iokit/IOKit/pwr_mgt/IOPMchangeNoteList.h

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
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   8  * "License").  You may not use this file except in compliance with the
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  10  * http://www.apple.com/publicsource and read it before using this file.
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  22 #include <libkern/c++/OSObject.h>
  23 #include <IOKit/IOReturn.h>
  24
  25 class IOPowerConnection;
  26
  27 // This is a list of State Changes which are in progress.  Its purpose is to keep track of the
  28 // notifications and acknowledgements caused by state change.  A change is added to the list
  29 // when either our parent notifies us that the power domain is changing state or when we decide
  30 // to change power to our device or domain.
  31 //
  32 // A change is removed from the list when all interested parties have been informed of the upcoming
  33 // change, all of them have acknowledged the notification, the change has been made, all interested
  34 // parties have been informed that the change was made, and all of them have acknowledged.
  35 //
  36 // The list is strictly first-in, first-out.  It is implemented as a circular list in a linear
  37 // array.  There are two pointers into the array.  The circular list is empty when these two
  38 // pointers are equal.
  39
  40 // More specifically, a change note is put into the array when one of these things happens:
  41 //   the device decides it is idle and needs to reduce power. (changePowerStateTo)
  42 //   the device decides it is not idle and needs to increase power. (changePowerStateTo)
  43 //   the controlling driver requests a state change. (changePowerStateTo)
  44 //   some client needs to use the device but it is powered down. (makeUsable)
  45 //   the parent says the domain power is changing. (powerStateWillChangeTo)
  46 //   a child says it no longer needs power, and all other children are similarly idle. (requestDomainState)
  47 //.  a child wants more power in the domain so it can raise its power state. (requestDomainState)
  48 //
  49 // A change note is removed from the array when all interested drivers and power domain
  50 // children have acknowledged the change.
  51
  52 // Each change note contains:
  53 // A flag field which describes the change.
  54 // Which power state the device will be in after the change.
  55 // The power flags which describe the result of this change.
  56
  57 struct changeNoteItem{
  58 unsigned long           flags;
  59 unsigned long           newStateNumber;
  60 IOPMPowerFlags          outputPowerCharacter;
  61 IOPMPowerFlags          inputPowerRequirement;
  62 IOPMPowerFlags          domainState;
  63 IOPowerConnection *     parent;
  64 IOPMPowerFlags          singleParentState;
  65 IOPMPowerFlags          capabilityFlags;
  66 };
  67
  68 typedef struct changeNoteItem changeNoteItem;
  69
  70
  71                                         // flags field
  72
  73 #define IOPMParentInitiated             1               // this power change initiated by our  parent
  74 #define IOPMWeInitiated         2               // this power change initiated by this device (not parent)
  75 #define IOPMNotDone             4               // we couldn't make this change
  76 #define IOPMNotInUse            8               // this list element not currently in use
  77 #define IOPMDomainWillChange    16              // parent change started by PowerDomainWillChangeTo
  78 #define IOPMDomainDidChange     32              // parent change started by PowerDomainDidChangeTo
  79
  80
  81 // Length of change note list is maximum 5.  There cannot be two adjacent device-initiated change notes unless
  82 // one is currently being actioned, because two adjacent in-active device-initiated changes are always collapsed
  83 // into one, and there cannot be more than two parent-initiated change notes in the queue (from one parent),
  84 // because the parent does not
  85 // initiate a change (by calling domainStateWillChange) until everybody has acknowledged the previous one
  86 // (by calling domainStateDidChange), although if we are the last to send that acknowledgement, the change we
  87 // are acknowledging will still be in the queue as we acknowledge, and at that point the parent can give us another
  88 // (by callingdomainStateWillChange).  So we need room for two parent changes, two non-adjacent device changes,
  89 // one more per additional parent, say two more,
  90 // and room for one more device change to get into the queue before collapsing it with its neighbor.  In this case, seven
  91 // entryies suffices.  Or, we need
  92 // room for two adjacent device changes (one in progress), a parent change, another device change, another parent change,
  93 // another device change, another parent change, another device change, plus
  94 // one more device change to get into the queue before collapsing it with its neighbor.  Nine entries in this case.
  95 // I'm not sure what irrationallity causes me to code for twenty entries in the queue.
  96 #define IOPMMaxChangeNotes 20
  97
  98 class IOPMchangeNoteList :public OSObject
  99 {
 100 OSDeclareDefaultStructors(IOPMchangeNoteList)
 101
 102 private:
 103     unsigned long               firstInList;            // points to oldest active change note in list
 104     unsigned long               firstUnused;            // points just beyond newest change note in list
 105
 106 public:
 107
 108         changeNoteItem          changeNote[IOPMMaxChangeNotes];
 109
 110
 111 void initialize ( void );
 112
 113 long createChangeNote ( void );
 114
 115 long currentChange ( void );
 116
 117 long latestChange ( void );
 118
 119 IOReturn releaseHeadChangeNote ( void );
 120
 121 IOReturn releaseTailChangeNote ( void );
 122
 123 bool changeNoteInUse ( unsigned long ordinal );
 124
 125 long nextChangeNote ( unsigned long ordinal );
 126
 127 unsigned long increment (unsigned long ordinal );
 128
 129 unsigned long decrement (unsigned long ordinal );
 130
 131 long previousChangeNote (unsigned long ordinal );
 132
 133 bool listEmpty ( void );
 134
 135 };