aboutsummaryrefslogtreecommitdiffstats
path: root/drivers/video/udlfb.c
blob: 2c8364e9b632dafec12912307e55393ba7dc2fcd (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
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
/*
 * udlfb.c -- Framebuffer driver for DisplayLink USB controller
 *
 * Copyright (C) 2009 Roberto De Ioris <roberto@unbit.it>
 * Copyright (C) 2009 Jaya Kumar <jayakumar.lkml@gmail.com>
 * Copyright (C) 2009 Bernie Thompson <bernie@plugable.com>
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License v2. See the file COPYING in the main directory of this archive for
 * more details.
 *
 * Layout is based on skeletonfb by James Simmons and Geert Uytterhoeven,
 * usb-skeleton by GregKH.
 *
 * Device-specific portions based on information from Displaylink, with work
 * from Florian Echtler, Henrik Bjerregaard Pedersen, and others.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/usb.h>
#include <linux/uaccess.h>
#include <linux/mm.h>
#include <linux/fb.h>
#include <linux/vmalloc.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <video/udlfb.h>
#include "edid.h"

static struct fb_fix_screeninfo dlfb_fix = {
	.id =           "udlfb",
	.type =         FB_TYPE_PACKED_PIXELS,
	.visual =       FB_VISUAL_TRUECOLOR,
	.xpanstep =     0,
	.ypanstep =     0,
	.ywrapstep =    0,
	.accel =        FB_ACCEL_NONE,
};

static const u32 udlfb_info_flags = FBINFO_DEFAULT | FBINFO_READS_FAST |
		FBINFO_VIRTFB |
		FBINFO_HWACCEL_IMAGEBLIT | FBINFO_HWACCEL_FILLRECT |
		FBINFO_HWACCEL_COPYAREA | FBINFO_MISC_ALWAYS_SETPAR;

/*
 * There are many DisplayLink-based products, all with unique PIDs. We are able
 * to support all volume ones (circa 2009) with a single driver, so we match
 * globally on VID. TODO: Probe() needs to detect when we might be running
 * "future" chips, and bail on those, so a compatible driver can match.
 */
static struct usb_device_id id_table[] = {
	{.idVendor = 0x17e9, .match_flags = USB_DEVICE_ID_MATCH_VENDOR,},
	{},
};
MODULE_DEVICE_TABLE(usb, id_table);

/* module options */
static int console;   /* Optionally allow fbcon to consume first framebuffer */
static int fb_defio;  /* Optionally enable experimental fb_defio mmap support */

/* dlfb keeps a list of urbs for efficient bulk transfers */
static void dlfb_urb_completion(struct urb *urb);
static struct urb *dlfb_get_urb(struct dlfb_data *dev);
static int dlfb_submit_urb(struct dlfb_data *dev, struct urb * urb, size_t len);
static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size);
static void dlfb_free_urb_list(struct dlfb_data *dev);

/*
 * All DisplayLink bulk operations start with 0xAF, followed by specific code
 * All operations are written to buffers which then later get sent to device
 */
static char *dlfb_set_register(char *buf, u8 reg, u8 val)
{
	*buf++ = 0xAF;
	*buf++ = 0x20;
	*buf++ = reg;
	*buf++ = val;
	return buf;
}

static char *dlfb_vidreg_lock(char *buf)
{
	return dlfb_set_register(buf, 0xFF, 0x00);
}

static char *dlfb_vidreg_unlock(char *buf)
{
	return dlfb_set_register(buf, 0xFF, 0xFF);
}

/*
 * On/Off for driving the DisplayLink framebuffer to the display
 *  0x00 H and V sync on
 *  0x01 H and V sync off (screen blank but powered)
 *  0x07 DPMS powerdown (requires modeset to come back)
 */
static char *dlfb_enable_hvsync(char *buf, bool enable)
{
	if (enable)
		return dlfb_set_register(buf, 0x1F, 0x00);
	else
		return dlfb_set_register(buf, 0x1F, 0x07);
}

static char *dlfb_set_color_depth(char *buf, u8 selection)
{
	return dlfb_set_register(buf, 0x00, selection);
}

static char *dlfb_set_base16bpp(char *wrptr, u32 base)
{
	/* the base pointer is 16 bits wide, 0x20 is hi byte. */
	wrptr = dlfb_set_register(wrptr, 0x20, base >> 16);
	wrptr = dlfb_set_register(wrptr, 0x21, base >> 8);
	return dlfb_set_register(wrptr, 0x22, base);
}

/*
 * DisplayLink HW has separate 16bpp and 8bpp framebuffers.
 * In 24bpp modes, the low 323 RGB bits go in the 8bpp framebuffer
 */
static char *dlfb_set_base8bpp(char *wrptr, u32 base)
{
	wrptr = dlfb_set_register(wrptr, 0x26, base >> 16);
	wrptr = dlfb_set_register(wrptr, 0x27, base >> 8);
	return dlfb_set_register(wrptr, 0x28, base);
}

static char *dlfb_set_register_16(char *wrptr, u8 reg, u16 value)
{
	wrptr = dlfb_set_register(wrptr, reg, value >> 8);
	return dlfb_set_register(wrptr, reg+1, value);
}

/*
 * This is kind of weird because the controller takes some
 * register values in a different byte order than other registers.
 */
static char *dlfb_set_register_16be(char *wrptr, u8 reg, u16 value)
{
	wrptr = dlfb_set_register(wrptr, reg, value);
	return dlfb_set_register(wrptr, reg+1, value >> 8);
}

/*
 * LFSR is linear feedback shift register. The reason we have this is
 * because the display controller needs to minimize the clock depth of
 * various counters used in the display path. So this code reverses the
 * provided value into the lfsr16 value by counting backwards to get
 * the value that needs to be set in the hardware comparator to get the
 * same actual count. This makes sense once you read above a couple of
 * times and think about it from a hardware perspective.
 */
static u16 dlfb_lfsr16(u16 actual_count)
{
	u32 lv = 0xFFFF; /* This is the lfsr value that the hw starts with */

	while (actual_count--) {
		lv =	 ((lv << 1) |
			(((lv >> 15) ^ (lv >> 4) ^ (lv >> 2) ^ (lv >> 1)) & 1))
			& 0xFFFF;
	}

	return (u16) lv;
}

/*
 * This does LFSR conversion on the value that is to be written.
 * See LFSR explanation above for more detail.
 */
static char *dlfb_set_register_lfsr16(char *wrptr, u8 reg, u16 value)
{
	return dlfb_set_register_16(wrptr, reg, dlfb_lfsr16(value));
}

/*
 * This takes a standard fbdev screeninfo struct and all of its monitor mode
 * details and converts them into the DisplayLink equivalent register commands.
 */
static char *dlfb_set_vid_cmds(char *wrptr, struct fb_var_screeninfo *var)
{
	u16 xds, yds;
	u16 xde, yde;
	u16 yec;

	/* x display start */
	xds = var->left_margin + var->hsync_len;
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x01, xds);
	/* x display end */
	xde = xds + var->xres;
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x03, xde);

	/* y display start */
	yds = var->upper_margin + var->vsync_len;
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x05, yds);
	/* y display end */
	yde = yds + var->yres;
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x07, yde);

	/* x end count is active + blanking - 1 */
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x09,
			xde + var->right_margin - 1);

	/* libdlo hardcodes hsync start to 1 */
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0B, 1);

	/* hsync end is width of sync pulse + 1 */
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x0D, var->hsync_len + 1);

	/* hpixels is active pixels */
	wrptr = dlfb_set_register_16(wrptr, 0x0F, var->xres);

	/* yendcount is vertical active + vertical blanking */
	yec = var->yres + var->upper_margin + var->lower_margin +
			var->vsync_len;
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x11, yec);

	/* libdlo hardcodes vsync start to 0 */
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x13, 0);

	/* vsync end is width of vsync pulse */
	wrptr = dlfb_set_register_lfsr16(wrptr, 0x15, var->vsync_len);

	/* vpixels is active pixels */
	wrptr = dlfb_set_register_16(wrptr, 0x17, var->yres);

	/* convert picoseconds to 5kHz multiple for pclk5k = x * 1E12/5k */
	wrptr = dlfb_set_register_16be(wrptr, 0x1B,
			200*1000*1000/var->pixclock);

	return wrptr;
}

/*
 * This takes a standard fbdev screeninfo struct that was fetched or prepared
 * and then generates the appropriate command sequence that then drives the
 * display controller.
 */
static int dlfb_set_video_mode(struct dlfb_data *dev,
				struct fb_var_screeninfo *var)
{
	char *buf;
	char *wrptr;
	int retval = 0;
	int writesize;
	struct urb *urb;

	if (!atomic_read(&dev->usb_active))
		return -EPERM;

	urb = dlfb_get_urb(dev);
	if (!urb)
		return -ENOMEM;

	buf = (char *) urb->transfer_buffer;

	/*
	* This first section has to do with setting the base address on the
	* controller * associated with the display. There are 2 base
	* pointers, currently, we only * use the 16 bpp segment.
	*/
	wrptr = dlfb_vidreg_lock(buf);
	wrptr = dlfb_set_color_depth(wrptr, 0x00);
	/* set base for 16bpp segment to 0 */
	wrptr = dlfb_set_base16bpp(wrptr, 0);
	/* set base for 8bpp segment to end of fb */
	wrptr = dlfb_set_base8bpp(wrptr, dev->info->fix.smem_len);

	wrptr = dlfb_set_vid_cmds(wrptr, var);
	wrptr = dlfb_enable_hvsync(wrptr, true);
	wrptr = dlfb_vidreg_unlock(wrptr);

	writesize = wrptr - buf;

	retval = dlfb_submit_urb(dev, urb, writesize);

	return retval;
}

static int dlfb_ops_mmap(struct fb_info *info, struct vm_area_struct *vma)
{
	unsigned long start = vma->vm_start;
	unsigned long size = vma->vm_end - vma->vm_start;
	unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
	unsigned long page, pos;

	if (offset + size > info->fix.smem_len)
		return -EINVAL;

	pos = (unsigned long)info->fix.smem_start + offset;

	pr_notice("mmap() framebuffer addr:%lu size:%lu\n",
		  pos, size);

	while (size > 0) {
		page = vmalloc_to_pfn((void *)pos);
		if (remap_pfn_range(vma, start, page, PAGE_SIZE, PAGE_SHARED))
			return -EAGAIN;

		start += PAGE_SIZE;
		pos += PAGE_SIZE;
		if (size > PAGE_SIZE)
			size -= PAGE_SIZE;
		else
			size = 0;
	}

	vma->vm_flags |= VM_RESERVED;	/* avoid to swap out this VMA */
	return 0;
}

/*
 * Trims identical data from front and back of line
 * Sets new front buffer address and width
 * And returns byte count of identical pixels
 * Assumes CPU natural alignment (unsigned long)
 * for back and front buffer ptrs and width
 */
static int dlfb_trim_hline(const u8 *bback, const u8 **bfront, int *width_bytes)
{
	int j, k;
	const unsigned long *back = (const unsigned long *) bback;
	const unsigned long *front = (const unsigned long *) *bfront;
	const int width = *width_bytes / sizeof(unsigned long);
	int identical = width;
	int start = width;
	int end = width;

	prefetch((void *) front);
	prefetch((void *) back);

	for (j = 0; j < width; j++) {
		if (back[j] != front[j]) {
			start = j;
			break;
		}
	}

	for (k = width - 1; k > j; k--) {
		if (back[k] != front[k]) {
			end = k+1;
			break;
		}
	}

	identical = start + (width - end);
	*bfront = (u8 *) &front[start];
	*width_bytes = (end - start) * sizeof(unsigned long);

	return identical * sizeof(unsigned long);
}

/*
 * Render a command stream for an encoded horizontal line segment of pixels.
 *
 * A command buffer holds several commands.
 * It always begins with a fresh command header
 * (the protocol doesn't require this, but we enforce it to allow
 * multiple buffers to be potentially encoded and sent in parallel).
 * A single command encodes one contiguous horizontal line of pixels
 *
 * The function relies on the client to do all allocation, so that
 * rendering can be done directly to output buffers (e.g. USB URBs).
 * The function fills the supplied command buffer, providing information
 * on where it left off, so the client may call in again with additional
 * buffers if the line will take several buffers to complete.
 *
 * A single command can transmit a maximum of 256 pixels,
 * regardless of the compression ratio (protocol design limit).
 * To the hardware, 0 for a size byte means 256
 *
 * Rather than 256 pixel commands which are either rl or raw encoded,
 * the rlx command simply assumes alternating raw and rl spans within one cmd.
 * This has a slightly larger header overhead, but produces more even results.
 * It also processes all data (read and write) in a single pass.
 * Performance benchmarks of common cases show it having just slightly better
 * compression than 256 pixel raw or rle commands, with similar CPU consumpion.
 * But for very rl friendly data, will compress not quite as well.
 */
static void dlfb_compress_hline(
	const uint16_t **pixel_start_ptr,
	const uint16_t *const pixel_end,
	uint32_t *device_address_ptr,
	uint8_t **command_buffer_ptr,
	const uint8_t *const cmd_buffer_end)
{
	const uint16_t *pixel = *pixel_start_ptr;
	uint32_t dev_addr  = *device_address_ptr;
	uint8_t *cmd = *command_buffer_ptr;
	const int bpp = 2;

	while ((pixel_end > pixel) &&
	       (cmd_buffer_end - MIN_RLX_CMD_BYTES > cmd)) {
		uint8_t *raw_pixels_count_byte = 0;
		uint8_t *cmd_pixels_count_byte = 0;
		const uint16_t *raw_pixel_start = 0;
		const uint16_t *cmd_pixel_start, *cmd_pixel_end = 0;

		prefetchw((void *) cmd); /* pull in one cache line at least */

		*cmd++ = 0xAF;
		*cmd++ = 0x6B;
		*cmd++ = (uint8_t) ((dev_addr >> 16) & 0xFF);
		*cmd++ = (uint8_t) ((dev_addr >> 8) & 0xFF);
		*cmd++ = (uint8_t) ((dev_addr) & 0xFF);

		cmd_pixels_count_byte = cmd++; /*  we'll know this later */
		cmd_pixel_start = pixel;

		raw_pixels_count_byte = cmd++; /*  we'll know this later */
		raw_pixel_start = pixel;

		cmd_pixel_end = pixel + min(MAX_CMD_PIXELS + 1,
			min((int)(pixel_end - pixel),
			    (int)(cmd_buffer_end - cmd) / bpp));

		prefetch_range((void *) pixel, (cmd_pixel_end - pixel) * bpp);

		while (pixel < cmd_pixel_end) {
			const uint16_t * const repeating_pixel = pixel;

			*(uint16_t *)cmd = cpu_to_be16p(pixel);
			cmd += 2;
			pixel++;

			if (unlikely((pixel < cmd_pixel_end) &&
				     (*pixel == *repeating_pixel))) {
				/* go back and fill in raw pixel count */
				*raw_pixels_count_byte = ((repeating_pixel -
						raw_pixel_start) + 1) & 0xFF;

				while ((pixel < cmd_pixel_end)
				       && (*pixel == *repeating_pixel)) {
					pixel++;
				}

				/* immediately after raw data is repeat byte */
				*cmd++ = ((pixel - repeating_pixel) - 1) & 0xFF;

				/* Then start another raw pixel span */
				raw_pixel_start = pixel;
				raw_pixels_count_byte = cmd++;
			}
		}

		if (pixel > raw_pixel_start) {
			/* finalize last RAW span */
			*raw_pixels_count_byte = (pixel-raw_pixel_start) & 0xFF;
		}

		*cmd_pixels_count_byte = (pixel - cmd_pixel_start) & 0xFF;
		dev_addr += (pixel - cmd_pixel_start) * bpp;
	}

	if (cmd_buffer_end <= MIN_RLX_CMD_BYTES + cmd) {
		/* Fill leftover bytes with no-ops */
		if (cmd_buffer_end > cmd)
			memset(cmd, 0xAF, cmd_buffer_end - cmd);
		cmd = (uint8_t *) cmd_buffer_end;
	}

	*command_buffer_ptr = cmd;
	*pixel_start_ptr = pixel;
	*device_address_ptr = dev_addr;

	return;
}

/*
 * There are 3 copies of every pixel: The front buffer that the fbdev
 * client renders to, the actual framebuffer across the USB bus in hardware
 * (that we can only write to, slowly, and can never read), and (optionally)
 * our shadow copy that tracks what's been sent to that hardware buffer.
 */
static int dlfb_render_hline(struct dlfb_data *dev, struct urb **urb_ptr,
			      const char *front, char **urb_buf_ptr,
			      u32 byte_offset, u32 byte_width,
			      int *ident_ptr, int *sent_ptr)
{
	const u8 *line_start, *line_end, *next_pixel;
	u32 dev_addr = dev->base16 + byte_offset;
	struct urb *urb = *urb_ptr;
	u8 *cmd = *urb_buf_ptr;
	u8 *cmd_end = (u8 *) urb->transfer_buffer + urb->transfer_buffer_length;

	line_start = (u8 *) (front + byte_offset);
	next_pixel = line_start;
	line_end = next_pixel + byte_width;

	if (dev->backing_buffer) {
		int offset;
		const u8 *back_start = (u8 *) (dev->backing_buffer
						+ byte_offset);

		*ident_ptr += dlfb_trim_hline(back_start, &next_pixel,
			&byte_width);

		offset = next_pixel - line_start;
		line_end = next_pixel + byte_width;
		dev_addr += offset;
		back_start += offset;
		line_start += offset;

		memcpy((char *)back_start, (char *) line_start,
		       byte_width);
	}

	while (next_pixel < line_end) {

		dlfb_compress_hline((const uint16_t **) &next_pixel,
			     (const uint16_t *) line_end, &dev_addr,
			(u8 **) &cmd, (u8 *) cmd_end);

		if (cmd >= cmd_end) {
			int len = cmd - (u8 *) urb->transfer_buffer;
			if (dlfb_submit_urb(dev, urb, len))
				return 1; /* lost pixels is set */
			*sent_ptr += len;
			urb = dlfb_get_urb(dev);
			if (!urb)
				return 1; /* lost_pixels is set */
			*urb_ptr = urb;
			cmd = urb->transfer_buffer;
			cmd_end = &cmd[urb->transfer_buffer_length];
		}
	}

	*urb_buf_ptr = cmd;

	return 0;
}

int dlfb_handle_damage(struct dlfb_data *dev, int x, int y,
	       int width, int height, char *data)
{
	int i, ret;
	char *cmd;
	cycles_t start_cycles, end_cycles;
	int bytes_sent = 0;
	int bytes_identical = 0;
	struct urb *urb;
	int aligned_x;

	start_cycles = get_cycles();

	aligned_x = DL_ALIGN_DOWN(x, sizeof(unsigned long));
	width = DL_ALIGN_UP(width + (x-aligned_x), sizeof(unsigned long));
	x = aligned_x;

	if ((width <= 0) ||
	    (x + width > dev->info->var.xres) ||
	    (y + height > dev->info->var.yres))
		return -EINVAL;

	if (!atomic_read(&dev->usb_active))
		return 0;

	urb = dlfb_get_urb(dev);
	if (!urb)
		return 0;
	cmd = urb->transfer_buffer;

	for (i = y; i < y + height ; i++) {
		const int line_offset = dev->info->fix.line_length * i;
		const int byte_offset = line_offset + (x * BPP);

		if (dlfb_render_hline(dev, &urb,
				      (char *) dev->info->fix.smem_start,
				      &cmd, byte_offset, width * BPP,
				      &bytes_identical, &bytes_sent))
			goto error;
	}

	if (cmd > (char *) urb->transfer_buffer) {
		/* Send partial buffer remaining before exiting */
		int len = cmd - (char *) urb->transfer_buffer;
		ret = dlfb_submit_urb(dev, urb, len);
		bytes_sent += len;
	} else
		dlfb_urb_completion(urb);

error:
	atomic_add(bytes_sent, &dev->bytes_sent);
	atomic_add(bytes_identical, &dev->bytes_identical);
	atomic_add(width*height*2, &dev->bytes_rendered);
	end_cycles = get_cycles();
	atomic_add(((unsigned int) ((end_cycles - start_cycles)
		    >> 10)), /* Kcycles */
		   &dev->cpu_kcycles_used);

	return 0;
}

/*
 * Path triggered by usermode clients who write to filesystem
 * e.g. cat filename > /dev/fb1
 * Not used by X Windows or text-mode console. But useful for testing.
 * Slow because of extra copy and we must assume all pixels dirty.
 */
static ssize_t dlfb_ops_write(struct fb_info *info, const char __user *buf,
			  size_t count, loff_t *ppos)
{
	ssize_t result;
	struct dlfb_data *dev = info->par;
	u32 offset = (u32) *ppos;

	result = fb_sys_write(info, buf, count, ppos);

	if (result > 0) {
		int start = max((int)(offset / info->fix.line_length) - 1, 0);
		int lines = min((u32)((result / info->fix.line_length) + 1),
				(u32)info->var.yres);

		dlfb_handle_damage(dev, 0, start, info->var.xres,
			lines, info->screen_base);
	}

	return result;
}

/* hardware has native COPY command (see libdlo), but not worth it for fbcon */
static void dlfb_ops_copyarea(struct fb_info *info,
				const struct fb_copyarea *area)
{

	struct dlfb_data *dev = info->par;

	sys_copyarea(info, area);

	dlfb_handle_damage(dev, area->dx, area->dy,
			area->width, area->height, info->screen_base);
}

static void dlfb_ops_imageblit(struct fb_info *info,
				const struct fb_image *image)
{
	struct dlfb_data *dev = info->par;

	sys_imageblit(info, image);

	dlfb_handle_damage(dev, image->dx, image->dy,
			image->width, image->height, info->screen_base);
}

static void dlfb_ops_fillrect(struct fb_info *info,
			  const struct fb_fillrect *rect)
{
	struct dlfb_data *dev = info->par;

	sys_fillrect(info, rect);

	dlfb_handle_damage(dev, rect->dx, rect->dy, rect->width,
			      rect->height, info->screen_base);
}

/*
 * NOTE: fb_defio.c is holding info->fbdefio.mutex
 *   Touching ANY framebuffer memory that triggers a page fault
 *   in fb_defio will cause a deadlock, when it also tries to
 *   grab the same mutex.
 */
static void dlfb_dpy_deferred_io(struct fb_info *info,
				struct list_head *pagelist)
{
	struct page *cur;
	struct fb_deferred_io *fbdefio = info->fbdefio;
	struct dlfb_data *dev = info->par;
	struct urb *urb;
	char *cmd;
	cycles_t start_cycles, end_cycles;
	int bytes_sent = 0;
	int bytes_identical = 0;
	int bytes_rendered = 0;

	if (!fb_defio)
		return;

	if (!atomic_read(&dev->usb_active))
		return;

	start_cycles = get_cycles();

	urb = dlfb_get_urb(dev);
	if (!urb)
		return;

	cmd = urb->transfer_buffer;

	/* walk the written page list and render each to device */
	list_for_each_entry(cur, &fbdefio->pagelist, lru) {

		if (dlfb_render_hline(dev, &urb, (char *) info->fix.smem_start,
				  &cmd, cur->index << PAGE_SHIFT,
				  PAGE_SIZE, &bytes_identical, &bytes_sent))
			goto error;
		bytes_rendered += PAGE_SIZE;
	}

	if (cmd > (char *) urb->transfer_buffer) {
		/* Send partial buffer remaining before exiting */
		int len = cmd - (char *) urb->transfer_buffer;
		dlfb_submit_urb(dev, urb, len);
		bytes_sent += len;
	} else
		dlfb_urb_completion(urb);

error:
	atomic_add(bytes_sent, &dev->bytes_sent);
	atomic_add(bytes_identical, &dev->bytes_identical);
	atomic_add(bytes_rendered, &dev->bytes_rendered);
	end_cycles = get_cycles();
	atomic_add(((unsigned int) ((end_cycles - start_cycles)
		    >> 10)), /* Kcycles */
		   &dev->cpu_kcycles_used);
}

static int dlfb_get_edid(struct dlfb_data *dev, char *edid, int len)
{
	int i;
	int ret;
	char *rbuf;

	rbuf = kmalloc(2, GFP_KERNEL);
	if (!rbuf)
		return 0;

	for (i = 0; i < len; i++) {
		ret = usb_control_msg(dev->udev,
				    usb_rcvctrlpipe(dev->udev, 0), (0x02),
				    (0x80 | (0x02 << 5)), i << 8, 0xA1, rbuf, 2,
				    HZ);
		if (ret < 1) {
			pr_err("Read EDID byte %d failed err %x\n", i, ret);
			i--;
			break;
		}
		edid[i] = rbuf[1];
	}

	kfree(rbuf);

	return i;
}

static int dlfb_ops_ioctl(struct fb_info *info, unsigned int cmd,
				unsigned long arg)
{

	struct dlfb_data *dev = info->par;
	struct dloarea *area = NULL;

	if (!atomic_read(&dev->usb_active))
		return 0;

	/* TODO: Update X server to get this from sysfs instead */
	if (cmd == DLFB_IOCTL_RETURN_EDID) {
		char *edid = (char *)arg;
		if (copy_to_user(edid, dev->edid, dev->edid_size))
			return -EFAULT;
		return 0;
	}

	/* TODO: Help propose a standard fb.h ioctl to report mmap damage */
	if (cmd == DLFB_IOCTL_REPORT_DAMAGE) {

		/*
		 * If we have a damage-aware client, turn fb_defio "off"
		 * To avoid perf imact of unecessary page fault handling.
		 * Done by resetting the delay for this fb_info to a very
		 * long period. Pages will become writable and stay that way.
		 * Reset to normal value when all clients have closed this fb.
		 */
		if (info->fbdefio)
			info->fbdefio->delay = DL_DEFIO_WRITE_DISABLE;

		area = (struct dloarea *)arg;

		if (area->x < 0)
			area->x = 0;

		if (area->x > info->var.xres)
			area->x = info->var.xres;

		if (area->y < 0)
			area->y = 0;

		if (area->y > info->var.yres)
			area->y = info->var.yres;

		dlfb_handle_damage(dev, area->x, area->y, area->w, area->h,
			   info->screen_base);
	}

	return 0;
}

/* taken from vesafb */
static int
dlfb_ops_setcolreg(unsigned regno, unsigned red, unsigned green,
	       unsigned blue, unsigned transp, struct fb_info *info)
{
	int err = 0;

	if (regno >= info->cmap.len)
		return 1;

	if (regno < 16) {
		if (info->var.red.offset == 10) {
			/* 1:5:5:5 */
			((u32 *) (info->pseudo_palette))[regno] =
			    ((red & 0xf800) >> 1) |
			    ((green & 0xf800) >> 6) | ((blue & 0xf800) >> 11);
		} else {
			/* 0:5:6:5 */
			((u32 *) (info->pseudo_palette))[regno] =
			    ((red & 0xf800)) |
			    ((green & 0xfc00) >> 5) | ((blue & 0xf800) >> 11);
		}
	}

	return err;
}

/*
 * It's common for several clients to have framebuffer open simultaneously.
 * e.g. both fbcon and X. Makes things interesting.
 * Assumes caller is holding info->lock (for open and release at least)
 */
static int dlfb_ops_open(struct fb_info *info, int user)
{
	struct dlfb_data *dev = info->par;

	/*
	 * fbcon aggressively connects to first framebuffer it finds,
	 * preventing other clients (X) from working properly. Usually
	 * not what the user wants. Fail by default with option to enable.
	 */
	if ((user == 0) & (!console))
		return -EBUSY;

	/* If the USB device is gone, we don't accept new opens */
	if (dev->virtualized)
		return -ENODEV;

	dev->fb_count++;

	kref_get(&dev->kref);

	if (fb_defio && (info->fbdefio == NULL)) {
		/* enable defio at last moment if not disabled by client */

		struct fb_deferred_io *fbdefio;

		fbdefio = kmalloc(sizeof(struct fb_deferred_io), GFP_KERNEL);

		if (fbdefio) {
			fbdefio->delay = DL_DEFIO_WRITE_DELAY;
			fbdefio->deferred_io = dlfb_dpy_deferred_io;
		}

		info->fbdefio = fbdefio;
		fb_deferred_io_init(info);
	}

	pr_notice("open /dev/fb%d user=%d fb_info=%p count=%d\n",
	    info->node, user, info, dev->fb_count);

	return 0;
}

/*
 * Called when all client interfaces to start transactions have been disabled,
 * and all references to our device instance (dlfb_data) are released.
 * Every transaction must have a reference, so we know are fully spun down
 */
static void dlfb_free(struct kref *kref)
{
	struct dlfb_data *dev = container_of(kref, struct dlfb_data, kref);

	/* this function will wait for all in-flight urbs to complete */
	if (dev->urbs.count > 0)
		dlfb_free_urb_list(dev);

	if (dev->backing_buffer)
		vfree(dev->backing_buffer);

	kfree(dev->edid);

	pr_warn("freeing dlfb_data %p\n", dev);

	kfree(dev);
}

static void dlfb_release_urb_work(struct work_struct *work)
{
	struct urb_node *unode = container_of(work, struct urb_node,
					      release_urb_work.work);

	up(&unode->dev->urbs.limit_sem);
}

static void dlfb_free_framebuffer_work(struct work_struct *work)
{
	struct dlfb_data *dev = container_of(work, struct dlfb_data,
					     free_framebuffer_work.work);
	struct fb_info *info = dev->info;
	int node = info->node;

	unregister_framebuffer(info);

	if (info->cmap.len != 0)
		fb_dealloc_cmap(&info->cmap);
	if (info->monspecs.modedb)
		fb_destroy_modedb(info->monspecs.modedb);
	if (info->screen_base)
		vfree(info->screen_base);

	fb_destroy_modelist(&info->modelist);

	dev->info = 0;

	/* Assume info structure is freed after this point */
	framebuffer_release(info);

	pr_warn("fb_info for /dev/fb%d has been freed\n", node);

	/* ref taken in probe() as part of registering framebfufer */
	kref_put(&dev->kref, dlfb_free);
}

/*
 * Assumes caller is holding info->lock mutex (for open and release at least)
 */
static int dlfb_ops_release(struct fb_info *info, int user)
{
	struct dlfb_data *dev = info->par;

	dev->fb_count--;

	/* We can't free fb_info here - fbmem will touch it when we return */
	if (dev->virtualized && (dev->fb_count == 0))
		schedule_delayed_work(&dev->free_framebuffer_work, HZ);

	if ((dev->fb_count == 0) && (info->fbdefio)) {
		fb_deferred_io_cleanup(info);
		kfree(info->fbdefio);
		info->fbdefio = NULL;
		info->fbops->fb_mmap = dlfb_ops_mmap;
	}

	pr_warn("released /dev/fb%d user=%d count=%d\n",
		  info->node, user, dev->fb_count);

	kref_put(&dev->kref, dlfb_free);

	return 0;
}

/*
 * Check whether a video mode is supported by the DisplayLink chip
 * We start from monitor's modes, so don't need to filter that here
 */
static int dlfb_is_valid_mode(struct fb_videomode *mode,
		struct fb_info *info)
{
	struct dlfb_data *dev = info->par;

	if (mode->xres * mode->yres > dev->sku_pixel_limit) {
		pr_warn("%dx%d beyond chip capabilities\n",
		       mode->xres, mode->yres);
		return 0;
	}

	pr_info("%dx%d valid mode\n", mode->xres, mode->yres);

	return 1;
}

static void dlfb_var_color_format(struct fb_var_screeninfo *var)
{
	const struct fb_bitfield red = { 11, 5, 0 };
	const struct fb_bitfield green = { 5, 6, 0 };
	const struct fb_bitfield blue = { 0, 5, 0 };

	var->bits_per_pixel = 16;
	var->red = red;
	var->green = green;
	var->blue = blue;
}

static int dlfb_ops_check_var(struct fb_var_screeninfo *var,
				struct fb_info *info)
{
	struct fb_videomode mode;

	/* TODO: support dynamically changing framebuffer size */
	if ((var->xres * var->yres * 2) > info->fix.smem_len)
		return -EINVAL;

	/* set device-specific elements of var unrelated to mode */
	dlfb_var_color_format(var);

	fb_var_to_videomode(&mode, var);

	if (!dlfb_is_valid_mode(&mode, info))
		return -EINVAL;

	return 0;
}

static int dlfb_ops_set_par(struct fb_info *info)
{
	struct dlfb_data *dev = info->par;
	int result;
	u16 *pix_framebuffer;
	int i;

	pr_notice("set_par mode %dx%d\n", info->var.xres, info->var.yres);

	result = dlfb_set_video_mode(dev, &info->var);

	if ((result == 0) && (dev->fb_count == 0)) {

		/* paint greenscreen */

		pix_framebuffer = (u16 *) info->screen_base;
		for (i = 0; i < info->fix.smem_len / 2; i++)
			pix_framebuffer[i] = 0x37e6;

		dlfb_handle_damage(dev, 0, 0, info->var.xres, info->var.yres,
				   info->screen_base);
	}

	return result;
}

/*
 * In order to come back from full DPMS off, we need to set the mode again
 */
static int dlfb_ops_blank(int blank_mode, struct fb_info *info)
{
	struct dlfb_data *dev = info->par;

	if (blank_mode != FB_BLANK_UNBLANK) {
		char *bufptr;
		struct urb *urb;

		urb = dlfb_get_urb(dev);
		if (!urb)
			return 0;

		bufptr = (char *) urb->transfer_buffer;
		bufptr = dlfb_vidreg_lock(bufptr);
		bufptr = dlfb_enable_hvsync(bufptr, false);
		bufptr = dlfb_vidreg_unlock(bufptr);

		dlfb_submit_urb(dev, urb, bufptr -
				(char *) urb->transfer_buffer);
	} else {
		dlfb_set_video_mode(dev, &info->var);
	}

	return 0;
}

static struct fb_ops dlfb_ops = {
	.owner = THIS_MODULE,
	.fb_read = fb_sys_read,
	.fb_write = dlfb_ops_write,
	.fb_setcolreg = dlfb_ops_setcolreg,
	.fb_fillrect = dlfb_ops_fillrect,
	.fb_copyarea = dlfb_ops_copyarea,
	.fb_imageblit = dlfb_ops_imageblit,
	.fb_mmap = dlfb_ops_mmap,
	.fb_ioctl = dlfb_ops_ioctl,
	.fb_open = dlfb_ops_open,
	.fb_release = dlfb_ops_release,
	.fb_blank = dlfb_ops_blank,
	.fb_check_var = dlfb_ops_check_var,
	.fb_set_par = dlfb_ops_set_par,
};


/*
 * Assumes &info->lock held by caller
 * Assumes no active clients have framebuffer open
 */
static int dlfb_realloc_framebuffer(struct dlfb_data *dev, struct fb_info *info)
{
	int retval = -ENOMEM;
	int old_len = info->fix.smem_len;
	int new_len;
	unsigned char *old_fb = info->screen_base;
	unsigned char *new_fb;
	unsigned char *new_back;

	pr_warn("Reallocating framebuffer. Addresses will change!\n");

	new_len = info->fix.line_length * info->var.yres;

	if (PAGE_ALIGN(new_len) > old_len) {
		/*
		 * Alloc system memory for virtual framebuffer
		 */
		new_fb = vmalloc(new_len);
		if (!new_fb) {
			pr_err("Virtual framebuffer alloc failed\n");
			goto error;
		}

		if (info->screen_base) {
			memcpy(new_fb, old_fb, old_len);
			vfree(info->screen_base);
		}

		info->screen_base = new_fb;
		info->fix.smem_len = PAGE_ALIGN(new_len);
		info->fix.smem_start = (unsigned long) new_fb;
		info->flags = udlfb_info_flags;

		/*
		 * Second framebuffer copy to mirror the framebuffer state
		 * on the physical USB device. We can function without this.
		 * But with imperfect damage info we may send pixels over USB
		 * that were, in fact, unchanged - wasting limited USB bandwidth
		 */
		new_back = vzalloc(new_len);
		if (!new_back)
			pr_info("No shadow/backing buffer allocated\n");
		else {
			if (dev->backing_buffer)
				vfree(dev->backing_buffer);
			dev->backing_buffer = new_back;
		}
	}

	retval = 0;

error:
	return retval;
}

/*
 * 1) Get EDID from hw, or use sw default
 * 2) Parse into various fb_info structs
 * 3) Allocate virtual framebuffer memory to back highest res mode
 *
 * Parses EDID into three places used by various parts of fbdev:
 * fb_var_screeninfo contains the timing of the monitor's preferred mode
 * fb_info.monspecs is full parsed EDID info, including monspecs.modedb
 * fb_info.modelist is a linked list of all monitor & VESA modes which work
 *
 * If EDID is not readable/valid, then modelist is all VESA modes,
 * monspecs is NULL, and fb_var_screeninfo is set to safe VESA mode
 * Returns 0 if successful
 */
static int dlfb_setup_modes(struct dlfb_data *dev,
			   struct fb_info *info,
			   char *default_edid, size_t default_edid_size)
{
	int i;
	const struct fb_videomode *default_vmode = NULL;
	int result = 0;
	char *edid;
	int tries = 3;

	if (info->dev) /* only use mutex if info has been registered */
		mutex_lock(&info->lock);

	edid = kmalloc(EDID_LENGTH, GFP_KERNEL);
	if (!edid) {
		result = -ENOMEM;
		goto error;
	}

	fb_destroy_modelist(&info->modelist);
	memset(&info->monspecs, 0, sizeof(info->monspecs));

	/*
	 * Try to (re)read EDID from hardware first
	 * EDID data may return, but not parse as valid
	 * Try again a few times, in case of e.g. analog cable noise
	 */
	while (tries--) {

		i = dlfb_get_edid(dev, edid, EDID_LENGTH);

		if (i >= EDID_LENGTH)
			fb_edid_to_monspecs(edid, &info->monspecs);

		if (info->monspecs.modedb_len > 0) {
			dev->edid = edid;
			dev->edid_size = i;
			break;
		}
	}

	/* If that fails, use a previously returned EDID if available */
	if (info->monspecs.modedb_len == 0) {

		pr_err("Unable to get valid EDID from device/display\n");

		if (dev->edid) {
			fb_edid_to_monspecs(dev->edid, &info->monspecs);
			if (info->monspecs.modedb_len > 0)
				pr_err("Using previously queried EDID\n");
		}
	}

	/* If that fails, use the default EDID we were handed */
	if (info->monspecs.modedb_len == 0) {
		if (default_edid_size >= EDID_LENGTH) {
			fb_edid_to_monspecs(default_edid, &info->monspecs);
			if (info->monspecs.modedb_len > 0) {
				memcpy(edid, default_edid, default_edid_size);
				dev->edid = edid;
				dev->edid_size = default_edid_size;
				pr_err("Using default/backup EDID\n");
			}
		}
	}

	/* If we've got modes, let's pick a best default mode */
	if (info->monspecs.modedb_len > 0) {

		for (i = 0; i < info->monspecs.modedb_len; i++) {
			if (dlfb_is_valid_mode(&info->monspecs.modedb[i], info))
				fb_add_videomode(&info->monspecs.modedb[i],
					&info->modelist);
			else /* if we've removed top/best mode */
				info->monspecs.misc &= ~FB_MISC_1ST_DETAIL;
		}

		default_vmode = fb_find_best_display(&info->monspecs,
						     &info->modelist);
	}

	/* If everything else has failed, fall back to safe default mode */
	if (default_vmode == NULL) {

		struct fb_videomode fb_vmode = {0};

		/*
		 * Add the standard VESA modes to our modelist
		 * Since we don't have EDID, there may be modes that
		 * overspec monitor and/or are incorrect aspect ratio, etc.
		 * But at least the user has a chance to choose
		 */
		for (i = 0; i < VESA_MODEDB_SIZE; i++) {
			if (dlfb_is_valid_mode((struct fb_videomode *)
						&vesa_modes[i], info))
				fb_add_videomode(&vesa_modes[i],
						 &info->modelist);
		}

		/*
		 * default to resolution safe for projectors
		 * (since they are most common case without EDID)
		 */
		fb_vmode.xres = 800;
		fb_vmode.yres = 600;
		fb_vmode.refresh = 60;
		default_vmode = fb_find_nearest_mode(&fb_vmode,
						     &info->modelist);
	}

	/* If we have good mode and no active clients*/
	if ((default_vmode != NULL) && (dev->fb_count == 0)) {

		fb_videomode_to_var(&info->var, default_vmode);
		dlfb_var_color_format(&info->var);

		/*
		 * with mode size info, we can now alloc our framebuffer.
		 */
		memcpy(&info->fix, &dlfb_fix, sizeof(dlfb_fix));
		info->fix.line_length = info->var.xres *
			(info->var.bits_per_pixel / 8);

		result = dlfb_realloc_framebuffer(dev, info);

	} else
		result = -EINVAL;

error:
	if (edid && (dev->edid != edid))
		kfree(edid);

	if (info->dev)
		mutex_unlock(&info->lock);

	return result;
}

static ssize_t metrics_bytes_rendered_show(struct device *fbdev,
				   struct device_attribute *a, char *buf) {
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;
	return snprintf(buf, PAGE_SIZE, "%u\n",
			atomic_read(&dev->bytes_rendered));
}

static ssize_t metrics_bytes_identical_show(struct device *fbdev,
				   struct device_attribute *a, char *buf) {
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;
	return snprintf(buf, PAGE_SIZE, "%u\n",
			atomic_read(&dev->bytes_identical));
}

static ssize_t metrics_bytes_sent_show(struct device *fbdev,
				   struct device_attribute *a, char *buf) {
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;
	return snprintf(buf, PAGE_SIZE, "%u\n",
			atomic_read(&dev->bytes_sent));
}

static ssize_t metrics_cpu_kcycles_used_show(struct device *fbdev,
				   struct device_attribute *a, char *buf) {
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;
	return snprintf(buf, PAGE_SIZE, "%u\n",
			atomic_read(&dev->cpu_kcycles_used));
}

static ssize_t edid_show(
			struct file *filp,
			struct kobject *kobj, struct bin_attribute *a,
			 char *buf, loff_t off, size_t count) {
	struct device *fbdev = container_of(kobj, struct device, kobj);
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;

	if (dev->edid == NULL)
		return 0;

	if ((off >= dev->edid_size) || (count > dev->edid_size))
		return 0;

	if (off + count > dev->edid_size)
		count = dev->edid_size - off;

	pr_info("sysfs edid copy %p to %p, %d bytes\n",
		dev->edid, buf, (int) count);

	memcpy(buf, dev->edid, count);

	return count;
}

static ssize_t edid_store(
			struct file *filp,
			struct kobject *kobj, struct bin_attribute *a,
			char *src, loff_t src_off, size_t src_size) {
	struct device *fbdev = container_of(kobj, struct device, kobj);
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;

	/* We only support write of entire EDID at once, no offset*/
	if ((src_size != EDID_LENGTH) || (src_off != 0))
		return 0;

	dlfb_setup_modes(dev, fb_info, src, src_size);

	if (dev->edid && (memcmp(src, dev->edid, src_size) == 0)) {
		pr_info("sysfs written EDID is new default\n");
		dlfb_ops_set_par(fb_info);
		return src_size;
	} else
		return 0;
}

static ssize_t metrics_reset_store(struct device *fbdev,
			   struct device_attribute *attr,
			   const char *buf, size_t count)
{
	struct fb_info *fb_info = dev_get_drvdata(fbdev);
	struct dlfb_data *dev = fb_info->par;

	atomic_set(&dev->bytes_rendered, 0);
	atomic_set(&dev->bytes_identical, 0);
	atomic_set(&dev->bytes_sent, 0);
	atomic_set(&dev->cpu_kcycles_used, 0);

	return count;
}

static struct bin_attribute edid_attr = {
	.attr.name = "edid",
	.attr.mode = 0666,
	.size = EDID_LENGTH,
	.read = edid_show,
	.write = edid_store
};

static struct device_attribute fb_device_attrs[] = {
	__ATTR_RO(metrics_bytes_rendered),
	__ATTR_RO(metrics_bytes_identical),
	__ATTR_RO(metrics_bytes_sent),
	__ATTR_RO(metrics_cpu_kcycles_used),
	__ATTR(metrics_reset, S_IWUSR, NULL, metrics_reset_store),
};

/*
 * This is necessary before we can communicate with the display controller.
 */
static int dlfb_select_std_channel(struct dlfb_data *dev)
{
	int ret;
	u8 set_def_chn[] = {	   0x57, 0xCD, 0xDC, 0xA7,
				0x1C, 0x88, 0x5E, 0x15,
				0x60, 0xFE, 0xC6, 0x97,
				0x16, 0x3D, 0x47, 0xF2  };

	ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
			NR_USB_REQUEST_CHANNEL,
			(USB_DIR_OUT | USB_TYPE_VENDOR), 0, 0,
			set_def_chn, sizeof(set_def_chn), USB_CTRL_SET_TIMEOUT);
	return ret;
}

static int dlfb_parse_vendor_descriptor(struct dlfb_data *dev,
					struct usb_device *usbdev)
{
	char *desc;
	char *buf;
	char *desc_end;

	u8 total_len = 0;

	buf = kzalloc(MAX_VENDOR_DESCRIPTOR_SIZE, GFP_KERNEL);
	if (!buf)
		return false;
	desc = buf;

	total_len = usb_get_descriptor(usbdev, 0x5f, /* vendor specific */
				    0, desc, MAX_VENDOR_DESCRIPTOR_SIZE);
	if (total_len > 5) {
		pr_info("vendor descriptor length:%x data:%02x %02x %02x %02x" \
			"%02x %02x %02x %02x %02x %02x %02x\n",
			total_len, desc[0],
			desc[1], desc[2], desc[3], desc[4], desc[5], desc[6],
			desc[7], desc[8], desc[9], desc[10]);

		if ((desc[0] != total_len) || /* descriptor length */
		    (desc[1] != 0x5f) ||   /* vendor descriptor type */
		    (desc[2] != 0x01) ||   /* version (2 bytes) */
		    (desc[3] != 0x00) ||
		    (desc[4] != total_len - 2)) /* length after type */
			goto unrecognized;

		desc_end = desc + total_len;
		desc += 5; /* the fixed header we've already parsed */

		while (desc < desc_end) {
			u8 length;
			u16 key;

			key = *((u16 *) desc);
			desc += sizeof(u16);
			length = *desc;
			desc++;

			switch (key) {
			case 0x0200: { /* max_area */
				u32 max_area;
				max_area = le32_to_cpu(*((u32 *)desc));
				pr_warn("DL chip limited to %d pixel modes\n",
					max_area);
				dev->sku_pixel_limit = max_area;
				break;
			}
			default:
				break;
			}
			desc += length;
		}
	}

	goto success;

unrecognized:
	/* allow udlfb to load for now even if firmware unrecognized */
	pr_err("Unrecognized vendor firmware descriptor\n");

success:
	kfree(buf);
	return true;
}
static int dlfb_usb_probe(struct usb_interface *interface,
			const struct usb_device_id *id)
{
	struct usb_device *usbdev;
	struct dlfb_data *dev = 0;
	struct fb_info *info = 0;
	int retval = -ENOMEM;
	int i;

	/* usb initialization */

	usbdev = interface_to_usbdev(interface);

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (dev == NULL) {
		err("dlfb_usb_probe: failed alloc of dev struct\n");
		goto error;
	}

	/* we need to wait for both usb and fbdev to spin down on disconnect */
	kref_init(&dev->kref); /* matching kref_put in usb .disconnect fn */
	kref_get(&dev->kref); /* matching kref_put in free_framebuffer_work */

	dev->udev = usbdev;
	dev->gdev = &usbdev->dev; /* our generic struct device * */
	usb_set_intfdata(interface, dev);

	pr_info("%s %s - serial #%s\n",
		usbdev->manufacturer, usbdev->product, usbdev->serial);
	pr_info("vid_%04x&pid_%04x&rev_%04x driver's dlfb_data struct at %p\n",
		usbdev->descriptor.idVendor, usbdev->descriptor.idProduct,
		usbdev->descriptor.bcdDevice, dev);
	pr_info("console enable=%d\n", console);
	pr_info("fb_defio enable=%d\n", fb_defio);

	dev->sku_pixel_limit = 2048 * 1152; /* default to maximum */

	if (!dlfb_parse_vendor_descriptor(dev, usbdev)) {
		pr_err("firmware not recognized. Assume incompatible device\n");
		goto error;
	}

	if (!dlfb_alloc_urb_list(dev, WRITES_IN_FLIGHT, MAX_TRANSFER)) {
		retval = -ENOMEM;
		pr_err("dlfb_alloc_urb_list failed\n");
		goto error;
	}

	/* We don't register a new USB class. Our client interface is fbdev */

	/* allocates framebuffer driver structure, not framebuffer memory */
	info = framebuffer_alloc(0, &usbdev->dev);
	if (!info) {
		retval = -ENOMEM;
		pr_err("framebuffer_alloc failed\n");
		goto error;
	}

	dev->info = info;
	info->par = dev;
	info->pseudo_palette = dev->pseudo_palette;
	info->fbops = &dlfb_ops;

	retval = fb_alloc_cmap(&info->cmap, 256, 0);
	if (retval < 0) {
		pr_err("fb_alloc_cmap failed %x\n", retval);
		goto error;
	}

	INIT_DELAYED_WORK(&dev->free_framebuffer_work,
			  dlfb_free_framebuffer_work);

	INIT_LIST_HEAD(&info->modelist);

	retval = dlfb_setup_modes(dev, info, NULL, 0);
	if (retval != 0) {
		pr_err("unable to find common mode for display and adapter\n");
		goto error;
	}

	/* ready to begin using device */

	atomic_set(&dev->usb_active, 1);
	dlfb_select_std_channel(dev);

	dlfb_ops_check_var(&info->var, info);
	dlfb_ops_set_par(info);

	retval = register_framebuffer(info);
	if (retval < 0) {
		pr_err("register_framebuffer failed %d\n", retval);
		goto error;
	}

	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
		device_create_file(info->dev, &fb_device_attrs[i]);

	device_create_bin_file(info->dev, &edid_attr);

	pr_info("DisplayLink USB device /dev/fb%d attached. %dx%d resolution."
			" Using %dK framebuffer memory\n", info->node,
			info->var.xres, info->var.yres,
			((dev->backing_buffer) ?
			info->fix.smem_len * 2 : info->fix.smem_len) >> 10);
	return 0;

error:
	if (dev) {

		if (info) {
			if (info->cmap.len != 0)
				fb_dealloc_cmap(&info->cmap);
			if (info->monspecs.modedb)
				fb_destroy_modedb(info->monspecs.modedb);
			if (info->screen_base)
				vfree(info->screen_base);

			fb_destroy_modelist(&info->modelist);

			framebuffer_release(info);
		}

		if (dev->backing_buffer)
			vfree(dev->backing_buffer);

		kref_put(&dev->kref, dlfb_free); /* ref for framebuffer */
		kref_put(&dev->kref, dlfb_free); /* last ref from kref_init */

		/* dev has been deallocated. Do not dereference */
	}

	return retval;
}

static void dlfb_usb_disconnect(struct usb_interface *interface)
{
	struct dlfb_data *dev;
	struct fb_info *info;
	int i;

	dev = usb_get_intfdata(interface);
	info = dev->info;

	pr_info("USB disconnect starting\n");

	/* we virtualize until all fb clients release. Then we free */
	dev->virtualized = true;

	/* When non-active we'll update virtual framebuffer, but no new urbs */
	atomic_set(&dev->usb_active, 0);

	/* remove udlfb's sysfs interfaces */
	for (i = 0; i < ARRAY_SIZE(fb_device_attrs); i++)
		device_remove_file(info->dev, &fb_device_attrs[i]);
	device_remove_bin_file(info->dev, &edid_attr);

	usb_set_intfdata(interface, NULL);

	/* if clients still have us open, will be freed on last close */
	if (dev->fb_count == 0)
		schedule_delayed_work(&dev->free_framebuffer_work, 0);

	/* release reference taken by kref_init in probe() */
	kref_put(&dev->kref, dlfb_free);

	/* consider dlfb_data freed */

	return;
}

static struct usb_driver dlfb_driver = {
	.name = "udlfb",
	.probe = dlfb_usb_probe,
	.disconnect = dlfb_usb_disconnect,
	.id_table = id_table,
};

static int __init dlfb_module_init(void)
{
	int res;

	res = usb_register(&dlfb_driver);
	if (res)
		err("usb_register failed. Error number %d", res);

	return res;
}

static void __exit dlfb_module_exit(void)
{
	usb_deregister(&dlfb_driver);
}

module_init(dlfb_module_init);
module_exit(dlfb_module_exit);

static void dlfb_urb_completion(struct urb *urb)
{
	struct urb_node *unode = urb->context;
	struct dlfb_data *dev = unode->dev;
	unsigned long flags;

	/* sync/async unlink faults aren't errors */
	if (urb->status) {
		if (!(urb->status == -ENOENT ||
		    urb->status == -ECONNRESET ||
		    urb->status == -ESHUTDOWN)) {
			pr_err("%s - nonzero write bulk status received: %d\n",
				__func__, urb->status);
			atomic_set(&dev->lost_pixels, 1);
		}
	}

	urb->transfer_buffer_length = dev->urbs.size; /* reset to actual */

	spin_lock_irqsave(&dev->urbs.lock, flags);
	list_add_tail(&unode->entry, &dev->urbs.list);
	dev->urbs.available++;
	spin_unlock_irqrestore(&dev->urbs.lock, flags);

	/*
	 * When using fb_defio, we deadlock if up() is called
	 * while another is waiting. So queue to another process.
	 */
	if (fb_defio)
		schedule_delayed_work(&unode->release_urb_work, 0);
	else
		up(&dev->urbs.limit_sem);
}

static void dlfb_free_urb_list(struct dlfb_data *dev)
{
	int count = dev->urbs.count;
	struct list_head *node;
	struct urb_node *unode;
	struct urb *urb;
	int ret;
	unsigned long flags;

	pr_notice("Waiting for completes and freeing all render urbs\n");

	/* keep waiting and freeing, until we've got 'em all */
	while (count--) {

		/* Getting interrupted means a leak, but ok at shutdown*/
		ret = down_interruptible(&dev->urbs.limit_sem);
		if (ret)
			break;

		spin_lock_irqsave(&dev->urbs.lock, flags);

		node = dev->urbs.list.next; /* have reserved one with sem */
		list_del_init(node);

		spin_unlock_irqrestore(&dev->urbs.lock, flags);

		unode = list_entry(node, struct urb_node, entry);
		urb = unode->urb;

		/* Free each separately allocated piece */
		usb_free_coherent(urb->dev, dev->urbs.size,
				  urb->transfer_buffer, urb->transfer_dma);
		usb_free_urb(urb);
		kfree(node);
	}

}

static int dlfb_alloc_urb_list(struct dlfb_data *dev, int count, size_t size)
{
	int i = 0;
	struct urb *urb;
	struct urb_node *unode;
	char *buf;

	spin_lock_init(&dev->urbs.lock);

	dev->urbs.size = size;
	INIT_LIST_HEAD(&dev->urbs.list);

	while (i < count) {
		unode = kzalloc(sizeof(struct urb_node), GFP_KERNEL);
		if (!unode)
			break;
		unode->dev = dev;

		INIT_DELAYED_WORK(&unode->release_urb_work,
			  dlfb_release_urb_work);

		urb = usb_alloc_urb(0, GFP_KERNEL);
		if (!urb) {
			kfree(unode);
			break;
		}
		unode->urb = urb;

		buf = usb_alloc_coherent(dev->udev, MAX_TRANSFER, GFP_KERNEL,
					 &urb->transfer_dma);
		if (!buf) {
			kfree(unode);
			usb_free_urb(urb);
			break;
		}

		/* urb->transfer_buffer_length set to actual before submit */
		usb_fill_bulk_urb(urb, dev->udev, usb_sndbulkpipe(dev->udev, 1),
			buf, size, dlfb_urb_completion, unode);
		urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

		list_add_tail(&unode->entry, &dev->urbs.list);

		i++;
	}

	sema_init(&dev->urbs.limit_sem, i);
	dev->urbs.count = i;
	dev->urbs.available = i;

	pr_notice("allocated %d %d byte urbs\n", i, (int) size);

	return i;
}

static struct urb *dlfb_get_urb(struct dlfb_data *dev)
{
	int ret = 0;
	struct list_head *entry;
	struct urb_node *unode;
	struct urb *urb = NULL;
	unsigned long flags;

	/* Wait for an in-flight buffer to complete and get re-queued */
	ret = down_timeout(&dev->urbs.limit_sem, GET_URB_TIMEOUT);
	if (ret) {
		atomic_set(&dev->lost_pixels, 1);
		pr_warn("wait for urb interrupted: %x available: %d\n",
		       ret, dev->urbs.available);
		goto error;
	}

	spin_lock_irqsave(&dev->urbs.lock, flags);

	BUG_ON(list_empty(&dev->urbs.list)); /* reserved one with limit_sem */
	entry = dev->urbs.list.next;
	list_del_init(entry);
	dev->urbs.available--;

	spin_unlock_irqrestore(&dev->urbs.lock, flags);

	unode = list_entry(entry, struct urb_node, entry);
	urb = unode->urb;

error:
	return urb;
}

static int dlfb_submit_urb(struct dlfb_data *dev, struct urb *urb, size_t len)
{
	int ret;

	BUG_ON(len > dev->urbs.size);

	urb->transfer_buffer_length = len; /* set to actual payload len */
	ret = usb_submit_urb(urb, GFP_KERNEL);
	if (ret) {
		dlfb_urb_completion(urb); /* because no one else will */
		atomic_set(&dev->lost_pixels, 1);
		pr_err("usb_submit_urb error %x\n", ret);
	}
	return ret;
}

module_param(console, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
MODULE_PARM_DESC(console, "Allow fbcon to consume first framebuffer found");

module_param(fb_defio, bool, S_IWUSR | S_IRUSR | S_IWGRP | S_IRGRP);
MODULE_PARM_DESC(fb_defio, "Enable fb_defio mmap support. *Experimental*");

MODULE_AUTHOR("Roberto De Ioris <roberto@unbit.it>, "
	      "Jaya Kumar <jayakumar.lkml@gmail.com>, "
	      "Bernie Thompson <bernie@plugable.com>");
MODULE_DESCRIPTION("DisplayLink kernel framebuffer driver");
MODULE_LICENSE("GPL");