1 | ; Project name : XTIDE Universal BIOS |
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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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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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36 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_ENABLE_IRQ |
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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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42 | |
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43 | ;-------------------------------------------------------------------- |
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44 | ; AccessDPT_GetLCHS |
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45 | ; Parameters: |
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46 | ; DS:DI: Ptr to Disk Parameter Table |
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47 | ; Returns: |
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48 | ; AX: Number of L-CHS sectors per track |
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49 | ; BX: Number of L-CHS cylinders |
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50 | ; DX: Number of L-CHS heads |
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51 | ; Corrupts registers: |
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52 | ; CX |
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53 | ;-------------------------------------------------------------------- |
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54 | AccessDPT_GetLCHS: |
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55 | ; Load CHS from DPT |
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56 | eMOVZX ax, BYTE [di+DPT.bSectors] |
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57 | mov bx, [di+DPT.dwCylinders] |
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58 | cwd |
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59 | mov dl, [di+DPT.bHeads] |
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60 | |
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61 | ; Only need to limit sectors for LBA assist |
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62 | test BYTE [di+DPT.bFlagsLow], FLG_DRVNHEAD_LBA |
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63 | jz SHORT AccessDPT_ShiftPCHinBXDXtoLCH |
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64 | |
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65 | cmp WORD [di+DPT.dwCylinders+2], BYTE 0 |
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66 | jnz SHORT .Return_MAX_LCHS_CYLINDERS |
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67 | |
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68 | ; Limit cylinders to 1024 |
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69 | cmp bx, MAX_LCHS_CYLINDERS |
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70 | jb SHORT .Return |
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71 | ALIGN JUMP_ALIGN |
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72 | .Return_MAX_LCHS_CYLINDERS: |
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73 | mov bx, MAX_LCHS_CYLINDERS |
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74 | ALIGN JUMP_ALIGN, ret |
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75 | .Return: |
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76 | ret |
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77 | |
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78 | |
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79 | ;-------------------------------------------------------------------- |
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80 | ; AccessDPT_ShiftPCHinBXDXtoLCH |
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81 | ; Parameters: |
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82 | ; BX: P-CHS cylinders (1...16383) |
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83 | ; DX: P-CHS heads (1...16) |
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84 | ; Returns: |
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85 | ; BX: Number of L-CHS cylinders (1...1024) |
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86 | ; DX: Number of L-CHS heads (1...255) |
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87 | ; CX: Number of bits shifted |
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88 | ; Corrupts registers: |
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89 | ; Nothing |
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90 | ;-------------------------------------------------------------------- |
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91 | AccessDPT_ShiftPCHinBXDXtoLCH: |
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92 | xor cx, cx |
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93 | .ShiftLoop: |
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94 | cmp bx, MAX_LCHS_CYLINDERS ; Need to shift? |
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95 | jbe SHORT .LimitHeadsTo255 ; If not, return |
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96 | inc cx ; Increment shift count |
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97 | shr bx, 1 ; Halve cylinders |
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98 | shl dx, 1 ; Double heads |
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99 | jmp SHORT .ShiftLoop |
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100 | .LimitHeadsTo255: ; DOS does not support drives with 256 heads |
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101 | sub dl, dh ; DH set only when 256 logical heads |
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102 | xor dh, dh |
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103 | ret |
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104 | |
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105 | |
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106 | ;-------------------------------------------------------------------- |
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107 | ; Returns pointer to DRVPARAMS for master or slave drive. |
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108 | ; |
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109 | ; AccessDPT_GetPointerToDRVPARAMStoCSBX |
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110 | ; Parameters: |
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111 | ; DS:DI: Ptr to Disk Parameter Table |
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112 | ; Returns: |
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113 | ; CS:BX: Ptr to DRVPARAMS |
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114 | ; Corrupts registers: |
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115 | ; Nothing |
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116 | ;-------------------------------------------------------------------- |
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117 | ALIGN JUMP_ALIGN |
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118 | AccessDPT_GetPointerToDRVPARAMStoCSBX: |
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119 | eMOVZX bx, [di+DPT.bIdevarsOffset] ; CS:BX points to IDEVARS |
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120 | add bx, BYTE IDEVARS.drvParamsMaster ; CS:BX points to Master Drive DRVPARAMS |
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121 | test BYTE [di+DPT.bFlagsLow], FLGL_DPT_SLAVE |
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122 | jz SHORT .ReturnPointerToDRVPARAMS |
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123 | add bx, BYTE DRVPARAMS_size ; CS:BX points to Slave Drive DRVPARAMS |
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124 | .ReturnPointerToDRVPARAMS: |
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125 | ret |
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126 | |
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127 | ;-------------------------------------------------------------------- |
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128 | ; AccessDPT_GetUnshiftedAddressModeToALZF |
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129 | ; Parameters: |
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130 | ; DS:DI: Ptr to Disk Parameter Table |
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131 | ; Returns: |
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132 | ; AL: Addressing Mode (L-CHS, P-CHS, LBA28, LBA48) |
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133 | ; unshifted (still shifted where it is in bFlagsLow) |
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134 | ; ZF: Set based on value in AL |
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135 | ; Corrupts registers: |
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136 | ; AL |
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137 | ;-------------------------------------------------------------------- |
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138 | ; |
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139 | ; Converted to a macro since only called in two places, and the call/ret overhead |
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140 | ; is not worth it for these two instructions (4 bytes total) |
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141 | ; |
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142 | %macro AccessDPT_GetUnshiftedAddressModeToALZF 0 |
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143 | mov al, [di+DPT.bFlagsLow] |
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144 | and al, MASKL_DPT_ADDRESSING_MODE |
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145 | %endmacro |
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146 | |
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147 | |
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