| 1 | ; Project name : XTIDE Universal BIOS
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| 2 | ; Description : Functions for finding Disk Parameter Table.
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| 3 |
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| 4 | ; Section containing code
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| 5 | SECTION .text
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| 6 |
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| 7 | ;--------------------------------------------------------------------
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| 8 | ; Checks if drive is handled by this BIOS, and return DPT pointer.
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| 9 | ;
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| 10 | ; FindDPT_ForDriveNumberInDL
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| 11 | ; Parameters:
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| 12 | ; DL: Drive number
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| 13 | ; DS: RAMVARS segment
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| 14 | ; Returns:
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| 15 | ; CF: Cleared if drive is handled by this BIOS
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| 16 | ; Set if drive belongs to some other BIOS
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| 17 | ; DI: DPT Pointer if drive is handled by this BIOS
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| 18 | ; Zero if drive belongs to some other BIOS
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| 19 | ; Corrupts registers:
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| 20 | ; Nothing
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| 21 | ;--------------------------------------------------------------------
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| 22 | ALIGN JUMP_ALIGN
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| 23 | FindDPT_ForDriveNumberInDL:
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| 24 | xchg di, ax ; Save the contents of AX in DI
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| 25 |
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| 26 | ;
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| 27 | ; Check Our Hard Disks
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| 28 | ;
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| 29 | mov ax, [RAMVARS.wDrvCntAndFirst] ; Drive count to AH, First number to AL
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| 30 | add ah, al ; One past last drive to AH
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| 31 |
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| 32 | %ifdef MODULE_SERIAL_FLOPPY
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| 33 | cmp dl, ah ; Above last supported?
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| 34 | jae SHORT .HardDiskNotHandledByThisBIOS
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| 35 |
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| 36 | cmp dl, al ; Below first supported?
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| 37 | jae SHORT .CalcDPTForDriveNumber
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| 38 |
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| 39 | ALIGN JUMP_ALIGN
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| 40 | .HardDiskNotHandledByThisBIOS:
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| 41 | ;
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| 42 | ; Check Our Floppy Disks
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| 43 | ;
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| 44 | call RamVars_UnpackFlopCntAndFirstToAL
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| 45 | cbw ; normally 0h, could be ffh if no drives present
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| 46 | adc ah, al ; if no drives present, still ffh (ffh + ffh + 1 = ffh)
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| 47 | js SHORT .DiskIsNotHandledByThisBIOS
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| 48 | cmp ah, dl ; Check second drive if two, first drive if only one
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| 49 | jz SHORT .CalcDPTForDriveNumber
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| 50 | cmp al, dl ; Check first drive in all cases, redundant but OK to repeat
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| 51 | jnz SHORT .DiskIsNotHandledByThisBIOS
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| 52 | %else
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| 53 | cmp dl, ah ; Above last supported?
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| 54 | jae SHORT .DiskIsNotHandledByThisBIOS
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| 55 |
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| 56 | cmp dl, al ; Below first supported?
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| 57 | jb SHORT .DiskIsNotHandledByThisBIOS
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| 58 | %endif
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| 59 | ; fall-through to CalcDPTForDriveNumber
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| 60 |
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| 61 | ;--------------------------------------------------------------------
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| 62 | ; Finds Disk Parameter Table for drive number.
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| 63 | ; Note intended to be called except by FindDPT_ForDriveNumber
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| 64 | ;
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| 65 | ; CalcDPTForDriveNumber
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| 66 | ; Parameters:
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| 67 | ; DL: Drive number
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| 68 | ; DS: RAMVARS segment
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| 69 | ; DI: Saved copy of AX from entry at FindDPT_ForDriveNumber
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| 70 | ; Returns:
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| 71 | ; DS:DI: Ptr to DPT
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| 72 | ; CF: Clear
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| 73 | ; Corrupts registers:
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| 74 | ; Nothing
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| 75 | ;--------------------------------------------------------------------
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| 76 | ALIGN JUMP_ALIGN
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| 77 | .CalcDPTForDriveNumber:
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| 78 | push dx
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| 79 |
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| 80 | %ifdef MODULE_SERIAL_FLOPPY
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| 81 | mov ax, [RAMVARS.wDrvCntAndFirst]
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| 82 |
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| 83 | test dl, dl
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| 84 | js .harddisk
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| 85 |
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| 86 | call RamVars_UnpackFlopCntAndFirstToAL
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| 87 | add dl, ah ; add in end of hard disk DPT list, floppies start immediately after
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| 88 |
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| 89 | ALIGN JUMP_ALIGN
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| 90 | .harddisk:
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| 91 | sub dl, al ; subtract off beginning of either hard disk or floppy list (as appropriate)
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| 92 | %else
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| 93 | sub dl, [RAMVARS.bFirstDrv] ; subtract off beginning of hard disk list
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| 94 | %endif
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| 95 |
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| 96 | .CalcDPTForNewDrive:
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| 97 | mov al, LARGEST_DPT_SIZE
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| 98 |
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| 99 | mul dl
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| 100 | add ax, BYTE RAMVARS_size ; Clears CF (will not oveflow)
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| 101 |
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| 102 | pop dx
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| 103 |
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| 104 | xchg di, ax ; Restore AX from entry at FindDPT_ForDriveNumber, put DPT pointer in DI
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| 105 | ret
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| 106 |
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| 107 | ALIGN JUMP_ALIGN
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| 108 | .DiskIsNotHandledByThisBIOS:
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| 109 | ;
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| 110 | ; Drive not found...
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| 111 | ;
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| 112 | xor ax, ax ; Clear DPT pointer
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| 113 | stc ; Is not supported by our BIOS
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| 114 |
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| 115 | xchg di, ax ; Restore AX from save at top
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| 116 | ret
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| 117 |
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| 118 | ;--------------------------------------------------------------------
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| 119 | ; Finds pointer to first unused Disk Parameter Table.
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| 120 | ; Should only be used before DetectDrives is complete (not valid after this time).
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| 121 | ;
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| 122 | ; FindDPT_ForNewDriveToDSDI
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| 123 | ; Parameters:
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| 124 | ; DS: RAMVARS segment
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| 125 | ; Returns:
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| 126 | ; DS:DI: Ptr to first unused DPT
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| 127 | ; Corrupts registers:
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| 128 | ; AX
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| 129 | ;--------------------------------------------------------------------
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| 130 | ALIGN JUMP_ALIGN
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| 131 | FindDPT_ForNewDriveToDSDI:
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| 132 | push dx
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| 133 |
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| 134 | %ifdef MODULE_SERIAL_FLOPPY
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| 135 | mov dx, [RAMVARS.wDrvCntAndFlopCnt]
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| 136 | add dl, dh
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| 137 | %else
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| 138 | mov dl, [RAMVARS.bDrvCnt]
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| 139 | %endif
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| 140 |
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| 141 | jmp short FindDPT_ForDriveNumberInDL.CalcDPTForNewDrive
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| 142 |
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| 143 | ;--------------------------------------------------------------------
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| 144 | ; IterateToDptWithFlagsHighInBL
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| 145 | ; Parameters:
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| 146 | ; DS:DI: Ptr to DPT to examine
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| 147 | ; BL: Bit(s) to test in DPT.bFlagsHigh
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| 148 | ; Returns:
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| 149 | ; CF: Clear if wanted DPT found
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| 150 | ; Set if wrong DPT
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| 151 | ; Corrupts registers:
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| 152 | ; Nothing
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| 153 | ;--------------------------------------------------------------------
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| 154 | ALIGN JUMP_ALIGN
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| 155 | IterateToDptWithFlagsHighInBL:
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| 156 | test BYTE [di+DPT.bFlagsHigh], bl ; Clears CF
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| 157 | jnz SHORT .ReturnRightDPT
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| 158 | stc
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| 159 | .ReturnRightDPT:
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| 160 | ret
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| 161 |
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| 162 | ;--------------------------------------------------------------------
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| 163 | ; FindDPT_ToDSDIforSerialDevice
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| 164 | ; Parameters:
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| 165 | ; DS: RAMVARS segment
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| 166 | ; Returns:
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| 167 | ; DS:DI: Ptr to DPT
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| 168 | ; CF: Set if wanted DPT found
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| 169 | ; Cleared if DPT not found
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| 170 | ; Corrupts registers:
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| 171 | ; SI
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| 172 | ;--------------------------------------------------------------------
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| 173 | ALIGN JUMP_ALIGN
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| 174 | FindDPT_ToDSDIforSerialDevice:
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| 175 | mov bl, FLGH_DPT_SERIAL_DEVICE
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| 176 | ; fall-through
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| 177 |
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| 178 | ;--------------------------------------------------------------------
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| 179 | ; FindDPT_ToDSDIforFlagsHigh
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| 180 | ; Parameters:
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| 181 | ; DS: RAMVARS segment
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| 182 | ; BL: Bit(s) to test in DPT.bFlagsHigh
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| 183 | ; Returns:
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| 184 | ; DS:DI: Ptr to DPT
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| 185 | ; CF: Set if wanted DPT found
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| 186 | ; Cleared if DPT not found
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| 187 | ; Corrupts registers:
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| 188 | ; SI
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| 189 | ;--------------------------------------------------------------------
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| 190 | ALIGN JUMP_ALIGN
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| 191 | FindDPT_ToDSDIforFlagsHighInBL:
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| 192 | mov si, IterateToDptWithFlagsHighInBL
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| 193 | ; Fall to IterateAllDPTs
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| 194 |
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| 195 | ;--------------------------------------------------------------------
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| 196 | ; Iterates all Disk Parameter Tables.
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| 197 | ;
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| 198 | ; IterateAllDPTs
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| 199 | ; Parameters:
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| 200 | ; AX,BX,DX: Parameters to callback function
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| 201 | ; CS:SI: Ptr to callback function
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| 202 | ; Callback routine should return CF=clear if found
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| 203 | ; DS: RAMVARS segment
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| 204 | ; Returns:
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| 205 | ; DS:DI: Ptr to wanted DPT (if found)
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| 206 | ; If not found, points to first empty DPT
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| 207 | ; CF: Clear if wanted DPT found
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| 208 | ; Set if DPT not found, or no DPTs present
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| 209 | ; Corrupts registers:
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| 210 | ; Nothing unless corrupted by callback function
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| 211 | ;--------------------------------------------------------------------
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| 212 | ALIGN JUMP_ALIGN
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| 213 | IterateAllDPTs:
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| 214 | push cx
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| 215 |
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| 216 | mov di, RAMVARS_size ; Point DS:DI to first DPT
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| 217 |
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| 218 | mov cl, [RAMVARS.bDrvCnt]
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| 219 | xor ch, ch ; Clears CF
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| 220 |
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| 221 | jcxz .NotFound ; Return if no drives
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| 222 |
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| 223 | ALIGN JUMP_ALIGN
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| 224 | .LoopWhileDPTsLeft:
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| 225 | call si ; Is wanted DPT?
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| 226 | jnc SHORT .Found ; If so, return
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| 227 | add di, BYTE LARGEST_DPT_SIZE ; Point to next DPT
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| 228 | loop .LoopWhileDPTsLeft
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| 229 |
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| 230 | ALIGN JUMP_ALIGN
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| 231 | .NotFound:
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| 232 | stc
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| 233 |
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| 234 | ALIGN JUMP_ALIGN
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| 235 | .Found:
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| 236 | pop cx
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| 237 | ret
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| 238 |
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