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Annotation of XNU/iokit/Kernel/IOBufferMemoryDescriptor.cpp, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1998-2000 Apple Computer, Inc. All rights reserved.
        !             3:  *
        !             4:  * @APPLE_LICENSE_HEADER_START@
        !             5:  * 
        !             6:  * The contents of this file constitute Original Code as defined in and
        !             7:  * are subject to the Apple Public Source License Version 1.1 (the
        !             8:  * "License").  You may not use this file except in compliance with the
        !             9:  * License.  Please obtain a copy of the License at
        !            10:  * http://www.apple.com/publicsource and read it before using this file.
        !            11:  * 
        !            12:  * This Original Code and all software distributed under the License are
        !            13:  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
        !            14:  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
        !            15:  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
        !            16:  * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
        !            17:  * License for the specific language governing rights and limitations
        !            18:  * under the License.
        !            19:  * 
        !            20:  * @APPLE_LICENSE_HEADER_END@
        !            21:  */
        !            22: #include <IOKit/assert.h>
        !            23: #include <IOKit/system.h>
        !            24: 
        !            25: #include <IOKit/IOLib.h>
        !            26: #include <IOKit/IOBufferMemoryDescriptor.h>
        !            27: 
        !            28: #define super IOGeneralMemoryDescriptor
        !            29: OSDefineMetaClassAndStructors(IOBufferMemoryDescriptor,
        !            30:                                IOGeneralMemoryDescriptor);
        !            31: 
        !            32: /*
        !            33:  * initWithCapacity:
        !            34:  *
        !            35:  * Initialize a new IOBufferMemoryDescriptor with a buffer large enough to
        !            36:  * hold capacity bytes.  The descriptor's length is initially set to zero.
        !            37:  */
        !            38: bool IOBufferMemoryDescriptor::initWithCapacity(vm_size_t   inCapacity,
        !            39:                                                 IODirection inDirection,
        !            40:                                                 bool        inContiguous)
        !            41: {
        !            42:     if (!inCapacity)
        !            43:         return false;
        !            44: 
        !            45:     /* Allocate a wired-down buffer inside kernel space. */
        !            46:     _buffer       = (inContiguous) ?
        !            47:                                IOMallocContiguous(inCapacity, inCapacity, 0) :
        !            48:                                 IOMalloc(inCapacity);
        !            49:     _contiguous   = inContiguous;
        !            50:     _capacity     = inCapacity;
        !            51:     _physAddrs    = 0;
        !            52:     _physSegCount = 0;
        !            53: 
        !            54:     if (!_buffer)
        !            55:         return false;
        !            56: 
        !            57:     if (!super::initWithAddress(_buffer, inCapacity, inDirection))
        !            58:        return false;
        !            59: 
        !            60:     /* Precompute virtual-to-physical page mappings. */
        !            61:     vm_address_t inBuffer = (vm_address_t) _buffer;
        !            62:     _physSegCount = atop(trunc_page(inBuffer + inCapacity - 1) -
        !            63:                          trunc_page(inBuffer)) + 1;
        !            64:     _physAddrs = IONew(IOPhysicalAddress, _physSegCount);
        !            65:     if (!_physAddrs)
        !            66:        return false;
        !            67: 
        !            68:     inBuffer = trunc_page(inBuffer);
        !            69:     for (unsigned i = 0; i < _physSegCount; i++) {
        !            70:         _physAddrs[i] = pmap_extract(get_task_pmap(kernel_task), inBuffer);
        !            71:         assert(_physAddrs[i]); /* supposed to be wired */
        !            72:         inBuffer += page_size;
        !            73:     }
        !            74: 
        !            75:     // start out with no data
        !            76:     setLength(0);
        !            77:     
        !            78:     return true;
        !            79: }
        !            80: 
        !            81: /*
        !            82:  * withCapacity:
        !            83:  *
        !            84:  * Returns a new IOBufferMemoryDescriptor with a buffer large enough to
        !            85:  * hold capacity bytes.  The descriptor's length is initially set to zero.
        !            86:  */
        !            87: IOBufferMemoryDescriptor *
        !            88: IOBufferMemoryDescriptor::withCapacity(vm_size_t   inCapacity,
        !            89:                                        IODirection inDirection,
        !            90:                                        bool        inContiguous)
        !            91: {
        !            92:     IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
        !            93:     
        !            94:     if (me && !me->initWithCapacity(inCapacity, inDirection, inContiguous)) {
        !            95:        me->release();
        !            96:        me = 0;
        !            97:     }
        !            98:     return me;
        !            99: }
        !           100: 
        !           101: /*
        !           102:  * initWithBytes:
        !           103:  *
        !           104:  * Initialize a new IOBufferMemoryDescriptor preloaded with bytes (copied).
        !           105:  * The descriptor's length and capacity are set to the input buffer's size.
        !           106:  */
        !           107: bool IOBufferMemoryDescriptor::initWithBytes(const void * inBytes,
        !           108:                                              vm_size_t    inLength,
        !           109:                                              IODirection  inDirection,
        !           110:                                              bool         inContiguous)
        !           111: {
        !           112:     if (!initWithCapacity(inLength, inDirection, inContiguous))
        !           113:         return false;
        !           114: 
        !           115:     if (!appendBytes(inBytes, inLength))
        !           116:         return false;
        !           117: 
        !           118:     return true;
        !           119: }
        !           120: 
        !           121: /*
        !           122:  * withBytes:
        !           123:  *
        !           124:  * Returns a new IOBufferMemoryDescriptor preloaded with bytes (copied).
        !           125:  * The descriptor's length and capacity are set to the input buffer's size.
        !           126:  */
        !           127: IOBufferMemoryDescriptor *
        !           128: IOBufferMemoryDescriptor::withBytes(const void * inBytes,
        !           129:                                     vm_size_t    inLength,
        !           130:                                     IODirection  inDirection,
        !           131:                                     bool         inContiguous)
        !           132: {
        !           133:     IOBufferMemoryDescriptor *me = new IOBufferMemoryDescriptor;
        !           134: 
        !           135:     if (me && !me->initWithBytes(inBytes, inLength, inDirection, inContiguous)){
        !           136:         me->release();
        !           137:         me = 0;
        !           138:     }
        !           139:     return me;
        !           140: }
        !           141: 
        !           142: /*
        !           143:  * free:
        !           144:  *
        !           145:  * Free resources
        !           146:  */
        !           147: void IOBufferMemoryDescriptor::free()
        !           148: {
        !           149:     if (_physAddrs)
        !           150:         IODelete(_physAddrs, IOPhysicalAddress, _physSegCount);
        !           151: 
        !           152:     super::free();
        !           153: 
        !           154:     if (_buffer) {
        !           155:         if (_contiguous)
        !           156:             IOFreeContiguous(_buffer, _capacity);
        !           157:         else
        !           158:             IOFree(_buffer, _capacity);
        !           159:     }
        !           160: }
        !           161: 
        !           162: /*
        !           163:  * getCapacity:
        !           164:  *
        !           165:  * Get the buffer capacity
        !           166:  */
        !           167: vm_size_t IOBufferMemoryDescriptor::getCapacity() const
        !           168: {
        !           169:     return _capacity;
        !           170: }
        !           171: 
        !           172: /*
        !           173:  * setLength:
        !           174:  *
        !           175:  * Change the buffer length of the memory descriptor.  When a new buffer is
        !           176:  * created with initWithBytes, the descriptor's length is set to capacity,
        !           177:  * or its length is initially zero.  This method allows one to resize the
        !           178:  * buffer length up to capacity or less.  This eliminates the need to
        !           179:  * destroy and create new buffers when different sizes are needed.  The
        !           180:  * descriptor position is implicitly reset to zero as a result of this call.
        !           181:  */
        !           182: void IOBufferMemoryDescriptor::setLength(vm_size_t length)
        !           183: {
        !           184:     assert(length <= _capacity);
        !           185: 
        !           186:     _length = length;
        !           187:     _singleRange.v.length = length;
        !           188: }
        !           189: 
        !           190: /*
        !           191:  * setDirection:
        !           192:  *
        !           193:  * Change the direction of the transfer.  This method allows one to redirect
        !           194:  * the descriptor's transfer direction.  This eliminates the need to destroy
        !           195:  * and create new buffers when different transfer directions are needed.
        !           196:  */
        !           197: void IOBufferMemoryDescriptor::setDirection(IODirection direction)
        !           198: {
        !           199:     _direction = direction;
        !           200: }
        !           201: 
        !           202: /*
        !           203:  * appendBytes:
        !           204:  *
        !           205:  * Add some data to the end of the buffer.  This method automatically
        !           206:  * maintains the memory descriptor buffer length.  Note that appendBytes
        !           207:  * will not copy past the end of the memory descriptor's current capacity.
        !           208:  */
        !           209: bool
        !           210: IOBufferMemoryDescriptor::appendBytes(const void * bytes, vm_size_t withLength)
        !           211: {
        !           212:     vm_size_t actualBytesToCopy = min(withLength, _capacity - _length);
        !           213: 
        !           214:     assert(_length <= _capacity);
        !           215:     bcopy(/* from */ bytes, (void *)(_singleRange.v.address + _length),
        !           216:           actualBytesToCopy);
        !           217:     _length += actualBytesToCopy;
        !           218:     _singleRange.v.length += actualBytesToCopy;
        !           219: 
        !           220:     return true;
        !           221: }
        !           222: 
        !           223: /*
        !           224:  * getBytesNoCopy:
        !           225:  *
        !           226:  * Return the virtual address of the beginning of the buffer
        !           227:  */
        !           228: void * IOBufferMemoryDescriptor::getBytesNoCopy()
        !           229: {
        !           230:     return (void *)_singleRange.v.address;
        !           231: }
        !           232: 
        !           233: /*
        !           234:  * getBytesNoCopy:
        !           235:  *
        !           236:  * Return the virtual address of an offset from the beginning of the buffer
        !           237:  */
        !           238: void *
        !           239: IOBufferMemoryDescriptor::getBytesNoCopy(vm_size_t start, vm_size_t withLength)
        !           240: {
        !           241:     if (start < _length && (start + withLength) <= _length)
        !           242:         return (void *)(_singleRange.v.address + start);
        !           243:     return 0;
        !           244: }
        !           245: 
        !           246: /*
        !           247:  * getPhysicalSegment:
        !           248:  *
        !           249:  * Get the physical address of the buffer, relative to the current position.
        !           250:  * If the current position is at the end of the buffer, a zero is returned.
        !           251:  */
        !           252: IOPhysicalAddress
        !           253: IOBufferMemoryDescriptor::getPhysicalSegment(IOByteCount offset,
        !           254:                                        IOPhysicalLength * lengthOfSegment)
        !           255: {
        !           256:     if( offset != _position)
        !           257:        setPosition( offset );
        !           258: 
        !           259:     assert(_position <= _length);
        !           260: 
        !           261:     /* Fail gracefully if the position is at (or past) the end-of-buffer. */
        !           262:     if (_position >= _length) {
        !           263:         *lengthOfSegment = 0;
        !           264:         return 0;
        !           265:     }
        !           266: 
        !           267:     /* Compute the largest contiguous physical length possible. */
        !           268:     vm_address_t actualPos  = _singleRange.v.address + _position;
        !           269:     vm_address_t actualPage = trunc_page(actualPos);
        !           270:     unsigned     physInd    = atop(actualPage-trunc_page(_singleRange.v.address));
        !           271: 
        !           272:     vm_size_t physicalLength = actualPage + page_size - actualPos;
        !           273:     for (unsigned index = physInd + 1; index < _physSegCount &&
        !           274:          _physAddrs[index] == _physAddrs[index-1] + page_size; index++) {
        !           275:         physicalLength += page_size;
        !           276:     }
        !           277: 
        !           278:     /* Clip contiguous physical length at the end-of-buffer. */
        !           279:     if (physicalLength > _length - _position)
        !           280:         physicalLength = _length - _position;
        !           281: 
        !           282:     *lengthOfSegment = physicalLength;
        !           283:     return _physAddrs[physInd] + (actualPos - actualPage);
        !           284: }

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