iokit/IOKit/IODMACommand.h

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  28 #ifndef _IODMACOMMAND_H
  29 #define _IODMACOMMAND_H
  30
  31 #include <IOKit/IOCommand.h>
  32 #include <IOKit/IOMemoryDescriptor.h>
  33 class IOMapper;
  34
  35 /**************************** class IODMACommand ***************************/
  36
  37 /*!
  38     @class IODMACommand
  39     @abstract A mechanism to convert memory references to I/O bus addresses.
  40     @discussion The IODMACommand is supersedes the IOMemoryCursor and greatly enhances the functionality and power of it.  The command can be specified to output 64 bit physical addresses and also allows driver writers bypass mapping hardware or get addresses suitable for non-snooped DMA.
  41 <br><br>
  42     The command is designed to be very easily subclassable.  Most driver writers need to associate some DMA operations with their memory descriptor and usually use a C structure for that purpose.  This structure is often kept in a linked list.  This IODMACommand has built it <kern/queue.h> linkage and can be derived and 'public:' variables added, giving the developer a structure that can associate a memory descriptor with a particular dma command but will also allow the developer to generate that command and keep the state necessary for tracking it.
  43 <br><br>
  44     It is envisaged that a pool of IODMACommands will be created at driver initialisation and each command will be kept in an IOCommandPool while not in use.  However if developers wishes to maintain their own free lists that is certainly possible.  See the <kern/queue.h> and <xnu/iokit/Kernel/IOCommandPool> for sample code on manipulating the command's doubly linked list entries.
  45 <br><br>
  46     The IODMACommand can be used in a 'weak-linked' manner.  To do this you must avoid using any static member functions.  Use the, much slower but safe, weakWithSpecification function.  On success a dma command instance will be returned.  This instance can then be used to clone as many commands as is needed.  Remember deriving from this class can not be done weakly, that is no weak subclassing!
  47 */
  48
  49 class IODMACommand : public IOCommand
  50 {
  51     OSDeclareDefaultStructors(IODMACommand);
  52
  53 friend class IODMAEventSource;
  54
  55 public:
  56
  57 /*!
  58     @typedef Segment32
  59     @discussion A 32 bit I/O bus address/length pair
  60 */
  61     struct Segment32 {
  62         UInt32 fIOVMAddr, fLength;
  63     };
  64
  65 /*!
  66     @typedef Segment64
  67     @discussion A 64 bit I/O bus address/length pair
  68 */
  69     struct Segment64 {
  70         UInt64 fIOVMAddr, fLength;
  71     };
  72
  73 /*! @enum MappingOptions
  74     @abstract Mapping types to indicate the desired mapper type for translating memory descriptors into I/O DMA Bus addresses.
  75     @constant kNonCoherent      Used by drivers for non-coherent transfers, implies unmapped memmory
  76     @constant kMapped           Allow a driver to define addressing size
  77     @constant kBypassed         Allow drivers to bypass any mapper
  78     @constant kMaxMappingOptions        Internal use only
  79 */
  80     enum MappingOptions {
  81         kMapped       = 0x00000000,
  82         kBypassed     = 0x00000001,
  83         kNonCoherent  = 0x00000002,
  84         kTypeMask     = 0x0000000f,
  85
  86         kNoCacheStore = 0x00000010,     // Memory in descriptor
  87         kOnChip       = 0x00000020,     // Indicates DMA is on South Bridge
  88         kIterateOnly  = 0x00000040      // DMACommand will be used as a cursor only
  89     };
  90
  91 /*! @enum SynchronizeOptions
  92     @abstract Options for the synchronize method.
  93     @constant kForceDoubleBuffer Copy the entire prepared range to a new page aligned buffer.
  94 */
  95     enum SynchronizeOptions {
  96         kForceDoubleBuffer = 0x01000000
  97     };
  98
  99 /*!
 100     @typedef SegmentFunction
 101     @discussion Pointer to a C function that translates a 64 segment and outputs a single desired segment to the array at the requested index. There are a group of pre-implemented SegmentFunctions that may be usefull to the developer below.
 102     @param segment The 64Bit I/O bus address and length.
 103     @param segments Base of the output vector of DMA address length pairs.
 104     @param segmentIndex Index to output 'segment' in the 'segments' array.
 105     @result Returns true if segment encoding succeeded.  false may be returned if the current segment does not fit in an output segment, i.e. a 38bit address wont fit into a 32 encoding.
 106 */
 107     typedef bool (*SegmentFunction)(IODMACommand *target,
 108                                     Segment64 segment,
 109                                     void     *segments,
 110                                     UInt32    segmentIndex);
 111
 112     // -------------- Preimplemented output functions ----------------
 113
 114 /*! @function OutputHost32
 115     @abstract Output host natural Segment32 output segment function.
 116 */
 117     static bool OutputHost32(IODMACommand *target,
 118             Segment64 seg, void *segs, UInt32 ind);
 119
 120 /*! @defined kIODMACommandOutputHost32
 121     @abstract Output host natural Segment32 output segment function.
 122  */
 123 #define kIODMACommandOutputHost32   (IODMACommand::OutputHost32)
 124
 125 /*! @function OutputBig32
 126     @abstract Output big-endian Segment32 output segment function.
 127 */
 128     static bool OutputBig32(IODMACommand *target,
 129             Segment64 seg, void *segs, UInt32 ind);
 130
 131 /*! @defined kIODMACommandOutputBig32
 132     @abstract Output big-endian Segment32 output segment function.
 133  */
 134 #define kIODMACommandOutputBig32    (IODMACommand::OutputBig32)
 135
 136 /*! @function OutputLittle32
 137     @abstract Output little-endian Segment32 output segment function.
 138 */
 139     static bool OutputLittle32(IODMACommand *target,
 140             Segment64 seg, void *segs, UInt32 ind);
 141
 142 /*! @defined kIODMACommandOutputLittle32
 143     @abstract Output little-endian Segment32 output segment function.
 144 */
 145 #define kIODMACommandOutputLittle32 (IODMACommand::OutputLittle32)
 146
 147 /*! @function OutputHost64
 148     @abstract Output host natural Segment64 output segment function.
 149 */
 150     static bool OutputHost64(IODMACommand *target,
 151             Segment64 seg, void *segs, UInt32 ind);
 152
 153 /*! @defined kIODMACommandOutputHost64
 154     @abstract Output host natural Segment64 output segment function.
 155 */
 156 #define kIODMACommandOutputHost64   (IODMACommand::OutputHost64)
 157
 158 /*! @function OutputBig64
 159     @abstract Output big-endian Segment64 output segment function.
 160 */
 161     static bool OutputBig64(IODMACommand *target,
 162             Segment64 seg, void *segs, UInt32 ind);
 163
 164 /*! @defined kIODMACommandOutputLittle64
 165     @abstract Output little-endian Segment64 output segment function.
 166 */
 167 #define kIODMACommandOutputBig64    (IODMACommand::OutputBig64)
 168
 169 /*! @function OutputLittle64
 170     @abstract Output little-endian Segment64 output segment function.
 171 */
 172     static bool OutputLittle64(IODMACommand *target,
 173             Segment64 seg, void *segs, UInt32 ind);
 174
 175 /*! @defined kIODMACommandOutputBig64
 176     @abstract Output big-endian Segment64 output segment function.
 177 */
 178 #define kIODMACommandOutputLittle64 (IODMACommand::OutputLittle64)
 179
 180 /*! @function withSpecification
 181     @abstract Creates and initializes an IODMACommand in one operation.
 182     @discussion Factory function to create and initialize an IODMACommand in one operation.
 183     @param outSegFunc SegmentFunction to call to output one physical segment. A set of nine commonly required segment functions are provided.
 184     @param numAddressBits Number of bits that the hardware uses on its internal address bus. Typically 32 but may be more on modern hardware.  A 0 implies no-restriction other than that implied by the output segment function.
 185     @param maxSegmentSize Maximum allowable size for one segment.  If 0 is passed the maximum segment size is unlimited.
 186     @param mappingOptions is the type of mapping that is required to translate an IOMemoryDescriptor into the desired number of bits.  For instance if your hardware only supports 32 bits but must run on machines with > 4G of RAM some mapping will be required.  Number of bits will be specified in numAddressBits, see below.This parameter can take 3 values:- kNonCoherent - used for non-coherent hardware transfers, Mapped - Validate that all I/O bus generated addresses are within the number of addressing bits specified, Bypassed indicates that bypassed addressing is required, this is used when the hardware transferes are into coherent memory but no mapping is required.  See also prepare() for failure cases.
 187     @param maxTransferSize Maximum size of an entire transfer.  Defaults to 0 indicating no maximum.
 188     @param alignment Alignment restriction, in bytes, on I/O bus addresses.  Defaults to single byte alignment.
 189     @param mapper For mapping types kMapped & kBypassed mapper is used to define the hardware that will perform the mapping, defaults to the system mapper.
 190     @result Returns a new memory cursor if successfully created and initialized, 0 otherwise.
 191 */
 192     static IODMACommand *
 193         withSpecification(SegmentFunction  outSegFunc,
 194                           UInt8            numAddressBits,
 195                           UInt64           maxSegmentSize,
 196                           MappingOptions   mappingOptions = kMapped,
 197                           UInt64           maxTransferSize = 0,
 198                           UInt32           alignment = 1,
 199                           IOMapper        *mapper = 0,
 200                           void            *refCon = 0);
 201
 202 /*! @function weakWithSpecification
 203     @abstract Creates and initialises an IODMACommand in one operation if this version of the operating system supports it.
 204     @discussion Factory function to create and initialise an IODMACommand in one operation.  The function allows a developer to 'weak' link with IODMACommand.  This function will return kIOReturnUnsupported if the IODMACommand is unavailable.  This function is actually fairly slow so it will be better to call it once then clone the successfully create command using cloneCommand (q.v.).
 205     @param newCommand Output reference variable of the newly created IODMACommand.
 206     @param outSegFunc SegmentFunction to call to output one physical segment. A set of nine commonly required segment functions are provided.
 207     @param numAddressBits Number of bits that the hardware uses on its internal address bus. Typically 32 but may be more on modern hardware.  A 0 implies no-restriction other than that implied by the output segment function.
 208     @param maxSegmentSize Maximum allowable size for one segment. Zero is treated as an unlimited segment size.
 209     @param mapType is the type of mapping that is required to translate an IOMemoryDescriptor into the desired number of bits.  For instance if your hardware only supports 32 bits but must run on machines with > 4G of RAM some mapping will be required.  Number of bits will be specified in numAddressBits, see below.  This parameter can take 3 values:- kNonCoherent - used for non-coherent hardware transfers, Mapped - Validate that all I/O bus generated addresses are within the number of addressing bits specified, Bypassed indicates that bypassed addressing is required, this is used when the hardware transfers are into coherent memory but no mapping is required.  See also prepare() for failure cases.
 210     @param maxTransferSize Maximum size of an entire transfer.  Defaults to 0 indicating no maximum.
 211     @param alignment Alignment restriction, in bytes, on I/O bus addresses.  Defaults to single byte alignment.
 212     @param mapper For mapping types kMapped & kBypassed mapper is used to define the hardware that will perform the mapping, defaults to the system mapper.
 213     @result kIOReturnSuccess if everything is OK, otherwise kIOReturnBadArgument if newCommand is NULL, kIOReturnUnsupported if the kernel doesn't export IODMACommand or IOReturnError if the new command fails to init, q.v. initWithSpecification.
 214 */
 215     // Note that the function has the attribute always_inline.
 216     // The point of this function is to make a call into the kernel
 217     // without generating an undefined symbol.  If the client could call
 218     // the code as a function then the goal of no undefined symbols
 219     // would be lost thus defeating the purpose.
 220     static inline IOReturn weakWithSpecification
 221             (IODMACommand   **newCommand,
 222              SegmentFunction outSegFunc,
 223              UInt8           numAddressBits,
 224              UInt64          maxSegmentSize,
 225              MappingOptions  mapType = kMapped,
 226              UInt64          maxTransferSize = 0,
 227              UInt32          alignment = 1,
 228              IOMapper       *mapper = 0,
 229              void           *refCon = 0) __attribute__((always_inline));
 230
 231 /*!
 232     @function cloneCommand
 233     @abstract Creates a new command based on the specification of the current one.
 234     @discussion Factory function to create and initialise an IODMACommand in one operation.  The current command's specification will be duplicated in the new object, but however none of its state will be duplicated.  This means that it is safe to clone a command even if it is currently active and running, however you must be certain that the command to be duplicated does have a valid reference for the duration.
 235     @result Returns a new memory cursor if successfully created and initialised, 0 otherwise.
 236 */
 237     virtual IODMACommand *cloneCommand(void *refCon = 0);
 238
 239 /*! @function initWithSpecification
 240     @abstract Primary initializer for the IODMACommand class.
 241     @param outSegFunc SegmentFunction to call to output one physical segment. A set of nine commonly required segment functions are provided.
 242     @param numAddressBits Number of bits that the hardware uses on its internal address bus. Typically 32 but may be more on modern hardware.  A 0 implies no-restriction other than that implied by the output segment function.
 243     @param maxSegmentSize Maximum allowable size for one segment.  Defaults to 0 which means any size.
 244     @param mappingOptions is the type of mapping that is required to translate an IOMemoryDescriptor into the desired number of bits.  For instance if your hardware only supports 32 bits but must run on machines with > 4G of RAM some mapping will be required.  Number of bits will be specified in numAddressBits, see below.This parameter can take 3 values:- kNonCoherent - used for non-coherent hardware transfers, Mapped - Validate that all I/O bus generated addresses are within the number of addressing bits specified, Bypassed indicates that bypassed addressing is required, this is used when the hardware transferes are into coherent memory but no mapping is required.  See also prepare() for failure cases.
 245     @param maxTransferSize Maximum size of an entire transfer.  Defaults to 0 indicating no maximum.
 246     @param alignment Alignment restriction, in bytes, on I/O bus addresses.  Defaults to single byte alignment.
 247     @param mapper For mapping types kMapped & kBypassed mapper is used to define the hardware that will perform the mapping, defaults to the system mapper.
 248     @result Can fail if the mapping type is not recognised, if one of the 3 mandatory parameters are set to 0, if a 32 bit output function is selected when more than 32 bits of address is required or, if kBypassed is requested on a machine that doesn't support bypassing.  Returns true otherwise.
 249 */
 250     virtual bool initWithSpecification( SegmentFunction  outSegFunc,
 251                                         UInt8     numAddressBits,
 252                                         UInt64    maxSegmentSize,
 253                                         MappingOptions mappingOptions = kMapped,
 254                                         UInt64    maxTransferSize = 0,
 255                                         UInt32    alignment = 1,
 256                                         IOMapper *mapper = 0,
 257                                         void     *refCon = 0);
 258
 259 /*! @function setMemoryDescriptor
 260     @abstract Sets and resets the DMACommand's current memory descriptor
 261     @discussion The DMA command will configure itself based on the information that it finds in the memory descriptor.  It looks for things like the direction of the memory descriptor and whether the current memory descriptor is already mapped into some IOMMU.  As a programmer convenience it can also prepare the memory descriptor immediately.  See prepare().  Note the IODMACommand is designed to used multiple times with a succession of memory descriptors, making the pooling of commands possible.  It is an error though to attempt to reset a currently prepared() DMA command.  Warning: This routine may block so never try to autoprepare an IODMACommand while in a gated context, i.e. one of the WorkLoops action call outs.
 262     @param mem A pointer to the current I/Os memory descriptor.
 263     @param autoPrepare An optional boolean variable that will call the prepare() function automatically after the memory descriptor is processed. Defaults to true.
 264     @result Returns kIOReturnSuccess, kIOReturnBusy if currently prepared, kIOReturnNoSpace if the length(mem) >= Maximum Transfer Size or the error codes returned by prepare() (qv).
 265 */
 266     virtual IOReturn setMemoryDescriptor(const IOMemoryDescriptor *mem,
 267                                          bool autoPrepare = true);
 268
 269 /*! @function clearMemoryDescriptor
 270     @abstract Clears the DMACommand's current memory descriptor
 271     @discussion completes and invalidates the cache if the DMA command is currently active, copies all data from bounce buffers if necessary and releases all resources acquired during setMemoryDescriptor.
 272     @param autoComplete An optional boolean variable that will call the complete() function automatically before the memory descriptor is processed. Defaults to true.
 273 */
 274     virtual IOReturn clearMemoryDescriptor(bool autoComplete = true);
 275
 276 /*! @function getMemoryDescriptor
 277     @abstract Get the current memory descriptor
 278 */
 279     virtual const IOMemoryDescriptor *getMemoryDescriptor() const;
 280
 281 /*! @function prepare
 282     @abstract Prepare the memory for an I/O transfer.
 283     @discussion Allocate the mapping resources neccessary for this transfer, specifying a sub range of the IOMemoryDescriptor that will be the target of the I/O.  The complete() method frees these resources.  Data may be copied to buffers for kIODirectionOut memory descriptors, depending on hardware mapping resource availabilty or alignment restrictions.  It should be noted that the this function may block and should only be called on the clients context, i.e never call this routine while gated; also the call itself is not thread safe though this should be an issue as each IODMACommand is independant.
 284     @param offset defines the starting offset in the memory descriptor the DMA command will operate on. genIOVMSegments will produce its results based on the offset and length passed to the prepare method.
 285     @param length defines the ending position in the memory descriptor the DMA command will operate on. genIOVMSegments will produce its results based on the offset and length passed to the prepare method.
 286     @param flushCache Flush the caches for the memory descriptor and make certain that the memory cycles are complete.  Defaults to true for kNonCoherent and is ignored by the other types.
 287     @param synchronize Copy any buffered data back from the target IOMemoryDescriptor.  Defaults to true, if synchronize() is being used to explicitly copy data, passing false may avoid an unneeded copy.
 288     @result An IOReturn code. */
 289
 290     virtual IOReturn prepare(UInt64 offset = 0, UInt64 length = 0, bool flushCache = true, bool synchronize = true);
 291
 292 /*! @function complete
 293     @abstract Complete processing of DMA mappings after an I/O transfer is finished.
 294     @discussion This method should not be called unless a prepare was previously issued; the prepare() and complete() must occur in pairs, before and after an I/O transfer
 295     @param invalidCache Invalidate the caches for the memory descriptor.  Defaults to true for kNonCoherent and is ignored by the other types.
 296     @param synchronize Copy any buffered data back to the target IOMemoryDescriptor.  Defaults to true, if synchronize() is being used to explicitly copy data, passing false may avoid an unneeded copy.
 297     @result kIOReturnNotReady if not prepared, kIOReturnSuccess otherwise. */
 298
 299     virtual IOReturn complete(bool invalidateCache = true, bool synchronize = true);
 300
 301 /*! @function synchronize
 302     @abstract Bring IOMemoryDescriptor and IODMACommand buffers into sync.
 303     @discussion This method should not be called unless a prepare was previously issued. If needed a caller may synchronize any IODMACommand buffers with the original IOMemoryDescriptor buffers.
 304     @param options Specifies the direction of the copy:
 305         kIODirectionOut copy IOMemoryDesciptor memory to any IODMACommand buffers. By default this action takes place automatically at prepare().
 306         kIODirectionIn copy any IODMACommand buffers back to the IOMemoryDescriptor. By default this action takes place automatically at complete().
 307         kForceDoubleBuffer copy the entire prepared range to a new page aligned buffer.
 308     @result kIOReturnNotReady if not prepared, kIOReturnBadArgument if invalid options are passed, kIOReturnSuccess otherwise. */
 309
 310     virtual IOReturn synchronize(IOOptionBits options);
 311
 312 /*! @function genIOVMSegments
 313     @abstract Generates a physical scatter/gather for the current DMA command
 314     @discussion Generates a list of physical segments from the given memory descriptor, relative to the current position of the descriptor.  The constraints that are set during initialisation will be respected. This function maintains the state across multiple calls for efficiency.  However the state is discarded if the new offset is not the expected one.
 315     @param offset input/output parameter, defines the starting and ending offset in the memory descriptor, relative to any offset passed to the prepare() method.
 316     @param segments Void pointer to base of output physical scatter/gather list.  Always passed directly onto the SegmentFunction.
 317     @param numSegments Input/output parameter Number of segments that can fit in the segment array and returns number of segments generated.
 318     @result kIOReturnSuccess on success, kIOReturnOverrun if the memory descriptor is exhausted, kIOReturnMessageTooLarge if the output segment function's address bits has insufficient resolution for a segment, kIOReturnNotReady if the DMA command has not be prepared, kIOReturnBadArgument if the DMA command doesn't have a memory descriptor yet or some of the parameters are NULL and kIOReturnNotReady if the DMA command is not prepared.
 319 */
 320     virtual IOReturn genIOVMSegments(UInt64 *offset,
 321                                      void   *segments,
 322                                      UInt32 *numSegments);
 323
 324 private:
 325     virtual UInt64 transfer( IOOptionBits transferOp, UInt64 offset, void * buffer, UInt64 length );
 326
 327 public:
 328
 329 /*! @function writeBytes
 330     @abstract Copy data to the IODMACommand's buffer from the specified buffer.
 331     @discussion This method copies data to the IODMACommand's memory at the given offset, from the caller's buffer. The IODMACommand must be prepared, and the offset is relative to the prepared offset.
 332     @param offset A byte offset into the IODMACommand's memory, relative to the prepared offset.
 333     @param bytes The caller supplied buffer to copy the data from.
 334     @param length The length of the data to copy.
 335     @result The number of bytes copied, zero will be returned if the specified offset is beyond the prepared length of the IODMACommand. */
 336
 337     UInt64 writeBytes(UInt64 offset, const void *bytes, UInt64 length);
 338
 339 /*! @function readBytes
 340     @abstract Copy data from the IODMACommand's buffer to the specified buffer.
 341     @discussion This method copies data from the IODMACommand's memory at the given offset, to the caller's buffer. The IODMACommand must be prepared, and the offset is relative to the prepared offset.
 342     @param offset A byte offset into the IODMACommand's memory, relative to the prepared offset.
 343     @param bytes The caller supplied buffer to copy the data to.
 344     @param length The length of the data to copy.
 345     @result The number of bytes copied, zero will be returned if the specified offset is beyond the prepared length of the IODMACommand. */
 346
 347     UInt64 readBytes(UInt64 offset, void *bytes, UInt64 length);
 348
 349 /*! @function gen32IOVMSegments
 350     @abstract Helper function for a type checked call to genIOVMSegments(qv), for use with an IODMACommand set up with the output function kIODMACommandOutputHost32, kIODMACommandOutputBig32, or kIODMACommandOutputLittle32. If the output function of the IODMACommand is not a 32 bit function, results will be incorrect.
 351 */
 352     inline IOReturn gen32IOVMSegments(UInt64   *offset,
 353                                       Segment32 *segments,
 354                                       UInt32     *numSegments)
 355     { return genIOVMSegments(offset, segments, numSegments); };
 356
 357 /*! @function gen64IOVMSegments
 358     @abstract Helper function for a type checked call to genIOVMSegments(qv), for use with an IODMACommand set up with the output function kIODMACommandOutputHost64, kIODMACommandOutputBig64, or kIODMACommandOutputLittle64. If the output function of the IODMACommand is not a 64 bit function, results will be incorrect.
 359 */
 360     inline IOReturn gen64IOVMSegments(UInt64    *offset,
 361                                       Segment64 *segments,
 362                                       UInt32    *numSegments)
 363     { return genIOVMSegments(offset, segments, numSegments); };
 364
 365     virtual void free();
 366
 367 private:
 368     typedef IOReturn (*InternalSegmentFunction)(
 369                                     void         *reference,
 370                                     IODMACommand *target,
 371                                     Segment64     segment,
 372                                     void         *segments,
 373                                     UInt32        segmentIndex);
 374
 375     IOReturn genIOVMSegments(InternalSegmentFunction outSegFunc,
 376                                   void   *reference,
 377                                   UInt64 *offsetP,
 378                                   void   *segmentsP,
 379                                   UInt32 *numSegmentsP);
 380
 381     static IOReturn clientOutputSegment(
 382             void *reference, IODMACommand *target,
 383             Segment64 segment, void *vSegList, UInt32 outSegIndex);
 384
 385     static IOReturn segmentOp(
 386                         void         *reference,
 387                         IODMACommand *target,
 388                         Segment64     segment,
 389                         void         *segments,
 390                         UInt32        segmentIndex);
 391     IOReturn walkAll(UInt8 op);
 392
 393 public:
 394
 395 /*! @function prepareWithSpecification
 396     @abstract Prepare the memory for an I/O transfer with a new specification.
 397     @discussion Allocate the mapping resources neccessary for this transfer, specifying a sub range of the IOMemoryDescriptor that will be the target of the I/O.  The complete() method frees these resources.  Data may be copied to buffers for kIODirectionOut memory descriptors, depending on hardware mapping resource availabilty or alignment restrictions.  It should be noted that the this function may block and should only be called on the clients context, i.e never call this routine while gated; also the call itself is not thread safe though this should be an issue as each IODMACommand is independant.
 398     @param outSegFunc SegmentFunction to call to output one physical segment. A set of nine commonly required segment functions are provided.
 399     @param numAddressBits Number of bits that the hardware uses on its internal address bus. Typically 32 but may be more on modern hardware.  A 0 implies no-restriction other than that implied by the output segment function.
 400     @param maxSegmentSize Maximum allowable size for one segment.  Defaults to 0 which means any size.
 401     @param mappingOptions is the type of mapping that is required to translate an IOMemoryDescriptor into the desired number of bits.  For instance if your hardware only supports 32 bits but must run on machines with > 4G of RAM some mapping will be required.  Number of bits will be specified in numAddressBits, see below.This parameter can take 3 values:- kNonCoherent - used for non-coherent hardware transfers, Mapped - Validate that all I/O bus generated addresses are within the number of addressing bits specified, Bypassed indicates that bypassed addressing is required, this is used when the hardware transferes are into coherent memory but no mapping is required.  See also prepare() for failure cases.
 402     @param maxTransferSize Maximum size of an entire transfer.  Defaults to 0 indicating no maximum.
 403     @param alignment Alignment restriction, in bytes, on I/O bus addresses.  Defaults to single byte alignment.
 404     @param mapper For mapping types kMapped & kBypassed mapper is used to define the hardware that will perform the mapping, defaults to the system mapper.
 405     @param offset defines the starting offset in the memory descriptor the DMA command will operate on. genIOVMSegments will produce its results based on the offset and length passed to the prepare method.
 406     @param length defines the ending position in the memory descriptor the DMA command will operate on. genIOVMSegments will produce its results based on the offset and length passed to the prepare method.
 407     @param flushCache Flush the caches for the memory descriptor and make certain that the memory cycles are complete.  Defaults to true for kNonCoherent and is ignored by the other types.
 408     @param synchronize Copy any buffered data back from the target IOMemoryDescriptor.  Defaults to true, if synchronize() is being used to explicitly copy data, passing false may avoid an unneeded copy.
 409     @result An IOReturn code. Can fail if the mapping type is not recognised, if one of the 3 mandatory parameters are set to 0, if a 32 bit output function is selected when more than 32 bits of address is required or, if kBypassed is requested on a machine that doesn't support bypassing.
 410 */
 411
 412     virtual IOReturn prepareWithSpecification(SegmentFunction   outSegFunc,
 413                                               UInt8             numAddressBits,
 414                                               UInt64            maxSegmentSize,
 415                                               MappingOptions    mappingOptions = kMapped,
 416                                               UInt64            maxTransferSize = 0,
 417                                               UInt32            alignment = 1,
 418                                               IOMapper          *mapper = 0,
 419                                               UInt64            offset = 0,
 420                                               UInt64            length = 0,
 421                                               bool              flushCache = true,
 422                                               bool              synchronize = true);
 423
 424     static IOReturn transferSegment(
 425                         void         *reference,
 426                         IODMACommand *target,
 427                         Segment64     segment,
 428                         void         *segments,
 429                         UInt32        segmentIndex);
 430
 431 private:
 432     OSMetaClassDeclareReservedUsed(IODMACommand,  0);
 433     OSMetaClassDeclareReservedUsed(IODMACommand,  1);
 434     OSMetaClassDeclareReservedUnused(IODMACommand,  2);
 435     OSMetaClassDeclareReservedUnused(IODMACommand,  3);
 436     OSMetaClassDeclareReservedUnused(IODMACommand,  4);
 437     OSMetaClassDeclareReservedUnused(IODMACommand,  5);
 438     OSMetaClassDeclareReservedUnused(IODMACommand,  6);
 439     OSMetaClassDeclareReservedUnused(IODMACommand,  7);
 440     OSMetaClassDeclareReservedUnused(IODMACommand,  8);
 441     OSMetaClassDeclareReservedUnused(IODMACommand,  9);
 442     OSMetaClassDeclareReservedUnused(IODMACommand, 10);
 443     OSMetaClassDeclareReservedUnused(IODMACommand, 11);
 444     OSMetaClassDeclareReservedUnused(IODMACommand, 12);
 445     OSMetaClassDeclareReservedUnused(IODMACommand, 13);
 446     OSMetaClassDeclareReservedUnused(IODMACommand, 14);
 447     OSMetaClassDeclareReservedUnused(IODMACommand, 15);
 448
 449 public:
 450 /*! @var fRefCon Reference Constant, client defined publicly avialable */
 451     void *fRefCon;
 452
 453 protected:
 454
 455 /*! @var fMaxSegmentSize Maximum size of one segment in a scatter/gather list */
 456     UInt64  fMaxSegmentSize;
 457
 458 /*! @var fMaxTransferSize
 459     Maximum size of a transfer that this memory cursor is allowed to generate */
 460     UInt64  fMaxTransferSize;
 461
 462 /*! @var fBypassMask
 463     Mask to be ored into the address to bypass the given iommu's mapping. */
 464     UInt64  fBypassMask;
 465
 466 /*! @var fMapper
 467     Client defined mapper. */
 468     IOMapper *fMapper;
 469
 470 /*! @var fMemory
 471     memory descriptor for current I/O. */
 472     const IOMemoryDescriptor *fMemory;
 473
 474 /*! @var fOutSeg The action method called when an event has been delivered */
 475     SegmentFunction fOutSeg;
 476
 477 /*! @var fAlignMask
 478     Alignment restriction mask. */
 479     UInt32  fAlignMask;
 480
 481 /*! @var fNumAddressBits
 482     Number of bits that the hardware can address */
 483     UInt32 fNumAddressBits;
 484
 485 /*! @var fNumSegments
 486     Number of contiguous segments required for the current memory descriptor and desired mapping */
 487     UInt32  fNumSegments;
 488
 489 /*! @var fMappingOptions
 490     What type of I/O virtual address mapping is required for this command */
 491     MappingOptions  fMappingOptions;
 492
 493 /*! @var fActive
 494     fActive indicates that this DMA command is currently prepared and ready to go */
 495     UInt32 fActive;
 496
 497 /*! @var reserved
 498     Reserved for future use.  (Internal use only)  */
 499     struct IODMACommandInternal * reserved;
 500 };
 501
 502 IOReturn IODMACommand::
 503 weakWithSpecification(IODMACommand **newCommand,
 504                       SegmentFunction  outSegFunc,
 505                       UInt8     numAddressBits,
 506                       UInt64    maxSegmentSize,
 507                       MappingOptions mapType,
 508                       UInt64    maxTransferSize,
 509                       UInt32    alignment,
 510                       IOMapper *mapper,
 511                       void     *refCon)
 512 {
 513     if (!newCommand)
 514         return kIOReturnBadArgument;
 515
 516     IODMACommand *self = (IODMACommand *)
 517         OSMetaClass::allocClassWithName("IODMACommand");
 518     if (!self)
 519         return kIOReturnUnsupported;
 520
 521     IOReturn ret;
 522     bool inited = self->
 523         initWithSpecification(outSegFunc,
 524                               numAddressBits, maxSegmentSize, mapType,
 525                               maxTransferSize, alignment, mapper, refCon);
 526     if (inited)
 527         ret =  kIOReturnSuccess;
 528     else {
 529         self->release();
 530         self = 0;
 531         ret = kIOReturnError;
 532     }
 533
 534     *newCommand = self;
 535     return ret;
 536 };
 537 #endif /* !_IODMACOMMAND_H */
 538