summaryrefslogtreecommitdiffstats
path: root/qemu/roms/vgabios/vbe.c
blob: 1fab2f9e630847c5a6820905b2959839e96346b0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
// ============================================================================================
//  
//  Copyright (C) 2002 Jeroen Janssen
//
//  This library is free software; you can redistribute it and/or
//  modify it under the terms of the GNU Lesser General Public
//  License as published by the Free Software Foundation; either
//  version 2 of the License, or (at your option) any later version.
//
//  This library is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//  Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with this library; if not, write to the Free Software
//  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
// 
// ============================================================================================
//  
//  This VBE is part of the VGA Bios specific to the plex86/bochs Emulated VGA card. 
//  You can NOT drive any physical vga card with it. 
//
// ============================================================================================
//  
//  This VBE Bios is based on information taken from :
//   - VESA BIOS EXTENSION (VBE) Core Functions Standard Version 3.0 located at www.vesa.org
//
// ============================================================================================


// defines available

// disable VESA/VBE2 check in vbe info
//#define VBE2_NO_VESA_CHECK


#include "vbe.h"
#include "vbetables.h"

// The current OEM Software Revision of this VBE Bios
#define VBE_OEM_SOFTWARE_REV 0x0002;

extern char vbebios_copyright;
extern char vbebios_vendor_name;
extern char vbebios_product_name;
extern char vbebios_product_revision;

ASM_START
// FIXME: 'merge' these (c) etc strings with the vgabios.c strings?
_vbebios_copyright:
.ascii       "Bochs/Plex86 VBE(C) 2003 http://savannah.nongnu.org/projects/vgabios/"
.byte        0x00

_vbebios_vendor_name:
.ascii       "Bochs/Plex86 Developers"
.byte        0x00

_vbebios_product_name:
.ascii       "Bochs/Plex86 VBE Adapter"
.byte        0x00

_vbebios_product_revision:
.ascii       "$Id$"
.byte        0x00

_vbebios_info_string:
.ascii      "Bochs VBE Display Adapter enabled"
.byte	0x0a,0x0d
.byte	0x0a,0x0d
.byte	0x00

_no_vbebios_info_string:
.ascii      "NO Bochs VBE Support available!"
.byte	0x0a,0x0d
.byte	0x0a,0x0d
.byte 0x00

#if defined(USE_BX_INFO) || defined(DEBUG)
msg_vbe_init:
.ascii      "VBE Bios $Id$"
.byte	0x0a,0x0d, 0x00
#endif

  .align 2
vesa_pm_start:
  dw vesa_pm_set_window - vesa_pm_start
  dw vesa_pm_set_display_start - vesa_pm_start
  dw vesa_pm_unimplemented - vesa_pm_start
  dw vesa_pm_io_ports_table - vesa_pm_start
vesa_pm_io_ports_table:
  dw VBE_DISPI_IOPORT_INDEX
  dw VBE_DISPI_IOPORT_INDEX + 1
  dw VBE_DISPI_IOPORT_DATA
  dw VBE_DISPI_IOPORT_DATA + 1
  dw 0xffff
  dw 0xffff

  USE32
vesa_pm_set_window:
  cmp  bx, #0x00
  je  vesa_pm_set_display_window1
  mov  ax, #0x0100
  ret
vesa_pm_set_display_window1:
  mov  ax, dx
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BANK
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  in   ax, dx
  pop  dx
  cmp  dx, ax
  jne  illegal_window
  mov  ax, #0x004f
  ret
illegal_window:
  mov  ax, #0x014f
  ret

vesa_pm_set_display_start:
  cmp  bl, #0x80
  je   vesa_pm_set_display_start1
  cmp  bl, #0x00
  je   vesa_pm_set_display_start1
  mov  ax, #0x0100
  ret
vesa_pm_set_display_start1:
; convert offset to (X, Y) coordinate 
; (would be simpler to change Bochs VBE API...)
  push eax
  push ecx
  push edx
  push esi
  push edi
  shl edx, #16
  and ecx, #0xffff
  or ecx, edx
  shl ecx, #2
  mov eax, ecx

  push eax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_VIRT_WIDTH
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  movzx ecx, ax

  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BPP
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  movzx esi, ax
  pop  eax

  cmp esi, #4
  jz bpp4_mode
  add esi, #7
  shr esi, #3
  imul ecx, esi
  xor edx, edx
  div ecx
  mov edi, eax
  mov eax, edx
  xor edx, edx
  div esi
  jmp set_xy_regs

bpp4_mode:
  shr ecx, #1
  xor edx, edx
  div ecx
  mov edi, eax
  mov eax, edx
  shl eax, #1

set_xy_regs:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_X_OFFSET
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx

  mov  ax, di
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_Y_OFFSET
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx

  pop edi
  pop esi
  pop edx
  pop ecx
  pop eax
  mov  ax, #0x004f
  ret

vesa_pm_unimplemented:
  mov ax, #0x014f
  ret
  USE16
vesa_pm_end:

; DISPI ioport functions

dispi_get_id:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_ID
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

dispi_set_id:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_ID
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret
ASM_END

static void dispi_set_xres(xres)
  Bit16u xres;
{
ASM_START
  push bp
  mov  bp, sp
  push ax
  push dx

  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_XRES
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  mov  ax, 4[bp] ; xres
  out  dx, ax

  pop  dx
  pop  ax
  pop  bp
ASM_END
}

static void dispi_set_yres(yres)
  Bit16u yres;
{
  outw(VBE_DISPI_IOPORT_INDEX,VBE_DISPI_INDEX_YRES);
  outw(VBE_DISPI_IOPORT_DATA,yres);
}

static void dispi_set_bpp(bpp)
  Bit16u bpp;
{
  outw(VBE_DISPI_IOPORT_INDEX,VBE_DISPI_INDEX_BPP);
  outw(VBE_DISPI_IOPORT_DATA,bpp);
}

ASM_START
; AL = bits per pixel / AH = bytes per pixel
dispi_get_bpp:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BPP
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  mov  ah, al
  shr  ah, 3
  test al, #0x07
  jz   get_bpp_noinc
  inc  ah
get_bpp_noinc:
  pop  dx
  ret

; get display capabilities

_dispi_get_max_xres:
  push dx
  push bx
  call dispi_get_enable
  mov  bx, ax
  or   ax, # VBE_DISPI_GETCAPS
  call _dispi_set_enable
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_XRES
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  push ax
  mov  ax, bx
  call _dispi_set_enable
  pop  ax
  pop  bx
  pop  dx
  ret

_dispi_get_max_bpp:
  push dx
  push bx
  call dispi_get_enable
  mov  bx, ax
  or   ax, # VBE_DISPI_GETCAPS
  call _dispi_set_enable
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BPP
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  push ax
  mov  ax, bx
  call _dispi_set_enable
  pop  ax
  pop  bx
  pop  dx
  ret

_dispi_set_enable:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_ENABLE
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret

dispi_get_enable:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_ENABLE
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

_dispi_set_bank:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BANK
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret

dispi_get_bank:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BANK
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret
ASM_END

static void dispi_set_bank_farcall()
{
ASM_START
  cmp bx,#0x0100
  je dispi_set_bank_farcall_get
  or bx,bx
  jnz dispi_set_bank_farcall_error
  mov ax,dx
  push dx
  push ax
  mov ax,# VBE_DISPI_INDEX_BANK
  mov dx,# VBE_DISPI_IOPORT_INDEX
  out dx,ax
  pop ax
  mov dx,# VBE_DISPI_IOPORT_DATA
  out dx,ax
  in  ax,dx
  pop dx
  cmp dx,ax
  jne dispi_set_bank_farcall_error
  mov ax, #0x004f
  retf
dispi_set_bank_farcall_get:
  mov ax,# VBE_DISPI_INDEX_BANK
  mov dx,# VBE_DISPI_IOPORT_INDEX
  out dx,ax
  mov dx,# VBE_DISPI_IOPORT_DATA
  in ax,dx
  mov dx,ax
  retf
dispi_set_bank_farcall_error:
  mov ax,#0x014F
  retf
ASM_END
}

ASM_START
dispi_set_x_offset:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_X_OFFSET
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret

dispi_get_x_offset:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_X_OFFSET
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

dispi_set_y_offset:
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_Y_OFFSET
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret

dispi_get_y_offset:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_Y_OFFSET
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

vga_set_virt_width:
  push ax
  push bx
  push dx
  mov  bx, ax
  call dispi_get_bpp
  cmp  al, #0x04
  ja   set_width_svga
  shr  bx, #1
set_width_svga:
  shr  bx, #3
  mov  dx, # VGAREG_VGA_CRTC_ADDRESS
  mov  ah, bl
  mov  al, #0x13
  out  dx, ax
  pop  dx
  pop  bx
  pop  ax
  ret

dispi_set_virt_width:
  call vga_set_virt_width
  push dx
  push ax
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_VIRT_WIDTH
  out  dx, ax
  pop  ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  out  dx, ax
  pop  dx
  ret

dispi_get_virt_width:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_VIRT_WIDTH
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

dispi_get_virt_height:
  push dx
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_VIRT_HEIGHT
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  pop  dx
  ret

_vga_compat_setup:
  push ax
  push dx

  ; set CRT X resolution
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_XRES
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  push ax
  mov  dx, # VGAREG_VGA_CRTC_ADDRESS
  mov  ax, #0x0011
  out  dx, ax
  pop  ax
  push ax
  shr  ax, #3
  dec  ax
  mov  ah, al
  mov  al, #0x01
  out  dx, ax
  pop  ax
  call vga_set_virt_width

  ; set CRT Y resolution
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_YRES
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  dec  ax
  push ax
  mov  dx, # VGAREG_VGA_CRTC_ADDRESS
  mov  ah, al
  mov  al, #0x12
  out  dx, ax
  pop  ax
  mov  al, #0x07
  out  dx, al
  inc  dx
  in   al, dx
  and  al, #0xbd
  test ah, #0x01
  jz   bit8_clear
  or   al, #0x02
bit8_clear:
  test ah, #0x02
  jz   bit9_clear
  or   al, #0x40
bit9_clear:
  out  dx, al

  ; other settings
  mov  dx, # VGAREG_VGA_CRTC_ADDRESS
  mov  ax, #0x0009
  out  dx, ax
  mov  al, #0x17
  out  dx, al
  mov  dx, # VGAREG_VGA_CRTC_DATA
  in   al, dx
  or   al, #0x03
  out  dx, al
  mov  dx, # VGAREG_ACTL_RESET
  in   al, dx
  mov  dx, # VGAREG_ACTL_ADDRESS
  mov  al, #0x10
  out  dx, al
  mov  dx, # VGAREG_ACTL_READ_DATA
  in   al, dx
  or   al, #0x01
  mov  dx, # VGAREG_ACTL_ADDRESS
  out  dx, al
  mov  al, #0x20
  out  dx, al
  mov  dx, # VGAREG_GRDC_ADDRESS
  mov  ax, #0x0506
  out  dx, ax
  mov  dx, # VGAREG_SEQU_ADDRESS
  mov  ax, #0x0f02
  out  dx, ax

  ; settings for >= 8bpp
  mov  dx, # VBE_DISPI_IOPORT_INDEX
  mov  ax, # VBE_DISPI_INDEX_BPP
  out  dx, ax
  mov  dx, # VBE_DISPI_IOPORT_DATA
  in   ax, dx
  cmp  al, #0x08
  jb   vga_compat_end
  mov  dx, # VGAREG_VGA_CRTC_ADDRESS
  mov  al, #0x14
  out  dx, al
  mov  dx, # VGAREG_VGA_CRTC_DATA
  in   al, dx
  or   al, #0x40
  out  dx, al
  mov  dx, # VGAREG_ACTL_RESET
  in   al, dx
  mov  dx, # VGAREG_ACTL_ADDRESS
  mov  al, #0x10
  out  dx, al
  mov  dx, # VGAREG_ACTL_READ_DATA
  in   al, dx
  or   al, #0x40
  mov  dx, # VGAREG_ACTL_ADDRESS
  out  dx, al
  mov  al, #0x20
  out  dx, al
  mov  dx, # VGAREG_SEQU_ADDRESS
  mov  al, #0x04
  out  dx, al
  mov  dx, # VGAREG_SEQU_DATA
  in   al, dx
  or   al, #0x08
  out  dx, al
  mov  dx, # VGAREG_GRDC_ADDRESS
  mov  al, #0x05
  out  dx, al
  mov  dx, # VGAREG_GRDC_DATA
  in   al, dx
  and  al, #0x9f
  or   al, #0x40
  out  dx, al

vga_compat_end:
  pop  dx
  pop  ax
ASM_END


// ModeInfo helper function
static ModeInfoListItem* mode_info_find_mode(mode, using_lfb)
  Bit16u mode; Boolean using_lfb;
{
  ModeInfoListItem  *cur_info=&mode_info_list;

  while (cur_info->mode != VBE_VESA_MODE_END_OF_LIST)
  {
    if (cur_info->mode == mode)
    {
      if (!using_lfb)
      {
        return cur_info;
      }
      else if (cur_info->info.ModeAttributes & VBE_MODE_ATTRIBUTE_LINEAR_FRAME_BUFFER_MODE)
      {
        return cur_info;
      }
      else
      {
        cur_info++;
      }
    }
    else
    {
      cur_info++;
    }
  }

  return 0;
}

ASM_START

; Has VBE display - Returns true if VBE display detected

_vbe_has_vbe_display:
  push ds
  push bx
  mov  ax, # BIOSMEM_SEG
  mov  ds, ax
  mov  bx, # BIOSMEM_VBE_FLAG
  mov  al, [bx]
  and  al, #0x01
  xor  ah, ah
  pop  bx
  pop  ds
  ret

; VBE Init - Initialise the Vesa Bios Extension Code
; This function does a sanity check on the host side display code interface.

vbe_init:
  mov  ax, # VBE_DISPI_ID0
  call dispi_set_id
  call dispi_get_id
  cmp  ax, # VBE_DISPI_ID0
  jne  no_vbe_interface
  push ds
  push bx
  mov  ax, # BIOSMEM_SEG
  mov  ds, ax
  mov  bx, # BIOSMEM_VBE_FLAG
  mov  al, #0x01
  mov  [bx], al
  pop  bx
  pop  ds
  mov  ax, # VBE_DISPI_ID5
  call dispi_set_id
no_vbe_interface:
#if defined(USE_BX_INFO) || defined(DEBUG)
  mov  bx, #msg_vbe_init
  push bx
  call _printf
  inc  sp
  inc  sp
#endif
  ret

; VBE Display Info - Display information on screen about the VBE

vbe_display_info:
  call _vbe_has_vbe_display
  test ax, ax
  jz   no_vbe_flag
  mov  ax, #0xc000
  mov  ds, ax
  mov  si, #_vbebios_info_string
  jmp  _display_string
no_vbe_flag:
  mov  ax, #0xc000
  mov  ds, ax
  mov  si, #_no_vbebios_info_string
  jmp  _display_string

; helper function for memory size calculation

lmulul:
  and eax, #0x0000FFFF
  shl ebx, #16
  or  eax, ebx
  SEG SS
  mul eax, dword ptr [di]
  mov ebx, eax
  shr ebx, #16
  ret
ASM_END

/** Function 00h - Return VBE Controller Information
 * 
 * Input:
 *              AX      = 4F00h
 *              ES:DI   = Pointer to buffer in which to place VbeInfoBlock structure
 *                        (VbeSignature should be VBE2 when VBE 2.0 information is desired and
 *                        the info block is 512 bytes in size)
 * Output:
 *              AX      = VBE Return Status
 * 
 */
void vbe_biosfn_return_controller_information(AX, ES, DI)
Bit16u *AX;Bit16u ES;Bit16u DI;
{
        Bit16u            ss=get_SS();
        VbeInfoBlock      vbe_info_block;
        Bit16u            status;
        Bit16u            result;
        Bit16u            vbe2_info;
        Bit16u            cur_mode=0;
        Bit16u            cur_ptr=34;
        Bit16u            size_64k;
        ModeInfoListItem  *cur_info=&mode_info_list;

        status = read_word(ss, AX);

#ifdef DEBUG
        printf("VBE vbe_biosfn_return_vbe_info ES%x DI%x AX%x\n",ES,DI,status);
#endif

        vbe2_info = 0;
#ifdef VBE2_NO_VESA_CHECK
#else
        // get vbe_info_block into local variable
        memcpyb(ss, &vbe_info_block, ES, DI, sizeof(vbe_info_block));

        // check for VBE2 signature
        if (((vbe_info_block.VbeSignature[0] == 'V') &&
             (vbe_info_block.VbeSignature[1] == 'B') &&
             (vbe_info_block.VbeSignature[2] == 'E') &&
             (vbe_info_block.VbeSignature[3] == '2')) ||

            ((vbe_info_block.VbeSignature[0] == 'V') &&
             (vbe_info_block.VbeSignature[1] == 'E') &&
             (vbe_info_block.VbeSignature[2] == 'S') &&
             (vbe_info_block.VbeSignature[3] == 'A')) )
        {
                vbe2_info = 1;
#ifdef DEBUG
                printf("VBE correct VESA/VBE2 signature found\n");
#endif
        }
#endif

        // VBE Signature
        vbe_info_block.VbeSignature[0] = 'V';
        vbe_info_block.VbeSignature[1] = 'E';
        vbe_info_block.VbeSignature[2] = 'S';
        vbe_info_block.VbeSignature[3] = 'A';

        // VBE Version supported
        vbe_info_block.VbeVersion = 0x0200;

        // OEM String
        vbe_info_block.OemStringPtr_Seg = 0xc000;
        vbe_info_block.OemStringPtr_Off = &vbebios_copyright;

        // Capabilities
        vbe_info_block.Capabilities[0] = VBE_CAPABILITY_8BIT_DAC;
        vbe_info_block.Capabilities[1] = 0;
        vbe_info_block.Capabilities[2] = 0;
        vbe_info_block.Capabilities[3] = 0;

        // VBE Video Mode Pointer (dynamicly generated from the mode_info_list)
        vbe_info_block.VideoModePtr_Seg= ES ;
        vbe_info_block.VideoModePtr_Off= DI + 34;

        // VBE Total Memory (in 64k blocks)
        outw(VBE_DISPI_IOPORT_INDEX, VBE_DISPI_INDEX_VIDEO_MEMORY_64K);
        vbe_info_block.TotalMemory = inw(VBE_DISPI_IOPORT_DATA);

        if (vbe2_info)
        {
                // OEM Stuff
                vbe_info_block.OemSoftwareRev = VBE_OEM_SOFTWARE_REV;
                vbe_info_block.OemVendorNamePtr_Seg = 0xc000;
                vbe_info_block.OemVendorNamePtr_Off = &vbebios_vendor_name;
                vbe_info_block.OemProductNamePtr_Seg = 0xc000;
                vbe_info_block.OemProductNamePtr_Off = &vbebios_product_name;
                vbe_info_block.OemProductRevPtr_Seg = 0xc000;
                vbe_info_block.OemProductRevPtr_Off = &vbebios_product_revision;

                // copy updates in vbe_info_block back
                memcpyb(ES, DI, ss, &vbe_info_block, sizeof(vbe_info_block));
        }
        else
        {
                // copy updates in vbe_info_block back (VBE 1.x compatibility)
                memcpyb(ES, DI, ss, &vbe_info_block, 256);
        }

        do
        {
                size_64k = (Bit16u)((Bit32u)cur_info->info.XResolution * cur_info->info.XResolution * cur_info->info.BitsPerPixel) >> 19;

                if ((cur_info->info.XResolution <= dispi_get_max_xres()) &&
                    (cur_info->info.BitsPerPixel <= dispi_get_max_bpp()) &&
                    (size_64k <= vbe_info_block.TotalMemory)) {
#ifdef DEBUG
                  printf("VBE found mode %x => %x\n", cur_info->mode,cur_mode);
#endif
                  write_word(ES, DI + cur_ptr, cur_info->mode);
                  cur_mode++;
                  cur_ptr+=2;
                } else {
#ifdef DEBUG
                  printf("VBE mode %x (xres=%x / bpp=%02x) not supported \n", cur_info->mode,cur_info->info.XResolution,cur_info->info.BitsPerPixel);
#endif
                }
                cur_info++;
        } while (cur_info->mode != VBE_VESA_MODE_END_OF_LIST);

        // Add vesa mode list terminator
        write_word(ES, DI + cur_ptr, cur_info->mode);

        result = 0x4f;

        write_word(ss, AX, result);
}


/** Function 01h - Return VBE Mode Information
 * 
 * Input:
 *              AX      = 4F01h
 *              CX      = Mode Number
 *              ES:DI   = Pointer to buffer in which to place ModeInfoBlock structure
 * Output:
 *              AX      = VBE Return Status
 * 
 */
void vbe_biosfn_return_mode_information(AX, CX, ES, DI)
Bit16u *AX;Bit16u CX; Bit16u ES;Bit16u DI;
{
        Bit16u            result=0x0100;
        Bit16u            ss=get_SS();
        ModeInfoBlock     info;
        ModeInfoListItem  *cur_info;
        Boolean           using_lfb;
        Bit16u            lfb_addr;

#ifdef DEBUG
        printf("VBE vbe_biosfn_return_mode_information ES%x DI%x CX%x\n",ES,DI,CX);
#endif

        using_lfb=((CX & VBE_MODE_LINEAR_FRAME_BUFFER) == VBE_MODE_LINEAR_FRAME_BUFFER);

        CX = (CX & 0x1ff);

        cur_info = mode_info_find_mode(CX, using_lfb, &cur_info);

        if (cur_info != 0)
        {
#ifdef DEBUG
                printf("VBE found mode %x\n",CX);
#endif
                memsetb(ss, &info, 0, sizeof(ModeInfoBlock));
                memcpyb(ss, &info, 0xc000, &(cur_info->info), sizeof(ModeInfoBlockCompact));
                if (using_lfb) {
                  info.NumberOfBanks = 1;
                }
#ifdef PCI_VID
                lfb_addr = pci_get_lfb_addr(PCI_VID);
#else
                lfb_addr = 0;
#endif
                if (lfb_addr > 0) {
                  info.PhysBasePtr = ((Bit32u)lfb_addr << 16);
                }
                if (info.WinAAttributes & VBE_WINDOW_ATTRIBUTE_RELOCATABLE) {
                  info.WinFuncPtr = 0xC0000000UL;
                  *(Bit16u *)&(info.WinFuncPtr) = (Bit16u)(dispi_set_bank_farcall);
                }

                result = 0x4f;
        }
        else
        {
#ifdef DEBUG
                printf("VBE *NOT* found mode %x\n",CX);
#endif
                result = 0x100;
        }

        if (result == 0x4f)
        {
                // copy updates in mode_info_block back
                memcpyb(ES, DI, ss, &info, sizeof(info));
        }

        write_word(ss, AX, result);
}

/** Function 02h - Set VBE Mode
 * 
 * Input:
 *              AX      = 4F02h
 *              BX      = Desired Mode to set
 *              ES:DI   = Pointer to CRTCInfoBlock structure
 * Output:
 *              AX      = VBE Return Status
 * 
 */
void vbe_biosfn_set_mode(AX, BX, ES, DI)
Bit16u *AX;Bit16u BX; Bit16u ES;Bit16u DI;
{
        Bit16u            ss = get_SS();
        Bit16u            result;
        ModeInfoListItem  *cur_info;
        Boolean           using_lfb;
        Bit8u             no_clear;
        Bit8u             lfb_flag;

        using_lfb=((BX & VBE_MODE_LINEAR_FRAME_BUFFER) == VBE_MODE_LINEAR_FRAME_BUFFER);
        lfb_flag=using_lfb?VBE_DISPI_LFB_ENABLED:0;
        no_clear=((BX & VBE_MODE_PRESERVE_DISPLAY_MEMORY) == VBE_MODE_PRESERVE_DISPLAY_MEMORY)?VBE_DISPI_NOCLEARMEM:0;

        BX = (BX & 0x1ff);

        //result=read_word(ss,AX);

        // check for non vesa mode
        if (BX<VBE_MODE_VESA_DEFINED)
        {
                Bit8u   mode;

                dispi_set_enable(VBE_DISPI_DISABLED);
                // call the vgabios in order to set the video mode
                // this allows for going back to textmode with a VBE call (some applications expect that to work)

                mode=(BX & 0xff);
                biosfn_set_video_mode(mode);
                result = 0x4f;
        }

        cur_info = mode_info_find_mode(BX, using_lfb, &cur_info);

        if (cur_info != 0)
        {
#ifdef DEBUG
                printf("VBE found mode %x, setting:\n", BX);
                printf("\txres%x yres%x bpp%x\n",
                        cur_info->info.XResolution,
                        cur_info->info.YResolution,
                        cur_info->info.BitsPerPixel);
#endif

                // first disable current mode (when switching between vesa modi)
                dispi_set_enable(VBE_DISPI_DISABLED);

                if (cur_info->info.BitsPerPixel == 4)
                {
                  biosfn_set_video_mode(0x6a);
                }

                dispi_set_bpp(cur_info->info.BitsPerPixel);
                dispi_set_xres(cur_info->info.XResolution);
                dispi_set_yres(cur_info->info.YResolution);
                dispi_set_bank(0);
                dispi_set_enable(VBE_DISPI_ENABLED | no_clear | lfb_flag);
                vga_compat_setup();

                write_word(BIOSMEM_SEG,BIOSMEM_VBE_MODE,BX);
                write_byte(BIOSMEM_SEG,BIOSMEM_VIDEO_CTL,(0x60 | no_clear));

                result = 0x4f;
        }
        else
        {
#ifdef DEBUG
                printf("VBE *NOT* found mode %x\n" , BX);
#endif
                result = 0x100;

                // FIXME: redirect non VBE modi to normal VGA bios operation
                //        (switch back to VGA mode
                if (BX == 3)
                        result = 0x4f;
        }

        write_word(ss, AX, result);
}

/** Function 03h - Return Current VBE Mode
 * 
 * Input:
 *              AX      = 4F03h
 * Output:
 *              AX      = VBE Return Status
 *              BX      = Current VBE Mode
 * 
 */
ASM_START
vbe_biosfn_return_current_mode:
  push ds
  mov  ax, # BIOSMEM_SEG
  mov  ds, ax
  call dispi_get_enable
  and  ax, # VBE_DISPI_ENABLED
  jz   no_vbe_mode
  mov  bx, # BIOSMEM_VBE_MODE
  mov  ax, [bx]
  mov  bx, ax
  jnz  vbe_03_ok
no_vbe_mode:
  mov  bx, # BIOSMEM_CURRENT_MODE
  mov  al, [bx]
  mov  bl, al
  xor  bh, bh
vbe_03_ok:
  mov  ax, #0x004f
  pop  ds
  ret
ASM_END


Bit16u vbe_biosfn_read_video_state_size()
{
    return 9 * 2;
}

void vbe_biosfn_save_video_state(ES, BX)
     Bit16u ES; Bit16u BX;
{
    Bit16u enable, i;

    outw(VBE_DISPI_IOPORT_INDEX,VBE_DISPI_INDEX_ENABLE);
    enable = inw(VBE_DISPI_IOPORT_DATA);
    write_word(ES, BX, enable);
    BX += 2;
    if (!(enable & VBE_DISPI_ENABLED)) 
        return;
    for(i = VBE_DISPI_INDEX_XRES; i <= VBE_DISPI_INDEX_Y_OFFSET; i++) {
        if (i != VBE_DISPI_INDEX_ENABLE) {
            outw(VBE_DISPI_IOPORT_INDEX, i);
            write_word(ES, BX, inw(VBE_DISPI_IOPORT_DATA));
            BX += 2;
        }
    }
}


void vbe_biosfn_restore_video_state(ES, BX)
     Bit16u ES; Bit16u BX;
{
    Bit16u enable, i;

    enable = read_word(ES, BX);
    BX += 2;

    if (!(enable & VBE_DISPI_ENABLED)) {
        outw(VBE_DISPI_IOPORT_INDEX,VBE_DISPI_INDEX_ENABLE);
        outw(VBE_DISPI_IOPORT_DATA, enable);
    } else {
        outw(VBE_DISPI_IOPORT_INDEX, VBE_DISPI_INDEX_XRES);
        outw(VBE_DISPI_IOPORT_DATA, read_word(ES, BX));
        BX += 2;
        outw(VBE_DISPI_IOPORT_INDEX, VBE_DISPI_INDEX_YRES);
        outw(VBE_DISPI_IOPORT_DATA, read_word(ES, BX));
        BX += 2;
        outw(VBE_DISPI_IOPORT_INDEX, VBE_DISPI_INDEX_BPP);
        outw(VBE_DISPI_IOPORT_DATA, read_word(ES, BX));
        BX += 2;
        outw(VBE_DISPI_IOPORT_INDEX,VBE_DISPI_INDEX_ENABLE);
        outw(VBE_DISPI_IOPORT_DATA, enable);

        for(i = VBE_DISPI_INDEX_BANK; i <= VBE_DISPI_INDEX_Y_OFFSET; i++) {
            outw(VBE_DISPI_IOPORT_INDEX, i);
            outw(VBE_DISPI_IOPORT_DATA, read_word(ES, BX));
            BX += 2;
        }
    }
}

/** Function 04h - Save/Restore State
 * 
 * Input:
 *              AX      = 4F04h
 *              DL      = 00h Return Save/Restore State buffer size
 *                        01h Save State
 *                        02h Restore State
 *              CX      = Requested states
 *              ES:BX   = Pointer to buffer (if DL <> 00h)
 * Output:
 *              AX      = VBE Return Status
 *              BX      = Number of 64-byte blocks to hold the state buffer (if DL=00h)
 * 
 */
void vbe_biosfn_save_restore_state(AX, CX, DX, ES, BX)
Bit16u *AX; Bit16u CX; Bit16u DX; Bit16u ES; Bit16u *BX;
{
    Bit16u ss=get_SS();
    Bit16u result, val;

    result = 0x4f;
    switch(GET_DL()) {
    case 0x00:
        val = biosfn_read_video_state_size2(CX);
#ifdef DEBUG
        printf("VGA state size=%x\n", val);
#endif
        if (CX & 8)
            val += vbe_biosfn_read_video_state_size();
        write_word(ss, BX, val);
        break;
    case 0x01:
        val = read_word(ss, BX);
        val = biosfn_save_video_state(CX, ES, val);
#ifdef DEBUG
        printf("VGA save_state offset=%x\n", val);
#endif
        if (CX & 8)
            vbe_biosfn_save_video_state(ES, val);
        break;
    case 0x02:
        val = read_word(ss, BX);
        val = biosfn_restore_video_state(CX, ES, val);
#ifdef DEBUG
        printf("VGA restore_state offset=%x\n", val);
#endif
        if (CX & 8)
            vbe_biosfn_restore_video_state(ES, val);
        break;
    default:
        // function failed
        result = 0x100;
        break;
    }
    write_word(ss, AX, result);
}

/** Function 05h - Display Window Control
 * 
 * Input:
 *              AX      = 4F05h
 *     (16-bit) BH      = 00h Set memory window
 *                      = 01h Get memory window
 *              BL      = Window number
 *                      = 00h Window A
 *                      = 01h Window B
 *              DX      = Window number in video memory in window
 *                        granularity units (Set Memory Window only)
 * Note:
 *              If this function is called while in a linear frame buffer mode,
 *              this function must fail with completion code AH=03h
 * 
 * Output:
 *              AX      = VBE Return Status
 *              DX      = Window number in window granularity units
 *                        (Get Memory Window only)
 */
ASM_START
vbe_biosfn_display_window_control:
  cmp  bl, #0x00
  jne  vbe_05_failed
  cmp  bh, #0x01
  je   get_display_window
  jb   set_display_window
  mov  ax, #0x0100
  ret
set_display_window:
  mov  ax, dx
  call _dispi_set_bank
  call dispi_get_bank
  cmp  ax, dx
  jne  vbe_05_failed
  mov  ax, #0x004f
  ret
get_display_window:
  call dispi_get_bank
  mov  dx, ax
  mov  ax, #0x004f
  ret
vbe_05_failed:
  mov  ax, #0x014f
  ret
ASM_END


/** Function 06h - Set/Get Logical Scan Line Length
 *
 * Input:
 *              AX      = 4F06h
 *              BL      = 00h Set Scan Line Length in Pixels
 *                      = 01h Get Scan Line Length
 *                      = 02h Set Scan Line Length in Bytes
 *                      = 03h Get Maximum Scan Line Length
 *              CX      = If BL=00h Desired Width in Pixels
 *                        If BL=02h Desired Width in Bytes
 *                        (Ignored for Get Functions)
 * 
 * Output: 
 *              AX      = VBE Return Status
 *              BX      = Bytes Per Scan Line
 *              CX      = Actual Pixels Per Scan Line
 *                        (truncated to nearest complete pixel)
 *              DX      = Maximum Number of Scan Lines 
 */
ASM_START
vbe_biosfn_set_get_logical_scan_line_length:
  mov  ax, cx
  cmp  bl, #0x01
  je   get_logical_scan_line_length
  cmp  bl, #0x02
  je   set_logical_scan_line_bytes
  jb   set_logical_scan_line_pixels
  mov  ax, #0x0100
  ret
set_logical_scan_line_bytes:
  push ax
  call dispi_get_bpp
  xor  bh, bh
  mov  bl, ah
  or   bl, bl
  jnz  no_4bpp_1
  shl  ax, #3
  mov  bl, #1
no_4bpp_1:
  xor  dx, dx
  pop  ax
  div  bx
set_logical_scan_line_pixels:
  call dispi_set_virt_width
get_logical_scan_line_length:
  call dispi_get_bpp
  xor  bh, bh
  mov  bl, ah
  call dispi_get_virt_width
  mov  cx, ax
  or   bl, bl
  jnz  no_4bpp_2
  shr  ax, #3
  mov  bl, #1
no_4bpp_2:
  mul  bx
  mov  bx, ax
  call dispi_get_virt_height
  mov  dx, ax
  mov  ax, #0x004f
  ret
ASM_END


/** Function 07h - Set/Get Display Start
 * 
 * Input(16-bit):
 *              AX      = 4F07h
 *              BH      = 00h Reserved and must be 00h
 *              BL      = 00h Set Display Start
 *                      = 01h Get Display Start
 *                      = 02h Schedule Display Start (Alternate)
 *                      = 03h Schedule Stereoscopic Display Start
 *                      = 04h Get Scheduled Display Start Status
 *                      = 05h Enable Stereoscopic Mode
 *                      = 06h Disable Stereoscopic Mode
 *                      = 80h Set Display Start during Vertical Retrace
 *                      = 82h Set Display Start during Vertical Retrace (Alternate)
 *                      = 83h Set Stereoscopic Display Start during Vertical Retrace
 *              ECX     = If BL=02h/82h Display Start Address in bytes
 *                        If BL=03h/83h Left Image Start Address in bytes
 *              EDX     = If BL=03h/83h Right Image Start Address in bytes
 *              CX      = If BL=00h/80h First Displayed Pixel In Scan Line
 *              DX      = If BL=00h/80h First Displayed Scan Line
 *
 * Output:
 *              AX      = VBE Return Status
 *              BH      = If BL=01h Reserved and will be 0
 *              CX      = If BL=01h First Displayed Pixel In Scan Line
 *                        If BL=04h 0 if flip has not occurred, not 0 if it has
 *              DX      = If BL=01h First Displayed Scan Line
 *
 * Input(32-bit): 
 *              BH      = 00h Reserved and must be 00h
 *              BL      = 00h Set Display Start
 *                      = 80h Set Display Start during Vertical Retrace
 *              CX      = Bits 0-15 of display start address
 *              DX      = Bits 16-31 of display start address
 *              ES      = Selector for memory mapped registers 
 */
ASM_START
vbe_biosfn_set_get_display_start:
  cmp  bl, #0x80
  je   set_display_start
  cmp  bl, #0x01
  je   get_display_start
  jb   set_display_start
  mov  ax, #0x0100
  ret
set_display_start:
  mov  ax, cx
  call dispi_set_x_offset
  mov  ax, dx
  call dispi_set_y_offset
  mov  ax, #0x004f
  ret
get_display_start:
  call dispi_get_x_offset
  mov  cx, ax
  call dispi_get_y_offset
  mov  dx, ax
  xor  bh, bh
  mov  ax, #0x004f
  ret
ASM_END
  

/** Function 08h - Set/Get Dac Palette Format
 * 
 * Input:
 *              AX      = 4F08h
 *              BL      = 00h set DAC palette width
 *                      = 01h get DAC palette width
 *              BH      = If BL=00h: desired number of bits per primary color
 * Output:
 *              AX      = VBE Return Status
 *              BH      = current number of bits per primary color (06h = standard VGA)
 */
ASM_START
vbe_biosfn_set_get_dac_palette_format:
  cmp  bl, #0x01
  je   get_dac_palette_format
  jb   set_dac_palette_format
  mov  ax, #0x0100
  ret
set_dac_palette_format:
  call dispi_get_enable
  cmp  bh, #0x06
  je   set_normal_dac
  cmp  bh, #0x08
  jne  vbe_08_unsupported
  or   ax, # VBE_DISPI_8BIT_DAC
  jnz  set_dac_mode
set_normal_dac:
  and  ax, #~ VBE_DISPI_8BIT_DAC
set_dac_mode:
  call _dispi_set_enable
get_dac_palette_format:
  mov  bh, #0x06
  call dispi_get_enable
  and  ax, # VBE_DISPI_8BIT_DAC
  jz   vbe_08_ok
  mov  bh, #0x08
vbe_08_ok:
  mov  ax, #0x004f
  ret
vbe_08_unsupported:
  mov  ax, #0x014f
  ret
ASM_END


/** Function 09h - Set/Get Palette Data
 * 
 * Input:
 *              AX      = 4F09h
 * Output:
 *              AX      = VBE Return Status
 *
 * FIXME: incomplete API description, Input & Output
 */
void vbe_biosfn_set_get_palette_data(AX)
{
}

/** Function 0Ah - Return VBE Protected Mode Interface
 * Input:    AX   = 4F0Ah   VBE 2.0 Protected Mode Interface
 *           BL   = 00h          Return protected mode table
 *
 *
 * Output:   AX   =         Status
 *           ES   =         Real Mode Segment of Table
 *           DI   =         Offset of Table
 *           CX   =         Length of Table including protected mode code
 *                          (for copying purposes)
 */
ASM_START
vbe_biosfn_return_protected_mode_interface:
  test bl, bl
  jnz _fail
  mov di, #0xc000
  mov es, di
  mov di, # vesa_pm_start
  mov cx, # vesa_pm_end
  sub cx, di
  mov ax, #0x004f
  ret
_fail:
  mov ax, #0x014f
  ret
ASM_END