reactos操作系统实现(112)

IdeReadWrite函数主要实现了IDE设备的读和写命令发送。具体实现函数如下：

#001 ULONG

#002 NTAPI

#003 IdeReadWrite(

#004 IN PVOID HwDeviceExtension,

#005 IN PSCSI_REQUEST_BLOCK Srb

#006 )

#007

#008 /*++

#009

#010 Routine Description:

#011

#012 This routine handles IDE read and writes.

#013

#014 Arguments:

#015

#016 HwDeviceExtension - HBA miniport driver's adapter data storage

#017 Srb - IO request packet

#018

#019 Return Value:

#020

#021 SRB status

#022

#023 --*/

#024

#025 {

获取驱动程序扩展对象和基地址寄存器。

#026 PHW_DEVICE_EXTENSION deviceExtension = HwDeviceExtension;

#027 PIDE_REGISTERS_1 baseIoAddress1 = deviceExtension->BaseIoAddress1[Srb->TargetId >> 1];

#028 PIDE_REGISTERS_2 baseIoAddress2 = deviceExtension->BaseIoAddress2[Srb->TargetId >> 1];

#029 ULONG startingSector,i;

#030 ULONG wordCount;

#031 UCHAR statusByte,statusByte2;

#032 UCHAR cylinderHigh,cylinderLow,drvSelect,sectorNumber;

#033

#034 //

#035 // Select device 0 or 1.

#036 //

#037

选择IDE设备0，还是设备1.

#038 ScsiPortWritePortUchar(&baseIoAddress1->DriveSelect,

#039 (UCHAR)(((Srb->TargetId & 0x1) << 4) | 0xA0));

#040

等待选择设备命令完成。

#041 WaitOnBusy(baseIoAddress2,statusByte2);

#042

如果命令没有执行成功就返回。

#043 if (statusByte2 & IDE_STATUS_BUSY) {

#044 DebugPrint((1,

#045 "IdeReadWrite: Returning BUSY status/n"));

#046 return SRB_STATUS_BUSY;

#047 }

#048

#049 //

#050 // Set data buffer pointer and words left.

#051 //

#052

设置输出或读取缓冲区和传送的字节个数。

#053 deviceExtension->DataBuffer = (PUSHORT)Srb->DataBuffer;

#054 deviceExtension->WordsLeft = Srb->DataTransferLength / 2;

#055

#056 //

#057 // Indicate expecting an interrupt.

#058 //

#059

设置期望使用中断响应。

#060 deviceExtension->ExpectingInterrupt = TRUE;

#061

#062 //

#063 // Set up sector count register. Round up to next block.

#064 //

#065

设置要传送的扇区寄器。

#066 ScsiPortWritePortUchar(&baseIoAddress1->BlockCount,

#067 (UCHAR)((Srb->DataTransferLength + 0x1FF) / 0x200));

#068

#069 //

#070 // Get starting sector number from CDB.

#071 //

#072

从SRB请求的CDB块计算开始的扇区。

#073 startingSector = ((PCDB)Srb->Cdb)->CDB10.LogicalBlockByte3 |

#074 ((PCDB)Srb->Cdb)->CDB10.LogicalBlockByte2 << 8 |

#075 ((PCDB)Srb->Cdb)->CDB10.LogicalBlockByte1 << 16 |

#076 ((PCDB)Srb->Cdb)->CDB10.LogicalBlockByte0 << 24;

#077

#078 DebugPrint((2,

#079 "IdeReadWrite: Starting sector is %x,Number of bytes %x/n",

#080 startingSector,

#081 Srb->DataTransferLength));

#082

#083 //

#084 // Set up sector number register.

#085 //

#086

计算扇区开始位置，并写入到寄存器。

#087 sectorNumber = (UCHAR)((startingSector % deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack) + 1);

#088 ScsiPortWritePortUchar(&baseIoAddress1->BlockNumber,sectorNumber);

#089

#090 //

#091 // Set up cylinder low register.

#092 //

#093

下面开始计算柱面位置。

#094 cylinderLow = (UCHAR)(startingSector / (deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack *

#095 deviceExtension->IdentifyData[Srb->TargetId].NumberOfHeads));

#096 ScsiPortWritePortUchar(&baseIoAddress1->CylinderLow,cylinderLow);

#097

#098 //

#099 // Set up cylinder high register.

#100 //

#101

#102 cylinderHigh = (UCHAR)((startingSector / (deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack *

#103 deviceExtension->IdentifyData[Srb->TargetId].NumberOfHeads)) >> 8);

#104 ScsiPortWritePortUchar(&baseIoAddress1->CylinderHigh,cylinderHigh);

#105

#106 //

#107 // Set up head and drive select register.

#108 //

#109

计算磁头位置。

#110 drvSelect = (UCHAR)(((startingSector / deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack) %

#111 deviceExtension->IdentifyData[Srb->TargetId].NumberOfHeads) |((Srb->TargetId & 0x1) << 4) | 0xA0);

#112 ScsiPortWritePortUchar(&baseIoAddress1->DriveSelect,drvSelect);

#113

#114 DebugPrint((2,

#115 "IdeReadWrite: Cylinder %x Head %x Sector %x/n",

#116 startingSector /

#117 (deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack *

#118 deviceExtension->IdentifyData[Srb->TargetId].NumberOfHeads),

#119 (startingSector /

#120 deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack) %

#121 deviceExtension->IdentifyData[Srb->TargetId].NumberOfHeads,

#122 startingSector %

#123 deviceExtension->IdentifyData[Srb->TargetId].SectorsPerTrack + 1));

#124

#125 //

#126 // Check if write request.

#127 //

#128

开始发送读或写命令给IDE设备。

#129 if (Srb->SrbFlags & SRB_FLAGS_DATA_IN) {

#130

#131 //

#132 // Send read command.

#133 //

#134

这里是读取扇区数据，所以发送读取命令给IDE设备。

#135 if (deviceExtension->MaximumBlockXfer[Srb->TargetId]) {

#136 ScsiPortWritePortUchar(&baseIoAddress1->Command,

#137 IDE_COMMAND_READ_MULTIPLE);

#138

#139 } else {

#140 ScsiPortWritePortUchar(&baseIoAddress1->Command,

#141 IDE_COMMAND_READ);

#142 }

#143 } else {

#144

#145

#146 //

#147 // Send write command.

#148 //

#149

这里是写入数据到IDE设备，所以发送写入命令。

#150 if (deviceExtension->MaximumBlockXfer[Srb->TargetId]) {

#151 wordCount = 256 * deviceExtension->MaximumBlockXfer[Srb->TargetId];

#152

#153 if (deviceExtension->WordsLeft < wordCount) {

#154

#155 //

#156 // Transfer only words requested.

#157 //

#158

#159 wordCount = deviceExtension->WordsLeft;

#160

#161 }

#162 ScsiPortWritePortUchar(&baseIoAddress1->Command,

#163 IDE_COMMAND_WRITE_MULTIPLE);

#164

#165 } else {

#166 wordCount = 256;

#167 ScsiPortWritePortUchar(&baseIoAddress1->Command,

#168 IDE_COMMAND_WRITE);

#169 }

#170

#171 //

#172 // Wait for BSY and DRQ.

#173 //

#174

等待读取或写入命令完成。

#175 WaitOnBaseBusy(baseIoAddress1,statusByte);

#176

如果设备还是忙状态，说明读取或写命令有问题。

#177 if (statusByte & IDE_STATUS_BUSY) {

#178

#179 DebugPrint((1,

#180 "IdeReadWrite 2: Returning BUSY status %x/n",

#181 statusByte));

#182 return SRB_STATUS_BUSY;

#183 }

#184

#185 for (i = 0; i < 1000; i++) {

#186 GetBaseStatus(baseIoAddress1,statusByte);

#187 if (statusByte & IDE_STATUS_DRQ) {

#188 break;

#189 }

#190 ScsiPortStallExecution(200);

#191

#192 }

#193

如果不是状态IDE_STATUS_DRQ，说明处理命令出错了。

#194 if (!(statusByte & IDE_STATUS_DRQ)) {

#195

#196 DebugPrint((1,

#197 "IdeReadWrite: DRQ never asserted (%x) original status (%x)/n",

#198 statusByte,

#199 statusByte2));

#200

#201 deviceExtension->WordsLeft = 0;

#202

#203 //

#204 // Clear interrupt expecting flag.

#205 //

#206

#207 deviceExtension->ExpectingInterrupt = FALSE;

#208

#209 //

#210 // Clear current SRB.

#211 //

#212

#213 deviceExtension->CurrentSrb = NULL;

#214

#215 return SRB_STATUS_TIMEOUT;

#216 }

#217

#218 //

#219 // Write next 256 words.

#220 //

#221

写512个字节到IDE设备。

#222 WriteBuffer(baseIoAddress1,

#223 deviceExtension->DataBuffer,

#224 wordCount);

#225

#226 //

#227 // Adjust buffer address and words left count.

#228 //

#229

计算已经传送的字节数。

#230 deviceExtension->WordsLeft -= wordCount;

#231 deviceExtension->DataBuffer += wordCount;

#232

#233 }

#234

#235 //

#236 // Wait for interrupt.

#237 //

#238

#239 return SRB_STATUS_PENDING;

#240

#241} // end IdeReadWrite()

（编辑：李大同）

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