iokit/IOKit/IOCommandGate.h

   1 /*
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  27  */
  28 /*[
  29     1999-8-10   Godfrey van der Linden(gvdl)
  30         Created.
  31 ]*/
  32 /*! @language embedded-c++ */
  33
  34 #ifndef _IOKIT_IOCOMMANDGATE_H
  35 #define _IOKIT_IOCOMMANDGATE_H
  36
  37 #include <IOKit/IOEventSource.h>
  38
  39 /*!
  40     @class IOCommandGate : public IOEventSource
  41     @abstract Single-threaded work loop client request mechanism.
  42     @discussion An IOCommandGate instance is an extremely lightweight mechanism
  43 that executes an action on the driver's work loop.  Although the code does not
  44 technically execute on the work loop itself, a single-threaded work loop semantic
  45 is maintained for this event source using the work loop gate.  The command gate
  46 tests for a potential self dead lock by checking if the runCommand request is
  47 made from the work loop's thread, it doesn't check for a mutual dead lock though
  48 where a pair of work loop's dead lock each other.
  49 <br><br>
  50         The IOCommandGate is a lighter weight version of the IOCommandQueue and
  51 should be used in preference.  Generally use a command queue whenever you need a
  52 client to submit a request to a work loop.  A typical command gate action would
  53 check if the hardware is active, if so it will add the request to a pending
  54 queue internal to the device or the device's family.  Otherwise if the hardware
  55 is inactive then this request can be acted upon immediately.
  56 <br><br>
  57     CAUTION: The runAction, runCommand, and attemptCommand functions cannot be called from an interrupt context.
  58
  59 */
  60 class IOCommandGate : public IOEventSource
  61 {
  62     OSDeclareDefaultStructors(IOCommandGate)
  63
  64 public:
  65 /*!
  66     @typedef Action
  67     @discussion Type and arguments of callout C function that is used when
  68 a runCommand is executed by a client.  Cast to this type when you want a C++
  69 member function to be used.  Note the arg1 - arg3 parameters are straight pass
  70 through from the runCommand to the action callout.
  71     @param owner
  72         Target of the function, can be used as a refcon.  The owner is set
  73 during initialisation of the IOCommandGate instance.     Note if a C++ function
  74 was specified this parameter is implicitly the first paramter in the target
  75 member function's parameter list.
  76     @param arg0 Argument to action from run operation.
  77     @param arg1 Argument to action from run operation.
  78     @param arg2 Argument to action from run operation.
  79     @param arg3 Argument to action from run operation.
  80 */
  81     typedef IOReturn (*Action)(OSObject *owner,
  82                                void *arg0, void *arg1,
  83                                void *arg2, void *arg3);
  84
  85 protected:
  86
  87 /*! @struct ExpansionData
  88     @discussion This structure will be used to expand the capablilties of the IOWorkLoop in the future.
  89     */
  90     struct ExpansionData { };
  91
  92 /*! @var reserved
  93     Reserved for future use.  (Internal use only)  */
  94     ExpansionData *reserved;
  95
  96 public:
  97 /*! @function commandGate
  98     @abstract Factory method to create and initialise an IOCommandGate, See $link init.
  99     @result Returns a pointer to the new command gate if sucessful, 0 otherwise. */
 100     static IOCommandGate *commandGate(OSObject *owner, Action action = 0);
 101
 102 /*! @function init
 103     @abstract Class initialiser.
 104     @discussion Initialiser for IOCommandGate operates only on newly 'newed'
 105 objects.  Shouldn't be used to re-init an existing instance.
 106     @param owner        Owner of this, newly created, instance of the IOCommandGate.  This argument will be used as the first parameter in the action callout.
 107     @param action
 108         Pointer to a C function that is called whenever a client of the
 109 IOCommandGate calls runCommand.  NB Can be a C++ member function but caller
 110 must cast the member function to $link IOCommandGate::Action and they will get a
 111 compiler warning.  Defaults to zero, see $link IOEventSource::setAction.
 112     @result True if inherited classes initialise successfully. */
 113     virtual bool init(OSObject *owner, Action action = 0);
 114
 115     // Superclass overrides
 116     virtual void free() APPLE_KEXT_OVERRIDE;
 117     virtual void setWorkLoop(IOWorkLoop *inWorkLoop) APPLE_KEXT_OVERRIDE;
 118
 119 /*! @function runCommand
 120     @abstract Single thread a command with the target work loop.
 121     @discussion Client function that causes the current action to be called in
 122 a single threaded manner.  Beware the work loop's gate is recursive and command
 123 gates can cause direct or indirect re-entrancy.  When the executing on a
 124 client's thread runCommand will sleep until the work loop's gate opens for
 125 execution of client actions, the action is single threaded against all other
 126 work loop event sources.  If the command is disabled the attempt to run a command will be stalled until enable is called.
 127     @param arg0 Parameter for action of command gate, defaults to 0.
 128     @param arg1 Parameter for action of command gate, defaults to 0.
 129     @param arg2 Parameter for action of command gate, defaults to 0.
 130     @param arg3 Parameter for action of command gate, defaults to 0.
 131     @result kIOReturnSuccess if successful. kIOReturnAborted if a disabled command gate is free()ed before being reenabled, kIOReturnNoResources if no action available.
 132 */
 133     virtual IOReturn runCommand(void *arg0 = 0, void *arg1 = 0,
 134                                 void *arg2 = 0, void *arg3 = 0);
 135
 136 /*! @function runAction
 137     @abstract Single thread a call to an action with the target work loop.
 138     @discussion Client function that causes the given action to be called in
 139 a single threaded manner.  Beware the work loop's gate is recursive and command
 140 gates can cause direct or indirect re-entrancy.  When the executing on a
 141 client's thread runAction will sleep until the work loop's gate opens for
 142 execution of client actions, the action is single threaded against all other
 143 work loop event sources.  If the command is disabled the attempt to run a command will be stalled until enable is called.
 144     @param action Pointer to function to be executed in the context of the work loop.
 145     @param arg0 Parameter for action parameter, defaults to 0.
 146     @param arg1 Parameter for action parameter, defaults to 0.
 147     @param arg2 Parameter for action parameter, defaults to 0.
 148     @param arg3 Parameter for action parameter, defaults to 0.
 149     @result The return value of action if it was called, kIOReturnBadArgument if action is not defined, kIOReturnAborted if a disabled command gate is free()ed before being reenabled.
 150 */
 151     virtual IOReturn runAction(Action action,
 152                                void *arg0 = 0, void *arg1 = 0,
 153                                void *arg2 = 0, void *arg3 = 0);
 154
 155 /*! @function attemptCommand
 156     @abstract Single thread a command with the target work loop.
 157     @discussion Client function that causes the current action to be called in
 158 a single threaded manner.  When the executing on a client's thread attemptCommand will fail if the work loop's gate is closed.
 159     @param arg0 Parameter for action of command gate, defaults to 0.
 160     @param arg1 Parameter for action of command gate, defaults to 0.
 161     @param arg2 Parameter for action of command gate, defaults to 0.
 162     @param arg3 Parameter for action of command gate, defaults to 0.
 163     @result kIOReturnSuccess if successful. kIOReturnNotPermitted if this event source is currently disabled, kIOReturnNoResources if no action available, kIOReturnCannotLock if lock attempt fails.
 164 */
 165     virtual IOReturn attemptCommand(void *arg0 = 0, void *arg1 = 0,
 166                                     void *arg2 = 0, void *arg3 = 0);
 167
 168 /*! @function attemptAction
 169     @abstract Single thread a call to an action with the target work loop.
 170     @discussion Client function that causes the given action to be called in
 171 a single threaded manner.  Beware the work loop's gate is recursive and command
 172 gates can cause direct or indirect re-entrancy.  When the executing on a
 173 client's thread attemptCommand will fail if the work loop's gate is closed.
 174     @param action Pointer to function to be executed in context of the work loop.
 175     @param arg0 Parameter for action parameter, defaults to 0.
 176     @param arg1 Parameter for action parameter, defaults to 0.
 177     @param arg2 Parameter for action parameter, defaults to 0.
 178     @param arg3 Parameter for action parameter, defaults to 0.
 179     @result kIOReturnSuccess if successful. kIOReturnBadArgument if action is not defined, kIOReturnNotPermitted if this event source is currently disabled, kIOReturnCannotLock if lock attempt fails.
 180
 181 */
 182     virtual IOReturn attemptAction(Action action,
 183                                    void *arg0 = 0, void *arg1 = 0,
 184                                    void *arg2 = 0, void *arg3 = 0);
 185
 186 /*! @function commandSleep
 187     @abstract Put a thread that is currently holding the command gate to sleep.
 188     @discussion Put a thread to sleep waiting for an event but release the gate first.  If the event occurs then the commandGate is closed before the function returns.
 189     @param event Pointer to an address.
 190     @param interruptible THREAD_UNINT, THREAD_INTERRUPTIBLE or THREAD_ABORTSAFE.  THREAD_UNINT specifies that the sleep cannot be interrupted by a signal.  THREAD_INTERRUPTIBLE specifies that the sleep may be interrupted by a "kill -9" signal.  THREAD_ABORTSAFE (the default value) specifies that the sleep may be interrupted by any user signal.
 191     @result THREAD_AWAKENED - normal wakeup, THREAD_TIMED_OUT - timeout expired, THREAD_INTERRUPTED - interrupted, THREAD_RESTART - restart operation entirely, kIOReturnNotPermitted if the calling thread does not hold the command gate. */
 192     virtual IOReturn commandSleep(void *event,
 193                                   UInt32 interruptible = THREAD_ABORTSAFE);
 194
 195 /*! @function commandWakeup
 196     @abstract Wakeup one or more threads that are asleep on an event.
 197     @param event Pointer to an address.
 198     @param oneThread true to only wake up at most one thread, false otherwise. */
 199     virtual void commandWakeup(void *event, bool oneThread = false);
 200
 201 /*! @function disable
 202     @abstract Disable the command gate
 203     @discussion When a command gate is disabled all future calls to runAction and runCommand will stall until the gate is enable()d later.  This can be used to block client threads when a system sleep is requested.  The IOWorkLoop thread itself will never stall, even when making runAction/runCommand calls.  This call must be made from a gated context, to clear potential race conditions.  */
 204     virtual void disable() APPLE_KEXT_OVERRIDE;
 205
 206 /*! @function enable
 207     @abstract Enable command gate, this will unblock any blocked Commands and Actions.
 208     @discussion  Enable the command gate.  The attemptAction/attemptCommand calls will now be enabled and can succeeed.  Stalled runCommand/runAction calls will be woken up. */
 209     virtual void enable() APPLE_KEXT_OVERRIDE;
 210
 211 /*! @function commandSleep
 212     @abstract Put a thread that is currently holding the command gate to sleep.
 213     @discussion Put a thread to sleep waiting for an event but release the gate first.  If the event occurs or timeout occurs then the commandGate is closed before the function returns.
 214     @param event Pointer to an address.
 215         @param deadline Clock deadline to timeout the sleep.
 216     @param interruptible THREAD_UNINT, THREAD_INTERRUPTIBLE or THREAD_ABORTSAFE.  THREAD_UNINT specifies that the sleep cannot be interrupted by a signal.  THREAD_INTERRUPTIBLE specifies that the sleep may be interrupted by a "kill -9" signal.  THREAD_ABORTSAFE specifies that the sleep may be interrupted by any user signal.
 217     @result THREAD_AWAKENED - normal wakeup, THREAD_TIMED_OUT - timeout expired, THREAD_INTERRUPTED - interrupted, THREAD_RESTART - restart operation entirely, kIOReturnNotPermitted if the calling thread does not hold the command gate. */
 218     virtual IOReturn commandSleep(void *event,
 219                                                                   AbsoluteTime deadline,
 220                                   UInt32 interruptible);
 221
 222 private:
 223 #if __LP64__
 224     OSMetaClassDeclareReservedUnused(IOCommandGate, 0);
 225 #else
 226     OSMetaClassDeclareReservedUsed(IOCommandGate, 0);
 227 #endif
 228     OSMetaClassDeclareReservedUnused(IOCommandGate, 1);
 229     OSMetaClassDeclareReservedUnused(IOCommandGate, 2);
 230     OSMetaClassDeclareReservedUnused(IOCommandGate, 3);
 231     OSMetaClassDeclareReservedUnused(IOCommandGate, 4);
 232     OSMetaClassDeclareReservedUnused(IOCommandGate, 5);
 233     OSMetaClassDeclareReservedUnused(IOCommandGate, 6);
 234     OSMetaClassDeclareReservedUnused(IOCommandGate, 7);
 235 };
 236
 237 #endif /* !_IOKIT_IOCOMMANDGATE_H */