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Obtain geometry info of non-standard sized floppy from BPB #4900

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Mar 13, 2024
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Obtain geometry info of non-standard sized floppy from BPB #4900

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69 changes: 51 additions & 18 deletions src/dos/drive_fat.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1557,7 +1557,7 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
char* ext = strrchr((char*)sysFilename, '.');
if(ext != NULL && (!strcasecmp(ext, ".hdi") || !strcasecmp(ext, ".nhd"))) is_hdd = true;
}
//LOG_MSG("is_hdd = %s", is_hdd ? "true" : "false");
bool is_pc98fd = (IS_PC98_ARCH && !is_hdd);

physToLogAdj = 0;
req_ver_major = req_ver_minor = 0;
Expand Down Expand Up @@ -1755,15 +1755,17 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
partSectOff = startSector;
partSectSize = countSector;
} else {
/* Get floppy disk parameters based on image size */
loadedDisk->Get_Geometry(&headscyl, &cylinders, &cylsector, &bytesector);
if (headscyl > 0 && cylinders > 0 && cylsector > 0 && bytesector > 0) // manually set geometry if value specified
loadedDisk->Set_Geometry(headscyl, cylinders,cylsector, bytesector);
else
/* Get floppy disk parameters based on image size */
loadedDisk->Get_Geometry(&headscyl, &cylinders, &cylsector, &bytesector);
/* Floppy disks don't have partitions */
partSectOff = 0;

if (loadedDisk->heads == 0 || loadedDisk->sectors == 0 || loadedDisk->cylinders == 0) {
created_successfully = false;
LOG_MSG("No geometry");
return;
/* Get_Geometry fails for some floppies with weird geometries, so try obtaining the geometry from BPB in such case */
LOG_MSG("drive_fat.cpp: No geometry, check your image. Try obtaining from BPB");
}
}

Expand Down Expand Up @@ -1935,6 +1937,27 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
bootbuffer.bpb.v.BPB_VolID = var_read((uint32_t*)var);

if(!is_hdd) {
if (loadedDisk->heads == 0 || loadedDisk->sectors == 0 || loadedDisk->cylinders == 0 || loadedDisk->sector_size == 0) { // Set geometry from BPB
headscyl = bootbuffer.bpb.v.BPB_NumHeads;
cylsector = bootbuffer.bpb.v.BPB_SecPerTrk;
bytesector = bootbuffer.bpb.v.BPB_BytsPerSec;
if(headscyl == 0 || cylsector == 0 || bytesector == 0 || loadedDisk->diskSizeK == 0 || ((bytesector & (bytesector - 1)) != 0)/*not a power of 2*/){
LOG_MSG("drive_fat.cpp: Illegal BPB value");
if(!IS_PC98_ARCH){
created_successfully = false;
return;
}
}
else {
cylinders = loadedDisk->diskSizeK * 1024 / headscyl / cylsector / bytesector;
loadedDisk->Set_Geometry(headscyl, cylinders, cylsector, bytesector);
LOG_MSG("drive_fat.cpp: Floppy geometry set from BPB information SS/C/H/S = %u/%u/%u/%u",
loadedDisk->sector_size,
loadedDisk->cylinders,
loadedDisk->heads,
loadedDisk->sectors);
}
}
/* Identify floppy format */
if((bootbuffer.BS_jmpBoot[0] == 0x69 || bootbuffer.BS_jmpBoot[0] == 0xe9 ||
(bootbuffer.BS_jmpBoot[0] == 0xeb && bootbuffer.BS_jmpBoot[2] == 0x90)) &&
Expand Down Expand Up @@ -1962,7 +1985,7 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
bootbuffer.magic1 = 0x55; // to silence warning
bootbuffer.magic2 = 0xaa;
}
else if(!IS_PC98_ARCH){
else if(!IS_PC98_ARCH && loadedDisk->diskSizeK <= 360){
/* Read media descriptor in FAT */
uint8_t sectorBuffer[512];
loadedDisk->Read_AbsoluteSector(1,&sectorBuffer);
Expand Down Expand Up @@ -2081,35 +2104,44 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
*
* Second, there are some HDI images that are valid yet the FAT filesystem reports a head count of 0
* for some reason (Touhou Project) */
if ((BPB.v.BPB_SecPerClus == 0) ||
bool pc98fd_sanity_failed = false;
if ((BPB.v.BPB_SecPerClus == 0) ||
(BPB.v.BPB_NumFATs == 0) ||
(BPB.v.BPB_NumHeads == 0 && !IS_PC98_ARCH) ||
//(BPB.v.BPB_NumHeads > headscyl && !IS_PC98_ARCH) ||
(BPB.v.BPB_SecPerTrk == 0 && !IS_PC98_ARCH) ||
(BPB.v.BPB_SecPerTrk > cylsector && !IS_PC98_ARCH)) {
(cylsector != 0 && BPB.v.BPB_SecPerTrk > cylsector && !IS_PC98_ARCH)) {
if (isipl1 && !IS_PC98_ARCH && (BPB.v.BPB_NumHeads == 0 || BPB.v.BPB_SecPerTrk == 0 || BPB.v.BPB_SecPerTrk > cylsector)) {
const char *msg = "Please restart DOSBox-X in PC-98 mode to mount HDI disk images.\r\n";
uint16_t n = (uint16_t)strlen(msg);
DOS_WriteFile (STDOUT,(uint8_t *)msg, &n);
}
LOG_MSG("Sanity checks failed");
created_successfully = false;
return;
LOG_MSG("drive_fat.cpp: Sanity checks failed");
if(!is_pc98fd){ // PC-98 replaces corrupted FDD BPB with correct values
created_successfully = false;
return;
}
else
pc98fd_sanity_failed = true;
}

/* Sanity check: Root directory count is nonzero if FAT16/FAT12, or is zero if FAT32 */
if (BPB.is_fat32()) {
if (BPB.v.BPB_RootEntCnt != 0) {
LOG_MSG("Sanity check fail: Root directory count != 0 and not FAT32");
LOG_MSG("drive_fat.cpp: Sanity check fail: Root directory count != 0 and FAT32");
created_successfully = false;
return;
}
}
else {
if (BPB.v.BPB_RootEntCnt == 0) {
LOG_MSG("Sanity check fail: Root directory count == 0 and not FAT32");
created_successfully = false;
return;
LOG_MSG("drive_fat.cpp: Sanity check fail: Root directory count == 0 and not FAT32");
if(!is_pc98fd){
created_successfully = false;
return;
}
else
pc98fd_sanity_failed = true;
}
}

Expand All @@ -2128,8 +2160,9 @@ void fatDrive::fatDriveInit(const char *sysFilename, uint32_t bytesector, uint32
* 16 16 & 15 10000 AND 01111 RESULT: 00000 (0)
* 17 17 & 16 10001 AND 10000 RESULT: 10000 (16) */
if (BPB.v.BPB_BytsPerSec < 128 || BPB.v.BPB_BytsPerSec > SECTOR_SIZE_MAX ||
(BPB.v.BPB_BytsPerSec & (BPB.v.BPB_BytsPerSec - 1)) != 0/*not a power of 2*/) {
if(IS_PC98_ARCH && !is_hdd && ((bytesector == 1024)||(bytesector == 512))) {
(BPB.v.BPB_BytsPerSec & (BPB.v.BPB_BytsPerSec - 1)) != 0/*not a power of 2*/
|| pc98fd_sanity_failed) {
if(is_pc98fd && ((bytesector == 1024)||(bytesector == 512))) {
LOG_MSG("Experimental: PC-98 autodetect BPB parameters when it is corrupted");
BPB.v.BPB_BytsPerSec = bytesector;
BPB.v.BPB_SecPerClus = 1;
Expand Down