iokit/IOKit/pwr_mgt/IOPMchangeNoteList.h

   1 /*
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  28 #include <libkern/c++/OSObject.h>
  29 #include <IOKit/IOReturn.h>
  30
  31 class IOPowerConnection;
  32
  33 // This is a list of State Changes which are in progress.  Its purpose is to keep track of the
  34 // notifications and acknowledgements caused by state change.  A change is added to the list
  35 // when either our parent notifies us that the power domain is changing state or when we decide
  36 // to change power to our device or domain.
  37 //
  38 // A change is removed from the list when all interested parties have been informed of the upcoming
  39 // change, all of them have acknowledged the notification, the change has been made, all interested
  40 // parties have been informed that the change was made, and all of them have acknowledged.
  41 //
  42 // The list is strictly first-in, first-out.  It is implemented as a circular list in a linear
  43 // array.  There are two pointers into the array.  The circular list is empty when these two
  44 // pointers are equal.
  45
  46 // More specifically, a change note is put into the array when one of these things happens:
  47 //   the device decides it is idle and needs to reduce power. (changePowerStateTo)
  48 //   the device decides it is not idle and needs to increase power. (changePowerStateTo)
  49 //   the controlling driver requests a state change. (changePowerStateTo)
  50 //   some client needs to use the device but it is powered down. (makeUsable)
  51 //   the parent says the domain power is changing. (powerStateWillChangeTo)
  52 //   a child says it no longer needs power, and all other children are similarly idle. (requestDomainState)
  53 //.  a child wants more power in the domain so it can raise its power state. (requestDomainState)
  54 //
  55 // A change note is removed from the array when all interested drivers and power domain
  56 // children have acknowledged the change.
  57
  58 // Each change note contains:
  59 // A flag field which describes the change.
  60 // Which power state the device will be in after the change.
  61 // The power flags which describe the result of this change.
  62
  63 struct changeNoteItem{
  64 unsigned long           flags;
  65 unsigned long           newStateNumber;
  66 IOPMPowerFlags          outputPowerCharacter;
  67 IOPMPowerFlags          inputPowerRequirement;
  68 IOPMPowerFlags          domainState;
  69 IOPowerConnection *     parent;
  70 IOPMPowerFlags          singleParentState;
  71 IOPMPowerFlags          capabilityFlags;
  72 };
  73
  74 typedef struct changeNoteItem changeNoteItem;
  75
  76
  77                                         // flags field
  78
  79 #define IOPMParentInitiated             1               // this power change initiated by our  parent
  80 #define IOPMWeInitiated         2               // this power change initiated by this device (not parent)
  81 #define IOPMNotDone             4               // we couldn't make this change
  82 #define IOPMNotInUse            8               // this list element not currently in use
  83 #define IOPMDomainWillChange    16              // parent change started by PowerDomainWillChangeTo
  84 #define IOPMDomainDidChange     32              // parent change started by PowerDomainDidChangeTo
  85
  86
  87 // Length of change note list is maximum 5.  There cannot be two adjacent device-initiated change notes unless
  88 // one is currently being actioned, because two adjacent in-active device-initiated changes are always collapsed
  89 // into one, and there cannot be more than two parent-initiated change notes in the queue (from one parent),
  90 // because the parent does not
  91 // initiate a change (by calling domainStateWillChange) until everybody has acknowledged the previous one
  92 // (by calling domainStateDidChange), although if we are the last to send that acknowledgement, the change we
  93 // are acknowledging will still be in the queue as we acknowledge, and at that point the parent can give us another
  94 // (by callingdomainStateWillChange).  So we need room for two parent changes, two non-adjacent device changes,
  95 // one more per additional parent, say two more,
  96 // and room for one more device change to get into the queue before collapsing it with its neighbor.  In this case, seven
  97 // entryies suffices.  Or, we need
  98 // room for two adjacent device changes (one in progress), a parent change, another device change, another parent change,
  99 // another device change, another parent change, another device change, plus
 100 // one more device change to get into the queue before collapsing it with its neighbor.  Nine entries in this case.
 101 // I'm not sure what irrationallity causes me to code for twenty entries in the queue.
 102 #define IOPMMaxChangeNotes 20
 103
 104 class IOPMchangeNoteList :public OSObject
 105 {
 106 OSDeclareDefaultStructors(IOPMchangeNoteList)
 107
 108 private:
 109     unsigned long               firstInList;            // points to oldest active change note in list
 110     unsigned long               firstUnused;            // points just beyond newest change note in list
 111
 112 public:
 113
 114         changeNoteItem          changeNote[IOPMMaxChangeNotes];
 115
 116
 117 void initialize ( void );
 118
 119 long createChangeNote ( void );
 120
 121 long currentChange ( void );
 122
 123 long latestChange ( void );
 124
 125 IOReturn releaseHeadChangeNote ( void );
 126
 127 IOReturn releaseTailChangeNote ( void );
 128
 129 bool changeNoteInUse ( unsigned long ordinal );
 130
 131 long nextChangeNote ( unsigned long ordinal );
 132
 133 unsigned long increment (unsigned long ordinal );
 134
 135 unsigned long decrement (unsigned long ordinal );
 136
 137 long previousChangeNote (unsigned long ordinal );
 138
 139 bool listEmpty ( void );
 140
 141 };