1 // 16bit code to access hard drives.
3 // Copyright (C) 2008 Kevin O'Connor <kevin@koconnor.net>
4 // Copyright (C) 2002 MandrakeSoft S.A.
6 // This file may be distributed under the terms of the GNU LGPLv3 license.
8 #include "disk.h" // floppy_13
9 #include "biosvar.h" // SET_BDA
10 #include "config.h" // CONFIG_*
11 #include "util.h" // debug_enter
12 #include "pic.h" // eoi_pic2
13 #include "bregs.h" // struct bregs
14 #include "pci.h" // pci_bdf_to_bus
15 #include "ata.h" // ATA_CB_DC
18 /****************************************************************
20 ****************************************************************/
23 __disk_ret(struct bregs *regs, u32 linecode, const char *fname)
26 if (regs->dl < EXTSTART_HD)
27 SET_BDA(floppy_last_status, code);
29 SET_BDA(disk_last_status, code);
31 __set_code_invalid(regs, linecode, fname);
33 set_code_success(regs);
37 __disk_ret_unimplemented(struct bregs *regs, u32 linecode, const char *fname)
40 if (regs->dl < EXTSTART_HD)
41 SET_BDA(floppy_last_status, code);
43 SET_BDA(disk_last_status, code);
44 __set_code_unimplemented(regs, linecode, fname);
48 __disk_stub(struct bregs *regs, int lineno, const char *fname)
50 __warn_unimplemented(regs, lineno, fname);
51 __disk_ret(regs, DISK_RET_SUCCESS | (lineno << 8), fname);
54 #define DISK_STUB(regs) \
55 __disk_stub((regs), __LINE__, __func__)
57 // Get the cylinders/heads/sectors for the given drive.
59 fillLCHS(struct drive_s *drive_g, u16 *nlc, u16 *nlh, u16 *nlspt)
61 if (CONFIG_CDROM_EMU && drive_g == GET_GLOBAL(cdemu_drive)) {
62 // Emulated drive - get info from ebda. (It's not possible to
63 // populate the geometry directly in the driveid because the
64 // geometry is only known after the bios segment is made
66 u16 ebda_seg = get_ebda_seg();
67 *nlc = GET_EBDA2(ebda_seg, cdemu.lchs.cylinders);
68 *nlh = GET_EBDA2(ebda_seg, cdemu.lchs.heads);
69 *nlspt = GET_EBDA2(ebda_seg, cdemu.lchs.spt);
72 *nlc = GET_GLOBAL(drive_g->lchs.cylinders);
73 *nlh = GET_GLOBAL(drive_g->lchs.heads);
74 *nlspt = GET_GLOBAL(drive_g->lchs.spt);
77 // Perform read/write/verify using old-style chs accesses
79 basic_access(struct bregs *regs, struct drive_s *drive_g, u16 command)
82 dop.drive_g = drive_g;
83 dop.command = command;
86 u16 cylinder = regs->ch | ((((u16)regs->cl) << 2) & 0x300);
87 u16 sector = regs->cl & 0x3f;
90 if (count > 128 || count == 0 || sector == 0) {
91 dprintf(1, "int13_harddisk: function %02x, parameter out of range!\n"
93 disk_ret(regs, DISK_RET_EPARAM);
99 fillLCHS(drive_g, &nlc, &nlh, &nlspt);
101 // sanity check on cyl heads, sec
102 if (cylinder >= nlc || head >= nlh || sector > nlspt) {
103 dprintf(1, "int13_harddisk: function %02x, parameters out of"
104 " range %04x/%04x/%04x!\n"
105 , regs->ah, cylinder, head, sector);
106 disk_ret(regs, DISK_RET_EPARAM);
110 // translate lchs to lba
111 dop.lba = (((((u32)cylinder * (u32)nlh) + (u32)head) * (u32)nlspt)
114 dop.buf_fl = MAKE_FLATPTR(regs->es, regs->bx);
116 int status = send_disk_op(&dop);
118 regs->al = dop.count;
120 disk_ret(regs, status);
123 // Perform read/write/verify using new-style "int13ext" accesses.
125 extended_access(struct bregs *regs, struct drive_s *drive_g, u16 command)
127 struct disk_op_s dop;
128 // Get lba and check.
129 dop.lba = GET_INT13EXT(regs, lba);
130 dop.command = command;
131 dop.drive_g = drive_g;
132 if (dop.lba >= GET_GLOBAL(drive_g->sectors)) {
133 dprintf(1, "int13_harddisk: function %02x. LBA out of range\n"
135 disk_ret(regs, DISK_RET_EPARAM);
139 dop.buf_fl = SEGOFF_TO_FLATPTR(GET_INT13EXT(regs, data));
140 dop.count = GET_INT13EXT(regs, count);
142 int status = send_disk_op(&dop);
144 SET_INT13EXT(regs, count, dop.count);
146 disk_ret(regs, status);
150 /****************************************************************
151 * Hard Drive functions
152 ****************************************************************/
154 // disk controller reset
156 disk_1300(struct bregs *regs, struct drive_s *drive_g)
158 struct disk_op_s dop;
159 dop.drive_g = drive_g;
160 dop.command = CMD_RESET;
161 int status = send_disk_op(&dop);
162 disk_ret(regs, status);
167 disk_1301(struct bregs *regs, struct drive_s *drive_g)
170 if (regs->dl < EXTSTART_HD)
172 v = GET_BDA(floppy_last_status);
174 v = GET_BDA(disk_last_status);
177 // XXX - clear disk_last_status?
182 disk_1302(struct bregs *regs, struct drive_s *drive_g)
184 basic_access(regs, drive_g, CMD_READ);
187 // write disk sectors
189 disk_1303(struct bregs *regs, struct drive_s *drive_g)
191 basic_access(regs, drive_g, CMD_WRITE);
194 // verify disk sectors
196 disk_1304(struct bregs *regs, struct drive_s *drive_g)
198 basic_access(regs, drive_g, CMD_VERIFY);
203 disk_1305(struct bregs *regs, struct drive_s *drive_g)
208 fillLCHS(drive_g, &nlc, &nlh, &nlspt);
210 u8 num_sectors = regs->al;
213 if (head >= nlh || num_sectors == 0 || num_sectors > nlspt) {
214 disk_ret(regs, DISK_RET_EPARAM);
218 struct disk_op_s dop;
219 dop.drive_g = drive_g;
220 dop.command = CMD_FORMAT;
222 dop.count = num_sectors;
223 dop.buf_fl = MAKE_FLATPTR(regs->es, regs->bx);
224 int status = send_disk_op(&dop);
225 disk_ret(regs, status);
228 // read disk drive parameters
230 disk_1308(struct bregs *regs, struct drive_s *drive_g)
232 u16 ebda_seg = get_ebda_seg();
233 // Get logical geometry from table
235 fillLCHS(drive_g, &nlc, &nlh, &nlspt);
239 if (regs->dl < EXTSTART_HD) {
241 count = GET_GLOBAL(Drives.floppycount);
243 if (CONFIG_CDROM_EMU && drive_g == GET_GLOBAL(cdemu_drive))
244 regs->bx = GET_EBDA2(ebda_seg, cdemu.media) * 2;
246 regs->bx = GET_GLOBAL(drive_g->floppy_type);
248 // set es & di to point to 11 byte diskette param table in ROM
250 regs->di = (u32)&diskette_param_table2;
251 } else if (regs->dl < EXTSTART_CD) {
253 count = GET_BDA(hdcount);
254 nlc--; // last sector reserved
256 // Not supported on CDROM
257 disk_ret(regs, DISK_RET_EPARAM);
261 if (CONFIG_CDROM_EMU && GET_EBDA2(ebda_seg, cdemu.active)) {
262 u8 emudrive = GET_EBDA2(ebda_seg, cdemu.emulated_extdrive);
263 if (((emudrive ^ regs->dl) & 0x80) == 0)
264 // Note extra drive due to emulation.
266 if (regs->dl < EXTSTART_HD && count > 2)
267 // Max of two floppy drives.
272 regs->ch = nlc & 0xff;
273 regs->cl = ((nlc >> 2) & 0xc0) | (nlspt & 0x3f);
276 disk_ret(regs, DISK_RET_SUCCESS);
280 // initialize drive parameters
282 disk_1309(struct bregs *regs, struct drive_s *drive_g)
287 // seek to specified cylinder
289 disk_130c(struct bregs *regs, struct drive_s *drive_g)
294 // alternate disk reset
296 disk_130d(struct bregs *regs, struct drive_s *drive_g)
303 disk_1310(struct bregs *regs, struct drive_s *drive_g)
305 // should look at 40:8E also???
307 struct disk_op_s dop;
308 dop.drive_g = drive_g;
309 dop.command = CMD_ISREADY;
310 int status = send_disk_op(&dop);
311 disk_ret(regs, status);
316 disk_1311(struct bregs *regs, struct drive_s *drive_g)
321 // controller internal diagnostic
323 disk_1314(struct bregs *regs, struct drive_s *drive_g)
328 // read disk drive size
330 disk_1315(struct bregs *regs, struct drive_s *drive_g)
332 disk_ret(regs, DISK_RET_SUCCESS);
333 if (regs->dl < EXTSTART_HD || regs->dl >= EXTSTART_CD) {
340 // Get logical geometry from table
342 fillLCHS(drive_g, &nlc, &nlh, &nlspt);
344 // Compute sector count seen by int13
345 u32 lba = (u32)(nlc - 1) * (u32)nlh * (u32)nlspt;
346 regs->cx = lba >> 16;
347 regs->dx = lba & 0xffff;
348 regs->ah = 3; // hard disk accessible
352 disk_1316(struct bregs *regs, struct drive_s *drive_g)
354 if (regs->dl >= EXTSTART_HD) {
356 disk_ret(regs, DISK_RET_EPARAM);
359 disk_ret(regs, DISK_RET_ECHANGED);
362 // IBM/MS installation check
364 disk_1341(struct bregs *regs, struct drive_s *drive_g)
366 regs->bx = 0xaa55; // install check
367 regs->cx = 0x0007; // ext disk access and edd, removable supported
368 disk_ret(regs, DISK_RET_SUCCESS);
369 regs->ah = 0x30; // EDD 3.0
372 // IBM/MS extended read
374 disk_1342(struct bregs *regs, struct drive_s *drive_g)
376 extended_access(regs, drive_g, CMD_READ);
379 // IBM/MS extended write
381 disk_1343(struct bregs *regs, struct drive_s *drive_g)
383 extended_access(regs, drive_g, CMD_WRITE);
388 disk_1344(struct bregs *regs, struct drive_s *drive_g)
390 extended_access(regs, drive_g, CMD_VERIFY);
395 disk_134500(struct bregs *regs, struct drive_s *drive_g)
397 u16 ebda_seg = get_ebda_seg();
398 int cdid = regs->dl - EXTSTART_CD;
399 u8 locks = GET_EBDA2(ebda_seg, cdrom_locks[cdid]);
402 disk_ret(regs, DISK_RET_ETOOMANYLOCKS);
405 SET_EBDA2(ebda_seg, cdrom_locks[cdid], locks + 1);
407 disk_ret(regs, DISK_RET_SUCCESS);
412 disk_134501(struct bregs *regs, struct drive_s *drive_g)
414 u16 ebda_seg = get_ebda_seg();
415 int cdid = regs->dl - EXTSTART_CD;
416 u8 locks = GET_EBDA2(ebda_seg, cdrom_locks[cdid]);
419 disk_ret(regs, DISK_RET_ENOTLOCKED);
423 SET_EBDA2(ebda_seg, cdrom_locks[cdid], locks);
424 regs->al = (locks ? 1 : 0);
425 disk_ret(regs, DISK_RET_SUCCESS);
430 disk_134502(struct bregs *regs, struct drive_s *drive_g)
432 int cdid = regs->dl - EXTSTART_CD;
433 u8 locks = GET_EBDA(cdrom_locks[cdid]);
434 regs->al = (locks ? 1 : 0);
435 disk_ret(regs, DISK_RET_SUCCESS);
439 disk_1345XX(struct bregs *regs, struct drive_s *drive_g)
441 disk_ret_unimplemented(regs, DISK_RET_EPARAM);
444 // IBM/MS lock/unlock drive
446 disk_1345(struct bregs *regs, struct drive_s *drive_g)
448 if (regs->dl < EXTSTART_CD) {
449 // Always success for HD
450 disk_ret(regs, DISK_RET_SUCCESS);
455 case 0x00: disk_134500(regs, drive_g); break;
456 case 0x01: disk_134501(regs, drive_g); break;
457 case 0x02: disk_134502(regs, drive_g); break;
458 default: disk_1345XX(regs, drive_g); break;
462 // IBM/MS eject media
464 disk_1346(struct bregs *regs, struct drive_s *drive_g)
466 if (regs->dl < EXTSTART_CD) {
467 // Volume Not Removable
468 disk_ret(regs, DISK_RET_ENOTREMOVABLE);
472 int cdid = regs->dl - EXTSTART_CD;
473 u8 locks = GET_EBDA(cdrom_locks[cdid]);
475 disk_ret(regs, DISK_RET_ELOCKED);
479 // FIXME should handle 0x31 no media in device
480 // FIXME should handle 0xb5 valid request failed
482 // Call removable media eject
484 memset(&br, 0, sizeof(br));
486 call16_int(0x15, &br);
488 if (br.ah || br.flags & F_CF) {
489 disk_ret(regs, DISK_RET_ELOCKED);
492 disk_ret(regs, DISK_RET_SUCCESS);
495 // IBM/MS extended seek
497 disk_1347(struct bregs *regs, struct drive_s *drive_g)
499 extended_access(regs, drive_g, CMD_SEEK);
502 // IBM/MS get drive parameters
504 disk_1348(struct bregs *regs, struct drive_s *drive_g)
506 u16 size = GET_INT13DPT(regs, size);
508 // Buffer is too small
510 disk_ret(regs, DISK_RET_EPARAM);
516 u8 type = GET_GLOBAL(drive_g->type);
517 u16 npc = GET_GLOBAL(drive_g->pchs.cylinders);
518 u16 nph = GET_GLOBAL(drive_g->pchs.heads);
519 u16 npspt = GET_GLOBAL(drive_g->pchs.spt);
520 u64 lba = GET_GLOBAL(drive_g->sectors);
521 u16 blksize = GET_GLOBAL(drive_g->blksize);
523 dprintf(DEBUG_HDL_13, "disk_1348 size=%d t=%d chs=%d,%d,%d lba=%d bs=%d\n"
524 , size, type, npc, nph, npspt, (u32)lba, blksize);
526 SET_INT13DPT(regs, size, 26);
527 if (type == DTYPE_ATAPI) {
528 // 0x74 = removable, media change, lockable, max values
529 SET_INT13DPT(regs, infos, 0x74);
530 SET_INT13DPT(regs, cylinders, 0xffffffff);
531 SET_INT13DPT(regs, heads, 0xffffffff);
532 SET_INT13DPT(regs, spt, 0xffffffff);
533 SET_INT13DPT(regs, sector_count, (u64)-1);
535 if (lba > (u64)npspt*nph*0x3fff) {
536 SET_INT13DPT(regs, infos, 0x00); // geometry is invalid
537 SET_INT13DPT(regs, cylinders, 0x3fff);
539 SET_INT13DPT(regs, infos, 0x02); // geometry is valid
540 SET_INT13DPT(regs, cylinders, (u32)npc);
542 SET_INT13DPT(regs, heads, (u32)nph);
543 SET_INT13DPT(regs, spt, (u32)npspt);
544 SET_INT13DPT(regs, sector_count, lba);
546 SET_INT13DPT(regs, blksize, blksize);
548 if (size < 30 || (type != DTYPE_ATA && type != DTYPE_ATAPI)) {
549 disk_ret(regs, DISK_RET_SUCCESS);
555 u16 ebda_seg = get_ebda_seg();
556 SET_INT13DPT(regs, size, 30);
558 SET_INT13DPT(regs, dpte_segment, ebda_seg);
559 SET_INT13DPT(regs, dpte_offset
560 , offsetof(struct extended_bios_data_area_s, dpte));
563 u8 ataid = GET_GLOBAL(drive_g->cntl_id);
564 u8 channel = ataid / 2;
565 u8 slave = ataid % 2;
566 u16 iobase1 = GET_GLOBAL(ATA_channels[channel].iobase1);
567 u16 iobase2 = GET_GLOBAL(ATA_channels[channel].iobase2);
568 u8 irq = GET_GLOBAL(ATA_channels[channel].irq);
571 if (type == DTYPE_ATA) {
572 u8 translation = GET_GLOBAL(drive_g->translation);
573 if (translation != TRANSLATION_NONE) {
574 options |= 1<<3; // CHS translation
575 if (translation == TRANSLATION_LBA)
577 if (translation == TRANSLATION_RECHS)
582 options |= 1<<5; // removable device
583 options |= 1<<6; // atapi device
585 options |= 1<<4; // lba translation
586 if (CONFIG_ATA_PIO32)
589 SET_EBDA2(ebda_seg, dpte.iobase1, iobase1);
590 SET_EBDA2(ebda_seg, dpte.iobase2, iobase2 + ATA_CB_DC);
591 SET_EBDA2(ebda_seg, dpte.prefix, ((slave ? ATA_CB_DH_DEV1 : ATA_CB_DH_DEV0)
593 SET_EBDA2(ebda_seg, dpte.unused, 0xcb);
594 SET_EBDA2(ebda_seg, dpte.irq, irq);
595 SET_EBDA2(ebda_seg, dpte.blkcount, 1);
596 SET_EBDA2(ebda_seg, dpte.dma, 0);
597 SET_EBDA2(ebda_seg, dpte.pio, 0);
598 SET_EBDA2(ebda_seg, dpte.options, options);
599 SET_EBDA2(ebda_seg, dpte.reserved, 0);
600 SET_EBDA2(ebda_seg, dpte.revision, 0x11);
602 u8 sum = checksum_far(
603 ebda_seg, (void*)offsetof(struct extended_bios_data_area_s, dpte), 15);
604 SET_EBDA2(ebda_seg, dpte.checksum, -sum);
607 disk_ret(regs, DISK_RET_SUCCESS);
612 SET_INT13DPT(regs, key, 0xbedd);
613 SET_INT13DPT(regs, dpi_length, 36);
614 SET_INT13DPT(regs, reserved1, 0);
615 SET_INT13DPT(regs, reserved2, 0);
617 int bdf = GET_GLOBAL(ATA_channels[channel].pci_bdf);
619 SET_INT13DPT(regs, host_bus[0], 'P');
620 SET_INT13DPT(regs, host_bus[1], 'C');
621 SET_INT13DPT(regs, host_bus[2], 'I');
622 SET_INT13DPT(regs, host_bus[3], 0);
624 u32 path = (pci_bdf_to_bus(bdf) | (pci_bdf_to_dev(bdf) << 8)
625 | (pci_bdf_to_fn(bdf) << 16));
626 SET_INT13DPT(regs, iface_path, path);
629 SET_INT13DPT(regs, host_bus[0], 'I');
630 SET_INT13DPT(regs, host_bus[1], 'S');
631 SET_INT13DPT(regs, host_bus[2], 'A');
632 SET_INT13DPT(regs, host_bus[3], 0);
634 SET_INT13DPT(regs, iface_path, iobase1);
637 SET_INT13DPT(regs, iface_type[0], 'A');
638 SET_INT13DPT(regs, iface_type[1], 'T');
639 SET_INT13DPT(regs, iface_type[2], 'A');
640 SET_INT13DPT(regs, iface_type[3], 0);
641 SET_INT13DPT(regs, iface_type[4], 0);
642 SET_INT13DPT(regs, iface_type[5], 0);
643 SET_INT13DPT(regs, iface_type[6], 0);
644 SET_INT13DPT(regs, iface_type[7], 0);
646 SET_INT13DPT(regs, device_path, slave);
648 SET_INT13DPT(regs, checksum
649 , -checksum_far(regs->ds, (void*)(regs->si+30), 35));
651 disk_ret(regs, DISK_RET_SUCCESS);
654 // IBM/MS extended media change
656 disk_1349(struct bregs *regs, struct drive_s *drive_g)
658 if (regs->dl < EXTSTART_CD) {
659 // Always success for HD
660 disk_ret(regs, DISK_RET_SUCCESS);
664 // always send changed ??
665 regs->ah = DISK_RET_ECHANGED;
669 disk_134e01(struct bregs *regs, struct drive_s *drive_g)
671 disk_ret(regs, DISK_RET_SUCCESS);
675 disk_134e03(struct bregs *regs, struct drive_s *drive_g)
677 disk_ret(regs, DISK_RET_SUCCESS);
681 disk_134e04(struct bregs *regs, struct drive_s *drive_g)
683 disk_ret(regs, DISK_RET_SUCCESS);
687 disk_134e06(struct bregs *regs, struct drive_s *drive_g)
689 disk_ret(regs, DISK_RET_SUCCESS);
693 disk_134eXX(struct bregs *regs, struct drive_s *drive_g)
695 disk_ret(regs, DISK_RET_EPARAM);
698 // IBM/MS set hardware configuration
700 disk_134e(struct bregs *regs, struct drive_s *drive_g)
703 case 0x01: disk_134e01(regs, drive_g); break;
704 case 0x03: disk_134e03(regs, drive_g); break;
705 case 0x04: disk_134e04(regs, drive_g); break;
706 case 0x06: disk_134e06(regs, drive_g); break;
707 default: disk_134eXX(regs, drive_g); break;
712 disk_13XX(struct bregs *regs, struct drive_s *drive_g)
714 disk_ret_unimplemented(regs, DISK_RET_EPARAM);
718 disk_13(struct bregs *regs, struct drive_s *drive_g)
722 // clear completion flag
723 SET_BDA(disk_interrupt_flag, 0);
726 case 0x00: disk_1300(regs, drive_g); break;
727 case 0x01: disk_1301(regs, drive_g); break;
728 case 0x02: disk_1302(regs, drive_g); break;
729 case 0x03: disk_1303(regs, drive_g); break;
730 case 0x04: disk_1304(regs, drive_g); break;
731 case 0x05: disk_1305(regs, drive_g); break;
732 case 0x08: disk_1308(regs, drive_g); break;
733 case 0x09: disk_1309(regs, drive_g); break;
734 case 0x0c: disk_130c(regs, drive_g); break;
735 case 0x0d: disk_130d(regs, drive_g); break;
736 case 0x10: disk_1310(regs, drive_g); break;
737 case 0x11: disk_1311(regs, drive_g); break;
738 case 0x14: disk_1314(regs, drive_g); break;
739 case 0x15: disk_1315(regs, drive_g); break;
740 case 0x16: disk_1316(regs, drive_g); break;
741 case 0x41: disk_1341(regs, drive_g); break;
742 case 0x42: disk_1342(regs, drive_g); break;
743 case 0x43: disk_1343(regs, drive_g); break;
744 case 0x44: disk_1344(regs, drive_g); break;
745 case 0x45: disk_1345(regs, drive_g); break;
746 case 0x46: disk_1346(regs, drive_g); break;
747 case 0x47: disk_1347(regs, drive_g); break;
748 case 0x48: disk_1348(regs, drive_g); break;
749 case 0x49: disk_1349(regs, drive_g); break;
750 case 0x4e: disk_134e(regs, drive_g); break;
751 default: disk_13XX(regs, drive_g); break;
756 floppy_13(struct bregs *regs, struct drive_s *drive_g)
758 // Only limited commands are supported on floppies.
769 disk_13(regs, drive_g);
771 default: disk_13XX(regs, drive_g); break;
776 /****************************************************************
778 ****************************************************************/
781 handle_legacy_disk(struct bregs *regs, u8 extdrive)
783 if (! CONFIG_DRIVES) {
784 // XXX - support handle_1301 anyway?
785 disk_ret(regs, DISK_RET_EPARAM);
789 if (extdrive < EXTSTART_HD) {
790 struct drive_s *drive_g = getDrive(EXTTYPE_FLOPPY, extdrive);
793 floppy_13(regs, drive_g);
797 struct drive_s *drive_g;
798 if (extdrive >= EXTSTART_CD)
799 drive_g = getDrive(EXTTYPE_CD, extdrive - EXTSTART_CD);
801 drive_g = getDrive(EXTTYPE_HD, extdrive - EXTSTART_HD);
804 disk_13(regs, drive_g);
808 // XXX - support 1301/1308/1315 anyway?
809 disk_ret(regs, DISK_RET_EPARAM);
813 handle_40(struct bregs *regs)
815 debug_enter(regs, DEBUG_HDL_40);
816 handle_legacy_disk(regs, regs->dl);
819 // INT 13h Fixed Disk Services Entry Point
821 handle_13(struct bregs *regs)
823 debug_enter(regs, DEBUG_HDL_13);
824 u8 extdrive = regs->dl;
826 if (CONFIG_CDROM_EMU) {
827 if (regs->ah == 0x4b) {
831 u16 ebda_seg = get_ebda_seg();
832 if (GET_EBDA2(ebda_seg, cdemu.active)) {
833 u8 emudrive = GET_EBDA2(ebda_seg, cdemu.emulated_extdrive);
834 if (extdrive == emudrive) {
835 // Access to an emulated drive.
836 struct drive_s *cdemu = GET_GLOBAL(cdemu_drive);
837 if (regs->ah > 0x16) {
838 // Only old-style commands supported.
839 disk_13XX(regs, cdemu);
842 disk_13(regs, cdemu);
845 if (extdrive < EXTSTART_CD && ((emudrive ^ extdrive) & 0x80) == 0)
846 // Adjust id to make room for emulated drive.
850 handle_legacy_disk(regs, extdrive);
853 // record completion in BIOS task complete flag
857 debug_isr(DEBUG_ISR_76);
858 SET_BDA(disk_interrupt_flag, 0xff);
862 // Old Fixed Disk Parameter Table (newer tables are in the ebda).
863 struct fdpt_s OldFDPT VAR16FIXED(0xe401);