aboutsummaryrefslogtreecommitdiff
path: root/drivers/i2c/i2c-core.c
blob: b9fa1d0320b43f3d01bcd8282dec9ce0a16c09a1 (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
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
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
/* i2c-core.c - a device driver for the iic-bus interface		     */
/* ------------------------------------------------------------------------- */
/*   Copyright (C) 1995-99 Simon G. Vogl

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.		     */
/* ------------------------------------------------------------------------- */

/* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
   All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
   SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
   Jean Delvare <khali@linux-fr.org>
   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
   Michael Lawnick <michael.lawnick.ext@nsn.com> */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/idr.h>
#include <linux/mutex.h>
#include <linux/of_device.h>
#include <linux/completion.h>
#include <linux/hardirq.h>
#include <linux/irqflags.h>
#include <linux/rwsem.h>
#include <linux/pm_runtime.h>
#include <asm/uaccess.h>

#include "i2c-core.h"


/* core_lock protects i2c_adapter_idr, and guarantees
   that device detection, deletion of detected devices, and attach_adapter
   and detach_adapter calls are serialized */
static DEFINE_MUTEX(core_lock);
static DEFINE_IDR(i2c_adapter_idr);

static struct device_type i2c_client_type;
static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);

/* ------------------------------------------------------------------------- */

static const struct i2c_device_id *i2c_match_id(const struct i2c_device_id *id,
						const struct i2c_client *client)
{
	while (id->name[0]) {
		if (strcmp(client->name, id->name) == 0)
			return id;
		id++;
	}
	return NULL;
}

static int i2c_device_match(struct device *dev, struct device_driver *drv)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;

	if (!client)
		return 0;

	/* Attempt an OF style match */
	if (of_driver_match_device(dev, drv))
		return 1;

	driver = to_i2c_driver(drv);
	/* match on an id table if there is one */
	if (driver->id_table)
		return i2c_match_id(driver->id_table, client) != NULL;

	return 0;
}

#ifdef	CONFIG_HOTPLUG

/* uevent helps with hotplug: modprobe -q $(MODALIAS) */
static int i2c_device_uevent(struct device *dev, struct kobj_uevent_env *env)
{
	struct i2c_client	*client = to_i2c_client(dev);

	if (add_uevent_var(env, "MODALIAS=%s%s",
			   I2C_MODULE_PREFIX, client->name))
		return -ENOMEM;
	dev_dbg(dev, "uevent\n");
	return 0;
}

#else
#define i2c_device_uevent	NULL
#endif	/* CONFIG_HOTPLUG */

static int i2c_device_probe(struct device *dev)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;
	int status;

	if (!client)
		return 0;

	driver = to_i2c_driver(dev->driver);
	if (!driver->probe || !driver->id_table)
		return -ENODEV;
	client->driver = driver;
	if (!device_can_wakeup(&client->dev))
		device_init_wakeup(&client->dev,
					client->flags & I2C_CLIENT_WAKE);
	dev_dbg(dev, "probe\n");

	status = driver->probe(client, i2c_match_id(driver->id_table, client));
	if (status) {
		client->driver = NULL;
		i2c_set_clientdata(client, NULL);
	}
	return status;
}

static int i2c_device_remove(struct device *dev)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_driver	*driver;
	int			status;

	if (!client || !dev->driver)
		return 0;

	driver = to_i2c_driver(dev->driver);
	if (driver->remove) {
		dev_dbg(dev, "remove\n");
		status = driver->remove(client);
	} else {
		dev->driver = NULL;
		status = 0;
	}
	if (status == 0) {
		client->driver = NULL;
		i2c_set_clientdata(client, NULL);
	}
	return status;
}

static void i2c_device_shutdown(struct device *dev)
{
	struct i2c_client *client = i2c_verify_client(dev);
	struct i2c_driver *driver;

	if (!client || !dev->driver)
		return;
	driver = to_i2c_driver(dev->driver);
	if (driver->shutdown)
		driver->shutdown(client);
}

#ifdef CONFIG_PM_SLEEP
static int i2c_legacy_suspend(struct device *dev, pm_message_t mesg)
{
	struct i2c_client *client = i2c_verify_client(dev);
	struct i2c_driver *driver;

	if (!client || !dev->driver)
		return 0;
	driver = to_i2c_driver(dev->driver);
	if (!driver->suspend)
		return 0;
	return driver->suspend(client, mesg);
}

static int i2c_legacy_resume(struct device *dev)
{
	struct i2c_client *client = i2c_verify_client(dev);
	struct i2c_driver *driver;

	if (!client || !dev->driver)
		return 0;
	driver = to_i2c_driver(dev->driver);
	if (!driver->resume)
		return 0;
	return driver->resume(client);
}

static int i2c_device_pm_suspend(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_suspend(dev);
	else
		return i2c_legacy_suspend(dev, PMSG_SUSPEND);
}

static int i2c_device_pm_resume(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_resume(dev);
	else
		return i2c_legacy_resume(dev);
}

static int i2c_device_pm_freeze(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_freeze(dev);
	else
		return i2c_legacy_suspend(dev, PMSG_FREEZE);
}

static int i2c_device_pm_thaw(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_thaw(dev);
	else
		return i2c_legacy_resume(dev);
}

static int i2c_device_pm_poweroff(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_poweroff(dev);
	else
		return i2c_legacy_suspend(dev, PMSG_HIBERNATE);
}

static int i2c_device_pm_restore(struct device *dev)
{
	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;

	if (pm)
		return pm_generic_restore(dev);
	else
		return i2c_legacy_resume(dev);
}
#else /* !CONFIG_PM_SLEEP */
#define i2c_device_pm_suspend	NULL
#define i2c_device_pm_resume	NULL
#define i2c_device_pm_freeze	NULL
#define i2c_device_pm_thaw	NULL
#define i2c_device_pm_poweroff	NULL
#define i2c_device_pm_restore	NULL
#endif /* !CONFIG_PM_SLEEP */

static void i2c_client_dev_release(struct device *dev)
{
	kfree(to_i2c_client(dev));
}

static ssize_t
show_name(struct device *dev, struct device_attribute *attr, char *buf)
{
	return sprintf(buf, "%s\n", dev->type == &i2c_client_type ?
		       to_i2c_client(dev)->name : to_i2c_adapter(dev)->name);
}

static ssize_t
show_modalias(struct device *dev, struct device_attribute *attr, char *buf)
{
	struct i2c_client *client = to_i2c_client(dev);
	return sprintf(buf, "%s%s\n", I2C_MODULE_PREFIX, client->name);
}

static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
static DEVICE_ATTR(modalias, S_IRUGO, show_modalias, NULL);

static struct attribute *i2c_dev_attrs[] = {
	&dev_attr_name.attr,
	/* modalias helps coldplug:  modprobe $(cat .../modalias) */
	&dev_attr_modalias.attr,
	NULL
};

static struct attribute_group i2c_dev_attr_group = {
	.attrs		= i2c_dev_attrs,
};

static const struct attribute_group *i2c_dev_attr_groups[] = {
	&i2c_dev_attr_group,
	NULL
};

static const struct dev_pm_ops i2c_device_pm_ops = {
	.suspend = i2c_device_pm_suspend,
	.resume = i2c_device_pm_resume,
	.freeze = i2c_device_pm_freeze,
	.thaw = i2c_device_pm_thaw,
	.poweroff = i2c_device_pm_poweroff,
	.restore = i2c_device_pm_restore,
	SET_RUNTIME_PM_OPS(
		pm_generic_runtime_suspend,
		pm_generic_runtime_resume,
		pm_generic_runtime_idle
	)
};

struct bus_type i2c_bus_type = {
	.name		= "i2c",
	.match		= i2c_device_match,
	.probe		= i2c_device_probe,
	.remove		= i2c_device_remove,
	.shutdown	= i2c_device_shutdown,
	.pm		= &i2c_device_pm_ops,
};
EXPORT_SYMBOL_GPL(i2c_bus_type);

static struct device_type i2c_client_type = {
	.groups		= i2c_dev_attr_groups,
	.uevent		= i2c_device_uevent,
	.release	= i2c_client_dev_release,
};


/**
 * i2c_verify_client - return parameter as i2c_client, or NULL
 * @dev: device, probably from some driver model iterator
 *
 * When traversing the driver model tree, perhaps using driver model
 * iterators like @device_for_each_child(), you can't assume very much
 * about the nodes you find.  Use this function to avoid oopses caused
 * by wrongly treating some non-I2C device as an i2c_client.
 */
struct i2c_client *i2c_verify_client(struct device *dev)
{
	return (dev->type == &i2c_client_type)
			? to_i2c_client(dev)
			: NULL;
}
EXPORT_SYMBOL(i2c_verify_client);


/* This is a permissive address validity check, I2C address map constraints
 * are purposedly not enforced, except for the general call address. */
static int i2c_check_client_addr_validity(const struct i2c_client *client)
{
	if (client->flags & I2C_CLIENT_TEN) {
		/* 10-bit address, all values are valid */
		if (client->addr > 0x3ff)
			return -EINVAL;
	} else {
		/* 7-bit address, reject the general call address */
		if (client->addr == 0x00 || client->addr > 0x7f)
			return -EINVAL;
	}
	return 0;
}

/* And this is a strict address validity check, used when probing. If a
 * device uses a reserved address, then it shouldn't be probed. 7-bit
 * addressing is assumed, 10-bit address devices are rare and should be
 * explicitly enumerated. */
static int i2c_check_addr_validity(unsigned short addr)
{
	/*
	 * Reserved addresses per I2C specification:
	 *  0x00       General call address / START byte
	 *  0x01       CBUS address
	 *  0x02       Reserved for different bus format
	 *  0x03       Reserved for future purposes
	 *  0x04-0x07  Hs-mode master code
	 *  0x78-0x7b  10-bit slave addressing
	 *  0x7c-0x7f  Reserved for future purposes
	 */
	if (addr < 0x08 || addr > 0x77)
		return -EINVAL;
	return 0;
}

static int __i2c_check_addr_busy(struct device *dev, void *addrp)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	int			addr = *(int *)addrp;

	if (client && client->addr == addr)
		return -EBUSY;
	return 0;
}

/* walk up mux tree */
static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result;

	result = device_for_each_child(&adapter->dev, &addr,
					__i2c_check_addr_busy);

	if (!result && parent)
		result = i2c_check_mux_parents(parent, addr);

	return result;
}

/* recurse down mux tree */
static int i2c_check_mux_children(struct device *dev, void *addrp)
{
	int result;

	if (dev->type == &i2c_adapter_type)
		result = device_for_each_child(dev, addrp,
						i2c_check_mux_children);
	else
		result = __i2c_check_addr_busy(dev, addrp);

	return result;
}

static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);
	int result = 0;

	if (parent)
		result = i2c_check_mux_parents(parent, addr);

	if (!result)
		result = device_for_each_child(&adapter->dev, &addr,
						i2c_check_mux_children);

	return result;
}

/**
 * i2c_lock_adapter - Get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 */
void i2c_lock_adapter(struct i2c_adapter *adapter)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

	if (parent)
		i2c_lock_adapter(parent);
	else
		rt_mutex_lock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_lock_adapter);

/**
 * i2c_trylock_adapter - Try to get exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 */
static int i2c_trylock_adapter(struct i2c_adapter *adapter)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

	if (parent)
		return i2c_trylock_adapter(parent);
	else
		return rt_mutex_trylock(&adapter->bus_lock);
}

/**
 * i2c_unlock_adapter - Release exclusive access to an I2C bus segment
 * @adapter: Target I2C bus segment
 */
void i2c_unlock_adapter(struct i2c_adapter *adapter)
{
	struct i2c_adapter *parent = i2c_parent_is_i2c_adapter(adapter);

	if (parent)
		i2c_unlock_adapter(parent);
	else
		rt_mutex_unlock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_unlock_adapter);

/**
 * i2c_new_device - instantiate an i2c device
 * @adap: the adapter managing the device
 * @info: describes one I2C device; bus_num is ignored
 * Context: can sleep
 *
 * Create an i2c device. Binding is handled through driver model
 * probe()/remove() methods.  A driver may be bound to this device when we
 * return from this function, or any later moment (e.g. maybe hotplugging will
 * load the driver module).  This call is not appropriate for use by mainboard
 * initialization logic, which usually runs during an arch_initcall() long
 * before any i2c_adapter could exist.
 *
 * This returns the new i2c client, which may be saved for later use with
 * i2c_unregister_device(); or NULL to indicate an error.
 */
struct i2c_client *
i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
	struct i2c_client	*client;
	int			status;

	client = kzalloc(sizeof *client, GFP_KERNEL);
	if (!client)
		return NULL;

	client->adapter = adap;

	client->dev.platform_data = info->platform_data;

	if (info->archdata)
		client->dev.archdata = *info->archdata;

	client->flags = info->flags;
	client->addr = info->addr;
	client->irq = info->irq;

	strlcpy(client->name, info->type, sizeof(client->name));

	/* Check for address validity */
	status = i2c_check_client_addr_validity(client);
	if (status) {
		dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx\n",
			client->flags & I2C_CLIENT_TEN ? 10 : 7, client->addr);
		goto out_err_silent;
	}

	/* Check for address business */
	status = i2c_check_addr_busy(adap, client->addr);
	if (status)
		goto out_err;

	client->dev.parent = &client->adapter->dev;
	client->dev.bus = &i2c_bus_type;
	client->dev.type = &i2c_client_type;
	client->dev.of_node = info->of_node;

	dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
		     client->addr);
	status = device_register(&client->dev);
	if (status)
		goto out_err;

	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
		client->name, dev_name(&client->dev));

	return client;

out_err:
	dev_err(&adap->dev, "Failed to register i2c client %s at 0x%02x "
		"(%d)\n", client->name, client->addr, status);
out_err_silent:
	kfree(client);
	return NULL;
}
EXPORT_SYMBOL_GPL(i2c_new_device);


/**
 * i2c_unregister_device - reverse effect of i2c_new_device()
 * @client: value returned from i2c_new_device()
 * Context: can sleep
 */
void i2c_unregister_device(struct i2c_client *client)
{
	device_unregister(&client->dev);
}
EXPORT_SYMBOL_GPL(i2c_unregister_device);


static const struct i2c_device_id dummy_id[] = {
	{ "dummy", 0 },
	{ },
};

static int dummy_probe(struct i2c_client *client,
		       const struct i2c_device_id *id)
{
	return 0;
}

static int dummy_remove(struct i2c_client *client)
{
	return 0;
}

static struct i2c_driver dummy_driver = {
	.driver.name	= "dummy",
	.probe		= dummy_probe,
	.remove		= dummy_remove,
	.id_table	= dummy_id,
};

/**
 * i2c_new_dummy - return a new i2c device bound to a dummy driver
 * @adapter: the adapter managing the device
 * @address: seven bit address to be used
 * Context: can sleep
 *
 * This returns an I2C client bound to the "dummy" driver, intended for use
 * with devices that consume multiple addresses.  Examples of such chips
 * include various EEPROMS (like 24c04 and 24c08 models).
 *
 * These dummy devices have two main uses.  First, most I2C and SMBus calls
 * except i2c_transfer() need a client handle; the dummy will be that handle.
 * And second, this prevents the specified address from being bound to a
 * different driver.
 *
 * This returns the new i2c client, which should be saved for later use with
 * i2c_unregister_device(); or NULL to indicate an error.
 */
struct i2c_client *i2c_new_dummy(struct i2c_adapter *adapter, u16 address)
{
	struct i2c_board_info info = {
		I2C_BOARD_INFO("dummy", address),
	};

	return i2c_new_device(adapter, &info);
}
EXPORT_SYMBOL_GPL(i2c_new_dummy);

/* ------------------------------------------------------------------------- */

/* I2C bus adapters -- one roots each I2C or SMBUS segment */

static void i2c_adapter_dev_release(struct device *dev)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	complete(&adap->dev_released);
}

/*
 * Let users instantiate I2C devices through sysfs. This can be used when
 * platform initialization code doesn't contain the proper data for
 * whatever reason. Also useful for drivers that do device detection and
 * detection fails, either because the device uses an unexpected address,
 * or this is a compatible device with different ID register values.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to provide incorrect parameters.
 */
static ssize_t
i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
		     const char *buf, size_t count)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	struct i2c_board_info info;
	struct i2c_client *client;
	char *blank, end;
	int res;

	memset(&info, 0, sizeof(struct i2c_board_info));

	blank = strchr(buf, ' ');
	if (!blank) {
		dev_err(dev, "%s: Missing parameters\n", "new_device");
		return -EINVAL;
	}
	if (blank - buf > I2C_NAME_SIZE - 1) {
		dev_err(dev, "%s: Invalid device name\n", "new_device");
		return -EINVAL;
	}
	memcpy(info.type, buf, blank - buf);

	/* Parse remaining parameters, reject extra parameters */
	res = sscanf(++blank, "%hi%c", &info.addr, &end);
	if (res < 1) {
		dev_err(dev, "%s: Can't parse I2C address\n", "new_device");
		return -EINVAL;
	}
	if (res > 1  && end != '\n') {
		dev_err(dev, "%s: Extra parameters\n", "new_device");
		return -EINVAL;
	}

	client = i2c_new_device(adap, &info);
	if (!client)
		return -EINVAL;

	/* Keep track of the added device */
	mutex_lock(&adap->userspace_clients_lock);
	list_add_tail(&client->detected, &adap->userspace_clients);
	mutex_unlock(&adap->userspace_clients_lock);
	dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
		 info.type, info.addr);

	return count;
}

/*
 * And of course let the users delete the devices they instantiated, if
 * they got it wrong. This interface can only be used to delete devices
 * instantiated by i2c_sysfs_new_device above. This guarantees that we
 * don't delete devices to which some kernel code still has references.
 *
 * Parameter checking may look overzealous, but we really don't want
 * the user to delete the wrong device.
 */
static ssize_t
i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
			const char *buf, size_t count)
{
	struct i2c_adapter *adap = to_i2c_adapter(dev);
	struct i2c_client *client, *next;
	unsigned short addr;
	char end;
	int res;

	/* Parse parameters, reject extra parameters */
	res = sscanf(buf, "%hi%c", &addr, &end);
	if (res < 1) {
		dev_err(dev, "%s: Can't parse I2C address\n", "delete_device");
		return -EINVAL;
	}
	if (res > 1  && end != '\n') {
		dev_err(dev, "%s: Extra parameters\n", "delete_device");
		return -EINVAL;
	}

	/* Make sure the device was added through sysfs */
	res = -ENOENT;
	mutex_lock(&adap->userspace_clients_lock);
	list_for_each_entry_safe(client, next, &adap->userspace_clients,
				 detected) {
		if (client->addr == addr) {
			dev_info(dev, "%s: Deleting device %s at 0x%02hx\n",
				 "delete_device", client->name, client->addr);

			list_del(&client->detected);
			i2c_unregister_device(client);
			res = count;
			break;
		}
	}
	mutex_unlock(&adap->userspace_clients_lock);

	if (res < 0)
		dev_err(dev, "%s: Can't find device in list\n",
			"delete_device");
	return res;
}

static DEVICE_ATTR(new_device, S_IWUSR, NULL, i2c_sysfs_new_device);
static DEVICE_ATTR(delete_device, S_IWUSR, NULL, i2c_sysfs_delete_device);

static struct attribute *i2c_adapter_attrs[] = {
	&dev_attr_name.attr,
	&dev_attr_new_device.attr,
	&dev_attr_delete_device.attr,
	NULL
};

static struct attribute_group i2c_adapter_attr_group = {
	.attrs		= i2c_adapter_attrs,
};

static const struct attribute_group *i2c_adapter_attr_groups[] = {
	&i2c_adapter_attr_group,
	NULL
};

struct device_type i2c_adapter_type = {
	.groups		= i2c_adapter_attr_groups,
	.release	= i2c_adapter_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_adapter_type);

#ifdef CONFIG_I2C_COMPAT
static struct class_compat *i2c_adapter_compat_class;
#endif

static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
{
	struct i2c_devinfo	*devinfo;

	down_read(&__i2c_board_lock);
	list_for_each_entry(devinfo, &__i2c_board_list, list) {
		if (devinfo->busnum == adapter->nr
				&& !i2c_new_device(adapter,
						&devinfo->board_info))
			dev_err(&adapter->dev,
				"Can't create device at 0x%02x\n",
				devinfo->board_info.addr);
	}
	up_read(&__i2c_board_lock);
}

static int i2c_do_add_adapter(struct i2c_driver *driver,
			      struct i2c_adapter *adap)
{
	/* Detect supported devices on that bus, and instantiate them */
	i2c_detect(adap, driver);

	/* Let legacy drivers scan this bus for matching devices */
	if (driver->attach_adapter) {
		/* We ignore the return code; if it fails, too bad */
		driver->attach_adapter(adap);
	}
	return 0;
}

static int __process_new_adapter(struct device_driver *d, void *data)
{
	return i2c_do_add_adapter(to_i2c_driver(d), data);
}

static int i2c_register_adapter(struct i2c_adapter *adap)
{
	int res = 0;

	/* Can't register until after driver model init */
	if (unlikely(WARN_ON(!i2c_bus_type.p))) {
		res = -EAGAIN;
		goto out_list;
	}

	/* Sanity checks */
	if (unlikely(adap->name[0] == '\0')) {
		pr_err("i2c-core: Attempt to register an adapter with "
		       "no name!\n");
		return -EINVAL;
	}
	if (unlikely(!adap->algo)) {
		pr_err("i2c-core: Attempt to register adapter '%s' with "
		       "no algo!\n", adap->name);
		return -EINVAL;
	}

	rt_mutex_init(&adap->bus_lock);
	mutex_init(&adap->userspace_clients_lock);
	INIT_LIST_HEAD(&adap->userspace_clients);

	/* Set default timeout to 1 second if not already set */
	if (adap->timeout == 0)
		adap->timeout = HZ;

	dev_set_name(&adap->dev, "i2c-%d", adap->nr);
	adap->dev.bus = &i2c_bus_type;
	adap->dev.type = &i2c_adapter_type;
	res = device_register(&adap->dev);
	if (res)
		goto out_list;

	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);

#ifdef CONFIG_I2C_COMPAT
	res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,
				       adap->dev.parent);
	if (res)
		dev_warn(&adap->dev,
			 "Failed to create compatibility class link\n");
#endif

	/* create pre-declared device nodes */
	if (adap->nr < __i2c_first_dynamic_bus_num)
		i2c_scan_static_board_info(adap);

	/* Notify drivers */
	mutex_lock(&core_lock);
	bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
	mutex_unlock(&core_lock);

	return 0;

out_list:
	mutex_lock(&core_lock);
	idr_remove(&i2c_adapter_idr, adap->nr);
	mutex_unlock(&core_lock);
	return res;
}

/**
 * i2c_add_adapter - declare i2c adapter, use dynamic bus number
 * @adapter: the adapter to add
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * doesn't matter.  Examples: for I2C adapters dynamically added by
 * USB links or PCI plugin cards.
 *
 * When this returns zero, a new bus number was allocated and stored
 * in adap->nr, and the specified adapter became available for clients.
 * Otherwise, a negative errno value is returned.
 */
int i2c_add_adapter(struct i2c_adapter *adapter)
{
	int	id, res = 0;

retry:
	if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
		return -ENOMEM;

	mutex_lock(&core_lock);
	/* "above" here means "above or equal to", sigh */
	res = idr_get_new_above(&i2c_adapter_idr, adapter,
				__i2c_first_dynamic_bus_num, &id);
	mutex_unlock(&core_lock);

	if (res < 0) {
		if (res == -EAGAIN)
			goto retry;
		return res;
	}

	adapter->nr = id;
	return i2c_register_adapter(adapter);
}
EXPORT_SYMBOL(i2c_add_adapter);

/**
 * i2c_add_numbered_adapter - declare i2c adapter, use static bus number
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * matters.  For example, use it for I2C adapters from system-on-chip CPUs,
 * or otherwise built in to the system's mainboard, and where i2c_board_info
 * is used to properly configure I2C devices.
 *
 * If no devices have pre-been declared for this bus, then be sure to
 * register the adapter before any dynamically allocated ones.  Otherwise
 * the required bus ID may not be available.
 *
 * When this returns zero, the specified adapter became available for
 * clients using the bus number provided in adap->nr.  Also, the table
 * of I2C devices pre-declared using i2c_register_board_info() is scanned,
 * and the appropriate driver model device nodes are created.  Otherwise, a
 * negative errno value is returned.
 */
int i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
	int	id;
	int	status;

	if (adap->nr & ~MAX_ID_MASK)
		return -EINVAL;

retry:
	if (idr_pre_get(&i2c_adapter_idr, GFP_KERNEL) == 0)
		return -ENOMEM;

	mutex_lock(&core_lock);
	/* "above" here means "above or equal to", sigh;
	 * we need the "equal to" result to force the result
	 */
	status = idr_get_new_above(&i2c_adapter_idr, adap, adap->nr, &id);
	if (status == 0 && id != adap->nr) {
		status = -EBUSY;
		idr_remove(&i2c_adapter_idr, id);
	}
	mutex_unlock(&core_lock);
	if (status == -EAGAIN)
		goto retry;

	if (status == 0)
		status = i2c_register_adapter(adap);
	return status;
}
EXPORT_SYMBOL_GPL(i2c_add_numbered_adapter);

static int i2c_do_del_adapter(struct i2c_driver *driver,
			      struct i2c_adapter *adapter)
{
	struct i2c_client *client, *_n;
	int res;

	/* Remove the devices we created ourselves as the result of hardware
	 * probing (using a driver's detect method) */
	list_for_each_entry_safe(client, _n, &driver->clients, detected) {
		if (client->adapter == adapter) {
			dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
				client->name, client->addr);
			list_del(&client->detected);
			i2c_unregister_device(client);
		}
	}

	if (!driver->detach_adapter)
		return 0;
	res = driver->detach_adapter(adapter);
	if (res)
		dev_err(&adapter->dev, "detach_adapter failed (%d) "
			"for driver [%s]\n", res, driver->driver.name);
	return res;
}

static int __unregister_client(struct device *dev, void *dummy)
{
	struct i2c_client *client = i2c_verify_client(dev);
	if (client && strcmp(client->name, "dummy"))
		i2c_unregister_device(client);
	return 0;
}

static int __unregister_dummy(struct device *dev, void *dummy)
{
	struct i2c_client *client = i2c_verify_client(dev);
	if (client)
		i2c_unregister_device(client);
	return 0;
}

static int __process_removed_adapter(struct device_driver *d, void *data)
{
	return i2c_do_del_adapter(to_i2c_driver(d), data);
}

/**
 * i2c_del_adapter - unregister I2C adapter
 * @adap: the adapter being unregistered
 * Context: can sleep
 *
 * This unregisters an I2C adapter which was previously registered
 * by @i2c_add_adapter or @i2c_add_numbered_adapter.
 */
int i2c_del_adapter(struct i2c_adapter *adap)
{
	int res = 0;
	struct i2c_adapter *found;
	struct i2c_client *client, *next;

	/* First make sure that this adapter was ever added */
	mutex_lock(&core_lock);
	found = idr_find(&i2c_adapter_idr, adap->nr);
	mutex_unlock(&core_lock);
	if (found != adap) {
		pr_debug("i2c-core: attempting to delete unregistered "
			 "adapter [%s]\n", adap->name);
		return -EINVAL;
	}

	/* Tell drivers about this removal */
	mutex_lock(&core_lock);
	res = bus_for_each_drv(&i2c_bus_type, NULL, adap,
			       __process_removed_adapter);
	mutex_unlock(&core_lock);
	if (res)
		return res;

	/* Remove devices instantiated from sysfs */
	mutex_lock(&adap->userspace_clients_lock);
	list_for_each_entry_safe(client, next, &adap->userspace_clients,
				 detected) {
		dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
			client->addr);
		list_del(&client->detected);
		i2c_unregister_device(client);
	}
	mutex_unlock(&adap->userspace_clients_lock);

	/* Detach any active clients. This can't fail, thus we do not
	 * check the returned value. This is a two-pass process, because
	 * we can't remove the dummy devices during the first pass: they
	 * could have been instantiated by real devices wishing to clean
	 * them up properly, so we give them a chance to do that first. */
	res = device_for_each_child(&adap->dev, NULL, __unregister_client);
	res = device_for_each_child(&adap->dev, NULL, __unregister_dummy);

#ifdef CONFIG_I2C_COMPAT
	class_compat_remove_link(i2c_adapter_compat_class, &adap->dev,
				 adap->dev.parent);
#endif

	/* device name is gone after device_unregister */
	dev_dbg(&adap->dev, "adapter [%s] unregistered\n", adap->name);

	/* clean up the sysfs representation */
	init_completion(&adap->dev_released);
	device_unregister(&adap->dev);

	/* wait for sysfs to drop all references */
	wait_for_completion(&adap->dev_released);

	/* free bus id */
	mutex_lock(&core_lock);
	idr_remove(&i2c_adapter_idr, adap->nr);
	mutex_unlock(&core_lock);

	/* Clear the device structure in case this adapter is ever going to be
	   added again */
	memset(&adap->dev, 0, sizeof(adap->dev));

	return 0;
}
EXPORT_SYMBOL(i2c_del_adapter);


/* ------------------------------------------------------------------------- */

int i2c_for_each_dev(void *data, int (*fn)(struct device *, void *))
{
	int res;

	mutex_lock(&core_lock);
	res = bus_for_each_dev(&i2c_bus_type, NULL, data, fn);
	mutex_unlock(&core_lock);

	return res;
}
EXPORT_SYMBOL_GPL(i2c_for_each_dev);

static int __process_new_driver(struct device *dev, void *data)
{
	if (dev->type != &i2c_adapter_type)
		return 0;
	return i2c_do_add_adapter(data, to_i2c_adapter(dev));
}

/*
 * An i2c_driver is used with one or more i2c_client (device) nodes to access
 * i2c slave chips, on a bus instance associated with some i2c_adapter.
 */

int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
{
	int res;

	/* Can't register until after driver model init */
	if (unlikely(WARN_ON(!i2c_bus_type.p)))
		return -EAGAIN;

	/* add the driver to the list of i2c drivers in the driver core */
	driver->driver.owner = owner;
	driver->driver.bus = &i2c_bus_type;

	/* When registration returns, the driver core
	 * will have called probe() for all matching-but-unbound devices.
	 */
	res = driver_register(&driver->driver);
	if (res)
		return res;

	/* Drivers should switch to dev_pm_ops instead. */
	if (driver->suspend)
		pr_warn("i2c-core: driver [%s] using legacy suspend method\n",
			driver->driver.name);
	if (driver->resume)
		pr_warn("i2c-core: driver [%s] using legacy resume method\n",
			driver->driver.name);

	pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);

	INIT_LIST_HEAD(&driver->clients);
	/* Walk the adapters that are already present */
	i2c_for_each_dev(driver, __process_new_driver);

	return 0;
}
EXPORT_SYMBOL(i2c_register_driver);

static int __process_removed_driver(struct device *dev, void *data)
{
	if (dev->type != &i2c_adapter_type)
		return 0;
	return i2c_do_del_adapter(data, to_i2c_adapter(dev));
}

/**
 * i2c_del_driver - unregister I2C driver
 * @driver: the driver being unregistered
 * Context: can sleep
 */
void i2c_del_driver(struct i2c_driver *driver)
{
	i2c_for_each_dev(driver, __process_removed_driver);

	driver_unregister(&driver->driver);
	pr_debug("i2c-core: driver [%s] unregistered\n", driver->driver.name);
}
EXPORT_SYMBOL(i2c_del_driver);

/* ------------------------------------------------------------------------- */

/**
 * i2c_use_client - increments the reference count of the i2c client structure
 * @client: the client being referenced
 *
 * Each live reference to a client should be refcounted. The driver model does
 * that automatically as part of driver binding, so that most drivers don't
 * need to do this explicitly: they hold a reference until they're unbound
 * from the device.
 *
 * A pointer to the client with the incremented reference counter is returned.
 */
struct i2c_client *i2c_use_client(struct i2c_client *client)
{
	if (client && get_device(&client->dev))
		return client;
	return NULL;
}
EXPORT_SYMBOL(i2c_use_client);

/**
 * i2c_release_client - release a use of the i2c client structure
 * @client: the client being no longer referenced
 *
 * Must be called when a user of a client is finished with it.
 */
void i2c_release_client(struct i2c_client *client)
{
	if (client)
		put_device(&client->dev);
}
EXPORT_SYMBOL(i2c_release_client);

struct i2c_cmd_arg {
	unsigned	cmd;
	void		*arg;
};

static int i2c_cmd(struct device *dev, void *_arg)
{
	struct i2c_client	*client = i2c_verify_client(dev);
	struct i2c_cmd_arg	*arg = _arg;

	if (client && client->driver && client->driver->command)
		client->driver->command(client, arg->cmd, arg->arg);
	return 0;
}

void i2c_clients_command(struct i2c_adapter *adap, unsigned int cmd, void *arg)
{
	struct i2c_cmd_arg	cmd_arg;

	cmd_arg.cmd = cmd;
	cmd_arg.arg = arg;
	device_for_each_child(&adap->dev, &cmd_arg, i2c_cmd);
}
EXPORT_SYMBOL(i2c_clients_command);

static int __init i2c_init(void)
{
	int retval;

	retval = bus_register(&i2c_bus_type);
	if (retval)
		return retval;
#ifdef CONFIG_I2C_COMPAT
	i2c_adapter_compat_class = class_compat_register("i2c-adapter");
	if (!i2c_adapter_compat_class) {
		retval = -ENOMEM;
		goto bus_err;
	}
#endif
	retval = i2c_add_driver(&dummy_driver);
	if (retval)
		goto class_err;
	return 0;

class_err:
#ifdef CONFIG_I2C_COMPAT
	class_compat_unregister(i2c_adapter_compat_class);
bus_err:
#endif
	bus_unregister(&i2c_bus_type);
	return retval;
}

static void __exit i2c_exit(void)
{
	i2c_del_driver(&dummy_driver);
#ifdef CONFIG_I2C_COMPAT
	class_compat_unregister(i2c_adapter_compat_class);
#endif
	bus_unregister(&i2c_bus_type);
}

/* We must initialize early, because some subsystems register i2c drivers
 * in subsys_initcall() code, but are linked (and initialized) before i2c.
 */
postcore_initcall(i2c_init);
module_exit(i2c_exit);

/* ----------------------------------------------------
 * the functional interface to the i2c busses.
 * ----------------------------------------------------
 */

/**
 * i2c_transfer - execute a single or combined I2C message
 * @adap: Handle to I2C bus
 * @msgs: One or more messages to execute before STOP is issued to
 *	terminate the operation; each message begins with a START.
 * @num: Number of messages to be executed.
 *
 * Returns negative errno, else the number of messages executed.
 *
 * Note that there is no requirement that each message be sent to
 * the same slave address, although that is the most common model.
 */
int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
{
	unsigned long orig_jiffies;
	int ret, try;

	/* REVISIT the fault reporting model here is weak:
	 *
	 *  - When we get an error after receiving N bytes from a slave,
	 *    there is no way to report "N".
	 *
	 *  - When we get a NAK after transmitting N bytes to a slave,
	 *    there is no way to report "N" ... or to let the master
	 *    continue executing the rest of this combined message, if
	 *    that's the appropriate response.
	 *
	 *  - When for example "num" is two and we successfully complete
	 *    the first message but get an error part way through the
	 *    second, it's unclear whether that should be reported as
	 *    one (discarding status on the second message) or errno
	 *    (discarding status on the first one).
	 */

	if (adap->algo->master_xfer) {
#ifdef DEBUG
		for (ret = 0; ret < num; ret++) {
			dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
				"len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD)
				? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
				(msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
		}
#endif

		if (in_atomic() || irqs_disabled()) {
			ret = i2c_trylock_adapter(adap);
			if (!ret)
				/* I2C activity is ongoing. */
				return -EAGAIN;
		} else {
			i2c_lock_adapter(adap);
		}

		/* Retry automatically on arbitration loss */
		orig_jiffies = jiffies;
		for (ret = 0, try = 0; try <= adap->retries; try++) {
			ret = adap->algo->master_xfer(adap, msgs, num);
			if (ret != -EAGAIN)
				break;
			if (time_after(jiffies, orig_jiffies + adap->timeout))
				break;
		}
		i2c_unlock_adapter(adap);

		return ret;
	} else {
		dev_dbg(&adap->dev, "I2C level transfers not supported\n");
		return -EOPNOTSUPP;
	}
}
EXPORT_SYMBOL(i2c_transfer);

/**
 * i2c_master_send - issue a single I2C message in master transmit mode
 * @client: Handle to slave device
 * @buf: Data that will be written to the slave
 * @count: How many bytes to write, must be less than 64k since msg.len is u16
 *
 * Returns negative errno, or else the number of bytes written.
 */
int i2c_master_send(const struct i2c_client *client, const char *buf, int count)
{
	int ret;
	struct i2c_adapter *adap = client->adapter;
	struct i2c_msg msg;

	msg.addr = client->addr;
	msg.flags = client->flags & I2C_M_TEN;
	msg.len = count;
	msg.buf = (char *)buf;

	ret = i2c_transfer(adap, &msg, 1);

	/* If everything went ok (i.e. 1 msg transmitted), return #bytes
	   transmitted, else error code. */
	return (ret == 1) ? count : ret;
}
EXPORT_SYMBOL(i2c_master_send);

/**
 * i2c_master_recv - issue a single I2C message in master receive mode
 * @client: Handle to slave device
 * @buf: Where to store data read from slave
 * @count: How many bytes to read, must be less than 64k since msg.len is u16
 *
 * Returns negative errno, or else the number of bytes read.
 */
int i2c_master_recv(const struct i2c_client *client, char *buf, int count)
{
	struct i2c_adapter *adap = client->adapter;
	struct i2c_msg msg;
	int ret;

	msg.addr = client->addr;
	msg.flags = client->flags & I2C_M_TEN;
	msg.flags |= I2C_M_RD;
	msg.len = count;
	msg.buf = buf;

	ret = i2c_transfer(adap, &msg, 1);

	/* If everything went ok (i.e. 1 msg transmitted), return #bytes
	   transmitted, else error code. */
	return (ret == 1) ? count : ret;
}
EXPORT_SYMBOL(i2c_master_recv);

/* ----------------------------------------------------
 * the i2c address scanning function
 * Will not work for 10-bit addresses!
 * ----------------------------------------------------
 */

/*
 * Legacy default probe function, mostly relevant for SMBus. The default
 * probe method is a quick write, but it is known to corrupt the 24RF08
 * EEPROMs due to a state machine bug, and could also irreversibly
 * write-protect some EEPROMs, so for address ranges 0x30-0x37 and 0x50-0x5f,
 * we use a short byte read instead. Also, some bus drivers don't implement
 * quick write, so we fallback to a byte read in that case too.
 * On x86, there is another special case for FSC hardware monitoring chips,
 * which want regular byte reads (address 0x73.) Fortunately, these are the
 * only known chips using this I2C address on PC hardware.
 * Returns 1 if probe succeeded, 0 if not.
 */
static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
{
	int err;
	union i2c_smbus_data dummy;

#ifdef CONFIG_X86
	if (addr == 0x73 && (adap->class & I2C_CLASS_HWMON)
	 && i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE_DATA))
		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
				     I2C_SMBUS_BYTE_DATA, &dummy);
	else
#endif
	if (!((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50)
	 && i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0,
				     I2C_SMBUS_QUICK, NULL);
	else if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE))
		err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
				     I2C_SMBUS_BYTE, &dummy);
	else {
		dev_warn(&adap->dev, "No suitable probing method supported\n");
		err = -EOPNOTSUPP;
	}

	return err >= 0;
}

static int i2c_detect_address(struct i2c_client *temp_client,
			      struct i2c_driver *driver)
{
	struct i2c_board_info info;
	struct i2c_adapter *adapter = temp_client->adapter;
	int addr = temp_client->addr;
	int err;

	/* Make sure the address is valid */
	err = i2c_check_addr_validity(addr);
	if (err) {
		dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
			 addr);
		return err;
	}

	/* Skip if already in use */
	if (i2c_check_addr_busy(adapter, addr))
		return 0;

	/* Make sure there is something at this address */
	if (!i2c_default_probe(adapter, addr))
		return 0;

	/* Finally call the custom detection function */
	memset(&info, 0, sizeof(struct i2c_board_info));
	info.addr = addr;
	err = driver->detect(temp_client, &info);
	if (err) {
		/* -ENODEV is returned if the detection fails. We catch it
		   here as this isn't an error. */
		return err == -ENODEV ? 0 : err;
	}

	/* Consistency check */
	if (info.type[0] == '\0') {
		dev_err(&adapter->dev, "%s detection function provided "
			"no name for 0x%x\n", driver->driver.name,
			addr);
	} else {
		struct i2c_client *client;

		/* Detection succeeded, instantiate the device */
		dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
			info.type, info.addr);
		client = i2c_new_device(adapter, &info);
		if (client)
			list_add_tail(&client->detected, &driver->clients);
		else
			dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n",
				info.type, info.addr);
	}
	return 0;
}

static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
{
	const unsigned short *address_list;
	struct i2c_client *temp_client;
	int i, err = 0;
	int adap_id = i2c_adapter_id(adapter);

	address_list = driver->address_list;
	if (!driver->detect || !address_list)
		return 0;

	/* Stop here if the classes do not match */
	if (!(adapter->class & driver->class))
		return 0;

	/* Set up a temporary client to help detect callback */
	temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
	if (!temp_client)
		return -ENOMEM;
	temp_client->adapter = adapter;

	for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
		dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
			"addr 0x%02x\n", adap_id, address_list[i]);
		temp_client->addr = address_list[i];
		err = i2c_detect_address(temp_client, driver);
		if (unlikely(err))
			break;
	}

	kfree(temp_client);
	return err;
}

int i2c_probe_func_quick_read(struct i2c_adapter *adap, unsigned short addr)
{
	return i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
			      I2C_SMBUS_QUICK, NULL) >= 0;
}
EXPORT_SYMBOL_GPL(i2c_probe_func_quick_read);

struct i2c_client *
i2c_new_probed_device(struct i2c_adapter *adap,
		      struct i2c_board_info *info,
		      unsigned short const *addr_list,
		      int (*probe)(struct i2c_adapter *, unsigned short addr))
{
	int i;

	if (!probe)
		probe = i2c_default_probe;

	for (i = 0; addr_list[i] != I2C_CLIENT_END; i++) {
		/* Check address validity */
		if (i2c_check_addr_validity(addr_list[i]) < 0) {
			dev_warn(&adap->dev, "Invalid 7-bit address "
				 "0x%02x\n", addr_list[i]);
			continue;
		}

		/* Check address availability */
		if (i2c_check_addr_busy(adap, addr_list[i])) {
			dev_dbg(&adap->dev, "Address 0x%02x already in "
				"use, not probing\n", addr_list[i]);
			continue;
		}

		/* Test address responsiveness */
		if (probe(adap, addr_list[i]))
			break;
	}

	if (addr_list[i] == I2C_CLIENT_END) {
		dev_dbg(&adap->dev, "Probing failed, no device found\n");
		return NULL;
	}

	info->addr = addr_list[i];
	return i2c_new_device(adap, info);
}
EXPORT_SYMBOL_GPL(i2c_new_probed_device);

struct i2c_adapter *i2c_get_adapter(int nr)
{
	struct i2c_adapter *adapter;

	mutex_lock(&core_lock);
	adapter = idr_find(&i2c_adapter_idr, nr);
	if (adapter && !try_module_get(adapter->owner))
		adapter = NULL;

	mutex_unlock(&core_lock);
	return adapter;
}
EXPORT_SYMBOL(i2c_get_adapter);

void i2c_put_adapter(struct i2c_adapter *adap)
{
	module_put(adap->owner);
}
EXPORT_SYMBOL(i2c_put_adapter);

/* The SMBus parts */

#define POLY    (0x1070U << 3)
static u8 crc8(u16 data)
{
	int i;

	for (i = 0; i < 8; i++) {
		if (data & 0x8000)
			data = data ^ POLY;
		data = data << 1;
	}
	return (u8)(data >> 8);
}

/* Incremental CRC8 over count bytes in the array pointed to by p */
static u8 i2c_smbus_pec(u8 crc, u8 *p, size_t count)
{
	int i;

	for (i = 0; i < count; i++)
		crc = crc8((crc ^ p[i]) << 8);
	return crc;
}

/* Assume a 7-bit address, which is reasonable for SMBus */
static u8 i2c_smbus_msg_pec(u8 pec, struct i2c_msg *msg)
{
	/* The address will be sent first */
	u8 addr = (msg->addr << 1) | !!(msg->flags & I2C_M_RD);
	pec = i2c_smbus_pec(pec, &addr, 1);

	/* The data buffer follows */
	return i2c_smbus_pec(pec, msg->buf, msg->len);
}

/* Used for write only transactions */
static inline void i2c_smbus_add_pec(struct i2c_msg *msg)
{
	msg->buf[msg->len] = i2c_smbus_msg_pec(0, msg);
	msg->len++;
}

/* Return <0 on CRC error
   If there was a write before this read (most cases) we need to take the
   partial CRC from the write part into account.
   Note that this function does modify the message (we need to decrease the
   message length to hide the CRC byte from the caller). */
static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
{
	u8 rpec = msg->buf[--msg->len];
	cpec = i2c_smbus_msg_pec(cpec, msg);

	if (rpec != cpec) {
		pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
			rpec, cpec);
		return -EBADMSG;
	}
	return 0;
}

/**
 * i2c_smbus_read_byte - SMBus "receive byte" protocol
 * @client: Handle to slave device
 *
 * This executes the SMBus "receive byte" protocol, returning negative errno
 * else the byte received from the device.
 */
s32 i2c_smbus_read_byte(const struct i2c_client *client)
{
	union i2c_smbus_data data;
	int status;

	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_READ, 0,
				I2C_SMBUS_BYTE, &data);
	return (status < 0) ? status : data.byte;
}
EXPORT_SYMBOL(i2c_smbus_read_byte);

/**
 * i2c_smbus_write_byte - SMBus "send byte" protocol
 * @client: Handle to slave device
 * @value: Byte to be sent
 *
 * This executes the SMBus "send byte" protocol, returning negative errno
 * else zero on success.
 */
s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value)
{
	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
	                      I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
}
EXPORT_SYMBOL(i2c_smbus_write_byte);

/**
 * i2c_smbus_read_byte_data - SMBus "read byte" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 *
 * This executes the SMBus "read byte" protocol, returning negative errno
 * else a data byte received from the device.
 */
s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command)
{
	union i2c_smbus_data data;
	int status;

	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_READ, command,
				I2C_SMBUS_BYTE_DATA, &data);
	return (status < 0) ? status : data.byte;
}
EXPORT_SYMBOL(i2c_smbus_read_byte_data);

/**
 * i2c_smbus_write_byte_data - SMBus "write byte" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 * @value: Byte being written
 *
 * This executes the SMBus "write byte" protocol, returning negative errno
 * else zero on success.
 */
s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command,
			      u8 value)
{
	union i2c_smbus_data data;
	data.byte = value;
	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
			      I2C_SMBUS_WRITE, command,
			      I2C_SMBUS_BYTE_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_byte_data);

/**
 * i2c_smbus_read_word_data - SMBus "read word" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 *
 * This executes the SMBus "read word" protocol, returning negative errno
 * else a 16-bit unsigned "word" received from the device.
 */
s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command)
{
	union i2c_smbus_data data;
	int status;

	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_READ, command,
				I2C_SMBUS_WORD_DATA, &data);
	return (status < 0) ? status : data.word;
}
EXPORT_SYMBOL(i2c_smbus_read_word_data);

/**
 * i2c_smbus_write_word_data - SMBus "write word" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 * @value: 16-bit "word" being written
 *
 * This executes the SMBus "write word" protocol, returning negative errno
 * else zero on success.
 */
s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command,
			      u16 value)
{
	union i2c_smbus_data data;
	data.word = value;
	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
			      I2C_SMBUS_WRITE, command,
			      I2C_SMBUS_WORD_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_word_data);

/**
 * i2c_smbus_process_call - SMBus "process call" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 * @value: 16-bit "word" being written
 *
 * This executes the SMBus "process call" protocol, returning negative errno
 * else a 16-bit unsigned "word" received from the device.
 */
s32 i2c_smbus_process_call(const struct i2c_client *client, u8 command,
			   u16 value)
{
	union i2c_smbus_data data;
	int status;
	data.word = value;

	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_WRITE, command,
				I2C_SMBUS_PROC_CALL, &data);
	return (status < 0) ? status : data.word;
}
EXPORT_SYMBOL(i2c_smbus_process_call);

/**
 * i2c_smbus_read_block_data - SMBus "block read" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 * @values: Byte array into which data will be read; big enough to hold
 *	the data returned by the slave.  SMBus allows at most 32 bytes.
 *
 * This executes the SMBus "block read" protocol, returning negative errno
 * else the number of data bytes in the slave's response.
 *
 * Note that using this function requires that the client's adapter support
 * the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality.  Not all adapter drivers
 * support this; its emulation through I2C messaging relies on a specific
 * mechanism (I2C_M_RECV_LEN) which may not be implemented.
 */
s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command,
			      u8 *values)
{
	union i2c_smbus_data data;
	int status;

	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_READ, command,
				I2C_SMBUS_BLOCK_DATA, &data);
	if (status)
		return status;

	memcpy(values, &data.block[1], data.block[0]);
	return data.block[0];
}
EXPORT_SYMBOL(i2c_smbus_read_block_data);

/**
 * i2c_smbus_write_block_data - SMBus "block write" protocol
 * @client: Handle to slave device
 * @command: Byte interpreted by slave
 * @length: Size of data block; SMBus allows at most 32 bytes
 * @values: Byte array which will be written.
 *
 * This executes the SMBus "block write" protocol, returning negative errno
 * else zero on success.
 */
s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
			       u8 length, const u8 *values)
{
	union i2c_smbus_data data;

	if (length > I2C_SMBUS_BLOCK_MAX)
		length = I2C_SMBUS_BLOCK_MAX;
	data.block[0] = length;
	memcpy(&data.block[1], values, length);
	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
			      I2C_SMBUS_WRITE, command,
			      I2C_SMBUS_BLOCK_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_block_data);

/* Returns the number of read bytes */
s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
				  u8 length, u8 *values)
{
	union i2c_smbus_data data;
	int status;

	if (length > I2C_SMBUS_BLOCK_MAX)
		length = I2C_SMBUS_BLOCK_MAX;
	data.block[0] = length;
	status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
				I2C_SMBUS_READ, command,
				I2C_SMBUS_I2C_BLOCK_DATA, &data);
	if (status < 0)
		return status;

	memcpy(values, &data.block[1], data.block[0]);
	return data.block[0];
}
EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);

s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
				   u8 length, const u8 *values)
{
	union i2c_smbus_data data;

	if (length > I2C_SMBUS_BLOCK_MAX)
		length = I2C_SMBUS_BLOCK_MAX;
	data.block[0] = length;
	memcpy(data.block + 1, values, length);
	return i2c_smbus_xfer(client->adapter, client->addr, client->flags,
			      I2C_SMBUS_WRITE, command,
			      I2C_SMBUS_I2C_BLOCK_DATA, &data);
}
EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data);

/* Simulate a SMBus command using the i2c protocol
   No checking of parameters is done!  */
static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
				   unsigned short flags,
				   char read_write, u8 command, int size,
				   union i2c_smbus_data *data)
{
	/* So we need to generate a series of msgs. In the case of writing, we
	  need to use only one message; when reading, we need two. We initialize
	  most things with sane defaults, to keep the code below somewhat
	  simpler. */
	unsigned char msgbuf0[I2C_SMBUS_BLOCK_MAX+3];
	unsigned char msgbuf1[I2C_SMBUS_BLOCK_MAX+2];
	int num = read_write == I2C_SMBUS_READ ? 2 : 1;
	struct i2c_msg msg[2] = { { addr, flags, 1, msgbuf0 },
	                          { addr, flags | I2C_M_RD, 0, msgbuf1 }
	                        };
	int i;
	u8 partial_pec = 0;
	int status;

	msgbuf0[0] = command;
	switch (size) {
	case I2C_SMBUS_QUICK:
		msg[0].len = 0;
		/* Special case: The read/write field is used as data */
		msg[0].flags = flags | (read_write == I2C_SMBUS_READ ?
					I2C_M_RD : 0);
		num = 1;
		break;
	case I2C_SMBUS_BYTE:
		if (read_write == I2C_SMBUS_READ) {
			/* Special case: only a read! */
			msg[0].flags = I2C_M_RD | flags;
			num = 1;
		}
		break;
	case I2C_SMBUS_BYTE_DATA:
		if (read_write == I2C_SMBUS_READ)
			msg[1].len = 1;
		else {
			msg[0].len = 2;
			msgbuf0[1] = data->byte;
		}
		break;
	case I2C_SMBUS_WORD_DATA:
		if (read_write == I2C_SMBUS_READ)
			msg[1].len = 2;
		else {
			msg[0].len = 3;
			msgbuf0[1] = data->word & 0xff;
			msgbuf0[2] = data->word >> 8;
		}
		break;
	case I2C_SMBUS_PROC_CALL:
		num = 2; /* Special case */
		read_write = I2C_SMBUS_READ;
		msg[0].len = 3;
		msg[1].len = 2;
		msgbuf0[1] = data->word & 0xff;
		msgbuf0[2] = data->word >> 8;
		break;
	case I2C_SMBUS_BLOCK_DATA:
		if (read_write == I2C_SMBUS_READ) {
			msg[1].flags |= I2C_M_RECV_LEN;
			msg[1].len = 1; /* block length will be added by
					   the underlying bus driver */
		} else {
			msg[0].len = data->block[0] + 2;
			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
				dev_err(&adapter->dev,
					"Invalid block write size %d\n",
					data->block[0]);
				return -EINVAL;
			}
			for (i = 1; i < msg[0].len; i++)
				msgbuf0[i] = data->block[i-1];
		}
		break;
	case I2C_SMBUS_BLOCK_PROC_CALL:
		num = 2; /* Another special case */
		read_write = I2C_SMBUS_READ;
		if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
			dev_err(&adapter->dev,
				"Invalid block write size %d\n",
				data->block[0]);
			return -EINVAL;
		}
		msg[0].len = data->block[0] + 2;
		for (i = 1; i < msg[0].len; i++)
			msgbuf0[i] = data->block[i-1];
		msg[1].flags |= I2C_M_RECV_LEN;
		msg[1].len = 1; /* block length will be added by
				   the underlying bus driver */
		break;
	case I2C_SMBUS_I2C_BLOCK_DATA:
		if (read_write == I2C_SMBUS_READ) {
			msg[1].len = data->block[0];
		} else {
			msg[0].len = data->block[0] + 1;
			if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
				dev_err(&adapter->dev,
					"Invalid block write size %d\n",
					data->block[0]);
				return -EINVAL;
			}
			for (i = 1; i <= data->block[0]; i++)
				msgbuf0[i] = data->block[i];
		}
		break;
	default:
		dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
		return -EOPNOTSUPP;
	}

	i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
				      && size != I2C_SMBUS_I2C_BLOCK_DATA);
	if (i) {
		/* Compute PEC if first message is a write */
		if (!(msg[0].flags & I2C_M_RD)) {
			if (num == 1) /* Write only */
				i2c_smbus_add_pec(&msg[0]);
			else /* Write followed by read */
				partial_pec = i2c_smbus_msg_pec(0, &msg[0]);
		}
		/* Ask for PEC if last message is a read */
		if (msg[num-1].flags & I2C_M_RD)
			msg[num-1].len++;
	}

	status = i2c_transfer(adapter, msg, num);
	if (status < 0)
		return status;

	/* Check PEC if last message is a read */
	if (i && (msg[num-1].flags & I2C_M_RD)) {
		status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
		if (status < 0)
			return status;
	}

	if (read_write == I2C_SMBUS_READ)
		switch (size) {
		case I2C_SMBUS_BYTE:
			data->byte = msgbuf0[0];
			break;
		case I2C_SMBUS_BYTE_DATA:
			data->byte = msgbuf1[0];
			break;
		case I2C_SMBUS_WORD_DATA:
		case I2C_SMBUS_PROC_CALL:
			data->word = msgbuf1[0] | (msgbuf1[1] << 8);
			break;
		case I2C_SMBUS_I2C_BLOCK_DATA:
			for (i = 0; i < data->block[0]; i++)
				data->block[i+1] = msgbuf1[i];
			break;
		case I2C_SMBUS_BLOCK_DATA:
		case I2C_SMBUS_BLOCK_PROC_CALL:
			for (i = 0; i < msgbuf1[0] + 1; i++)
				data->block[i] = msgbuf1[i];
			break;
		}
	return 0;
}

/**
 * i2c_smbus_xfer - execute SMBus protocol operations
 * @adapter: Handle to I2C bus
 * @addr: Address of SMBus slave on that bus
 * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
 * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
 * @command: Byte interpreted by slave, for protocols which use such bytes
 * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
 * @data: Data to be read or written
 *
 * This executes an SMBus protocol operation, and returns a negative
 * errno code else zero on success.
 */
s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
		   char read_write, u8 command, int protocol,
		   union i2c_smbus_data *data)
{
	unsigned long orig_jiffies;
	int try;
	s32 res;

	flags &= I2C_M_TEN | I2C_CLIENT_PEC;

	if (adapter->algo->smbus_xfer) {
		i2c_lock_adapter(adapter);

		/* Retry automatically on arbitration loss */
		orig_jiffies = jiffies;
		for (res = 0, try = 0; try <= adapter->retries; try++) {
			res = adapter->algo->smbus_xfer(adapter, addr, flags,
							read_write, command,
							protocol, data);
			if (res != -EAGAIN)
				break;
			if (time_after(jiffies,
				       orig_jiffies + adapter->timeout))
				break;
		}
		i2c_unlock_adapter(adapter);
	} else
		res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
					      command, protocol, data);

	return res;
}
EXPORT_SYMBOL(i2c_smbus_xfer);

MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
MODULE_DESCRIPTION("I2C-Bus main module");
MODULE_LICENSE("GPL");