1/* 2 * Copyright (c) 1998-2007 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, 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. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28/* 29Copyright (c) 1998 Apple Computer, Inc. All rights reserved. 30HISTORY 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 47class IOEventSource; 48class IOTimerEventSource; 49class 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*/ 58class IOWorkLoop : public OSObject 59{ 60 OSDeclareDefaultStructors(IOWorkLoop) 61 62public: 63/*! 64 @typedef Action 65 @discussion Type and arguments of callout C function that is used when 66a runCommand is executed by a client. Cast to this type when you want a C++ 67member function to be used. Note the arg1 - arg3 parameters are straight pass 68through 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 71was specified, this parameter is implicitly the first parameter in the target 72member 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 enum { 82 kPreciousStack = 0x00000001 83 }; 84 85private: 86/*! @function threadMainContinuation 87 @abstract Static function that calls the threadMain function. 88*/ 89 static void threadMainContinuation(IOWorkLoop *self); 90 91protected: 92 93/*! @typedef maintCommandEnum 94 @discussion Enumeration of commands that _maintCommand can deal with. 95 @constant mAddEvent Used to tag a Remove event source command. 96 @constant mRemoveEvent Used to tag a Remove event source command. 97*/ 98 typedef enum { mAddEvent, mRemoveEvent } maintCommandEnum; 99 100/*! @var gateLock 101 Mutual exclusion lock that is used by close and open Gate functions. 102 This is a recursive lock, which allows multiple layers of code to share a single IOWorkLoop without deadlock. This is common in IOKit since threads of execution tend to follow the service plane in the IORegistry, and multiple objects along the call path may acquire the gate for the same (shared) workloop. 103*/ 104 IORecursiveLock *gateLock; 105 106/*! @var eventChain 107 Pointer to first event source in linked list. 108*/ 109 IOEventSource *eventChain; 110 111/*! @var controlG 112 Internal control gate to maintain event system. 113*/ 114 IOCommandGate *controlG; 115 116/*! @var workToDoLock 117 The spin lock that is used to guard the 'workToDo' variable. 118*/ 119 IOSimpleLock *workToDoLock; 120 121/*! @var workThread 122 Work loop thread. 123*/ 124 IOThread workThread; 125 126/*! @var workToDo 127 Used to to indicate that an interrupt has fired and needs to be processed. 128*/ 129 volatile bool workToDo; 130 131/*! @var loopRestart 132 Set if an event chain has been changed and the system has to be rechecked from start. (Internal use only) 133*/ 134 bool loopRestart; 135 136/*! @struct ExpansionData 137 @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future. 138*/ 139 struct ExpansionData { 140 IOOptionBits options; 141 }; 142 143/*! @var reserved 144 Reserved for future use. (Internal use only) 145*/ 146 ExpansionData *reserved; 147 148/*! @function _maintRequest 149 @abstract Synchronous implementation of addEventSource and removeEventSource functions. 150 @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. 151 @return kIOReturnUnsupported if the command given is not implemented, kIOReturnSuccess otherwise. 152*/ 153 virtual IOReturn _maintRequest(void *command, void *data, void *, void *); 154 155/*! @function free 156 @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. 157<br><br> 158 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. 159*/ 160 virtual void free(); 161 162/*! @function threadMain 163 @discussion Work loop threads main function. This function consists of 3 164 loops: the outermost loop is the semaphore clear and wait loop, the middle 165 loop terminates when there is no more work, and the inside loop walks the 166 event list calling the checkForWork method in each event source. If an 167 event source has more work to do, it can set the more flag and the middle 168 loop will repeat. When no more work is outstanding the outermost will 169 sleep until an event is signalled. 170*/ 171 virtual void threadMain(); 172 173public: 174 175/*! @function workLoop 176 @abstract Factory member function to construct and intialize a work loop. 177 @result Returns a workLoop instance if constructed successfully, 0 otherwise. 178*/ 179 static IOWorkLoop *workLoop(); 180 181/*! @function workLoopWithOptions(IOOptionBits options) 182 @abstract Factory member function to constuct and intialize a work loop. 183 @param options Options - kPreciousStack to avoid stack deallocation on paging path. 184 @result Returns a workLoop instance if constructed successfully, 0 otherwise. 185*/ 186 static IOWorkLoop *workLoopWithOptions(IOOptionBits options); 187 188/*! @function init 189 @discussion Initializes an instance of the workloop. This method creates and initializes the signaling semaphore, the controller gate lock, and spawns the thread that will continue executing. 190 @result Returns true if initialized successfully, false otherwise. 191*/ 192 virtual bool init(); 193 194/*! @function getThread 195 @abstract Gets the workThread. 196 @result Returns workThread. 197*/ 198 virtual IOThread getThread() const; 199 200/*! @function onThread 201 @abstract Is the current execution context on the work thread? 202 @result Returns true if IOThreadSelf() == workThread. 203*/ 204 virtual bool onThread() const; 205 206/*! @function inGate 207 @abstract Is the current execution context holding the work-loop's gate? 208 @result Returns true if IOThreadSelf() is gate holder. 209*/ 210 virtual bool inGate() const; 211 212/*! @function addEventSource 213 @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. 214 @param newEvent Pointer to IOEventSource subclass to add. 215 @result Always returns kIOReturnSuccess. 216*/ 217 virtual IOReturn addEventSource(IOEventSource *newEvent); 218 219/*! @function removeEventSource 220 @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. 221 @param toRemove Pointer to IOEventSource subclass to remove. 222 @result Returns kIOReturnSuccess if successful, kIOReturnBadArgument if toRemove couldn't be found. 223*/ 224 virtual IOReturn removeEventSource(IOEventSource *toRemove); 225 226/*! @function enableAllEventSources 227 @abstract Calls enable() in all event sources. 228 @discussion For all event sources in eventChain, call enable() function. See IOEventSource::enable(). 229*/ 230 virtual void enableAllEventSources() const; 231 232/*! @function disableAllEventSources 233 @abstract Calls disable() in all event sources. 234 @discussion For all event sources in eventChain, call disable() function. See IOEventSource::disable(). 235*/ 236 virtual void disableAllEventSources() const; 237 238/*! @function enableAllInterrupts 239 @abstract Calls enable() in all interrupt event sources. 240 @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call enable() function. See IOEventSource::enable(). 241*/ 242 virtual void enableAllInterrupts() const; 243 244/*! @function disableAllInterrupts 245 @abstract Calls disable() in all interrupt event sources. 246 @discussion For all event sources (ES) for which IODynamicCast(IOInterruptEventSource, ES) is valid, in eventChain call disable() function. See IOEventSource::disable(). 247*/ 248 virtual void disableAllInterrupts() const; 249 250 251protected: 252 // Internal APIs used by event sources to control the thread 253 friend class IOEventSource; 254 friend class IOTimerEventSource; 255 virtual void signalWorkAvailable(); 256 virtual void openGate(); 257 virtual void closeGate(); 258 virtual bool tryCloseGate(); 259 virtual int sleepGate(void *event, UInt32 interuptibleType); 260 virtual void wakeupGate(void *event, bool oneThread); 261 262public: 263 /* methods available in Mac OS X 10.1 or later */ 264 265/*! @function runAction 266 @abstract Single thread a call to an action with the work-loop. 267 @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. 268 @param action Pointer to function to be executed in work-loop context. 269 @param arg0 Parameter for action parameter, defaults to 0. 270 @param arg1 Parameter for action parameter, defaults to 0. 271 @param arg2 Parameter for action parameter, defaults to 0. 272 @param arg3 Parameter for action parameter, defaults to 0. 273 @result Returns the value of the Action callout. 274*/ 275 OSMetaClassDeclareReservedUsed(IOWorkLoop, 0); 276 virtual IOReturn runAction(Action action, OSObject *target, 277 void *arg0 = 0, void *arg1 = 0, 278 void *arg2 = 0, void *arg3 = 0); 279 280/*! @function runEventSources 281 @discussion Consists of the inner 2 loops of the threadMain function(qv). 282 The outer loop terminates when there is no more work, and the inside loop 283 walks the event list calling the checkForWork method in each event source. 284 If an event source has more work to do, it can set the more flag and the 285 outer loop will repeat. 286<br><br> 287 This function can be used to clear a priority inversion between the normal 288 workloop thread and multimedia's real time threads. The problem is that 289 the interrupt action routine is often held off by high priority threads. 290 So if they want to get their data now they will have to call us and ask if 291 any data is available. The multi-media user client will arrange for this 292 function to be called, which causes any pending interrupts to be processed 293 and the completion routines called. By the time the function returns all 294 outstanding work will have been completed at the real time threads 295 priority. 296 297 @result Return false if the work loop is shutting down, true otherwise. 298*/ 299 OSMetaClassDeclareReservedUsed(IOWorkLoop, 1); 300 virtual bool runEventSources(); 301 302protected: 303 304 OSMetaClassDeclareReservedUnused(IOWorkLoop, 2); 305 OSMetaClassDeclareReservedUnused(IOWorkLoop, 3); 306 OSMetaClassDeclareReservedUnused(IOWorkLoop, 4); 307 OSMetaClassDeclareReservedUnused(IOWorkLoop, 5); 308 OSMetaClassDeclareReservedUnused(IOWorkLoop, 6); 309 OSMetaClassDeclareReservedUnused(IOWorkLoop, 7); 310}; 311 312#endif /* !__IOKIT_IOWORKLOOP_H */ 313