iokit/IOKit/pwr_mgt/IOPMchangeNoteList.h

   1 /*
   2  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
   3  *
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   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
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  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
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  23 #include <libkern/c++/OSObject.h>
  24 #include <IOKit/IOReturn.h>
  25
  26 class IOPowerConnection;
  27
  28 // This is a list of State Changes which are in progress.  Its purpose is to keep track of the
  29 // notifications and acknowledgements caused by state change.  A change is added to the list
  30 // when either our parent notifies us that the power domain is changing state or when we decide
  31 // to change power to our device or domain.
  32 //
  33 // A change is removed from the list when all interested parties have been informed of the upcoming
  34 // change, all of them have acknowledged the notification, the change has been made, all interested
  35 // parties have been informed that the change was made, and all of them have acknowledged.
  36 //
  37 // The list is strictly first-in, first-out.  It is implemented as a circular list in a linear
  38 // array.  There are two pointers into the array.  The circular list is empty when these two
  39 // pointers are equal.
  40
  41 // More specifically, a change note is put into the array when one of these things happens:
  42 //   the device decides it is idle and needs to reduce power. (changePowerStateTo)
  43 //   the device decides it is not idle and needs to increase power. (changePowerStateTo)
  44 //   the controlling driver requests a state change. (changePowerStateTo)
  45 //   some client needs to use the device but it is powered down. (makeUsable)
  46 //   the parent says the domain power is changing. (powerStateWillChangeTo)
  47 //   a child says it no longer needs power, and all other children are similarly idle. (requestDomainState)
  48 //.  a child wants more power in the domain so it can raise its power state. (requestDomainState)
  49 //
  50 // A change note is removed from the array when all interested drivers and power domain
  51 // children have acknowledged the change.
  52
  53 // Each change note contains:
  54 // A flag field which describes the change.
  55 // Which power state the device will be in after the change.
  56 // The power flags which describe the result of this change.
  57
  58 struct changeNoteItem{
  59 unsigned long           flags;
  60 unsigned long           newStateNumber;
  61 IOPMPowerFlags          outputPowerCharacter;
  62 IOPMPowerFlags          inputPowerRequirement;
  63 IOPMPowerFlags          domainState;
  64 IOPowerConnection *     parent;
  65 IOPMPowerFlags          singleParentState;
  66 IOPMPowerFlags          capabilityFlags;
  67 };
  68
  69 typedef struct changeNoteItem changeNoteItem;
  70
  71
  72                                         // flags field
  73
  74 #define IOPMParentInitiated             1               // this power change initiated by our  parent
  75 #define IOPMWeInitiated         2               // this power change initiated by this device (not parent)
  76 #define IOPMNotDone             4               // we couldn't make this change
  77 #define IOPMNotInUse            8               // this list element not currently in use
  78 #define IOPMDomainWillChange    16              // parent change started by PowerDomainWillChangeTo
  79 #define IOPMDomainDidChange     32              // parent change started by PowerDomainDidChangeTo
  80
  81
  82 // Length of change note list is maximum 5.  There cannot be two adjacent device-initiated change notes unless
  83 // one is currently being actioned, because two adjacent in-active device-initiated changes are always collapsed
  84 // into one, and there cannot be more than two parent-initiated change notes in the queue (from one parent),
  85 // because the parent does not
  86 // initiate a change (by calling domainStateWillChange) until everybody has acknowledged the previous one
  87 // (by calling domainStateDidChange), although if we are the last to send that acknowledgement, the change we
  88 // are acknowledging will still be in the queue as we acknowledge, and at that point the parent can give us another
  89 // (by callingdomainStateWillChange).  So we need room for two parent changes, two non-adjacent device changes,
  90 // one more per additional parent, say two more,
  91 // and room for one more device change to get into the queue before collapsing it with its neighbor.  In this case, seven
  92 // entryies suffices.  Or, we need
  93 // room for two adjacent device changes (one in progress), a parent change, another device change, another parent change,
  94 // another device change, another parent change, another device change, plus
  95 // one more device change to get into the queue before collapsing it with its neighbor.  Nine entries in this case.
  96 // I'm not sure what irrationallity causes me to code for twenty entries in the queue.
  97 #define IOPMMaxChangeNotes 20
  98
  99 class IOPMchangeNoteList :public OSObject
 100 {
 101 OSDeclareDefaultStructors(IOPMchangeNoteList)
 102
 103 private:
 104     unsigned long               firstInList;            // points to oldest active change note in list
 105     unsigned long               firstUnused;            // points just beyond newest change note in list
 106
 107 public:
 108
 109         changeNoteItem          changeNote[IOPMMaxChangeNotes];
 110
 111
 112 void initialize ( void );
 113
 114 long createChangeNote ( void );
 115
 116 long currentChange ( void );
 117
 118 long latestChange ( void );
 119
 120 IOReturn releaseHeadChangeNote ( void );
 121
 122 IOReturn releaseTailChangeNote ( void );
 123
 124 bool changeNoteInUse ( unsigned long ordinal );
 125
 126 long nextChangeNote ( unsigned long ordinal );
 127
 128 unsigned long increment (unsigned long ordinal );
 129
 130 unsigned long decrement (unsigned long ordinal );
 131
 132 long previousChangeNote (unsigned long ordinal );
 133
 134 bool listEmpty ( void );
 135
 136 };