iokit/IOKit/IOWorkLoop.h

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, 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,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
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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
  37 #ifndef __IOKIT_IOWORKLOOP_H
  38 #define __IOKIT_IOWORKLOOP_H
  39
  40 #include <libkern/c++/OSObject.h>
  41 #include <IOKit/IOReturn.h>
  42 #include <IOKit/IOLib.h>
  43 #include <IOKit/IOLocks.h>
  44
  45 #include <IOKit/system.h>
  46
  47 class IOEventSource;
  48 class IOTimerEventSource;
  49 class IOCommandGate;
  50
  51 /*! @class IOWorkLoop
  52     @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.
  53 <br><br>
  54         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.
  55 <br><br>
  56         When an event source is registered with a work loop it is informed of the semaphore to use to wake up the loop.
  57 */
  58 class IOWorkLoop : public OSObject
  59 {
  60     OSDeclareDefaultStructors(IOWorkLoop)
  61
  62 public:
  63 /*!
  64     @typedef Action
  65     @discussion Type and arguments of callout C function that is used when
  66 a runCommand is executed by a client.  Cast to this type when you want a C++
  67 member function to be used.  Note the arg1 - arg3 parameters are straight pass
  68 through from the runCommand to the action callout.
  69     @param target
  70         Target of the function, can be used as a refcon.  Note if a C++ function
  71 was specified, this parameter is implicitly the first parameter in the target
  72 member function's parameter list.
  73     @param arg0 Argument to action from run operation.
  74     @param arg1 Argument to action from run operation.
  75     @param arg2 Argument to action from run operation.
  76     @param arg3 Argument to action from run operation.
  77 */
  78     typedef IOReturn (*Action)(OSObject *target,
  79                                void *arg0, void *arg1,
  80                                void *arg2, void *arg3);
  81
  82 private:
  83 /*! @function threadMainContinuation
  84     @abstract Static function that calls the threadMain function.
  85 */
  86     static void threadMainContinuation(IOWorkLoop *self);
  87
  88 protected:
  89
  90 /*! @typedef maintCommandEnum
  91     @discussion Enumeration of commands that _maintCommand can deal with.
  92     @constant mAddEvent Used to tag a Remove event source command.
  93     @constant mRemoveEvent Used to tag a Remove event source command.
  94 */
  95     typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum;
  96
  97 /*! @var gateLock
  98     Mutual exclusion lock that is used by close and open Gate functions.
  99 */
 100     IORecursiveLock *gateLock;
 101
 102 /*! @var eventChain
 103     Pointer to first event source in linked list.
 104 */
 105     IOEventSource *eventChain;
 106
 107 /*! @var controlG
 108     Internal control gate to maintain event system.
 109 */
 110     IOCommandGate *controlG;
 111
 112 /*! @var workSpinLock
 113     The spin lock that is used to guard the 'workToDo' variable.
 114 */
 115     IOSimpleLock *workToDoLock;
 116
 117 /*! @var workThread
 118     Work loop thread.
 119 */
 120     IOThread workThread;
 121
 122 /*! @var workToDo
 123     Used to to indicate that an interrupt has fired and needs to be processed.
 124 */
 125     volatile bool workToDo;
 126
 127 /*! @var loopRestart
 128     Set if an event chain has been changed and the system has to be rechecked from start.  (Internal use only)
 129 */
 130     bool loopRestart;
 131
 132 /*! @struct ExpansionData
 133     @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
 134 */
 135     struct ExpansionData { };
 136
 137 /*! @var reserved
 138     Reserved for future use.  (Internal use only)
 139 */
 140     ExpansionData *reserved;
 141
 142 /*! @function _maintRequest
 143     @abstract Synchronous implementation of addEventSource and removeEventSource functions.
 144     @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.
 145     @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise.
 146 */
 147     virtual IOReturn _maintRequest(void *command, void *data, void *, void *);
 148
 149 /*! @function free
 150     @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.
 151 <br><br>
 152         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.
 153 */
 154     virtual void free();
 155
 156 /*! @function threadMain
 157     @discussion Work loop threads main function.  This function consists of 3
 158     loops: the outermost loop is the semaphore clear and wait loop, the middle
 159     loop terminates when there is no more work, and the inside loop walks the
 160     event list calling the checkForWork method in each event source.  If an
 161     event source has more work to do, it can set the more flag and the middle
 162     loop will repeat.  When no more work is outstanding the outermost will
 163     sleep until an event is signalled.
 164 */
 165     virtual void threadMain();
 166
 167 public:
 168
 169 /*! @function workLoop
 170     @abstract Factory member function to constuct and intialize a work loop.
 171     @result Returns a workLoop instance if constructed successfully, 0 otherwise.
 172 */
 173     static IOWorkLoop *workLoop();
 174
 175 /*! @function init
 176     @discussion Initializes an instance of the workloop.  This method creates and initialses the signaling semaphore and forks the thread that will continue executing.
 177     @result Returns true if initialized successfully, false otherwise.
 178 */
 179     virtual bool init();
 180
 181 /*! @function getThread
 182     @abstract Gets the workThread.
 183     @result Returns workThread.
 184 */
 185     virtual IOThread getThread() const;
 186
 187 /*! @function onThread
 188     @abstract Is the current execution context on the work thread?
 189     @result Returns true if IOThreadSelf() == workThread.
 190 */
 191     virtual bool onThread() const;
 192
 193 /*! @function inGate
 194     @abstract Is the current execution context holding the work-loop's gate?
 195     @result Returns true if IOThreadSelf() is gate holder.
 196 */
 197     virtual bool inGate() const;
 198
 199 /*! @function addEventSource
 200     @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.
 201     @param newEvent Pointer to IOEventSource subclass to add.
 202     @result Always returns kIOReturnSuccess.
 203 */
 204     virtual IOReturn addEventSource(IOEventSource *newEvent);
 205
 206 /*! @function removeEventSource
 207     @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.
 208     @param toRemove Pointer to IOEventSource subclass to remove.
 209     @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found.
 210 */
 211     virtual IOReturn removeEventSource(IOEventSource *toRemove);
 212
 213 /*! @function enableAllEventSources
 214     @abstract Calls enable() in all event sources.
 215     @discussion For all event sources in eventChain, call enable() function.  See IOEventSource::enable().
 216 */
 217     virtual void enableAllEventSources() const;
 218
 219 /*! @function disableAllEventSources
 220     @abstract Calls disable() in all event sources.
 221     @discussion For all event sources in eventChain, call disable() function.  See IOEventSource::disable().
 222 */
 223     virtual void disableAllEventSources() const;
 224
 225 /*! @function enableAllInterrupts
 226     @abstract Calls enable() in all interrupt event sources.
 227     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function.  See IOEventSource::enable().
 228 */
 229     virtual void enableAllInterrupts() const;
 230
 231 /*! @function disableAllInterrupts
 232     @abstract Calls disable() in all interrupt event sources.
 233     @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid,  in eventChain call disable() function.  See IOEventSource::disable().
 234 */
 235     virtual void disableAllInterrupts() const;
 236
 237
 238 protected:
 239     // Internal APIs used by event sources to control the thread
 240     friend class IOEventSource;
 241     friend class IOTimerEventSource;
 242     virtual void signalWorkAvailable();
 243     virtual void openGate();
 244     virtual void closeGate();
 245     virtual bool tryCloseGate();
 246     virtual int  sleepGate(void *event, UInt32 interuptibleType);
 247     virtual void wakeupGate(void *event, bool oneThread);
 248
 249 public:
 250     /* methods available in Mac OS X 10.1 or later */
 251
 252 /*! @function runAction
 253     @abstract Single thread a call to an action with the work-loop.
 254     @discussion Client function that causes the given action to be called in 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 execution of client actions, the action is single threaded against all other work-loop event sources.
 255     @param action Pointer to function to be executed in work-loop context.
 256     @param arg0 Parameter for action parameter, defaults to 0.
 257     @param arg1 Parameter for action parameter, defaults to 0.
 258     @param arg2 Parameter for action parameter, defaults to 0.
 259     @param arg3 Parameter for action parameter, defaults to 0.
 260     @result Returns the value of the Action callout.
 261 */
 262     OSMetaClassDeclareReservedUsed(IOWorkLoop, 0);
 263     virtual IOReturn runAction(Action action, OSObject *target,
 264                                void *arg0 = 0, void *arg1 = 0,
 265                                void *arg2 = 0, void *arg3 = 0);
 266
 267 #if !(defined(__ppc__) && defined(KPI_10_4_0_PPC_COMPAT))
 268 /*! @function runEventSources
 269     @discussion Consists of the inner 2 loops of the threadMain function(qv).
 270     The outer loop terminates when there is no more work, and the inside loop
 271     walks the event list calling the checkForWork method in each event source.
 272     If an event source has more work to do, it can set the more flag and the
 273     outer loop will repeat.
 274 <br><br>
 275     This function can be used to clear a priority inversion between the normal
 276     workloop thread and multimedia's real time threads.  The problem is that
 277     the interrupt action routine is often held off by high priority threads.
 278     So if they want to get their data now they will have to call us and ask if
 279     any data is available.  The multi-media user client will arrange for this
 280     function to be called, which causes any pending interrupts to be processed
 281     and the completion routines called.  By the time the function returns all
 282     outstanding work will have been completed at the real time threads
 283     priority.
 284
 285     @result Return false if the work loop is shutting down, true otherwise.
 286 */
 287     OSMetaClassDeclareReservedUsed(IOWorkLoop, 1);
 288     virtual bool runEventSources();
 289 #endif
 290
 291 protected:
 292
 293 #if (defined(__ppc__) && defined(KPI_10_4_0_PPC_COMPAT))
 294     OSMetaClassDeclareReservedUnused(IOWorkLoop, 1);
 295 #endif
 296     OSMetaClassDeclareReservedUnused(IOWorkLoop, 2);
 297     OSMetaClassDeclareReservedUnused(IOWorkLoop, 3);
 298     OSMetaClassDeclareReservedUnused(IOWorkLoop, 4);
 299     OSMetaClassDeclareReservedUnused(IOWorkLoop, 5);
 300     OSMetaClassDeclareReservedUnused(IOWorkLoop, 6);
 301     OSMetaClassDeclareReservedUnused(IOWorkLoop, 7);
 302 };
 303
 304 #endif /* !__IOKIT_IOWORKLOOP_H */