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 | js SHORT .DiskIsNotHandledByThisBIOS
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46 |
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47 | cbw ; Always 0h (no floppy drive covered above)
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48 | adc ah, al ; Add in first drive number and number of drives
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49 |
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50 | cmp ah, dl ; Check second drive if two, first drive if only one
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51 | jz SHORT .CalcDPTForDriveNumber
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52 | cmp al, dl ; Check first drive in all cases, redundant but OK to repeat
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53 | jnz SHORT .DiskIsNotHandledByThisBIOS
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54 | %else
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55 | cmp dl, ah ; Above last supported?
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56 | jae SHORT .DiskIsNotHandledByThisBIOS
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57 |
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58 | cmp dl, al ; Below first supported?
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59 | jb SHORT .DiskIsNotHandledByThisBIOS
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60 | %endif
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61 | ; fall-through to CalcDPTForDriveNumber
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62 |
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63 | ;--------------------------------------------------------------------
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64 | ; Finds Disk Parameter Table for drive number.
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65 | ; Not intended to be called except by FindDPT_ForDriveNumberInDL
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66 | ;
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67 | ; CalcDPTForDriveNumber
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68 | ; Parameters:
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69 | ; DL: Drive number
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70 | ; DS: RAMVARS segment
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71 | ; DI: Saved copy of AX from entry at FindDPT_ForDriveNumberInDL
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72 | ; Returns:
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73 | ; DS:DI: Ptr to DPT
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74 | ; CF: Clear
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75 | ; Corrupts registers:
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76 | ; Nothing
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77 | ;--------------------------------------------------------------------
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78 | ALIGN JUMP_ALIGN
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79 | .CalcDPTForDriveNumber:
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80 | push dx
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81 |
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82 | %ifdef MODULE_SERIAL_FLOPPY
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83 | mov ax, [RAMVARS.wDrvCntAndFirst]
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84 |
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85 | test dl, dl
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86 | js .harddisk
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87 |
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88 | call RamVars_UnpackFlopCntAndFirstToAL
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89 | add dl, ah ; add in end of hard disk DPT list, floppies start immediately after
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90 |
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91 | ALIGN JUMP_ALIGN
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92 | .harddisk:
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93 | sub dl, al ; subtract off beginning of either hard disk or floppy list (as appropriate)
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94 | %else
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95 | sub dl, [RAMVARS.bFirstDrv] ; subtract off beginning of hard disk list
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96 | %endif
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97 |
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98 | .CalcDPTForNewDrive:
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99 | mov al, LARGEST_DPT_SIZE
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100 |
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101 | mul dl
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102 | add ax, BYTE RAMVARS_size ; Clears CF (will not overflow)
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103 |
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104 | pop dx
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105 |
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106 | xchg di, ax ; Restore AX from entry at FindDPT_ForDriveNumber, put DPT pointer in DI
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107 | ret
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108 |
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109 | ALIGN JUMP_ALIGN
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110 | .DiskIsNotHandledByThisBIOS:
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111 | ;
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112 | ; Drive not found...
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113 | ;
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114 | xor ax, ax ; Clear DPT pointer
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115 | stc ; Is not supported by our BIOS
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116 |
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117 | xchg di, ax ; Restore AX from save at top
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118 | ret
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119 |
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120 |
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121 | ;--------------------------------------------------------------------
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122 | ; FindDPT_ForIdevarsOffsetInDL
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123 | ; Parameters:
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124 | ; DL: Offset to IDEVARS to search for
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125 | ; DS: RAMVARS segment
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126 | ; Returns:
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127 | ; DS:DI: Ptr to first DPT with same IDEVARS as in DL
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128 | ; CF: Clear if wanted DPT found
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129 | ; Set if DPT not found, or no DPTs present
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130 | ; Corrupts registers:
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131 | ; SI
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132 | ;--------------------------------------------------------------------
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133 | FindDPT_ForIdevarsOffsetInDL:
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134 | mov si, IterateFindFirstDPTforIdevars ; iteration routine (see below)
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135 | jmp SHORT FindDPT_IterateAllDPTs ; look for the first drive on this controller, if any
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136 |
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137 | ;--------------------------------------------------------------------
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138 | ; Iteration routine for FindDPT_ForIdevarsOffsetInDL,
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139 | ; for use with IterateAllDPTs
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140 | ;
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141 | ; Returns when DPT is found on the controller with Idevars offset in DL
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142 | ;
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143 | ; IterateFindFirstDPTforIdevars
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144 | ; DL: Offset to IDEVARS to search from DPTs
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145 | ; DS:DI: Ptr to DPT to examine
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146 | ; Returns:
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147 | ; CF: Clear if wanted DPT found
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148 | ; Set if wrong DPT
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149 | ;--------------------------------------------------------------------
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150 | IterateFindFirstDPTforIdevars:
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151 | cmp dl, [di+DPT.bIdevarsOffset] ; Clears CF if matched
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152 | je .done
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153 | stc ; Set CF for not found
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154 | .done:
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155 | ret
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156 |
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157 |
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158 | ;--------------------------------------------------------------------
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159 | ; Finds pointer to first unused Disk Parameter Table.
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160 | ; Should only be used before DetectDrives is complete (not valid after this time).
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161 | ;
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162 | ; FindDPT_ForNewDriveToDSDI
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163 | ; Parameters:
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164 | ; DS: RAMVARS segment
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165 | ; Returns:
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166 | ; DS:DI: Ptr to first unused DPT
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167 | ; Corrupts registers:
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168 | ; AX
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169 | ;--------------------------------------------------------------------
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170 | ALIGN JUMP_ALIGN
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171 | FindDPT_ForNewDriveToDSDI:
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172 | push dx
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173 |
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174 | %ifdef MODULE_SERIAL_FLOPPY
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175 | mov dx, [RAMVARS.wDrvCntAndFlopCnt]
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176 | add dl, dh
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177 | %else
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178 | mov dl, [RAMVARS.bDrvCnt]
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179 | %endif
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180 |
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181 | jmp short FindDPT_ForDriveNumberInDL.CalcDPTForNewDrive
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182 |
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183 | ;--------------------------------------------------------------------
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184 | ; IterateToDptWithFlagsHighInBL
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185 | ; Parameters:
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186 | ; DS:DI: Ptr to DPT to examine
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187 | ; BL: Bit(s) to test in DPT.bFlagsHigh
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188 | ; Returns:
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189 | ; CF: Clear if wanted DPT found
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190 | ; Set if wrong DPT
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191 | ; Corrupts registers:
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192 | ; Nothing
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193 | ;--------------------------------------------------------------------
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194 | ALIGN JUMP_ALIGN
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195 | IterateToDptWithFlagsHighInBL:
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196 | test [di+DPT.bFlagsHigh], bl ; Clears CF
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197 | jnz SHORT .ReturnRightDPT
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198 | stc
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199 | .ReturnRightDPT:
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200 | ret
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201 |
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202 | ;--------------------------------------------------------------------
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203 | ; FindDPT_ToDSDIforSerialDevice
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204 | ; Parameters:
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205 | ; DS: RAMVARS segment
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206 | ; Returns:
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207 | ; DS:DI: Ptr to DPT
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208 | ; CF: Set if wanted DPT found
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209 | ; Cleared if DPT not found
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210 | ; Corrupts registers:
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211 | ; SI
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212 | ;--------------------------------------------------------------------
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213 | %ifdef MODULE_SERIAL
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214 | ALIGN JUMP_ALIGN
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215 | FindDPT_ToDSDIforSerialDevice:
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216 | mov bl, FLGH_DPT_SERIAL_DEVICE
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217 | ; fall-through
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218 | %endif
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219 |
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220 | ;--------------------------------------------------------------------
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221 | ; FindDPT_ToDSDIforFlagsHigh
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222 | ; Parameters:
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223 | ; DS: RAMVARS segment
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224 | ; BL: Bit(s) to test in DPT.bFlagsHigh
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225 | ; Returns:
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226 | ; DS:DI: Ptr to DPT
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227 | ; CF: Set if wanted DPT found
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228 | ; Cleared if DPT not found
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229 | ; Corrupts registers:
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230 | ; SI
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231 | ;--------------------------------------------------------------------
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232 | ALIGN JUMP_ALIGN
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233 | FindDPT_ToDSDIforFlagsHighInBL:
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234 | mov si, IterateToDptWithFlagsHighInBL
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235 | ; Fall to IterateAllDPTs
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236 |
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237 | ;--------------------------------------------------------------------
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238 | ; Iterates all Disk Parameter Tables.
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239 | ;
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240 | ; FindDPT_IterateAllDPTs
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241 | ; Parameters:
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242 | ; AX,BX,DX: Parameters to callback function
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243 | ; CS:SI: Ptr to callback function
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244 | ; Callback routine should return CF=clear if found
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245 | ; DS: RAMVARS segment
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246 | ; Returns:
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247 | ; DS:DI: Ptr to wanted DPT (if found)
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248 | ; If not found, points to first empty DPT
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249 | ; CF: Clear if wanted DPT found
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250 | ; Set if DPT not found, or no DPTs present
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251 | ; Corrupts registers:
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252 | ; Nothing unless corrupted by callback function
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253 | ;--------------------------------------------------------------------
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254 | ALIGN JUMP_ALIGN
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255 | FindDPT_IterateAllDPTs:
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256 | push cx
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257 |
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258 | mov di, RAMVARS_size ; Point DS:DI to first DPT
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259 | eMOVZX cx, [RAMVARS.bDrvCnt]
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260 | jcxz .NotFound ; Return if no drives
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261 |
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262 | ALIGN JUMP_ALIGN
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263 | .LoopWhileDPTsLeft:
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264 | call si ; Is wanted DPT?
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265 | jnc SHORT .Found ; If so, return
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266 | add di, BYTE LARGEST_DPT_SIZE ; Point to next DPT
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267 | loop .LoopWhileDPTsLeft
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268 |
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269 | ALIGN JUMP_ALIGN
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270 | .NotFound:
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271 | stc
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272 |
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273 | ALIGN JUMP_ALIGN
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274 | .Found:
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275 | pop cx
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276 | ret
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277 |
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