source: xtideuniversalbios/trunk/XTIDE_Universal_BIOS/Src/VariablesAndDPTs/RamVars.asm@ 253

Last change on this file since 253 was 241, checked in by gregli@…, 13 years ago

Space optimizations in the Boot Menu and BootInfo routines, taking advantage of nested %s. Optimization in the init of RamVars to avoid writing the signature twice. Preparing for addition of serial floppy support, starting to break the assumption that our drives are always 80h or higher.
File size: 6.2 KB
Line 
1; Project name : XTIDE Universal BIOS
2; Description : Functions for accessings RAMVARS.
3
4; Section containing code
5SECTION .text
6
7;--------------------------------------------------------------------
8; Initializes RAMVARS.
9; Drive detection can be started after this function returns.
10;
11; RamVars_Initialize
12; Parameters:
13; Nothing
14; Returns:
15; DS: RAMVARS segment
16; Corrupts registers:
17; AX, CX, DI
18;--------------------------------------------------------------------
19RamVars_Initialize:
20 push es
21 ; Fall to .StealMemoryForRAMVARS
22
23;--------------------------------------------------------------------
24; .StealMemoryForRAMVARS
25; Parameters:
26; Nothing
27; Returns:
28; DS: RAMVARS segment
29; Corrupts registers:
30; AX
31;--------------------------------------------------------------------
32.StealMemoryForRAMVARS:
33 mov ax, LITE_MODE_RAMVARS_SEGMENT
34 test BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
35 jz SHORT .InitializeRamvars ; No need to steal RAM
36
37 LOAD_BDA_SEGMENT_TO ds, ax, ! ; Zero AX
38 mov al, [cs:ROMVARS.bStealSize]
39 sub [BDA.wBaseMem], ax
40 mov ax, [BDA.wBaseMem]
41 eSHL_IM ax, 6 ; Segment to first stolen kB (*=40h)
42 ; Fall to .InitializeRamvars
43
44;--------------------------------------------------------------------
45; .InitializeRamvars
46; Parameters:
47; AX: RAMVARS segment
48; Returns:
49; DS: RAMVARS segment
50; Corrupts registers:
51; AX, CX, DI, ES
52;--------------------------------------------------------------------
53.InitializeRamvars:
54 mov ds, ax
55 mov es, ax
56 mov cx, RAMVARS_size
57 xor di, di
58 call Memory_ZeroESDIwithSizeInCX
59 mov WORD [RAMVARS.wSignature], RAMVARS_SIGNATURE
60 ; Fall to .InitializeDriveTranslationAndReturn
61
62;--------------------------------------------------------------------
63; .InitializeDriveTranslationAndReturn
64; Parameters:
65; DS: RAMVARS segment
66; Returns:
67; Nothing
68; Corrupts registers:
69; AX
70;--------------------------------------------------------------------
71.InitializeDriveTranslationAndReturn:
72 pop es
73 jmp DriveXlate_Reset
74
75
76;--------------------------------------------------------------------
77; Returns segment to RAMVARS.
78; RAMVARS might be located at the top of interrupt vectors (0030:0000h)
79; or at the top of system base RAM.
80;
81; RamVars_GetSegmentToDS
82; Parameters:
83; Nothing
84; Returns:
85; DS: RAMVARS segment
86; Corrupts registers:
87; DI
88;--------------------------------------------------------------------
89ALIGN JUMP_ALIGN
90RamVars_GetSegmentToDS:
91 test BYTE [cs:ROMVARS.wFlags], FLG_ROMVARS_FULLMODE
92 jnz SHORT .GetStolenSegmentToDS
93%ifndef USE_186
94 mov di, LITE_MODE_RAMVARS_SEGMENT
95 mov ds, di
96%else
97 push LITE_MODE_RAMVARS_SEGMENT
98 pop ds
99%endif
100 ret
101
102ALIGN JUMP_ALIGN
103.GetStolenSegmentToDS:
104 LOAD_BDA_SEGMENT_TO ds, di
105 mov di, [BDA.wBaseMem] ; Load available base memory size in kB
106 eSHL_IM di, 6 ; Segment to first stolen kB (*=40h)
107ALIGN JUMP_ALIGN
108.LoopStolenKBs:
109 mov ds, di ; EBDA segment to DS
110 add di, BYTE 64 ; DI to next stolen kB
111 cmp WORD [RAMVARS.wSignature], RAMVARS_SIGNATURE
112 jne SHORT .LoopStolenKBs ; Loop until sign found (always found eventually)
113 ret
114
115
116;--------------------------------------------------------------------
117; Checks if INT 13h function is handled by this BIOS.
118;
119; RamVars_IsFunctionHandledByThisBIOS
120; Parameters:
121; AH: INT 13h function number
122; DL: Drive number
123; DS: RAMVARS segment
124; Returns:
125; CF: Set if function is handled by this BIOS
126; Cleared if function belongs to some other BIOS
127; Corrupts registers:
128; Nothing
129;--------------------------------------------------------------------
130ALIGN JUMP_ALIGN
131RamVars_IsFunctionHandledByThisBIOS:
132 test ah, ah ; Reset for all floppy and hard disk drives?
133 jz SHORT .FunctionIsHandledByOurBIOS
134 cmp ah, 08h ; Read Disk Drive Parameters?
135 jne SHORT RamVars_IsDriveHandledByThisBIOS
136 test dl, dl ; We do not handle floppy drives
137 jns SHORT .FunctionIsNotHandledByOurBIOS
138ALIGN JUMP_ALIGN
139.FunctionIsHandledByOurBIOS:
140 stc
141.FunctionIsNotHandledByOurBIOS:
142 ret
143
144;--------------------------------------------------------------------
145; Checks if drive is handled by this BIOS.
146;
147; RamVars_IsDriveHandledByThisBIOS
148; Parameters:
149; DL: Drive number
150; DS: RAMVARS segment
151; Returns:
152; CF: Set if drive is handled by this BIOS
153; Cleared if drive belongs to some other BIOS
154; Corrupts registers:
155; Nothing
156;--------------------------------------------------------------------
157ALIGN JUMP_ALIGN
158RamVars_IsDriveHandledByThisBIOS:
159 push ax
160 mov ax, [RAMVARS.wDrvCntAndFirst] ; Drive count to AL, First number to AH
161 add al, ah ; One past last drive to AL
162 cmp dl, al ; Above last supported?
163 jae SHORT .DriveNotHandledByThisBIOS
164 cmp ah, dl ; Below first supported?
165 ja SHORT .DriveNotHandledByThisBIOS
166 stc
167.DriveNotHandledByThisBIOS:
168 pop ax
169 ret
170
171
172;--------------------------------------------------------------------
173; RamVars_GetHardDiskCountFromBDAtoCX
174; Parameters:
175; DS: RAMVARS segment
176; Returns:
177; CX: Total hard disk count
178; Corrupts registers:
179; Nothing
180;--------------------------------------------------------------------
181ALIGN JUMP_ALIGN
182RamVars_GetHardDiskCountFromBDAtoCX:
183 push es
184 push dx
185
186 LOAD_BDA_SEGMENT_TO es, cx, ! ; Zero CX
187 call RamVars_GetCountOfKnownDrivesToDL
188 mov cl, [es:BDA.bHDCount]
189 MAX_U cl, dl
190
191 pop dx
192 pop es
193 ret
194
195;--------------------------------------------------------------------
196; RamVars_GetCountOfKnownDrivesToDL
197; Parameters:
198; DS: RAMVARS segment
199; Returns:
200; DL: Total hard disk count
201; Corrupts registers:
202; Nothing
203;--------------------------------------------------------------------
204ALIGN JUMP_ALIGN
205RamVars_GetCountOfKnownDrivesToDL:
206 mov dl, [RAMVARS.bFirstDrv] ; Number for our first drive
207 add dl, [RAMVARS.bDrvCnt] ; Our drives
208 and dl, 7Fh ; Clear HD bit for drive count
209 ret
210
211
212;--------------------------------------------------------------------
213; RamVars_GetIdeControllerCountToCX
214; Parameters:
215; Nothing
216; Returns:
217; CX: Number of IDE controllers to handle
218; Corrupts registers:
219; Nothing
220;--------------------------------------------------------------------
221RamVars_GetIdeControllerCountToCX:
222 eMOVZX cx, BYTE [cs:ROMVARS.bIdeCnt]
223 ret
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