IOMobileFramebuffer

IOMobileFramebuffer is a kernel extension for managing the screen framebuffer. It is controlled by the user-land framework IOMobileFramework.

Methods

Selector	Action	Input	Output
3	getDefaultSurface	-	IOSurfaceID surfaceID
4	swapBegin	-	IOMobileFramebufferSwapID swapID
5	swapEnd	struct IOMobileFramebufferSwapArg	-
6	swapWait	IOMobileFramebufferSwapID swapID, uint32_t waitOptions, (iOS 4.2+ only) uint64_t timeout_millis	-
7	getId	-	IOSwapNotificationID framebufferID
8	getDisplaySize	-	struct IOMobileFramebufferDisplaySize
9	setVSyncNotifications	size_t functionAddress (if 0, notification is disabled), size_t userData	-
12	requestPowerChange	uint32_t value	-
15	setDebugFlags	uint32_t ???[2]	uint32_t ???
17	setGammaTable	struct IOMobileFramebufferGammaTables	-
18	isMainDisplay	-	uint32_t result
19	setWhiteOnBlackMode	uint32_t value	-
22	setDisplayDevice	uint32_t value	-
27	getGammaTable	-	struct IOMobileFramebufferGammaTables
33(*)	setVideoPowerSaving	uint32_t value	-
50(**)	setBrightnessCorrection	uint32_t value	-

(*) - was 32 before 4.0

(**) - was 49 before 8.0

where

// This can be the first argument to a layer swap notification.
// In that case, the other two arguments are interpreted as
//   IOMobileFramebufferSwapID ''swapID'', uint32_t ''
// Swap notifications can be sent, for example, via -[EAGLContext sendNotification: forTransaction: onLayer:]
typedef uint32_t IOSwapNotificationID;

struct UInt32Rect {
  uint32_t x, y, width, height;
};

struct UInt8Bgra {
  uint8_t b, g, r, a;
};

// bits 0.. 3 - bit per layer
// bit 31 - bit for bg color
typedef uint32_t IOMobileFramebufferSwapFlags;

#if IOS_VERSION >= 7.0
const int NUM_LAYERS = 4;
#else
const int NUM_LAYERS = 3;
#endif

struct IOMobileFramebufferSwapArg {

#if IOS_VERSION >= 7.0
  int64_t timeStamps[3];
#endif

#if IOS_VERSION >= 8.0
  uint64_t imageSources[16]; // ?
  uint32_t numImageSources; // 0..16
  uint32_t ???; // padding?
#endif

  IOMobileFramebufferSwapID swapID;
  IOSurfaceID surfaceID[NUM_LAYERS];

  UInt32Rect bounds[NUM_LAYERS]; // surface source bounds

#if IOS_VERSION >= 4.3
  UInt32Rect uiSubRegion[NUM_LAYERS]; // ?
  uint32_t edgeMode[NUM_LAYERS]; // ?
  float32_t edgeCoverage[NUM_LAYERS]; // ?
#endif

  UInt32Rect frames[NUM_LAYERS]; // framebuffer target frame

  IOMobileFramebufferSwapFlags providedFlags; // which layers are provided for swap (in this structure)
  IOMobileFramebufferSwapFlags readyFlags; // which layers are ready to be swapped
                                           // (layers that aren't ready must be notified as ready later via layer swap notifications)
  
  UInt8Bgra bgColor;
  uint32_t gammaTable; // 0..2, index to gamma table to use
  
  uint32_t rotation[NUM_LAYERS]; // 0 - none, 1 - 90 left, 2 - 180, 3 - 90 right

#if IOS_VERSION >= 4.3
  uint32_t destEdgeAlpha; // ?
#endif
#if IOS_VERSION >= 7.0
  uint32_t ???[2];
#endif
};

struct IOMobileFramebufferDisplaySize {
  uint32_t width;
  uint32_t height;
};

struct IOMobileFramebufferGammaTables {
  struct GammaTable {

    // Each value has 2 bitfields: [0..9] and [10..19]. Meanings unknown.
#if IOS_VERSION >= 7.0
    uint32_t value[0x101];
#else
    uint32_t value[0x100];
#endif

  } gammaTable[3];
};

Sync Notification

The notification can be registered for a IOMobileFramebuffer connection by setting the mach port via IOConnectSetNotificationPort and then setting the data via method setVSyncNotifications.

It is sent in the format of an IO interest notification as follows:

struct IOMobileFramebufferSyncNotification {
  <standard message header (ID is 53)>
  <standard message port object - the service port>
  // note: no NDR

  uint32_t contentSize; // always sizeof(size_t)
  uint32_t contentType; // always 160 (service message)
  uint32_t userData[8]; // [1] is functionAddress, [2] is userData, rest ([0], [3..7]) are likely 0.
  
  // content:
  size_t timingData; // pointer to IOMobileFramebufferTimingData, driver-mapped memory
};

struct IOMobileFramebufferTimingData {
  int64 frameNumber;
  int64 currentTime;
  int64 frameDuration;
};