 228     friend class IOEventSource;
 229     friend class IOTimerEventSource;
 230     virtual void signalWorkAvailable();
 231     virtual void openGate();
 232     virtual void closeGate();
 233     virtual bool tryCloseGate();
 234     virtual int sleepGate(void *event, UInt32 interuptibleType);
 235     virtual void wakeupGate(void *event, bool oneThread);
 236
 237 public:
 238     /* methods available in Mac OS X 10.1 or later */
 239
 240 /*! @function runAction
 241     @abstract Single thread a call to an action with the work-loop.
 242     @discussion Client function that causes the given action to be called in
 243 a single threaded manner.  Beware: the work-loop's gate is recursive and runAction can cause direct or indirect re-entrancy.  When executing on a client's thread, runAction will sleep until the work-loop's gate opens for
 244 execution of client actions, the action is single threaded against all other work-loop event sources.
 245     @param action Pointer to function to be executed in work-loop context.
 246     @param arg0 Parameter for action parameter, defaults to 0.
 247     @param arg1 Parameter for action parameter, defaults to 0.
 248     @param arg2 Parameter for action parameter, defaults to 0.
 249     @param arg3 Parameter for action parameter, defaults to 0.
 250     @result Returns the value of the Action callout.
 251 */
 252     virtual IOReturn runAction(Action action, OSObject *target,
 253                                void *arg0 = 0, void *arg1 = 0,
 254                                void *arg2 = 0, void *arg3 = 0);
 255
 256 protected:
 257     OSMetaClassDeclareReservedUsed(IOWorkLoop, 0);
 258
 259     OSMetaClassDeclareReservedUnused(IOWorkLoop, 1);
 260     OSMetaClassDeclareReservedUnused(IOWorkLoop, 2);
 261     OSMetaClassDeclareReservedUnused(IOWorkLoop, 3);
 262     OSMetaClassDeclareReservedUnused(IOWorkLoop, 4);
 263     OSMetaClassDeclareReservedUnused(IOWorkLoop, 5);
 264     OSMetaClassDeclareReservedUnused(IOWorkLoop, 6);
 265     OSMetaClassDeclareReservedUnused(IOWorkLoop, 7);
 266 };
 267
 268 #endif /* !__IOKIT_IOWORKLOOP_H */