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additional comments about LBA detection

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This commit is contained in:
Kenneth J Davis 2023-12-20 00:35:01 -05:00
parent cab32344bb
commit de96d00402
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GPG Key ID: 59D5F216C38F11FD
1 changed files with 16 additions and 9 deletions
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25
kernel/initdisk.c
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@ -567,7 +567,7 @@ void DosDefinePartition(struct DriveParamS *driveParam,
/* Turn off LBA if not forced and the partition is within 1023 cyls and of the right type */ /* Turn off LBA if not forced and the partition is within 1023 cyls and of the right type */
/* the FileSystem type was internally converted to LBA_xxxx if a non-LBA partition /* the FileSystem type was internally converted to LBA_xxxx if a non-LBA partition
above cylinder 1023 was found */ above cylinder 1023 was found */
if (!InitKernelConfig.ForceLBA && !ExtLBAForce && !IsLBAPartition(pEntry->FileSystem)) if (!(InitKernelConfig.ForceLBA || IsLBAPartition(pEntry->FileSystem) || ExtLBAForce))
pddt->ddt_descflags &= ~DF_LBA; pddt->ddt_descflags &= ~DF_LBA;
pddt->ddt_ncyl = driveParam->chs.Cylinder; pddt->ddt_ncyl = driveParam->chs.Cylinder;
@ -642,24 +642,27 @@ STATIC int LBA_Get_Drive_Parameters(int drive, struct DriveParamS *driveParam, i
memset(driveParam, 0, sizeof *driveParam); memset(driveParam, 0, sizeof *driveParam);
drive |= 0x80; drive |= 0x80;
/* for tests - disable LBA support, /* use CHS if LBA support is not enabled by kernel configuration */
even if exists */
if (!InitKernelConfig.GlobalEnableLBAsupport) if (!InitKernelConfig.GlobalEnableLBAsupport)
{ {
if (firstPass && (InitKernelConfig.Verbose >= 1)) printf("LBA support disabled.\n");
goto StandardBios; goto StandardBios;
} }
/* check for LBA support */ /* check for LBA support */
regs.b.x = 0x55aa; regs.b.x = 0x55aa;
regs.a.b.h = 0x41; regs.a.b.h = 0x41;
regs.d.b.l = drive; regs.d.b.l = drive;
regs.flags = FLG_CARRY; /* ensure carry is set to force error if unsupported */
init_call_intr(0x13, &regs); init_call_intr(0x13, &regs);
if ((regs.flags & 0x01) || regs.b.x != 0xaa55 || (regs.c.x & 0x01) == 0) if ((regs.flags & FLG_CARRY) || regs.b.x != 0xaa55 || !(regs.c.x & 0x01))
{ {
/* error conditions: /* error conditions:
carry set or BX != 0xaa55 => no EDD spec compatible BIOS carry set or BX != 0xaa55 => no EDD spec compatible BIOS (LBA extensions not supported)
CX bit 1 clear => fixed disc access subset not supported */ CX bit 1 is set if BIOS supports fixed disk subset (Disk Address Packet [DAP] subset),
or clear if fixed disk access subset not supported by LBA extensions
*/
goto StandardBios; goto StandardBios;
} }
@ -678,7 +681,7 @@ STATIC int LBA_Get_Drive_Parameters(int drive, struct DriveParamS *driveParam, i
regs.d.b.l = drive; regs.d.b.l = drive;
init_call_intr(0x13, &regs); init_call_intr(0x13, &regs);
if (regs.flags & 0x01) if (regs.flags & FLG_CARRY)
{ {
/* carry flag set indicates failed LBA disk parameter query */ /* carry flag set indicates failed LBA disk parameter query */
goto StandardBios; goto StandardBios;
@ -916,6 +919,7 @@ BOOL ScanForPrimaryPartitions(struct DriveParamS * driveParam, int scan_type,
if (chs.Cylinder > 1023 || end.Cylinder > 1023) if (chs.Cylinder > 1023 || end.Cylinder > 1023)
{ {
/* if partition exceeds bounds of CHS addressing but LBA is not supported then skip partition */
if (!(driveParam->descflags & DF_LBA)) if (!(driveParam->descflags & DF_LBA))
{ {
printf printf
@ -929,8 +933,11 @@ BOOL ScanForPrimaryPartitions(struct DriveParamS * driveParam, int scan_type,
continue; continue;
} }
if (!InitKernelConfig.ForceLBA && !ExtLBAForce /* if partition exceeds bounds of CHS addressing and we can use LBA
&& !IsLBAPartition(pEntry->FileSystem)) but partition type indicates to use CHS then print warning
and force internal filesystem indicator to enable LBA
*/
if (!(InitKernelConfig.ForceLBA || IsLBAPartition(pEntry->FileSystem) || ExtLBAForce))
{ {
printf printf
("WARNING: Partition ID does not suggest LBA - part %s FS %02x.\n" ("WARNING: Partition ID does not suggest LBA - part %s FS %02x.\n"