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DOS FAT driver: When -o int 13 is in effect, automatically adjust disk geometry according to media byte so that DS_BLISS.EXE still works even if you initially image mounted a 1.44MB floppy image

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Jonathan Campbell 2024-07-18 07:42:05 -07:00
parent 13276da31b
commit 9fdafdbfe2
2 changed files with 17 additions and 1 deletions
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4
CHANGELOG
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@ -1,4 +1,8 @@
NEXT NEXT
- DOS FAT driver: If INT 13h reports disk change, adapt floppy
disk geometry to new disk image according to media byte. This
allows DS_BLISS to present it's 720K fake floppy even if the
user initially mounted a 1.44MB floppy to drive A: (joncampbell123).
- INT 10 mode list: Add "pitch" parameter. If nonzero, the value - INT 10 mode list: Add "pitch" parameter. If nonzero, the value
(in pixels) is how to program the pixels per scanline when (in pixels) is how to program the pixels per scanline when
setting the mode. setting the mode.

14
src/dos/drive_fat.cpp
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@ -3678,7 +3678,7 @@ void fatDrive::checkDiskChange(void) {
* existence by intercepting INT 13h for floppy I/O and then expecting MS-DOS to call INT 13h * existence by intercepting INT 13h for floppy I/O and then expecting MS-DOS to call INT 13h
* to read it. Furthermore, at some parts of the demo, the INT 13h hook changes the root * to read it. Furthermore, at some parts of the demo, the INT 13h hook changes the root
* directory and FAT table to make the next "disk" appear, even if the volume label does not. */ * directory and FAT table to make the next "disk" appear, even if the volume label does not. */
if (loadedDisk->detectDiskChange() && !BPB.is_fat32()) { if (loadedDisk->detectDiskChange() && !BPB.is_fat32() && partSectOff == 0) {
LOG(LOG_MISC,LOG_DEBUG)("FAT: disk change"); LOG(LOG_MISC,LOG_DEBUG)("FAT: disk change");
FAT_BootSector bootbuffer = {}; FAT_BootSector bootbuffer = {};
@ -3712,6 +3712,18 @@ void fatDrive::checkDiskChange(void) {
return; return;
} }
/* sometimes as part of INT 13h interception the new image will differ from the format we mounted against (DS_BLISS.EXE) */
/* TODO: Add any other format here */
if (BPB.v.BPB_Media == 0xF9) {
LOG(LOG_MISC,LOG_DEBUG)("NEW FAT: changing floppy geometry to 720k format according to media byte");
loadedDisk->Set_Geometry(2/*heads*/,80/*cylinders*/,9/*sectors*/,512/*sector size*/);
}
else if (BPB.v.BPB_Media == 0xF0) {
/* TODO: By the time DOS supported the 1.44MB format the BPB also provided the geometry too */
LOG(LOG_MISC,LOG_DEBUG)("NEW FAT: changing floppy geometry to 1.44M format according to media byte");
loadedDisk->Set_Geometry(2/*heads*/,80/*cylinders*/,18/*sectors*/,512/*sector size*/);
}
uint32_t RootDirSectors; uint32_t RootDirSectors;
uint32_t DataSectors; uint32_t DataSectors;