aboutsummaryrefslogtreecommitdiffstats
path: root/arch/i386/boot/video.S
blob: 8c2a6faeeae51b128e27b43e4669a7ac75dcf792 (plain) (blame)
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
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
/*	video.S
 *
 *	Display adapter & video mode setup, version 2.13 (14-May-99)
 *
 *	Copyright (C) 1995 -- 1998 Martin Mares <mj@ucw.cz>
 *	Based on the original setup.S code (C) Linus Torvalds and Mats Anderson
 *
 *	Rewritten to use GNU 'as' by Chris Noe <stiker@northlink.com> May 1999
 *
 *	For further information, look at Documentation/svga.txt.
 *
 */

#include <linux/config.h> /* for CONFIG_VIDEO_* */

/* Enable autodetection of SVGA adapters and modes. */
#undef CONFIG_VIDEO_SVGA

/* Enable autodetection of VESA modes */
#define CONFIG_VIDEO_VESA

/* Enable compacting of mode table */
#define CONFIG_VIDEO_COMPACT

/* Retain screen contents when switching modes */
#define CONFIG_VIDEO_RETAIN

/* Enable local mode list */
#undef CONFIG_VIDEO_LOCAL

/* Force 400 scan lines for standard modes (hack to fix bad BIOS behaviour */
#undef CONFIG_VIDEO_400_HACK

/* Hack that lets you force specific BIOS mode ID and specific dimensions */
#undef CONFIG_VIDEO_GFX_HACK
#define VIDEO_GFX_BIOS_AX 0x4f02	/* 800x600 on ThinkPad */
#define VIDEO_GFX_BIOS_BX 0x0102
#define VIDEO_GFX_DUMMY_RESOLUTION 0x6425	/* 100x37 */

/* This code uses an extended set of video mode numbers. These include:
 * Aliases for standard modes
 *	NORMAL_VGA (-1)
 *	EXTENDED_VGA (-2)
 *	ASK_VGA (-3)
 * Video modes numbered by menu position -- NOT RECOMMENDED because of lack
 * of compatibility when extending the table. These are between 0x00 and 0xff.
 */
#define VIDEO_FIRST_MENU 0x0000

/* Standard BIOS video modes (BIOS number + 0x0100) */
#define VIDEO_FIRST_BIOS 0x0100

/* VESA BIOS video modes (VESA number + 0x0200) */
#define VIDEO_FIRST_VESA 0x0200

/* Video7 special modes (BIOS number + 0x0900) */
#define VIDEO_FIRST_V7 0x0900

/* Special video modes */
#define VIDEO_FIRST_SPECIAL 0x0f00
#define VIDEO_80x25 0x0f00
#define VIDEO_8POINT 0x0f01
#define VIDEO_80x43 0x0f02
#define VIDEO_80x28 0x0f03
#define VIDEO_CURRENT_MODE 0x0f04
#define VIDEO_80x30 0x0f05
#define VIDEO_80x34 0x0f06
#define VIDEO_80x60 0x0f07
#define VIDEO_GFX_HACK 0x0f08
#define VIDEO_LAST_SPECIAL 0x0f09

/* Video modes given by resolution */
#define VIDEO_FIRST_RESOLUTION 0x1000

/* The "recalculate timings" flag */
#define VIDEO_RECALC 0x8000

/* Positions of various video parameters passed to the kernel */
/* (see also include/linux/tty.h) */
#define PARAM_CURSOR_POS	0x00
#define PARAM_VIDEO_PAGE	0x04
#define PARAM_VIDEO_MODE	0x06
#define PARAM_VIDEO_COLS	0x07
#define PARAM_VIDEO_EGA_BX	0x0a
#define PARAM_VIDEO_LINES	0x0e
#define PARAM_HAVE_VGA		0x0f
#define PARAM_FONT_POINTS	0x10

#define PARAM_LFB_WIDTH		0x12
#define PARAM_LFB_HEIGHT	0x14
#define PARAM_LFB_DEPTH		0x16
#define PARAM_LFB_BASE		0x18
#define PARAM_LFB_SIZE		0x1c
#define PARAM_LFB_LINELENGTH	0x24
#define PARAM_LFB_COLORS	0x26
#define PARAM_VESAPM_SEG	0x2e
#define PARAM_VESAPM_OFF	0x30
#define PARAM_LFB_PAGES		0x32
#define PARAM_VESA_ATTRIB	0x34
#define PARAM_CAPABILITIES	0x36

/* Define DO_STORE according to CONFIG_VIDEO_RETAIN */
#ifdef CONFIG_VIDEO_RETAIN
#define DO_STORE call store_screen
#else
#define DO_STORE
#endif /* CONFIG_VIDEO_RETAIN */

# This is the main entry point called by setup.S
# %ds *must* be pointing to the bootsector
video:	pushw	%ds		# We use different segments
	pushw	%ds		# FS contains original DS
	popw	%fs
	pushw	%cs		# DS is equal to CS
	popw	%ds
	pushw	%cs		# ES is equal to CS
	popw	%es
	xorw	%ax, %ax
	movw	%ax, %gs	# GS is zero
	cld
	call	basic_detect	# Basic adapter type testing (EGA/VGA/MDA/CGA)
#ifdef CONFIG_VIDEO_SELECT
	movw	%fs:(0x01fa), %ax		# User selected video mode
	cmpw	$ASK_VGA, %ax			# Bring up the menu
	jz	vid2

	call	mode_set			# Set the mode
	jc	vid1

	leaw	badmdt, %si			# Invalid mode ID
	call	prtstr
vid2:	call	mode_menu
vid1:
#ifdef CONFIG_VIDEO_RETAIN
	call	restore_screen			# Restore screen contents
#endif /* CONFIG_VIDEO_RETAIN */
	call	store_edid
#endif /* CONFIG_VIDEO_SELECT */
	call	mode_params			# Store mode parameters
	popw	%ds				# Restore original DS
	ret

# Detect if we have CGA, MDA, EGA or VGA and pass it to the kernel.
basic_detect:
	movb	$0, %fs:(PARAM_HAVE_VGA)
	movb	$0x12, %ah	# Check EGA/VGA
	movb	$0x10, %bl
	int	$0x10
	movw	%bx, %fs:(PARAM_VIDEO_EGA_BX)	# Identifies EGA to the kernel
	cmpb	$0x10, %bl			# No, it's a CGA/MDA/HGA card.
	je	basret

	incb	adapter
	movw	$0x1a00, %ax			# Check EGA or VGA?
	int	$0x10
	cmpb	$0x1a, %al			# 1a means VGA...
	jne	basret				# anything else is EGA.
	
	incb	%fs:(PARAM_HAVE_VGA)		# We've detected a VGA
	incb	adapter
basret:	ret

# Store the video mode parameters for later usage by the kernel.
# This is done by asking the BIOS except for the rows/columns
# parameters in the default 80x25 mode -- these are set directly,
# because some very obscure BIOSes supply insane values.
mode_params:
#ifdef CONFIG_VIDEO_SELECT
	cmpb	$0, graphic_mode
	jnz	mopar_gr
#endif
	movb	$0x03, %ah			# Read cursor position
	xorb	%bh, %bh
	int	$0x10
	movw	%dx, %fs:(PARAM_CURSOR_POS)
	movb	$0x0f, %ah			# Read page/mode/width
	int	$0x10
	movw	%bx, %fs:(PARAM_VIDEO_PAGE)
	movw	%ax, %fs:(PARAM_VIDEO_MODE)	# Video mode and screen width
	cmpb	$0x7, %al			# MDA/HGA => segment differs
	jnz	mopar0

	movw	$0xb000, video_segment
mopar0: movw	%gs:(0x485), %ax		# Font size
	movw	%ax, %fs:(PARAM_FONT_POINTS)	# (valid only on EGA/VGA)
	movw	force_size, %ax			# Forced size?
	orw	%ax, %ax
	jz	mopar1

	movb	%ah, %fs:(PARAM_VIDEO_COLS)
	movb	%al, %fs:(PARAM_VIDEO_LINES)
	ret

mopar1:	movb	$25, %al
	cmpb	$0, adapter			# If we are on CGA/MDA/HGA, the
	jz	mopar2				# screen must have 25 lines.

	movb	%gs:(0x484), %al		# On EGA/VGA, use the EGA+ BIOS
	incb	%al				# location of max lines.
mopar2: movb	%al, %fs:(PARAM_VIDEO_LINES)
	ret

#ifdef CONFIG_VIDEO_SELECT
# Fetching of VESA frame buffer parameters
mopar_gr:
	leaw	modelist+1024, %di
	movb	$0x23, %fs:(PARAM_HAVE_VGA)
	movw	16(%di), %ax
	movw	%ax, %fs:(PARAM_LFB_LINELENGTH)
	movw	18(%di), %ax
	movw	%ax, %fs:(PARAM_LFB_WIDTH)
	movw	20(%di), %ax
	movw	%ax, %fs:(PARAM_LFB_HEIGHT)
	movb	25(%di), %al
	movb	$0, %ah
	movw	%ax, %fs:(PARAM_LFB_DEPTH)
	movb	29(%di), %al	
	movb	$0, %ah
	movw	%ax, %fs:(PARAM_LFB_PAGES)
	movl	40(%di), %eax
	movl	%eax, %fs:(PARAM_LFB_BASE)
	movl	31(%di), %eax
	movl	%eax, %fs:(PARAM_LFB_COLORS)
	movl	35(%di), %eax
	movl	%eax, %fs:(PARAM_LFB_COLORS+4)
	movw	0(%di), %ax
	movw	%ax, %fs:(PARAM_VESA_ATTRIB)

# get video mem size
	leaw	modelist+1024, %di
	movw	$0x4f00, %ax
	int	$0x10
	xorl	%eax, %eax
	movw	18(%di), %ax
	movl	%eax, %fs:(PARAM_LFB_SIZE)

# store mode capabilities
	movl 10(%di), %eax
	movl %eax, %fs:(PARAM_CAPABILITIES)

# switching the DAC to 8-bit is for <= 8 bpp only
	movw	%fs:(PARAM_LFB_DEPTH), %ax
	cmpw	$8, %ax
	jg	dac_done

# get DAC switching capability
	xorl	%eax, %eax
	movb	10(%di), %al
	testb	$1, %al
	jz	dac_set

# attempt to switch DAC to 8-bit
	movw	$0x4f08, %ax
	movw	$0x0800, %bx
	int	$0x10
	cmpw	$0x004f, %ax
	jne     dac_set
	movb    %bh, dac_size		# store actual DAC size

dac_set:
# set color size to DAC size
	movb	dac_size, %al
	movb	%al, %fs:(PARAM_LFB_COLORS+0)
	movb	%al, %fs:(PARAM_LFB_COLORS+2)
	movb	%al, %fs:(PARAM_LFB_COLORS+4)
	movb	%al, %fs:(PARAM_LFB_COLORS+6)

# set color offsets to 0
	movb	$0, %fs:(PARAM_LFB_COLORS+1)
	movb	$0, %fs:(PARAM_LFB_COLORS+3)
	movb	$0, %fs:(PARAM_LFB_COLORS+5)
	movb	$0, %fs:(PARAM_LFB_COLORS+7)

dac_done:
# get protected mode interface informations
	movw	$0x4f0a, %ax
	xorw	%bx, %bx
	xorw	%di, %di
	int	$0x10
	cmp	$0x004f, %ax
	jnz	no_pm

	movw	%es, %fs:(PARAM_VESAPM_SEG)
	movw	%di, %fs:(PARAM_VESAPM_OFF)
no_pm:	ret

# The video mode menu
mode_menu:
	leaw	keymsg, %si			# "Return/Space/Timeout" message
	call	prtstr
	call	flush
nokey:	call	getkt

	cmpb	$0x0d, %al			# ENTER ?
	je	listm				# yes - manual mode selection

	cmpb	$0x20, %al			# SPACE ?
	je	defmd1				# no - repeat

	call 	beep
	jmp	nokey

defmd1:	ret					# No mode chosen? Default 80x25

listm:	call	mode_table			# List mode table
listm0:	leaw	name_bann, %si			# Print adapter name
	call	prtstr
	movw	card_name, %si
	orw	%si, %si
	jnz	an2

	movb	adapter, %al
	leaw	old_name, %si
	orb	%al, %al
	jz	an1

	leaw	ega_name, %si
	decb	%al
	jz	an1

	leaw	vga_name, %si
	jmp	an1

an2:	call	prtstr
	leaw	svga_name, %si
an1:	call	prtstr
	leaw	listhdr, %si			# Table header
	call	prtstr
	movb	$0x30, %dl			# DL holds mode number
	leaw	modelist, %si
lm1:	cmpw	$ASK_VGA, (%si)			# End?
	jz	lm2

	movb	%dl, %al			# Menu selection number
	call	prtchr
	call	prtsp2
	lodsw
	call	prthw				# Mode ID
	call	prtsp2
	movb	0x1(%si), %al
	call	prtdec				# Rows
	movb	$0x78, %al			# the letter 'x'
	call	prtchr
	lodsw
	call	prtdec				# Columns
	movb	$0x0d, %al			# New line
	call	prtchr
	movb	$0x0a, %al
	call	prtchr
	incb	%dl				# Next character
	cmpb	$0x3a, %dl
	jnz	lm1

	movb	$0x61, %dl
	jmp	lm1

lm2:	leaw	prompt, %si			# Mode prompt
	call	prtstr
	leaw	edit_buf, %di			# Editor buffer
lm3:	call	getkey
	cmpb	$0x0d, %al			# Enter?
	jz	lment

	cmpb	$0x08, %al			# Backspace?
	jz	lmbs

	cmpb	$0x20, %al			# Printable?
	jc	lm3

	cmpw	$edit_buf+4, %di		# Enough space?
	jz	lm3

	stosb
	call	prtchr
	jmp	lm3

lmbs:	cmpw	$edit_buf, %di			# Backspace
	jz	lm3

	decw	%di
	movb	$0x08, %al
	call	prtchr
	call	prtspc
	movb	$0x08, %al
	call	prtchr
	jmp	lm3
	
lment:	movb	$0, (%di)
	leaw	crlft, %si
	call	prtstr
	leaw	edit_buf, %si
	cmpb	$0, (%si)			# Empty string = default mode
	jz	lmdef

	cmpb	$0, 1(%si)			# One character = menu selection
	jz	mnusel

	cmpw	$0x6373, (%si)			# "scan" => mode scanning
	jnz	lmhx

	cmpw	$0x6e61, 2(%si)
	jz	lmscan

lmhx:	xorw	%bx, %bx			# Else => mode ID in hex
lmhex:	lodsb
	orb	%al, %al
	jz	lmuse1

	subb	$0x30, %al
	jc	lmbad

	cmpb	$10, %al
	jc	lmhx1

	subb	$7, %al
	andb	$0xdf, %al
	cmpb	$10, %al
	jc	lmbad

	cmpb	$16, %al
	jnc	lmbad

lmhx1:	shlw	$4, %bx
	orb	%al, %bl
	jmp	lmhex

lmuse1:	movw	%bx, %ax
	jmp	lmuse

mnusel:	lodsb					# Menu selection
	xorb	%ah, %ah
	subb	$0x30, %al
	jc	lmbad

	cmpb	$10, %al
	jc	lmuse
	
	cmpb	$0x61-0x30, %al
	jc	lmbad
	
	subb	$0x61-0x30-10, %al
	cmpb	$36, %al
	jnc	lmbad

lmuse:	call	mode_set
	jc	lmdef

lmbad:	leaw	unknt, %si
	call	prtstr
	jmp	lm2
lmscan:	cmpb	$0, adapter			# Scanning only on EGA/VGA
	jz	lmbad

	movw	$0, mt_end			# Scanning of modes is
	movb	$1, scanning			# done as new autodetection.
	call	mode_table
	jmp	listm0
lmdef:	ret

# Additional parts of mode_set... (relative jumps, you know)
setv7:						# Video7 extended modes
	DO_STORE
	subb	$VIDEO_FIRST_V7>>8, %bh
	movw	$0x6f05, %ax
	int	$0x10
	stc
	ret

_setrec:	jmp	setrec			# Ugly...
_set_80x25:	jmp	set_80x25

# Aliases for backward compatibility.
setalias:
	movw	$VIDEO_80x25, %ax
	incw	%bx
	jz	mode_set

	movb	$VIDEO_8POINT-VIDEO_FIRST_SPECIAL, %al
	incw	%bx
	jnz	setbad				# Fall-through!

# Setting of user mode (AX=mode ID) => CF=success
mode_set:
	movw	%ax, %fs:(0x01fa)		# Store mode for use in acpi_wakeup.S
	movw	%ax, %bx
	cmpb	$0xff, %ah
	jz	setalias

	testb	$VIDEO_RECALC>>8, %ah
	jnz	_setrec

	cmpb	$VIDEO_FIRST_RESOLUTION>>8, %ah
	jnc	setres
	
	cmpb	$VIDEO_FIRST_SPECIAL>>8, %ah
	jz	setspc
	
	cmpb	$VIDEO_FIRST_V7>>8, %ah
	jz	setv7
	
	cmpb	$VIDEO_FIRST_VESA>>8, %ah
	jnc	check_vesa
	
	orb	%ah, %ah
	jz	setmenu
	
	decb	%ah
	jz	setbios

setbad:	clc
	movb	$0, do_restore			# The screen needn't be restored
	ret

setvesa:
	DO_STORE
	subb	$VIDEO_FIRST_VESA>>8, %bh
	movw	$0x4f02, %ax			# VESA BIOS mode set call
	int	$0x10
	cmpw	$0x004f, %ax			# AL=4f if implemented
	jnz	setbad				# AH=0 if OK

	stc
	ret

setbios:
	DO_STORE
	int	$0x10				# Standard BIOS mode set call
	pushw	%bx
	movb	$0x0f, %ah			# Check if really set
	int	$0x10
	popw	%bx
	cmpb	%bl, %al
	jnz	setbad
	
	stc
	ret

setspc:	xorb	%bh, %bh			# Set special mode
	cmpb	$VIDEO_LAST_SPECIAL-VIDEO_FIRST_SPECIAL, %bl
	jnc	setbad
	
	addw	%bx, %bx
	jmp	*spec_inits(%bx)

setmenu:
	orb	%al, %al			# 80x25 is an exception
	jz	_set_80x25
	
	pushw	%bx				# Set mode chosen from menu
	call	mode_table			# Build the mode table
	popw	%ax
	shlw	$2, %ax
	addw	%ax, %si
	cmpw	%di, %si
	jnc	setbad
	
	movw	(%si), %ax			# Fetch mode ID
_m_s:	jmp	mode_set

setres:	pushw	%bx				# Set mode chosen by resolution
	call	mode_table
	popw	%bx
	xchgb	%bl, %bh
setr1:	lodsw
	cmpw	$ASK_VGA, %ax			# End of the list?
	jz	setbad
	
	lodsw
	cmpw	%bx, %ax
	jnz	setr1
	
	movw	-4(%si), %ax			# Fetch mode ID
	jmp	_m_s

check_vesa:
	leaw	modelist+1024, %di
	subb	$VIDEO_FIRST_VESA>>8, %bh
	movw	%bx, %cx			# Get mode information structure
	movw	$0x4f01, %ax
	int	$0x10
	addb	$VIDEO_FIRST_VESA>>8, %bh
	cmpw	$0x004f, %ax
	jnz	setbad

	movb	(%di), %al			# Check capabilities.
	andb	$0x19, %al
	cmpb	$0x09, %al
	jz	setvesa				# This is a text mode

	movb	(%di), %al			# Check capabilities.
	andb	$0x99, %al
	cmpb	$0x99, %al
	jnz	_setbad				# Doh! No linear frame buffer.

	subb	$VIDEO_FIRST_VESA>>8, %bh
	orw	$0x4000, %bx			# Use linear frame buffer
	movw	$0x4f02, %ax			# VESA BIOS mode set call
	int	$0x10
	cmpw	$0x004f, %ax			# AL=4f if implemented
	jnz	_setbad				# AH=0 if OK

	movb	$1, graphic_mode		# flag graphic mode
	movb	$0, do_restore			# no screen restore
	stc
	ret

_setbad:	jmp	setbad          	# Ugly...

# Recalculate vertical display end registers -- this fixes various
# inconsistencies of extended modes on many adapters. Called when
# the VIDEO_RECALC flag is set in the mode ID.

setrec:	subb	$VIDEO_RECALC>>8, %ah		# Set the base mode
	call	mode_set
	jnc	rct3

	movw	%gs:(0x485), %ax		# Font size in pixels
	movb	%gs:(0x484), %bl		# Number of rows
	incb	%bl
	mulb	%bl				# Number of visible
	decw	%ax				# scan lines - 1
	movw	$0x3d4, %dx
	movw	%ax, %bx
	movb	$0x12, %al			# Lower 8 bits
	movb	%bl, %ah
	outw	%ax, %dx
	movb	$0x07, %al		# Bits 8 and 9 in the overflow register
	call	inidx
	xchgb	%al, %ah
	andb	$0xbd, %ah
	shrb	%bh
	jnc	rct1
	orb	$0x02, %ah
rct1:	shrb	%bh
	jnc	rct2
	orb	$0x40, %ah
rct2:	movb	$0x07, %al
	outw	%ax, %dx
	stc
rct3:	ret

# Table of routines for setting of the special modes.
spec_inits:
	.word	set_80x25
	.word	set_8pixel
	.word	set_80x43
	.word	set_80x28
	.word	set_current
	.word	set_80x30
	.word	set_80x34
	.word	set_80x60
	.word	set_gfx

# Set the 80x25 mode. If already set, do nothing.
set_80x25:
	movw	$0x5019, force_size		# Override possibly broken BIOS
use_80x25:
#ifdef CONFIG_VIDEO_400_HACK
	movw	$0x1202, %ax			# Force 400 scan lines
	movb	$0x30, %bl
	int	$0x10
#else
	movb	$0x0f, %ah			# Get current mode ID
	int	$0x10
	cmpw	$0x5007, %ax	# Mode 7 (80x25 mono) is the only one available
	jz	st80		# on CGA/MDA/HGA and is also available on EGAM

	cmpw	$0x5003, %ax	# Unknown mode, force 80x25 color
	jnz	force3

st80:	cmpb	$0, adapter	# CGA/MDA/HGA => mode 3/7 is always 80x25
	jz	set80

	movb	%gs:(0x0484), %al	# This is EGA+ -- beware of 80x50 etc.
	orb	%al, %al		# Some buggy BIOS'es set 0 rows
	jz	set80
	
	cmpb	$24, %al		# It's hopefully correct
	jz	set80
#endif /* CONFIG_VIDEO_400_HACK */
force3:	DO_STORE
	movw	$0x0003, %ax			# Forced set
	int	$0x10
set80:	stc
	ret

# Set the 80x50/80x43 8-pixel mode. Simple BIOS calls.
set_8pixel:
	DO_STORE
	call	use_80x25			# The base is 80x25
set_8pt:
	movw	$0x1112, %ax			# Use 8x8 font
	xorb	%bl, %bl
	int	$0x10
	movw	$0x1200, %ax			# Use alternate print screen
	movb	$0x20, %bl
	int	$0x10
	movw	$0x1201, %ax			# Turn off cursor emulation
	movb	$0x34, %bl
	int	$0x10
	movb	$0x01, %ah			# Define cursor scan lines 6-7
	movw	$0x0607, %cx
	int	$0x10
set_current:
	stc
	ret

# Set the 80x28 mode. This mode works on all VGA's, because it's a standard
# 80x25 mode with 14-point fonts instead of 16-point.
set_80x28:
	DO_STORE
	call	use_80x25			# The base is 80x25
set14:	movw	$0x1111, %ax			# Use 9x14 font
	xorb	%bl, %bl
	int	$0x10
	movb	$0x01, %ah			# Define cursor scan lines 11-12
	movw	$0x0b0c, %cx
	int	$0x10
	stc
	ret

# Set the 80x43 mode. This mode is works on all VGA's.
# It's a 350-scanline mode with 8-pixel font.
set_80x43:
	DO_STORE
	movw	$0x1201, %ax			# Set 350 scans
	movb	$0x30, %bl
	int	$0x10
	movw	$0x0003, %ax			# Reset video mode
	int	$0x10
	jmp	set_8pt				# Use 8-pixel font

# Set the 80x30 mode (all VGA's). 480 scanlines, 16-pixel font.
set_80x30:
	call	use_80x25			# Start with real 80x25
	DO_STORE
	movw	$0x3cc, %dx			# Get CRTC port
	inb	%dx, %al
	movb	$0xd4, %dl
	rorb	%al				# Mono or color?
	jc	set48a

	movb	$0xb4, %dl
set48a:	movw	$0x0c11, %ax		# Vertical sync end (also unlocks CR0-7)
 	call	outidx
	movw	$0x0b06, %ax			# Vertical total
 	call	outidx
	movw	$0x3e07, %ax			# (Vertical) overflow
 	call	outidx
	movw	$0xea10, %ax			# Vertical sync start
 	call	outidx
	movw	$0xdf12, %ax			# Vertical display end
	call	outidx
	movw	$0xe715, %ax			# Vertical blank start
 	call	outidx
	movw	$0x0416, %ax			# Vertical blank end
 	call	outidx
	pushw	%dx
	movb	$0xcc, %dl			# Misc output register (read)
 	inb	%dx, %al
 	movb	$0xc2, %dl			# (write)
 	andb	$0x0d, %al	# Preserve clock select bits and color bit
 	orb	$0xe2, %al			# Set correct sync polarity
 	outb	%al, %dx
	popw	%dx
	movw	$0x501e, force_size
	stc					# That's all.
	ret

# Set the 80x34 mode (all VGA's). 480 scans, 14-pixel font.
set_80x34:
	call	set_80x30			# Set 480 scans
	call	set14				# And 14-pt font
	movw	$0xdb12, %ax			# VGA vertical display end
	movw	$0x5022, force_size
setvde:	call	outidx
	stc
	ret

# Set the 80x60 mode (all VGA's). 480 scans, 8-pixel font.
set_80x60:
	call	set_80x30			# Set 480 scans
	call	set_8pt				# And 8-pt font
	movw	$0xdf12, %ax			# VGA vertical display end
	movw	$0x503c, force_size
	jmp	setvde

# Special hack for ThinkPad graphics
set_gfx:
#ifdef CONFIG_VIDEO_GFX_HACK
	movw	$VIDEO_GFX_BIOS_AX, %ax
	movw	$VIDEO_GFX_BIOS_BX, %bx
	int	$0x10
	movw	$VIDEO_GFX_DUMMY_RESOLUTION, force_size
	stc
#endif
	ret

#ifdef CONFIG_VIDEO_RETAIN

# Store screen contents to temporary buffer.
store_screen:
	cmpb	$0, do_restore			# Already stored?
	jnz	stsr

	testb	$CAN_USE_HEAP, loadflags	# Have we space for storing?
	jz	stsr
	
	pushw	%ax
	pushw	%bx
	pushw	force_size			# Don't force specific size
	movw	$0, force_size
	call	mode_params			# Obtain params of current mode
	popw	force_size
	movb	%fs:(PARAM_VIDEO_LINES), %ah
	movb	%fs:(PARAM_VIDEO_COLS), %al
	movw	%ax, %bx			# BX=dimensions
	mulb	%ah
	movw	%ax, %cx			# CX=number of characters
	addw	%ax, %ax			# Calculate image size
	addw	$modelist+1024+4, %ax
	cmpw	heap_end_ptr, %ax
	jnc	sts1				# Unfortunately, out of memory

	movw	%fs:(PARAM_CURSOR_POS), %ax	# Store mode params
	leaw	modelist+1024, %di
	stosw
	movw	%bx, %ax
	stosw
	pushw	%ds				# Store the screen
	movw	video_segment, %ds
	xorw	%si, %si
	rep
	movsw
	popw	%ds
	incb	do_restore			# Screen will be restored later
sts1:	popw	%bx
	popw	%ax
stsr:	ret

# Restore screen contents from temporary buffer.
restore_screen:
	cmpb	$0, do_restore			# Has the screen been stored?
	jz	res1

	call	mode_params			# Get parameters of current mode
	movb	%fs:(PARAM_VIDEO_LINES), %cl
	movb	%fs:(PARAM_VIDEO_COLS), %ch
	leaw	modelist+1024, %si		# Screen buffer
	lodsw					# Set cursor position
	movw	%ax, %dx
	cmpb	%cl, %dh
	jc	res2
	
	movb	%cl, %dh
	decb	%dh
res2:	cmpb	%ch, %dl
	jc	res3
	
	movb	%ch, %dl
	decb	%dl
res3:	movb	$0x02, %ah
	movb	$0x00, %bh
	int	$0x10
	lodsw					# Display size
	movb	%ah, %dl			# DL=number of lines
	movb	$0, %ah				# BX=phys. length of orig. line
	movw	%ax, %bx
	cmpb	%cl, %dl			# Too many?
	jc	res4

	pushw	%ax
	movb	%dl, %al
	subb	%cl, %al
	mulb	%bl
	addw	%ax, %si
	addw	%ax, %si
	popw	%ax
	movb	%cl, %dl
res4:	cmpb	%ch, %al			# Too wide?
	jc	res5
	
	movb	%ch, %al			# AX=width of src. line
res5:	movb	$0, %cl
	xchgb	%ch, %cl
	movw	%cx, %bp			# BP=width of dest. line
	pushw	%es
	movw	video_segment, %es
	xorw	%di, %di			# Move the data
	addw	%bx, %bx			# Convert BX and BP to _bytes_
	addw	%bp, %bp
res6:	pushw	%si
	pushw	%di
	movw	%ax, %cx
	rep
	movsw
	popw	%di
	popw	%si
	addw	%bp, %di
	addw	%bx, %si
	decb	%dl
	jnz	res6
	
	popw	%es				# Done
res1:	ret
#endif /* CONFIG_VIDEO_RETAIN */

# Write to indexed VGA register (AL=index, AH=data, DX=index reg. port)
outidx:	outb	%al, %dx
	pushw	%ax
	movb	%ah, %al
	incw	%dx
	outb	%al, %dx
	decw	%dx
	popw	%ax
	ret

# Build the table of video modes (stored after the setup.S code at the
# `modelist' label. Each video mode record looks like:
#	.word	MODE-ID		(our special mode ID (see above))
#	.byte	rows		(number of rows)
#	.byte	columns		(number of columns)
# Returns address of the end of the table in DI, the end is marked
# with a ASK_VGA ID.
mode_table:
	movw	mt_end, %di			# Already filled?
	orw	%di, %di
	jnz	mtab1x
	
	leaw	modelist, %di			# Store standard modes:
	movl	$VIDEO_80x25 + 0x50190000, %eax	# The 80x25 mode (ALL)
	stosl
	movb	adapter, %al			# CGA/MDA/HGA -- no more modes
	orb	%al, %al
	jz	mtabe
	
	decb	%al
	jnz	mtabv
	
	movl	$VIDEO_8POINT + 0x502b0000, %eax	# The 80x43 EGA mode
	stosl
	jmp	mtabe

mtab1x:	jmp	mtab1

mtabv:	leaw	vga_modes, %si			# All modes for std VGA
	movw	$vga_modes_end-vga_modes, %cx
	rep	# I'm unable to use movsw as I don't know how to store a half
	movsb	# of the expression above to cx without using explicit shr.

	cmpb	$0, scanning			# Mode scan requested?
	jz	mscan1
	
	call	mode_scan
mscan1:

#ifdef CONFIG_VIDEO_LOCAL
	call	local_modes
#endif /* CONFIG_VIDEO_LOCAL */

#ifdef CONFIG_VIDEO_VESA
	call	vesa_modes			# Detect VESA VGA modes
#endif /* CONFIG_VIDEO_VESA */

#ifdef CONFIG_VIDEO_SVGA
	cmpb	$0, scanning			# Bypass when scanning
	jnz	mscan2
	
	call	svga_modes			# Detect SVGA cards & modes
mscan2:
#endif /* CONFIG_VIDEO_SVGA */

mtabe:

#ifdef CONFIG_VIDEO_COMPACT
	leaw	modelist, %si
	movw	%di, %dx
	movw	%si, %di
cmt1:	cmpw	%dx, %si			# Scan all modes
	jz	cmt2

	leaw	modelist, %bx			# Find in previous entries
	movw	2(%si), %cx
cmt3:	cmpw	%bx, %si
	jz	cmt4

	cmpw	2(%bx), %cx			# Found => don't copy this entry
	jz	cmt5

	addw	$4, %bx
	jmp	cmt3

cmt4:	movsl					# Copy entry
	jmp	cmt1

cmt5:	addw	$4, %si				# Skip entry
	jmp	cmt1

cmt2:
#endif	/* CONFIG_VIDEO_COMPACT */

	movw	$ASK_VGA, (%di)			# End marker
	movw	%di, mt_end
mtab1:	leaw	modelist, %si			# SI=mode list, DI=list end
ret0:	ret

# Modes usable on all standard VGAs
vga_modes:
	.word	VIDEO_8POINT
	.word	0x5032				# 80x50
	.word	VIDEO_80x43
	.word	0x502b				# 80x43
	.word	VIDEO_80x28
	.word	0x501c				# 80x28
	.word	VIDEO_80x30
	.word	0x501e				# 80x30
	.word	VIDEO_80x34
	.word	0x5022				# 80x34
	.word	VIDEO_80x60
	.word	0x503c				# 80x60
#ifdef CONFIG_VIDEO_GFX_HACK
	.word	VIDEO_GFX_HACK
	.word	VIDEO_GFX_DUMMY_RESOLUTION
#endif

vga_modes_end:
# Detect VESA modes.

#ifdef CONFIG_VIDEO_VESA
vesa_modes:
	cmpb	$2, adapter			# VGA only
	jnz	ret0

	movw	%di, %bp			# BP=original mode table end
	addw	$0x200, %di			# Buffer space
	movw	$0x4f00, %ax			# VESA Get card info call
	int	$0x10
	movw	%bp, %di
	cmpw	$0x004f, %ax			# Successful?
	jnz	ret0
	
	cmpw	$0x4556, 0x200(%di)
	jnz	ret0
	
	cmpw	$0x4153, 0x202(%di)
	jnz	ret0
	
	movw	$vesa_name, card_name		# Set name to "VESA VGA"
	pushw	%gs
	lgsw	0x20e(%di), %si			# GS:SI=mode list
	movw	$128, %cx			# Iteration limit
vesa1:
# gas version 2.9.1, using BFD version 2.9.1.0.23 buggers the next inst.
# XXX:	lodsw	%gs:(%si), %ax			# Get next mode in the list
	gs; lodsw
	cmpw	$0xffff, %ax			# End of the table?
	jz	vesar
	
	cmpw	$0x0080, %ax			# Check validity of mode ID
	jc	vesa2
	
	orb	%ah, %ah		# Valid IDs: 0x0000-0x007f/0x0100-0x07ff
	jz	vesan			# Certain BIOSes report 0x80-0xff!

	cmpw	$0x0800, %ax
	jnc	vesae

vesa2:	pushw	%cx
	movw	%ax, %cx			# Get mode information structure
	movw	$0x4f01, %ax
	int	$0x10
	movw	%cx, %bx			# BX=mode number
	addb	$VIDEO_FIRST_VESA>>8, %bh
	popw	%cx
	cmpw	$0x004f, %ax
	jnz	vesan			# Don't report errors (buggy BIOSES)

	movb	(%di), %al			# Check capabilities. We require
	andb	$0x19, %al			# a color text mode.
	cmpb	$0x09, %al
	jnz	vesan
	
	cmpw	$0xb800, 8(%di)		# Standard video memory address required
	jnz	vesan

	testb	$2, (%di)			# Mode characteristics supplied?
	movw	%bx, (%di)			# Store mode number
	jz	vesa3
	
	xorw	%dx, %dx
	movw	0x12(%di), %bx			# Width
	orb	%bh, %bh
	jnz	vesan
	
	movb	%bl, 0x3(%di)
	movw	0x14(%di), %ax			# Height
	orb	%ah, %ah
	jnz	vesan
	
	movb	%al, 2(%di)
	mulb	%bl
	cmpw	$8193, %ax		# Small enough for Linux console driver?
	jnc	vesan

	jmp	vesaok

vesa3:	subw	$0x8108, %bx	# This mode has no detailed info specified,
	jc	vesan		# so it must be a standard VESA mode.

	cmpw	$5, %bx
	jnc	vesan

	movw	vesa_text_mode_table(%bx), %ax
	movw	%ax, 2(%di)
vesaok:	addw	$4, %di				# The mode is valid. Store it.
vesan:	loop	vesa1			# Next mode. Limit exceeded => error
vesae:	leaw	vesaer, %si
	call	prtstr
	movw	%bp, %di			# Discard already found modes.
vesar:	popw	%gs
	ret

# Dimensions of standard VESA text modes
vesa_text_mode_table:
	.byte	60, 80				# 0108
	.byte	25, 132				# 0109
	.byte	43, 132				# 010A
	.byte	50, 132				# 010B
	.byte	60, 132				# 010C
#endif	/* CONFIG_VIDEO_VESA */

# Scan for video modes. A bit dirty, but should work.
mode_scan:
	movw	$0x0100, %cx			# Start with mode 0
scm1:	movb	$0, %ah				# Test the mode
	movb	%cl, %al
	int	$0x10
	movb	$0x0f, %ah
	int	$0x10
	cmpb	%cl, %al
	jnz	scm2				# Mode not set

	movw	$0x3c0, %dx			# Test if it's a text mode
	movb	$0x10, %al			# Mode bits
	call	inidx
	andb	$0x03, %al
	jnz	scm2
	
	movb	$0xce, %dl			# Another set of mode bits
	movb	$0x06, %al
	call	inidx
	shrb	%al
	jc	scm2
	
	movb	$0xd4, %dl			# Cursor location
	movb	$0x0f, %al
	call	inidx
	orb	%al, %al
	jnz	scm2
	
	movw	%cx, %ax			# Ok, store the mode
	stosw
	movb	%gs:(0x484), %al		# Number of rows
	incb	%al
	stosb
	movw	%gs:(0x44a), %ax		# Number of columns
	stosb
scm2:	incb	%cl
	jns	scm1
	
	movw	$0x0003, %ax			# Return back to mode 3
	int	$0x10
	ret

tstidx:	outw	%ax, %dx			# OUT DX,AX and inidx
inidx:	outb	%al, %dx			# Read from indexed VGA register
	incw	%dx			# AL=index, DX=index reg port -> AL=data
	inb	%dx, %al
	decw	%dx
	ret

# Try to detect type of SVGA card and supply (usually approximate) video
# mode table for it.

#ifdef CONFIG_VIDEO_SVGA
svga_modes:
	leaw	svga_table, %si			# Test all known SVGA adapters
dosvga:	lodsw
	movw	%ax, %bp			# Default mode table
	orw	%ax, %ax
	jz	didsv1

	lodsw					# Pointer to test routine
	pushw	%si
	pushw	%di
	pushw	%es
	movw	$0xc000, %bx
	movw	%bx, %es
	call	*%ax				# Call test routine
	popw	%es
	popw	%di
	popw	%si
	orw	%bp, %bp
	jz	dosvga
	
	movw	%bp, %si			# Found, copy the modes
	movb	svga_prefix, %ah
cpsvga:	lodsb
	orb	%al, %al
	jz	didsv
	
	stosw
	movsw
	jmp	cpsvga

didsv:	movw	%si, card_name			# Store pointer to card name
didsv1:	ret

# Table of all known SVGA cards. For each card, we store a pointer to
# a table of video modes supported by the card and a pointer to a routine
# used for testing of presence of the card. The video mode table is always
# followed by the name of the card or the chipset.
svga_table:
	.word	ati_md, ati_test
	.word	oak_md, oak_test
	.word	paradise_md, paradise_test
	.word	realtek_md, realtek_test
	.word	s3_md, s3_test
	.word	chips_md, chips_test
	.word	video7_md, video7_test
	.word	cirrus5_md, cirrus5_test
	.word	cirrus6_md, cirrus6_test
	.word	cirrus1_md, cirrus1_test
	.word	ahead_md, ahead_test
	.word	everex_md, everex_test
	.word	genoa_md, genoa_test
	.word	trident_md, trident_test
	.word	tseng_md, tseng_test
	.word	0

# Test routines and mode tables:

# S3 - The test algorithm was taken from the SuperProbe package
# for XFree86 1.2.1. Report bugs to Christoph.Niemann@linux.org
s3_test:
	movw	$0x0f35, %cx	# we store some constants in cl/ch
	movw	$0x03d4, %dx
	movb	$0x38, %al
	call	inidx
	movb	%al, %bh	# store current CRT-register 0x38
	movw	$0x0038, %ax
	call	outidx		# disable writing to special regs
	movb	%cl, %al	# check whether we can write special reg 0x35
	call	inidx
	movb	%al, %bl	# save the current value of CRT reg 0x35
	andb	$0xf0, %al	# clear bits 0-3
	movb	%al, %ah
	movb	%cl, %al	# and write it to CRT reg 0x35
	call	outidx
	call	inidx		# now read it back
	andb	%ch, %al	# clear the upper 4 bits
	jz	s3_2		# the first test failed. But we have a

	movb	%bl, %ah	# second chance
	movb	%cl, %al
	call	outidx
	jmp	s3_1		# do the other tests

s3_2:	movw	%cx, %ax	# load ah with 0xf and al with 0x35
	orb	%bl, %ah	# set the upper 4 bits of ah with the orig value
	call	outidx		# write ...
	call	inidx		# ... and reread 
	andb	%cl, %al	# turn off the upper 4 bits
	pushw	%ax
	movb	%bl, %ah	# restore old value in register 0x35
	movb	%cl, %al
	call	outidx
	popw	%ax
	cmpb	%ch, %al	# setting lower 4 bits was successful => bad
	je	no_s3		# writing is allowed => this is not an S3

s3_1:	movw	$0x4838, %ax	# allow writing to special regs by putting
	call	outidx		# magic number into CRT-register 0x38
	movb	%cl, %al	# check whether we can write special reg 0x35
	call	inidx
	movb	%al, %bl
	andb	$0xf0, %al
	movb	%al, %ah
	movb	%cl, %al
	call	outidx
	call	inidx
	andb	%ch, %al
	jnz	no_s3		# no, we can't write => no S3

	movw	%cx, %ax
	orb	%bl, %ah
	call	outidx
	call	inidx
	andb	%ch, %al
	pushw	%ax
	movb	%bl, %ah	# restore old value in register 0x35
	movb	%cl, %al
	call	outidx
	popw	%ax
	cmpb	%ch, %al
	jne	no_s31		# writing not possible => no S3
	movb	$0x30, %al
	call	inidx		# now get the S3 id ...
	leaw	idS3, %di
	movw	$0x10, %cx
	repne
	scasb
	je	no_s31

	movb	%bh, %ah
	movb	$0x38, %al
	jmp	s3rest

no_s3:	movb	$0x35, %al	# restore CRT register 0x35
	movb	%bl, %ah
	call	outidx
no_s31:	xorw	%bp, %bp	# Detection failed
s3rest:	movb	%bh, %ah
	movb	$0x38, %al	# restore old value of CRT register 0x38
	jmp	outidx

idS3:	.byte	0x81, 0x82, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95
	.byte	0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa8, 0xb0

s3_md:	.byte	0x54, 0x2b, 0x84
	.byte	0x55, 0x19, 0x84
	.byte	0
	.ascii	"S3"
	.byte	0

# ATI cards.
ati_test:
	leaw 	idati, %si
	movw	$0x31, %di
	movw	$0x09, %cx
	repe
	cmpsb
	je	atiok

	xorw	%bp, %bp
atiok:	ret

idati:	.ascii	"761295520"

ati_md:	.byte	0x23, 0x19, 0x84
	.byte	0x33, 0x2c, 0x84
	.byte	0x22, 0x1e, 0x64
	.byte	0x21, 0x19, 0x64
	.byte	0x58, 0x21, 0x50
	.byte	0x5b, 0x1e, 0x50
	.byte	0
	.ascii	"ATI"
	.byte	0

# AHEAD
ahead_test:
	movw	$0x200f, %ax
	movw	$0x3ce, %dx
	outw	%ax, %dx
	incw	%dx
	inb	%dx, %al
	cmpb	$0x20, %al
	je	isahed

	cmpb	$0x21, %al
	je	isahed
	
	xorw	%bp, %bp
isahed:	ret

ahead_md:
	.byte	0x22, 0x2c, 0x84
	.byte	0x23, 0x19, 0x84
	.byte	0x24, 0x1c, 0x84
	.byte	0x2f, 0x32, 0xa0
	.byte	0x32, 0x22, 0x50
	.byte	0x34, 0x42, 0x50
	.byte	0
	.ascii	"Ahead"
	.byte	0

# Chips & Tech.
chips_test:
	movw	$0x3c3, %dx
	inb	%dx, %al
	orb	$0x10, %al
	outb	%al, %dx
	movw	$0x104, %dx
	inb	%dx, %al
	movb	%al, %bl
	movw	$0x3c3, %dx
	inb	%dx, %al
	andb	$0xef, %al
	outb	%al, %dx
	cmpb	$0xa5, %bl
	je	cantok
	
	xorw	%bp, %bp
cantok:	ret

chips_md:
	.byte	0x60, 0x19, 0x84
	.byte	0x61, 0x32, 0x84
	.byte	0
	.ascii	"Chips & Technologies"
	.byte	0

# Cirrus Logic 5X0
cirrus1_test:
	movw	$0x3d4, %dx
	movb	$0x0c, %al
	outb	%al, %dx
	incw	%dx
	inb	%dx, %al
	movb	%al, %bl
	xorb	%al, %al
	outb	%al, %dx
	decw	%dx
	movb	$0x1f, %al
	outb	%al, %dx
	incw	%dx
	inb	%dx, %al
	movb	%al, %bh
	xorb	%ah, %ah
	shlb	$4, %al
	movw	%ax, %cx
	movb	%bh, %al
	shrb	$4, %al
	addw	%ax, %cx
	shlw	$8, %cx
	addw	$6, %cx
	movw	%cx, %ax
	movw	$0x3c4, %dx
	outw	%ax, %dx
	incw	%dx
	inb	%dx, %al
	andb	%al, %al
	jnz	nocirr
	
	movb	%bh, %al
	outb	%al, %dx
	inb	%dx, %al
	cmpb	$0x01, %al
	je	iscirr

nocirr:	xorw	%bp, %bp
iscirr: movw	$0x3d4, %dx
	movb	%bl, %al
	xorb	%ah, %ah
	shlw	$8, %ax
	addw	$0x0c, %ax
	outw	%ax, %dx
	ret

cirrus1_md:
	.byte	0x1f, 0x19, 0x84
	.byte	0x20, 0x2c, 0x84
	.byte	0x22, 0x1e, 0x84
	.byte	0x31, 0x25, 0x64
	.byte	0
	.ascii	"Cirrus Logic 5X0"
	.byte	0

# Cirrus Logic 54XX
cirrus5_test:
	movw	$0x3c4, %dx
	movb	$6, %al
	call	inidx
	movb	%al, %bl			# BL=backup
	movw	$6, %ax
	call	tstidx
	cmpb	$0x0f, %al
	jne	c5fail
	
	movw	$0x1206, %ax
	call	tstidx
	cmpb	$0x12, %al
	jne	c5fail
	
	movb	$0x1e, %al
	call	inidx
	movb	%al, %bh
	movb	%bh, %ah
	andb	$0xc0, %ah
	movb	$0x1e, %al
	call	tstidx
	andb	$0x3f, %al
	jne	c5xx
	
	movb	$0x1e, %al
	movb	%bh, %ah
	orb	$0x3f, %ah
	call	tstidx
	xorb	$0x3f, %al
	andb	$0x3f, %al
c5xx:	pushf
	movb	$0x1e, %al
	movb	%bh, %ah
	outw	%ax, %dx
	popf
	je	c5done

c5fail:	xorw	%bp, %bp
c5done:	movb	$6, %al
	movb	%bl, %ah
	outw	%ax, %dx
	ret

cirrus5_md:
	.byte	0x14, 0x19, 0x84
	.byte	0x54, 0x2b, 0x84
	.byte	0
	.ascii	"Cirrus Logic 54XX"
	.byte	0

# Cirrus Logic 64XX -- no known extra modes, but must be identified, because
# it's misidentified by the Ahead test.
cirrus6_test:
	movw	$0x3ce, %dx
	movb	$0x0a, %al
	call	inidx
	movb	%al, %bl	# BL=backup
	movw	$0xce0a, %ax
	call	tstidx
	orb	%al, %al
	jne	c2fail
	
	movw	$0xec0a, %ax
	call	tstidx
	cmpb	$0x01, %al
	jne	c2fail
	
	movb	$0xaa, %al
	call	inidx		# 4X, 5X, 7X and 8X are valid 64XX chip ID's. 
	shrb	$4, %al
	subb	$4, %al
	jz	c6done
	
	decb	%al
	jz	c6done
	
	subb	$2, %al
	jz	c6done
	
	decb	%al
	jz	c6done
	
c2fail:	xorw	%bp, %bp
c6done:	movb	$0x0a, %al
	movb	%bl, %ah
	outw	%ax, %dx
	ret

cirrus6_md:
	.byte	0
	.ascii	"Cirrus Logic 64XX"
	.byte	0

# Everex / Trident
everex_test:
	movw	$0x7000, %ax
	xorw	%bx, %bx
	int	$0x10
	cmpb	$0x70, %al
	jne	noevrx
	
	shrw	$4, %dx
	cmpw	$0x678, %dx
	je	evtrid
	
	cmpw	$0x236, %dx
	jne	evrxok

evtrid:	leaw	trident_md, %bp
evrxok:	ret

noevrx:	xorw	%bp, %bp
	ret

everex_md:
	.byte	0x03, 0x22, 0x50
	.byte	0x04, 0x3c, 0x50
	.byte	0x07, 0x2b, 0x64
	.byte	0x08, 0x4b, 0x64
	.byte	0x0a, 0x19, 0x84
	.byte	0x0b, 0x2c, 0x84
	.byte	0x16, 0x1e, 0x50
	.byte	0x18, 0x1b, 0x64
	.byte	0x21, 0x40, 0xa0
	.byte	0x40, 0x1e, 0x84
	.byte	0
	.ascii	"Everex/Trident"
	.byte	0

# Genoa.
genoa_test:
	leaw	idgenoa, %si			# Check Genoa 'clues'
	xorw	%ax, %ax
	movb	%es:(0x37), %al
	movw	%ax, %di
	movw	$0x04, %cx
	decw	%si
	decw	%di
l1:	incw	%si
	incw	%di
	movb	(%si), %al
	testb	%al, %al
	jz	l2

	cmpb	%es:(%di), %al
l2:	loope 	l1
	orw	%cx, %cx
	je	isgen
	
	xorw	%bp, %bp
isgen:	ret

idgenoa: .byte	0x77, 0x00, 0x99, 0x66

genoa_md:
	.byte	0x58, 0x20, 0x50
	.byte	0x5a, 0x2a, 0x64
	.byte	0x60, 0x19, 0x84
	.byte	0x61, 0x1d, 0x84
	.byte	0x62, 0x20, 0x84
	.byte	0x63, 0x2c, 0x84
	.byte	0x64, 0x3c, 0x84
	.byte	0x6b, 0x4f, 0x64
	.byte	0x72, 0x3c, 0x50
	.byte	0x74, 0x42, 0x50
	.byte	0x78, 0x4b, 0x64
	.byte	0
	.ascii	"Genoa"
	.byte	0

# OAK
oak_test:
	leaw	idoakvga, %si
	movw	$0x08, %di
	movw	$0x08, %cx
	repe
	cmpsb
	je	isoak
	
	xorw	%bp, %bp
isoak:	ret

idoakvga: .ascii  "OAK VGA "

oak_md: .byte	0x4e, 0x3c, 0x50
	.byte	0x4f, 0x3c, 0x84
	.byte	0x50, 0x19, 0x84
	.byte	0x51, 0x2b, 0x84
	.byte	0
	.ascii	"OAK"
	.byte	0

# WD Paradise.
paradise_test:
	leaw	idparadise, %si
	movw	$0x7d, %di
	movw	$0x04, %cx
	repe
	cmpsb
	je	ispara
	
	xorw	%bp, %bp
ispara:	ret

idparadise:	.ascii	"VGA="

paradise_md:
	.byte	0x41, 0x22, 0x50
	.byte	0x47, 0x1c, 0x84
	.byte	0x55, 0x19, 0x84
	.byte	0x54, 0x2c, 0x84
	.byte	0
	.ascii	"Paradise"
	.byte	0

# Trident.
trident_test:
	movw	$0x3c4, %dx
	movb	$0x0e, %al
	outb	%al, %dx
	incw	%dx
	inb	%dx, %al
	xchgb	%al, %ah
	xorb	%al, %al
	outb	%al, %dx
	inb	%dx, %al
	xchgb	%ah, %al
	movb	%al, %bl	# Strange thing ... in the book this wasn't
	andb	$0x02, %bl	# necessary but it worked on my card which
	jz	setb2		# is a trident. Without it the screen goes
				# blurred ...
	andb	$0xfd, %al
	jmp	clrb2		

setb2:	orb	$0x02, %al	
clrb2:	outb	%al, %dx
	andb	$0x0f, %ah
	cmpb	$0x02, %ah
	je	istrid

	xorw	%bp, %bp
istrid:	ret

trident_md:
	.byte	0x50, 0x1e, 0x50
	.byte	0x51, 0x2b, 0x50
	.byte	0x52, 0x3c, 0x50
	.byte	0x57, 0x19, 0x84
	.byte	0x58, 0x1e, 0x84
	.byte	0x59, 0x2b, 0x84
	.byte	0x5a, 0x3c, 0x84
	.byte	0
	.ascii	"Trident"
	.byte	0

# Tseng.
tseng_test:
	movw	$0x3cd, %dx
	inb	%dx, %al	# Could things be this simple ! :-)
	movb	%al, %bl
	movb	$0x55, %al
	outb	%al, %dx
	inb	%dx, %al
	movb	%al, %ah
	movb	%bl, %al
	outb	%al, %dx
	cmpb	$0x55, %ah
 	je	istsen

isnot:	xorw	%bp, %bp
istsen:	ret

tseng_md:
	.byte	0x26, 0x3c, 0x50
	.byte	0x2a, 0x28, 0x64
	.byte	0x23, 0x19, 0x84
	.byte	0x24, 0x1c, 0x84
	.byte	0x22, 0x2c, 0x84
	.byte	0x21, 0x3c, 0x84
	.byte	0
	.ascii	"Tseng"
	.byte	0

# Video7.
video7_test:
	movw	$0x3cc, %dx
	inb	%dx, %al
	movw	$0x3b4, %dx
	andb	$0x01, %al
	jz	even7

	movw	$0x3d4, %dx
even7:	movb	$0x0c, %al
	outb	%al, %dx
	incw	%dx
	inb	%dx, %al
	movb	%al, %bl
	movb	$0x55, %al
	outb	%al, %dx
	inb	%dx, %al
	decw	%dx
	movb	$0x1f, %al
	outb	%al, %dx
	incw	%dx
	inb	%dx, %al
	movb	%al, %bh
	decw	%dx
	movb	$0x0c, %al
	outb	%al, %dx
	incw	%dx
	movb	%bl, %al
	outb	%al, %dx
	movb	$0x55, %al
	xorb	$0xea, %al
	cmpb	%bh, %al
	jne	isnot
	
	movb	$VIDEO_FIRST_V7>>8, svga_prefix # Use special mode switching
	ret

video7_md:
	.byte	0x40, 0x2b, 0x50
	.byte	0x43, 0x3c, 0x50
	.byte	0x44, 0x3c, 0x64
	.byte	0x41, 0x19, 0x84
	.byte	0x42, 0x2c, 0x84
	.byte	0x45, 0x1c, 0x84
	.byte	0
	.ascii	"Video 7"
	.byte	0

# Realtek VGA
realtek_test:
	leaw	idrtvga, %si
	movw	$0x45, %di
	movw	$0x0b, %cx
	repe
	cmpsb
	je	isrt
	
	xorw	%bp, %bp
isrt:	ret

idrtvga:	.ascii	"REALTEK VGA"

realtek_md:
	.byte	0x1a, 0x3c, 0x50
	.byte	0x1b, 0x19, 0x84
	.byte	0x1c, 0x1e, 0x84
	.byte	0x1d, 0x2b, 0x84
	.byte	0x1e, 0x3c, 0x84
	.byte	0
	.ascii	"REALTEK"
	.byte	0

#endif	/* CONFIG_VIDEO_SVGA */

# User-defined local mode table (VGA only)
#ifdef CONFIG_VIDEO_LOCAL
local_modes:
	leaw	local_mode_table, %si
locm1:	lodsw
	orw	%ax, %ax
	jz	locm2
	
	stosw
	movsw
	jmp	locm1

locm2:	ret

# This is the table of local video modes which can be supplied manually
# by the user. Each entry consists of mode ID (word) and dimensions
# (byte for column count and another byte for row count). These modes
# are placed before all SVGA and VESA modes and override them if table
# compacting is enabled. The table must end with a zero word followed
# by NUL-terminated video adapter name.
local_mode_table:
	.word	0x0100				# Example: 40x25
	.byte	25,40
	.word	0
	.ascii	"Local"
	.byte	0
#endif	/* CONFIG_VIDEO_LOCAL */

# Read a key and return the ASCII code in al, scan code in ah
getkey:	xorb	%ah, %ah
	int	$0x16
	ret

# Read a key with a timeout of 30 seconds.
# The hardware clock is used to get the time.
getkt:	call	gettime
	addb	$30, %al			# Wait 30 seconds
	cmpb	$60, %al
	jl	lminute

	subb	$60, %al
lminute:
	movb	%al, %cl
again:	movb	$0x01, %ah
	int	$0x16
	jnz	getkey				# key pressed, so get it

	call	gettime
	cmpb	%cl, %al
	jne	again

	movb	$0x20, %al			# timeout, return `space'
	ret

# Flush the keyboard buffer
flush:	movb	$0x01, %ah
	int	$0x16
	jz	empty
	
	xorb	%ah, %ah
	int	$0x16
	jmp	flush

empty:	ret

# Print hexadecimal number.
prthw:	pushw	%ax
	movb	%ah, %al
	call	prthb
	popw	%ax
prthb:	pushw	%ax
	shrb	$4, %al
	call	prthn
	popw	%ax
	andb	$0x0f, %al
prthn:	cmpb	$0x0a, %al
	jc	prth1

	addb	$0x07, %al
prth1:	addb	$0x30, %al
	jmp	prtchr

# Print decimal number in al
prtdec:	pushw	%ax
	pushw	%cx
	xorb	%ah, %ah
	movb	$0x0a, %cl
	idivb	%cl
	cmpb	$0x09, %al
	jbe	lt100

	call	prtdec
	jmp	skip10

lt100:	addb	$0x30, %al
	call	prtchr
skip10:	movb	%ah, %al
	addb	$0x30, %al
	call	prtchr	
	popw	%cx
	popw	%ax
	ret

store_edid:
#ifdef CONFIG_FIRMWARE_EDID
	pushw	%es				# just save all registers
	pushw	%ax
	pushw	%bx
	pushw   %cx
	pushw	%dx
	pushw   %di

	pushw	%fs
	popw    %es

	movl	$0x13131313, %eax		# memset block with 0x13
	movw    $32, %cx
	movw	$0x140, %di
	cld
	rep
	stosl

	pushw   %es				# save ES
	xorw    %di, %di                        # Report Capability
	pushw   %di
	popw    %es                             # ES:DI must be 0:0
	movw	$0x4f15, %ax
	xorw	%bx, %bx
	xorw	%cx, %cx
	int	$0x10
	popw    %es                             # restore ES

	cmpb    $0x00, %ah                      # call successful
	jne     no_edid

	cmpb    $0x4f, %al                      # function supported
	jne     no_edid

	movw	$0x4f15, %ax                    # do VBE/DDC
	movw	$0x01, %bx
	movw	$0x00, %cx
	movw    $0x00, %dx
	movw	$0x140, %di
	int	$0x10

no_edid:
	popw	%di				# restore all registers
	popw	%dx
	popw	%cx
	popw	%bx
	popw	%ax
	popw	%es
#endif
	ret

# VIDEO_SELECT-only variables
mt_end:		.word	0	# End of video mode table if built
edit_buf:	.space	6	# Line editor buffer
card_name:	.word	0	# Pointer to adapter name
scanning:	.byte	0	# Performing mode scan
do_restore:	.byte	0	# Screen contents altered during mode change
svga_prefix:	.byte	VIDEO_FIRST_BIOS>>8	# Default prefix for BIOS modes
graphic_mode:	.byte	0	# Graphic mode with a linear frame buffer
dac_size:	.byte	6	# DAC bit depth

# Status messages
keymsg:		.ascii	"Press <RETURN> to see video modes available, "
		.ascii	"<SPACE> to continue or wait 30 secs"
		.byte	0x0d, 0x0a, 0

listhdr:	.byte	0x0d, 0x0a
		.ascii	"Mode:    COLSxROWS:"

crlft:		.byte	0x0d, 0x0a, 0

prompt:		.byte	0x0d, 0x0a
		.asciz	"Enter mode number or `scan': "

unknt:		.asciz	"Unknown mode ID. Try again."

badmdt:		.ascii	"You passed an undefined mode number."
		.byte	0x0d, 0x0a, 0

vesaer:		.ascii	"Error: Scanning of VESA modes failed. Please "
		.ascii	"report to <mj@ucw.cz>."
		.byte	0x0d, 0x0a, 0

old_name:	.asciz	"CGA/MDA/HGA"

ega_name:	.asciz	"EGA"

svga_name:	.ascii	" "

vga_name:	.asciz	"VGA"

vesa_name:	.asciz	"VESA"

name_bann:	.asciz	"Video adapter: "
#endif /* CONFIG_VIDEO_SELECT */

# Other variables:
adapter:	.byte	0	# Video adapter: 0=CGA/MDA/HGA,1=EGA,2=VGA
video_segment:	.word	0xb800	# Video memory segment
force_size:	.word	0	# Use this size instead of the one in BIOS vars