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Marcus spotted an error in the cylinder calculation in get_drive_parameters() - didn't

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have an effect on floppies or CD-ROMs, but would have on real hard drives that require
CHS access.
Changed the cylinder-to-regs conversion in BIOSDrive::ReadAt() (that one was actually
correct) to make it look similar to the conversion in the opposite direction in
get_drive_parameters().


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@14377 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler
2005-10-14 09:25:45 +00:00
parent b093987a7b
commit 7416092b83
1 changed files with 2 additions and 2 deletions
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src/system/boot/platform/bios_ia32/devices.cpp
+2 -2
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@@ -176,7 +176,7 @@ get_drive_parameters(uint8 drive, drive_parameters *parameters)
// fill drive_parameters structure with useful values
parameters->parameters_size = kParametersSizeVersion1;
parameters->flags = 0;
parameters->cylinders = (((regs.ecx << 8) & 0xc000) | ((regs.ecx >> 8) & 0xff)) + 1;
parameters->cylinders = (((regs.ecx & 0xc0) << 2) | ((regs.ecx >> 8) & 0xff)) + 1;
parameters->heads = ((regs.edx >> 8) & 0xff) + 1;
// heads and cylinders start counting from 0
parameters->sectors_per_track = regs.ecx & 0x3f;
@@ -433,7 +433,7 @@ BIOSDrive::ReadAt(void *cookie, off_t pos, void *buffer, size_t bufferSize)
struct bios_regs regs;
regs.eax = BIOS_READ | blocksRead;
regs.edx = fDriveID | (head << 8);
regs.ecx = sector | ((cylinder >> 8) << 6) | ((cylinder & 0xff) << 8);
regs.ecx = sector | ((cylinder >> 2) & 0xc0) | ((cylinder & 0xff) << 8);
regs.es = 0;
regs.ebx = kExtraSegmentScratch;
call_bios(0x13, &regs);