[99] | 1 | ; Project name : XTIDE Universal BIOS |
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[3] | 2 | ; Description : Functions for accessing DPT data. |
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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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[150] | 8 | ; AccessDPT_GetDriveSelectByteToAL |
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| 9 | ; Parameters: |
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| 10 | ; DS:DI: Ptr to Disk Parameter Table |
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| 11 | ; Returns: |
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| 12 | ; AL: Drive Select Byte |
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| 13 | ; Corrupts registers: |
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| 14 | ; Nothing |
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| 15 | ;-------------------------------------------------------------------- |
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| 16 | ALIGN JUMP_ALIGN |
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| 17 | AccessDPT_GetDriveSelectByteToAL: |
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| 18 | mov al, [di+DPT.wFlags] |
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| 19 | and al, FLG_DRVNHEAD_LBA | FLG_DRVNHEAD_DRV |
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| 20 | or al, MASK_DRVNHEAD_SET ; Bits set to 1 for old drives |
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| 21 | ret |
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| 22 | |
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| 23 | |
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| 24 | ;-------------------------------------------------------------------- |
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| 25 | ; AccessDPT_GetDeviceControlByteToAL |
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| 26 | ; Parameters: |
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| 27 | ; DS:DI: Ptr to Disk Parameter Table |
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| 28 | ; Returns: |
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| 29 | ; AL: Device Control Byte |
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| 30 | ; Corrupts registers: |
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| 31 | ; Nothing |
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| 32 | ;-------------------------------------------------------------------- |
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| 33 | ALIGN JUMP_ALIGN |
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| 34 | AccessDPT_GetDeviceControlByteToAL: |
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| 35 | xor al, al |
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[158] | 36 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_ENABLE_IRQ |
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[150] | 37 | jnz SHORT .EnableDeviceIrq |
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| 38 | or al, FLG_DEVCONTROL_nIEN ; Disable IRQ |
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| 39 | .EnableDeviceIrq: |
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| 40 | ret |
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| 41 | |
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[227] | 42 | |
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[150] | 43 | ;-------------------------------------------------------------------- |
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[227] | 44 | ; AccessDPT_GetLCHStoAXBLBH |
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[3] | 45 | ; Parameters: |
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| 46 | ; DS:DI: Ptr to Disk Parameter Table |
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| 47 | ; Returns: |
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[227] | 48 | ; AX: Number of L-CHS cylinders |
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| 49 | ; BL: Number of L-CHS heads |
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| 50 | ; BH: Number of L-CHS sectors per track |
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[3] | 51 | ; Corrupts registers: |
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[227] | 52 | ; CX, DX |
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[3] | 53 | ;-------------------------------------------------------------------- |
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[227] | 54 | AccessDPT_GetLCHStoAXBLBH: |
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| 55 | ; Return LBA-assisted CHS if LBA addressing used |
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[173] | 56 | test BYTE [di+DPT.bFlagsLow], FLG_DRVNHEAD_LBA |
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[227] | 57 | jz SHORT .ConvertPchsToLchs |
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[173] | 58 | |
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[227] | 59 | call AccessDPT_GetLbaSectorCountToBXDXAX |
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[358] | 60 | call LbaAssist_ConvertSectorCountFromBXDXAXtoLbaAssistedCHSinDXAXBLBH |
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| 61 | LIMIT_LBA_CYLINDERS_IN_DXAX_TO_LCHS_CYLINDERS |
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[227] | 62 | ret |
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[173] | 63 | |
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[227] | 64 | .ConvertPchsToLchs: |
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| 65 | mov ax, [di+DPT.wPchsCylinders] |
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| 66 | mov bx, [di+DPT.wPchsHeadsAndSectors] |
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[230] | 67 | ; Fall to AccessDPT_ShiftPCHinAXBLtoLCH |
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[227] | 68 | |
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| 69 | |
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| 70 | ;-------------------------------------------------------------------- |
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| 71 | ; AccessDPT_ShiftPCHinAXBLtoLCH |
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[173] | 72 | ; Parameters: |
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[227] | 73 | ; AX: P-CHS cylinders (1...16383) |
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| 74 | ; BL: P-CHS heads (1...16) |
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[173] | 75 | ; Returns: |
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[227] | 76 | ; AX: Number of L-CHS cylinders (1...1024) |
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| 77 | ; BL: Number of L-CHS heads (1...255) |
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[230] | 78 | ; CX: Number of bits shifted (4 at most) |
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[173] | 79 | ; Corrupts registers: |
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| 80 | ; Nothing |
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| 81 | ;-------------------------------------------------------------------- |
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[227] | 82 | AccessDPT_ShiftPCHinAXBLtoLCH: |
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[173] | 83 | xor cx, cx |
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| 84 | .ShiftLoop: |
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[227] | 85 | cmp ax, MAX_LCHS_CYLINDERS ; Need to shift? |
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[231] | 86 | jbe SHORT .Return ; If not, return |
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[173] | 87 | inc cx ; Increment shift count |
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[227] | 88 | shr ax, 1 ; Halve cylinders |
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| 89 | shl bl, 1 ; Double heads |
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[231] | 90 | jnz SHORT .ShiftLoop ; Falls through only on the last (4th) iteration and only if BL was 16 on entry |
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| 91 | dec bl ; DOS doesn't support drives with 256 heads so we limit heads to 255 |
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| 92 | ; We can save a byte here by using DEC BX if we don't care about BH |
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| 93 | .Return: |
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[173] | 94 | ret |
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| 95 | |
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[227] | 96 | |
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[173] | 97 | ;-------------------------------------------------------------------- |
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[230] | 98 | ; AccessDPT_GetLbaSectorCountToBXDXAX |
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| 99 | ; Parameters: |
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| 100 | ; DS:DI: Ptr to Disk Parameter Table |
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| 101 | ; Returns: |
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| 102 | ; BX:DX:AX: 48-bit sector count |
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| 103 | ; Corrupts registers: |
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| 104 | ; Nothing |
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| 105 | ;-------------------------------------------------------------------- |
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| 106 | AccessDPT_GetLbaSectorCountToBXDXAX: |
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| 107 | mov ax, [di+DPT.twLbaSectors] |
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| 108 | mov dx, [di+DPT.twLbaSectors+2] |
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| 109 | mov bx, [di+DPT.twLbaSectors+4] |
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| 110 | ret |
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| 111 | |
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| 112 | |
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| 113 | ;-------------------------------------------------------------------- |
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[3] | 114 | ; Returns pointer to DRVPARAMS for master or slave drive. |
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| 115 | ; |
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| 116 | ; AccessDPT_GetPointerToDRVPARAMStoCSBX |
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| 117 | ; Parameters: |
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| 118 | ; DS:DI: Ptr to Disk Parameter Table |
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| 119 | ; Returns: |
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| 120 | ; CS:BX: Ptr to DRVPARAMS |
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| 121 | ; Corrupts registers: |
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| 122 | ; Nothing |
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| 123 | ;-------------------------------------------------------------------- |
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| 124 | ALIGN JUMP_ALIGN |
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| 125 | AccessDPT_GetPointerToDRVPARAMStoCSBX: |
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[150] | 126 | eMOVZX bx, [di+DPT.bIdevarsOffset] ; CS:BX points to IDEVARS |
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| 127 | add bx, BYTE IDEVARS.drvParamsMaster ; CS:BX points to Master Drive DRVPARAMS |
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[158] | 128 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_SLAVE |
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[150] | 129 | jz SHORT .ReturnPointerToDRVPARAMS |
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| 130 | add bx, BYTE DRVPARAMS_size ; CS:BX points to Slave Drive DRVPARAMS |
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| 131 | .ReturnPointerToDRVPARAMS: |
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[3] | 132 | ret |
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[200] | 133 | |
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| 134 | ;-------------------------------------------------------------------- |
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| 135 | ; AccessDPT_GetUnshiftedAddressModeToALZF |
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| 136 | ; Parameters: |
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| 137 | ; DS:DI: Ptr to Disk Parameter Table |
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| 138 | ; Returns: |
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[230] | 139 | ; AL: Addressing Mode (L-CHS, P-CHS, LBA28, LBA48) |
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[200] | 140 | ; unshifted (still shifted where it is in bFlagsLow) |
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| 141 | ; ZF: Set based on value in AL |
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| 142 | ; Corrupts registers: |
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| 143 | ; AL |
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| 144 | ;-------------------------------------------------------------------- |
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[230] | 145 | ; |
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| 146 | ; Converted to a macro since only called in two places, and the call/ret overhead |
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[200] | 147 | ; is not worth it for these two instructions (4 bytes total) |
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| 148 | ; |
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| 149 | %macro AccessDPT_GetUnshiftedAddressModeToALZF 0 |
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| 150 | mov al, [di+DPT.bFlagsLow] |
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| 151 | and al, MASKL_DPT_ADDRESSING_MODE |
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| 152 | %endmacro |
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