reactos/drivers/storage/floppy/readwrite.c

   1 /*
   2  *  ReactOS Floppy Driver
   3  *  Copyright (C) 2004, Vizzini (vizzini@plasmic.com)
   4  *
   5  *  This program is free software; you can redistribute it and/or modify
   6  *  it under the terms of the GNU General Public License as published by
   7  *  the Free Software Foundation; either version 2 of the License, or
   8  *  (at your option) any later version.
   9  *
  10  *  This program is distributed in the hope that it will be useful,
  11  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  *  GNU General Public License for more details.
  14  *
  15  *  You should have received a copy of the GNU General Public License
  16  *  along with this program; if not, write to the Free Software
  17  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18  *
  19  * PROJECT:         ReactOS Floppy Driver
  20  * FILE:            readwrite.c
  21  * PURPOSE:         Read/Write handler routines
  22  * PROGRAMMER:      Vizzini (vizzini@plasmic.com)
  23  * REVISIONS:
  24  *                  15-Feb-2004 vizzini - Created
  25  * NOTES:
  26  *
  27  * READ/WRITE PROCESS
  28  *
  29  * This process is extracted from the Intel datasheet for the floppy controller.
  30  *
  31  * - Turn on the motor and set turnoff time
  32  * - Program the drive's data rate
  33  * - Seek
  34  * - Read ID
  35  * - Set up DMA
  36  * - Send read/write command to FDC
  37  * - Read result bytes
  38  *
  39  * This is mostly implemented in one big function, which watis on the SynchEvent
  40  * as many times as necessary to get through the process.  See ReadWritePassive() for
  41  * more details.
  42  *
  43  * NOTES:
  44  *     - Currently doesn't support partial-sector transfers, which is really just a failing
  45  *       of RWComputeCHS.  I've never seen Windows send a partial-sector request, though, so
  46  *       this may not be a bad thing.  Should be looked into, regardless.
  47  *
  48  * TODO: Break up ReadWritePassive and handle errors better
  49  * TODO: Figure out data rate issues
  50  * TODO: Media type detection
  51  * TODO: Figure out perf issue - waiting after call to read/write for about a second each time
  52  * TODO: Figure out specify timings
  53  */
  54
  55 #define NDEBUG
  56 #include <debug.h>
  57 #include <ntddk.h>
  58
  59 #include "floppy.h"
  60 #include "csqrtns.h"
  61 #include "hardware.h"
  62 #include "readwrite.h"
  63
  64 \f
  65 static IO_ALLOCATION_ACTION NTAPI MapRegisterCallback(PDEVICE_OBJECT DeviceObject,
  66                                                       PIRP Irp,
  67                                                       PVOID MapRegisterBase,
  68                                                       PVOID Context)
  69 /*
  70  * FUNCTION: Acquire map registers in prep for DMA
  71  * ARGUMENTS:
  72  *     DeviceObject: unused
  73  *     Irp: unused
  74  *     MapRegisterBase: returned to blocked thread via a member var
  75  *     Context: contains a pointer to the right ControllerInfo
  76  *     struct
  77  * RETURNS:
  78  *     KeepObject, because that's what the DDK says to do
  79  */
  80 {
  81   PCONTROLLER_INFO ControllerInfo = (PCONTROLLER_INFO)Context;
  82   UNREFERENCED_PARAMETER(DeviceObject);
  83   UNREFERENCED_PARAMETER(Irp);
  84
  85   DPRINT("floppy: MapRegisterCallback Called\n");
  86
  87   ControllerInfo->MapRegisterBase = MapRegisterBase;
  88   KeSetEvent(&ControllerInfo->SynchEvent, 0, FALSE);
  89
  90   return KeepObject;
  91 }
  92
  93 \f
  94 NTSTATUS NTAPI ReadWrite(PDEVICE_OBJECT DeviceObject,
  95                          PIRP Irp)
  96 /*
  97  * FUNCTION: Dispatch routine called for read or write IRPs
  98  * ARGUMENTS:
  99  * RETURNS:
 100  *     STATUS_PENDING if the IRP is queued
 101  *     STATUS_INVALID_PARAMETER if IRP is set up wrong
 102  * NOTES:
 103  *     - This function validates arguments to the IRP and then queues it
 104  *     - Note that this function is implicitly serialized by the queue logic.  Only
 105  *       one of these at a time is active in the system, no matter how many processors
 106  *       and threads we have.
 107  *     - This function stores the DeviceObject in the IRP's context area before dropping
 108  *       it onto the irp queue
 109  */
 110 {
 111   DPRINT("floppy: ReadWrite called\n");
 112
 113   ASSERT(DeviceObject);
 114   ASSERT(Irp);
 115
 116   if(!Irp->MdlAddress)
 117     {
 118       DPRINT("floppy: ReadWrite(): MDL not found in IRP - Completing with STATUS_INVALID_PARAMETER\n");
 119       Irp->IoStatus.Status = STATUS_INVALID_PARAMETER;
 120       Irp->IoStatus.Information = 0;
 121       IoCompleteRequest(Irp, IO_NO_INCREMENT);
 122       return STATUS_INVALID_PARAMETER;
 123     }
 124
 125   /*
 126    * Queue the irp to the thread.
 127    * The de-queue thread will look in DriverContext[0] for the Device Object.
 128    */
 129   Irp->Tail.Overlay.DriverContext[0] = DeviceObject;
 130   IoCsqInsertIrp(&Csq, Irp, NULL);
 131
 132   return STATUS_PENDING;
 133 }
 134
 135 \f
 136 static VOID NTAPI RWFreeAdapterChannel(PADAPTER_OBJECT AdapterObject)
 137 /*
 138  * FUNCTION: Free the adapter DMA channel that we allocated
 139  * ARGUMENTS:
 140  *     AdapterObject: the object with the map registers to free
 141  * NOTES:
 142  *     - This function is primarily needed because IoFreeAdapterChannel wants to
 143  *       be called at DISPATCH_LEVEL
 144  */
 145 {
 146   KIRQL Irql;
 147
 148   ASSERT(KeGetCurrentIrql() <= DISPATCH_LEVEL);
 149
 150   KeRaiseIrql(DISPATCH_LEVEL, &Irql);
 151   IoFreeAdapterChannel(AdapterObject);
 152   KeLowerIrql(Irql);
 153 }
 154
 155 \f
 156 static NTSTATUS NTAPI RWDetermineMediaType(PDRIVE_INFO DriveInfo)
 157 /*
 158  * FUNCTION: Determine the media type of the disk in the drive and fill in the geometry
 159  * ARGUMENTS:
 160  *     DriveInfo: drive to look at
 161  * RETURNS:
 162  *     STATUS_SUCCESS if the media was recognized and the geometry struct was filled in
 163  *     STATUS_UNRECOGNIZED_MEDIA if not
 164  *     STATUS_UNSUCCESSFUL if the controller can't be talked to
 165  * NOTES:
 166  *     - Expects the motor to already be running
 167  *     - Currently only supports 1.44MB 3.5" disks
 168  *     - PAGED_CODE because it waits
 169  * TODO:
 170  *     - Support more disk types
 171  */
 172 {
 173   UCHAR HeadLoadTime;
 174   UCHAR HeadUnloadTime;
 175   UCHAR StepRateTime;
 176
 177   PAGED_CODE();
 178
 179   DPRINT("floppy: RWDetermineMediaType called\n");
 180
 181   /*
 182    * This algorithm assumes that a 1.44MB floppy is in the drive.  If it's not,
 183    * it works backwards until the read works.  Note that only 1.44 has been tested
 184    * at all.
 185    */
 186
 187   do
 188     {
 189       int i;
 190
 191       /* Program data rate */
 192       if(HwSetDataRate(DriveInfo->ControllerInfo, DRSR_DSEL_500KBPS) != STATUS_SUCCESS)
 193         {
 194           DPRINT("floppy: RWDetermineMediaType(): unable to set data rate\n");
 195           return STATUS_UNSUCCESSFUL;
 196         }
 197
 198       /* Specify */
 199       HeadLoadTime = SPECIFY_HLT_500K;
 200       HeadUnloadTime = SPECIFY_HUT_500K;
 201       StepRateTime = SPECIFY_SRT_500K;
 202
 203       /* Don't disable DMA --> enable dma (dumb & confusing) */
 204       if(HwSpecify(DriveInfo->ControllerInfo, HeadLoadTime, HeadUnloadTime, StepRateTime, FALSE) != STATUS_SUCCESS)
 205         {
 206           DPRINT("floppy: RWDetermineMediaType(): specify failed\n");
 207           return STATUS_UNSUCCESSFUL;
 208         }
 209
 210       /* clear any spurious interrupts in preparation for recalibrate */
 211       KeClearEvent(&DriveInfo->ControllerInfo->SynchEvent);
 212
 213       /* Recalibrate --> head over first track */
 214       for(i=0; i < 2; i++)
 215         {
 216           NTSTATUS RecalStatus;
 217
 218           if(HwRecalibrate(DriveInfo) != STATUS_SUCCESS)
 219             {
 220               DPRINT("floppy: RWDetermineMediaType(): Recalibrate failed\n");
 221               return STATUS_UNSUCCESSFUL;
 222             }
 223
 224           /* Wait for the recalibrate to finish */
 225           WaitForControllerInterrupt(DriveInfo->ControllerInfo);
 226
 227           RecalStatus = HwRecalibrateResult(DriveInfo->ControllerInfo);
 228
 229           if(RecalStatus == STATUS_SUCCESS)
 230             break;
 231
 232           if(i == 1) /* failed for 2nd time */
 233             {
 234               DPRINT("floppy: RWDetermineMediaType(): RecalibrateResult failed\n");
 235               return STATUS_UNSUCCESSFUL;
 236             }
 237         }
 238
 239       /* clear any spurious interrupts */
 240       KeClearEvent(&DriveInfo->ControllerInfo->SynchEvent);
 241
 242       /* Try to read an ID */
 243       if(HwReadId(DriveInfo, 0) != STATUS_SUCCESS) /* read the first ID we find, from head 0 */
 244         {
 245           DPRINT("floppy: RWDetermineMediaType(): ReadId failed\n");
 246           return STATUS_UNSUCCESSFUL; /* if we can't even write to the controller, it's hopeless */
 247         }
 248
 249       /* Wait for the ReadID to finish */
 250       WaitForControllerInterrupt(DriveInfo->ControllerInfo);
 251
 252       if(HwReadIdResult(DriveInfo->ControllerInfo, NULL, NULL) != STATUS_SUCCESS)
 253         {
 254           DPRINT("floppy: RWDetermineMediaType(): ReadIdResult failed; continuing\n");
 255           continue;
 256         }
 257
 258       /* Found the media; populate the geometry now */
 259       DPRINT("FIXME: Hardcoded media type!\n");
 260       DPRINT("floppy: RWDetermineMediaType(): Found 1.44 media; returning success\n");
 261       DriveInfo->DiskGeometry.MediaType = GEOMETRY_144_MEDIATYPE;
 262       DriveInfo->DiskGeometry.Cylinders.QuadPart = GEOMETRY_144_CYLINDERS;
 263       DriveInfo->DiskGeometry.TracksPerCylinder = GEOMETRY_144_TRACKSPERCYLINDER;
 264       DriveInfo->DiskGeometry.SectorsPerTrack = GEOMETRY_144_SECTORSPERTRACK;
 265       DriveInfo->DiskGeometry.BytesPerSector = GEOMETRY_144_BYTESPERSECTOR;
 266       DriveInfo->BytesPerSectorCode = HW_512_BYTES_PER_SECTOR;
 267       return STATUS_SUCCESS;
 268     }
 269   while(FALSE);
 270
 271   DPRINT("floppy: RWDetermineMediaType(): failed to find media\n");
 272   return STATUS_UNRECOGNIZED_MEDIA;
 273 }
 274
 275 \f
 276 static NTSTATUS NTAPI RWSeekToCylinder(PDRIVE_INFO DriveInfo,
 277                                        UCHAR Cylinder)
 278 /*
 279  * FUNCTION: Seek a particular drive to a particular track
 280  * ARGUMENTS:
 281  *     DriveInfo: Drive to seek
 282  *     Cylinder: track to seek to
 283  * RETURNS:
 284  *     STATUS_SUCCESS if the head was successfully seeked
 285  *     STATUS_UNSUCCESSFUL if not
 286  * NOTES:
 287  *     - PAGED_CODE because it blocks
 288  */
 289 {
 290   UCHAR CurCylinder;
 291
 292   PAGED_CODE();
 293
 294   DPRINT("floppy: RWSeekToCylinder called drive 0x%x cylinder %d\n", DriveInfo, Cylinder);
 295
 296   /* Clear any spurious interrupts */
 297   KeClearEvent(&DriveInfo->ControllerInfo->SynchEvent);
 298
 299   /* queue seek command */
 300   if(HwSeek(DriveInfo, Cylinder) != STATUS_SUCCESS)
 301     {
 302       DPRINT("floppy: RWSeekToTrack(): unable to seek\n");
 303       return STATUS_UNSUCCESSFUL;
 304     }
 305
 306   WaitForControllerInterrupt(DriveInfo->ControllerInfo);
 307
 308   if(HwSenseInterruptStatus(DriveInfo->ControllerInfo) != STATUS_SUCCESS)
 309     {
 310       DPRINT("floppy: RWSeekToTrack(): unable to get seek results\n");
 311       return STATUS_UNSUCCESSFUL;
 312     }
 313
 314   /* read ID mark from head 0 to verify */
 315   if(HwReadId(DriveInfo, 0) != STATUS_SUCCESS)
 316     {
 317       DPRINT("floppy: RWSeekToTrack(): unable to queue ReadId\n");
 318       return STATUS_UNSUCCESSFUL;
 319     }
 320
 321   WaitForControllerInterrupt(DriveInfo->ControllerInfo);
 322
 323   if(HwReadIdResult(DriveInfo->ControllerInfo, &CurCylinder, NULL) != STATUS_SUCCESS)
 324     {
 325       DPRINT("floppy: RWSeekToTrack(): unable to get ReadId result\n");
 326       return STATUS_UNSUCCESSFUL;
 327     }
 328
 329   if(CurCylinder != Cylinder)
 330     {
 331       DPRINT("floppy: RWSeekToTrack(): Seeek to track failed; current cylinder is 0x%x\n", CurCylinder);
 332       return STATUS_UNSUCCESSFUL;
 333     }
 334
 335   DPRINT("floppy: RWSeekToCylinder: returning successfully, now on cyl %d\n", Cylinder);
 336
 337   return STATUS_SUCCESS;
 338 }
 339
 340 \f
 341 static NTSTATUS NTAPI RWComputeCHS(PDRIVE_INFO IN  DriveInfo,
 342                                    ULONG       IN  DiskByteOffset,
 343                                    PUCHAR      OUT Cylinder,
 344                                    PUCHAR      OUT Head,
 345                                    PUCHAR      OUT Sector)
 346 /*
 347  * FUNCTION: Compute the CHS from the absolute byte offset on disk
 348  * ARGUMENTS:
 349  *     DriveInfo: Drive to compute on
 350  *     DiskByteOffset: Absolute offset on disk of the starting byte
 351  *     Cylinder: Cylinder that the byte is on
 352  *     Head: Head that the byte is on
 353  *     Sector: Sector that the byte is on
 354  * RETURNS:
 355  *     STATUS_SUCCESS if CHS are determined correctly
 356  *     STATUS_UNSUCCESSFUL otherwise
 357  * NOTES:
 358  *     - Lots of ugly typecasts here
 359  *     - Sectors are 1-based!
 360  *     - This is really crummy code.  Please FIXME.
 361  */
 362 {
 363   ULONG AbsoluteSector;
 364   UCHAR SectorsPerCylinder = (UCHAR)DriveInfo->DiskGeometry.SectorsPerTrack * (UCHAR)DriveInfo->DiskGeometry.TracksPerCylinder;
 365
 366   DPRINT("floppy: RWComputeCHS: Called with offset 0x%x\n", DiskByteOffset);
 367
 368   /* First calculate the 1-based "absolute sector" based on the byte offset */
 369   ASSERT(!(DiskByteOffset % DriveInfo->DiskGeometry.BytesPerSector));         /* FIXME: Only handle full sector transfers atm */
 370
 371   /* AbsoluteSector is zero-based to make the math a little easier */
 372   AbsoluteSector = DiskByteOffset / DriveInfo->DiskGeometry.BytesPerSector;  /* Num full sectors */
 373
 374   /* Cylinder number is floor(AbsoluteSector / SectorsPerCylinder) */
 375   *Cylinder =  (CHAR)(AbsoluteSector / SectorsPerCylinder);
 376
 377   /* Head number is 0 if the sector within the cylinder < SectorsPerTrack; 1 otherwise */
 378   *Head =  AbsoluteSector % SectorsPerCylinder < DriveInfo->DiskGeometry.SectorsPerTrack ? 0 : 1;
 379
 380   /*
 381    * Sector number is the sector within the cylinder if on head 0; that minus SectorsPerTrack if it's on head 1
 382    * (lots of casts to placate msvc).  1-based!
 383    */
 384   *Sector =  ((UCHAR)(AbsoluteSector % SectorsPerCylinder) + 1) - ((*Head) * (UCHAR)DriveInfo->DiskGeometry.SectorsPerTrack);
 385
 386   DPRINT("floppy: RWComputeCHS: offset 0x%x is c:0x%x h:0x%x s:0x%x\n", DiskByteOffset, *Cylinder, *Head, *Sector);
 387
 388   /* Sanity checking */
 389   ASSERT(*Cylinder <= DriveInfo->DiskGeometry.Cylinders.QuadPart);
 390   ASSERT(*Head <= DriveInfo->DiskGeometry.TracksPerCylinder);
 391   ASSERT(*Sector <= DriveInfo->DiskGeometry.SectorsPerTrack);
 392
 393   return STATUS_SUCCESS;
 394 }
 395
 396 \f
 397 VOID NTAPI ReadWritePassive(PDRIVE_INFO DriveInfo,
 398                             PIRP Irp)
 399 /*
 400  * FUNCTION: Handle the first phase of a read or write IRP
 401  * ARGUMENTS:
 402  *     DeviceObject: DeviceObject that is the target of the IRP
 403  *     Irp: IRP to process
 404  * RETURNS:
 405  *     STATUS_VERIFY_REQUIRED if the media has changed and we need the filesystems to re-synch
 406  *     STATUS_SUCCESS otherwise
 407  * NOTES:
 408  *     - Must be called at PASSIVE_LEVEL
 409  *     - This function is about 250 lines longer than I wanted it to be.  Sorry.
 410  *
 411  * DETAILS:
 412  *  This routine manages the whole process of servicing a read or write request.  It goes like this:
 413  *    1) Check the DO_VERIFY_VOLUME flag and return if it's set
 414  *    2) Check the disk change line and notify the OS if it's set and return
 415  *    3) Detect the media if we haven't already
 416  *    4) Set up DiskByteOffset, Length, and WriteToDevice parameters
 417  *    5) Get DMA map registers
 418  *    6) Then, in a loop for each track, until all bytes are transferred:
 419  *      a) Compute the current CHS to set the read/write head to
 420  *      b) Seek to that spot
 421  *      c) Compute the last sector to transfer on that track
 422  *      d) Map the transfer through DMA
 423  *      e) Send the read or write command to the controller
 424  *      f) Read the results of the command
 425  */
 426 {
 427   PDEVICE_OBJECT DeviceObject = DriveInfo->DeviceObject;
 428   PIO_STACK_LOCATION Stack = IoGetCurrentIrpStackLocation(Irp);
 429   BOOLEAN WriteToDevice;
 430   ULONG Length;
 431   ULONG DiskByteOffset;
 432   KIRQL OldIrql;
 433   NTSTATUS Status;
 434   BOOLEAN DiskChanged;
 435   ULONG_PTR TransferByteOffset;
 436   UCHAR Gap;
 437
 438   PAGED_CODE();
 439
 440   DPRINT("floppy: ReadWritePassive called to %s 0x%x bytes from offset 0x%x\n",
 441            (Stack->MajorFunction == IRP_MJ_READ ? "read" : "write"),
 442            (Stack->MajorFunction == IRP_MJ_READ ? Stack->Parameters.Read.Length : Stack->Parameters.Write.Length),
 443            (Stack->MajorFunction == IRP_MJ_READ ? Stack->Parameters.Read.ByteOffset.u.LowPart :
 444             Stack->Parameters.Write.ByteOffset.u.LowPart));
 445
 446   /* Default return codes */
 447   Irp->IoStatus.Status = STATUS_UNSUCCESSFUL;
 448   Irp->IoStatus.Information = 0;
 449
 450   /*
 451    * Check to see if the volume needs to be verified.  If so,
 452    * we can get out of here quickly.
 453    */
 454   if(DeviceObject->Flags & DO_VERIFY_VOLUME && !(DeviceObject->Flags & SL_OVERRIDE_VERIFY_VOLUME))
 455     {
 456       DPRINT("floppy: ReadWritePassive(): DO_VERIFY_VOLUME set; Completing with  STATUS_VERIFY_REQUIRED\n");
 457       Irp->IoStatus.Status = STATUS_VERIFY_REQUIRED;
 458       IoCompleteRequest(Irp, IO_NO_INCREMENT);
 459       return;
 460     }
 461
 462   /*
 463    * Check the change line, and if it's set, return
 464    */
 465   StartMotor(DriveInfo);
 466   if(HwDiskChanged(DeviceObject->DeviceExtension, &DiskChanged) != STATUS_SUCCESS)
 467     {
 468       DPRINT("floppy: ReadWritePassive(): unable to detect disk change; Completing with STATUS_UNSUCCESSFUL\n");
 469       IoCompleteRequest(Irp, IO_NO_INCREMENT);
 470       StopMotor(DriveInfo->ControllerInfo);
 471       return;
 472     }
 473
 474   if(DiskChanged)
 475     {
 476       DPRINT("floppy: ReadWritePhase1(): signalling media changed; Completing with STATUS_MEDIA_CHANGED\n");
 477
 478       /* The following call sets IoStatus.Status and IoStatus.Information */
 479       SignalMediaChanged(DeviceObject, Irp);
 480
 481       /*
 482        * Guessing at something... see ioctl.c for more info
 483        */
 484       if(ResetChangeFlag(DriveInfo) == STATUS_NO_MEDIA_IN_DEVICE)
 485         Irp->IoStatus.Status = STATUS_NO_MEDIA_IN_DEVICE;
 486
 487       IoCompleteRequest(Irp, IO_NO_INCREMENT);
 488       StopMotor(DriveInfo->ControllerInfo);
 489       return;
 490     }
 491
 492   /*
 493    * Figure out the media type, if we don't know it already
 494    */
 495   if(DriveInfo->DiskGeometry.MediaType == Unknown)
 496     {
 497       if(RWDetermineMediaType(DriveInfo) != STATUS_SUCCESS)
 498         {
 499           DPRINT("floppy: ReadWritePassive(): unable to determine media type; completing with STATUS_UNSUCCESSFUL\n");
 500           IoCompleteRequest(Irp, IO_NO_INCREMENT);
 501           StopMotor(DriveInfo->ControllerInfo);
 502           return;
 503         }
 504
 505       if(DriveInfo->DiskGeometry.MediaType == Unknown)
 506         {
 507           DPRINT("floppy: ReadWritePassive(): Unknown media in drive; completing with STATUS_UNRECOGNIZED_MEDIA\n");
 508           Irp->IoStatus.Status = STATUS_UNRECOGNIZED_MEDIA;
 509           IoCompleteRequest(Irp, IO_NO_INCREMENT);
 510           StopMotor(DriveInfo->ControllerInfo);
 511           return;
 512         }
 513     }
 514
 515   /* Set up parameters for read or write */
 516   if(Stack->MajorFunction == IRP_MJ_READ)
 517     {
 518       Length = Stack->Parameters.Read.Length;
 519       DiskByteOffset = Stack->Parameters.Read.ByteOffset.u.LowPart;
 520       WriteToDevice = FALSE;
 521     }
 522   else
 523     {
 524       Length = Stack->Parameters.Write.Length;
 525       DiskByteOffset = Stack->Parameters.Write.ByteOffset.u.LowPart;
 526       WriteToDevice = TRUE;
 527     }
 528
 529   /*
 530    * FIXME:
 531    *   FloppyDeviceData.ReadWriteGapLength specify the value for the physical drive.
 532    *   We should set this value depend on the format of the inserted disk and possible
 533    *   depend on the request (read or write). A value of 0 results in one rotation
 534    *   between the sectors (7.2sec for reading a track).
 535    */
 536   Gap = DriveInfo->FloppyDeviceData.ReadWriteGapLength;
 537
 538   /*
 539    * Set up DMA transfer
 540    *
 541    * This is as good of a place as any to document something that used to confuse me
 542    * greatly (and I even wrote some of the kernel's DMA code, so if it confuses me, it
 543    * probably confuses at least a couple of other people too).
 544    *
 545    * MmGetMdlVirtualAddress() returns the virtal address, as mapped in the buffer's original
 546    * process context, of the MDL.  In other words:  say you start with a buffer at address X, then
 547    * you build an MDL out of that buffer called Mdl. If you call MmGetMdlVirtualAddress(Mdl), it
 548    * will return X.
 549    *
 550    * There are two parameters that the function looks at to produce X again, given the MDL:  the
 551    * first is the StartVa, which is the base virtual address of the page that the buffer starts
 552    * in.  If your buffer's virtual address is 0x12345678, StartVa will be 0x12345000, assuming 4K pages
 553    * (which is (almost) always the case on x86).  Note well: this address is only valid in the
 554    * process context that you initially built the MDL from.  The physical pages that make up
 555    * the MDL might perhaps be mapped in other process contexts too (or even in the system space,
 556    * above 0x80000000 (default; 0xc0000000 on current ReactOS or /3GB Windows)), but it will
 557    * (possibly) be mapped at a different address.
 558    *
 559    * The second parameter is the ByteOffset.  Given an original buffer address of 0x12345678,
 560    * the ByteOffset would be 0x678.  Because MDLs can only describe full pages (and therefore
 561    * StartVa always points to the start address of a page), the ByteOffset must be used to
 562    * find the real start of the buffer.
 563    *
 564    * In general, if you add the StartVa and ByteOffset together, you get back your original
 565    * buffer pointer, which you are free to use if you're sure you're in the right process
 566    * context.  You could tell by accessing the (hidden and not-to-be-used) Process member of
 567    * the MDL, but in general, if you have to ask whether or not you are in the right context,
 568    * then you shouldn't be using this address for anything anyway.  There are also security implications
 569    * (big ones, really, I wouldn't kid about this) to directly accessing a user's buffer by VA, so
 570    * Don't Do That.
 571    *
 572    * There is a somewhat weird but very common use of the virtual address associated with a MDL
 573    * that pops up often in the context of DMA.  DMA APIs (particularly MapTransfer()) need to
 574    * know where the memory is that they should DMA into and out of.  This memory is described
 575    * by a MDL.  The controller eventually needs to know a physical address on the host side,
 576    * which is generally a 32-bit linear address (on x86), and not just a page address.  Therefore,
 577    * the DMA APIs look at the ByteOffset field of the MDL to reconstruct the real address that
 578    * should be programmed into the DMA controller.
 579    *
 580    * It is often the case that a transfer needs to be broken down over more than one DMA operation,
 581    * particularly when it is a big transfer and the HAL doesn't give you enough map registers
 582    * to map the whole thing at once.  Therefore, the APIs need a way to tell how far into the MDL
 583    * they should look to transfer the next chunk of bytes.  Now, Microsoft could have designed
 584    * MapTransfer to take a  "MDL offset" argument, starting with 0, for how far into the buffer to
 585    * start, but it didn't.  Instead, MapTransfer asks for the virtual address of the MDL as an "index" into
 586    * the MDL.  The way it computes how far into the page to start the transfer is by masking off all but
 587    * the bottom 12 bits (on x86) of the number you supply as the CurrentVa and using *that* as the
 588    * ByteOffset instead of the one in the MDL.  (OK, this varies a bit by OS and version, but this
 589    * is the effect).
 590    *
 591    * In other words, you get a number back from MmGetMdlVirtualAddress that represents the start of your
 592    * buffer, and you pass it to the first MapTransfer call.  Then, for each successive operation
 593    * on the same buffer, you increment that address to point to the next spot in the MDL that
 594    * you want to DMA to/from.  The fact that the virtual address you're manipulating is probably not
 595    * mapped into the process context that you're running in is irrelevant, since it's only being
 596    * used to index into the MDL.
 597    */
 598
 599   /* Get map registers for DMA */
 600   KeRaiseIrql(DISPATCH_LEVEL, &OldIrql);
 601   Status = IoAllocateAdapterChannel(DriveInfo->ControllerInfo->AdapterObject, DeviceObject,
 602                                     DriveInfo->ControllerInfo->MapRegisters, MapRegisterCallback, DriveInfo->ControllerInfo);
 603   KeLowerIrql(OldIrql);
 604
 605   if(Status != STATUS_SUCCESS)
 606     {
 607       DPRINT("floppy: ReadWritePassive(): unable allocate an adapter channel; completing with STATUS_UNSUCCESSFUL\n");
 608       IoCompleteRequest(Irp, IO_NO_INCREMENT);
 609       StopMotor(DriveInfo->ControllerInfo);
 610       return ;
 611     }
 612
 613
 614   /*
 615    * Read from (or write to) the device
 616    *
 617    * This has to be called in a loop, as you can only transfer data to/from a single track at
 618    * a time.
 619    */
 620   TransferByteOffset = 0;
 621   while(TransferByteOffset < Length)
 622     {
 623       UCHAR Cylinder;
 624       UCHAR Head;
 625       UCHAR StartSector;
 626       ULONG CurrentTransferBytes;
 627       UCHAR CurrentTransferSectors;
 628
 629       DPRINT("floppy: ReadWritePassive(): iterating in while (TransferByteOffset = 0x%x of 0x%x total) - allocating %d registers\n",
 630                TransferByteOffset, Length, DriveInfo->ControllerInfo->MapRegisters);
 631
 632       KeClearEvent(&DriveInfo->ControllerInfo->SynchEvent);
 633
 634       /*
 635        * Compute starting CHS
 636        */
 637       if(RWComputeCHS(DriveInfo, DiskByteOffset+TransferByteOffset, &Cylinder, &Head, &StartSector) != STATUS_SUCCESS)
 638         {
 639           DPRINT("floppy: ReadWritePassive(): unable to compute CHS; completing with STATUS_UNSUCCESSFUL\n");
 640           RWFreeAdapterChannel(DriveInfo->ControllerInfo->AdapterObject);
 641           IoCompleteRequest(Irp, IO_NO_INCREMENT);
 642           StopMotor(DriveInfo->ControllerInfo);
 643           return;
 644         }
 645
 646       /*
 647        * Seek to the right track
 648        */
 649       if(!DriveInfo->ControllerInfo->ImpliedSeeks)
 650         {
 651           if(RWSeekToCylinder(DriveInfo, Cylinder) != STATUS_SUCCESS)
 652             {
 653               DPRINT("floppy: ReadWritePassive(): unable to seek; completing with STATUS_UNSUCCESSFUL\n");
 654               RWFreeAdapterChannel(DriveInfo->ControllerInfo->AdapterObject);
 655               IoCompleteRequest(Irp, IO_NO_INCREMENT);
 656               StopMotor(DriveInfo->ControllerInfo);
 657               return ;
 658             }
 659         }
 660
 661       /*
 662        * Compute last sector
 663        *
 664        * We can only ask for a transfer up to the end of the track.  Then we have to re-seek and do more.
 665        * TODO: Support the MT bit
 666        */
 667       DPRINT("floppy: ReadWritePassive(): computing number of sectors to transfer (StartSector 0x%x): ", StartSector);
 668
 669       /* 1-based sector number */
 670       if( (((DriveInfo->DiskGeometry.TracksPerCylinder - Head) * DriveInfo->DiskGeometry.SectorsPerTrack - StartSector) + 1 ) <
 671           (Length - TransferByteOffset) / DriveInfo->DiskGeometry.BytesPerSector)
 672         {
 673           CurrentTransferSectors = (UCHAR)((DriveInfo->DiskGeometry.TracksPerCylinder - Head) * DriveInfo->DiskGeometry.SectorsPerTrack - StartSector) + 1;
 674         }
 675       else
 676         {
 677           CurrentTransferSectors = (UCHAR)((Length - TransferByteOffset) / DriveInfo->DiskGeometry.BytesPerSector);
 678         }
 679
 680       DPRINT("0x%x\n", CurrentTransferSectors);
 681
 682       CurrentTransferBytes = CurrentTransferSectors * DriveInfo->DiskGeometry.BytesPerSector;
 683
 684       /*
 685        * Adjust to map registers
 686        * BUG: Does this take into account page crossings?
 687        */
 688       DPRINT("floppy: ReadWritePassive(): Trying to transfer 0x%x bytes\n", CurrentTransferBytes);
 689
 690       ASSERT(CurrentTransferBytes);
 691
 692       if(BYTES_TO_PAGES(CurrentTransferBytes) > DriveInfo->ControllerInfo->MapRegisters)
 693         {
 694           CurrentTransferSectors = (UCHAR)((DriveInfo->ControllerInfo->MapRegisters * PAGE_SIZE) /
 695                                             DriveInfo->DiskGeometry.BytesPerSector);
 696
 697           CurrentTransferBytes = CurrentTransferSectors * DriveInfo->DiskGeometry.BytesPerSector;
 698
 699           DPRINT("floppy: ReadWritePassive: limiting transfer to 0x%x bytes (0x%x sectors) due to map registers\n",
 700                    CurrentTransferBytes, CurrentTransferSectors);
 701         }
 702
 703       /* set up this round's dma operation */
 704       /* param 2 is ReadOperation --> opposite of WriteToDevice that IoMapTransfer takes.  BAD MS. */
 705       KeFlushIoBuffers(Irp->MdlAddress, !WriteToDevice, TRUE);
 706
 707       IoMapTransfer(DriveInfo->ControllerInfo->AdapterObject, Irp->MdlAddress,
 708                     DriveInfo->ControllerInfo->MapRegisterBase,
 709                     (PUCHAR)((ULONG_PTR)MmGetMdlVirtualAddress(Irp->MdlAddress) + TransferByteOffset),
 710                     &CurrentTransferBytes, WriteToDevice);
 711
 712       /*
 713        * Read or Write
 714        */
 715       KeClearEvent(&DriveInfo->ControllerInfo->SynchEvent);
 716
 717       /* Issue the read/write command to the controller.  Note that it expects the opposite of WriteToDevice. */
 718       if(HwReadWriteData(DriveInfo->ControllerInfo, !WriteToDevice, DriveInfo->UnitNumber, Cylinder, Head, StartSector,
 719                          DriveInfo->BytesPerSectorCode, DriveInfo->DiskGeometry.SectorsPerTrack, Gap, 0xff) != STATUS_SUCCESS)
 720         {
 721           DPRINT("floppy: ReadWritePassive(): HwReadWriteData returned failure; unable to read; completing with STATUS_UNSUCCESSFUL\n");
 722           RWFreeAdapterChannel(DriveInfo->ControllerInfo->AdapterObject);
 723           IoCompleteRequest(Irp, IO_NO_INCREMENT);
 724           StopMotor(DriveInfo->ControllerInfo);
 725           return ;
 726         }
 727
 728       DPRINT("floppy: ReadWritePassive(): HwReadWriteData returned -- waiting on event\n");
 729
 730       /*
 731        * At this point, we block and wait for an interrupt
 732        * FIXME: this seems to take too long
 733        */
 734       WaitForControllerInterrupt(DriveInfo->ControllerInfo);
 735
 736       /* Read is complete; flush & free adapter channel */
 737       IoFlushAdapterBuffers(DriveInfo->ControllerInfo->AdapterObject, Irp->MdlAddress,
 738                             DriveInfo->ControllerInfo->MapRegisterBase,
 739                             (PVOID)((ULONG_PTR)MmGetMdlVirtualAddress(Irp->MdlAddress) + TransferByteOffset),
 740                             CurrentTransferBytes, WriteToDevice);
 741
 742       /* Read the results from the drive */
 743       if(HwReadWriteResult(DriveInfo->ControllerInfo) != STATUS_SUCCESS)
 744         {
 745           DPRINT("floppy: ReadWritePassive(): HwReadWriteResult returned failure; unable to read; completing with STATUS_UNSUCCESSFUL\n");
 746           HwDumpRegisters(DriveInfo->ControllerInfo);
 747           RWFreeAdapterChannel(DriveInfo->ControllerInfo->AdapterObject);
 748           IoCompleteRequest(Irp, IO_NO_INCREMENT);
 749           StopMotor(DriveInfo->ControllerInfo);
 750           return ;
 751         }
 752
 753       TransferByteOffset += CurrentTransferBytes;
 754     }
 755
 756   RWFreeAdapterChannel(DriveInfo->ControllerInfo->AdapterObject);
 757
 758   /* That's all folks! */
 759   DPRINT("floppy: ReadWritePassive(): success; Completing with STATUS_SUCCESS\n");
 760   Irp->IoStatus.Status = STATUS_SUCCESS;
 761   Irp->IoStatus.Information = Length;
 762   IoCompleteRequest(Irp, IO_NO_INCREMENT);
 763   StopMotor(DriveInfo->ControllerInfo);
 764 }
 765