aboutsummaryrefslogblamecommitdiffstats
path: root/drivers/char/tty_io.c
blob: 4b1eef51ec5926d97918331f20740c3664067375 (plain) (tree)
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
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
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208































































































                                                                                         
                        

























































                                                                                   































                                                                 
                                                                   
































































                                                                          
                                                                              









                                                             



                                                     



                                                       

                                  


















                                                              

















































































































































































                                                                           

                                 



                             
                                 





                                                    









                                                      

                                    







                                      





                                                                    
 
                                                  




























                                                                                                     

                                                               

                                             

                             

                                          
                                              



                                                        
                                                       
 




                                                              
 

















































                                                                              

                                        


                                                                
                 
































































































































































































                                                                                  
                                                                 





























































































































































































































































































































































































































































































































































































































                                                                                            
                    

                                       

                   
















































































































































































































































































































































































































































































































































































































































































































































































































                                                                                          
                                                                    


                                        
                                               



















































































































































































                                                                               
                                                            

                                                                        
                                                                    























































                                                                            
                            
























                                                                        
                                        

                                                          











                                                                                   
                                          






































































































































































































                                                                                
                               































                                                                               
                                                                      












                                                                            
                                                                                           





































































































































































































                                                                                   












                                           
                                                     



























                                                                              
                                                                                  





                                                                                  
                                                                                      






                                                                               
                                                                                   







                                                                            
                                                                                





                      
/*
 *  linux/drivers/char/tty_io.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
 * or rs-channels. It also implements echoing, cooked mode etc.
 *
 * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
 *
 * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
 * tty_struct and tty_queue structures.  Previously there was an array
 * of 256 tty_struct's which was statically allocated, and the
 * tty_queue structures were allocated at boot time.  Both are now
 * dynamically allocated only when the tty is open.
 *
 * Also restructured routines so that there is more of a separation
 * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
 * the low-level tty routines (serial.c, pty.c, console.c).  This
 * makes for cleaner and more compact code.  -TYT, 9/17/92 
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 *
 * NOTE: pay no attention to the line discipline code (yet); its
 * interface is still subject to change in this version...
 * -- TYT, 1/31/92
 *
 * Added functionality to the OPOST tty handling.  No delays, but all
 * other bits should be there.
 *	-- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
 *
 * Rewrote canonical mode and added more termios flags.
 * 	-- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
 *
 * Reorganized FASYNC support so mouse code can share it.
 *	-- ctm@ardi.com, 9Sep95
 *
 * New TIOCLINUX variants added.
 *	-- mj@k332.feld.cvut.cz, 19-Nov-95
 * 
 * Restrict vt switching via ioctl()
 *      -- grif@cs.ucr.edu, 5-Dec-95
 *
 * Move console and virtual terminal code to more appropriate files,
 * implement CONFIG_VT and generalize console device interface.
 *	-- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
 *
 * Rewrote init_dev and release_dev to eliminate races.
 *	-- Bill Hawes <whawes@star.net>, June 97
 *
 * Added devfs support.
 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 13-Jan-1998
 *
 * Added support for a Unix98-style ptmx device.
 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
 *
 * Reduced memory usage for older ARM systems
 *      -- Russell King <rmk@arm.linux.org.uk>
 *
 * Move do_SAK() into process context.  Less stack use in devfs functions.
 * alloc_tty_struct() always uses kmalloc() -- Andrew Morton <andrewm@uow.edu.eu> 17Mar01
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/devpts_fs.h>
#include <linux/file.h>
#include <linux/console.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/device.h>
#include <linux/idr.h>
#include <linux/wait.h>
#include <linux/bitops.h>
#include <linux/delay.h>

#include <asm/uaccess.h>
#include <asm/system.h>

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>
#include <linux/devfs_fs_kernel.h>

#include <linux/kmod.h>

#undef TTY_DEBUG_HANGUP

#define TTY_PARANOIA_CHECK 1
#define CHECK_TTY_COUNT 1

struct termios tty_std_termios = {	/* for the benefit of tty drivers  */
	.c_iflag = ICRNL | IXON,
	.c_oflag = OPOST | ONLCR,
	.c_cflag = B38400 | CS8 | CREAD | HUPCL,
	.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
		   ECHOCTL | ECHOKE | IEXTEN,
	.c_cc = INIT_C_CC
};

EXPORT_SYMBOL(tty_std_termios);

/* This list gets poked at by procfs and various bits of boot up code. This
   could do with some rationalisation such as pulling the tty proc function
   into this file */
   
LIST_HEAD(tty_drivers);			/* linked list of tty drivers */

/* Semaphore to protect creating and releasing a tty. This is shared with
   vt.c for deeply disgusting hack reasons */
DECLARE_MUTEX(tty_sem);

#ifdef CONFIG_UNIX98_PTYS
extern struct tty_driver *ptm_driver;	/* Unix98 pty masters; for /dev/ptmx */
extern int pty_limit;		/* Config limit on Unix98 ptys */
static DEFINE_IDR(allocated_ptys);
static DECLARE_MUTEX(allocated_ptys_lock);
static int ptmx_open(struct inode *, struct file *);
#endif

extern void disable_early_printk(void);

static void initialize_tty_struct(struct tty_struct *tty);

static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
static ssize_t tty_write(struct file *, const char __user *, size_t, loff_t *);
ssize_t redirected_tty_write(struct file *, const char __user *, size_t, loff_t *);
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
int tty_ioctl(struct inode * inode, struct file * file,
	      unsigned int cmd, unsigned long arg);
static int tty_fasync(int fd, struct file * filp, int on);
static void release_mem(struct tty_struct *tty, int idx);


static struct tty_struct *alloc_tty_struct(void)
{
	struct tty_struct *tty;

	tty = kmalloc(sizeof(struct tty_struct), GFP_KERNEL);
	if (tty)
		memset(tty, 0, sizeof(struct tty_struct));
	return tty;
}

static inline void free_tty_struct(struct tty_struct *tty)
{
	kfree(tty->write_buf);
	kfree(tty);
}

#define TTY_NUMBER(tty) ((tty)->index + (tty)->driver->name_base)

char *tty_name(struct tty_struct *tty, char *buf)
{
	if (!tty) /* Hmm.  NULL pointer.  That's fun. */
		strcpy(buf, "NULL tty");
	else
		strcpy(buf, tty->name);
	return buf;
}

EXPORT_SYMBOL(tty_name);

int tty_paranoia_check(struct tty_struct *tty, struct inode *inode,
			      const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
	if (!tty) {
		printk(KERN_WARNING
			"null TTY for (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
	if (tty->magic != TTY_MAGIC) {
		printk(KERN_WARNING
			"bad magic number for tty struct (%d:%d) in %s\n",
			imajor(inode), iminor(inode), routine);
		return 1;
	}
#endif
	return 0;
}

static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
	struct list_head *p;
	int count = 0;
	
	file_list_lock();
	list_for_each(p, &tty->tty_files) {
		count++;
	}
	file_list_unlock();
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_SLAVE &&
	    tty->link && tty->link->count)
		count++;
	if (tty->count != count) {
		printk(KERN_WARNING "Warning: dev (%s) tty->count(%d) "
				    "!= #fd's(%d) in %s\n",
		       tty->name, tty->count, count, routine);
		return count;
       }	
#endif
	return 0;
}

/*
 *	This is probably overkill for real world processors but
 *	they are not on hot paths so a little discipline won't do 
 *	any harm.
 */
 
static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
{
	down(&tty->termios_sem);
	tty->termios->c_line = num;
	up(&tty->termios_sem);
}

/*
 *	This guards the refcounted line discipline lists. The lock
 *	must be taken with irqs off because there are hangup path
 *	callers who will do ldisc lookups and cannot sleep.
 */
 
static DEFINE_SPINLOCK(tty_ldisc_lock);
static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
static struct tty_ldisc tty_ldiscs[NR_LDISCS];	/* line disc dispatch table */

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
	unsigned long flags;
	int ret = 0;
	
	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	tty_ldiscs[disc] = *new_ldisc;
	tty_ldiscs[disc].num = disc;
	tty_ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
	tty_ldiscs[disc].refcount = 0;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	
	return ret;
}
EXPORT_SYMBOL(tty_register_ldisc);

int tty_unregister_ldisc(int disc)
{
	unsigned long flags;
	int ret = 0;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return -EINVAL;

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty_ldiscs[disc].refcount)
		ret = -EBUSY;
	else
		tty_ldiscs[disc].flags &= ~LDISC_FLAG_DEFINED;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	return ret;
}
EXPORT_SYMBOL(tty_unregister_ldisc);

struct tty_ldisc *tty_ldisc_get(int disc)
{
	unsigned long flags;
	struct tty_ldisc *ld;

	if (disc < N_TTY || disc >= NR_LDISCS)
		return NULL;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);

	ld = &tty_ldiscs[disc];
	/* Check the entry is defined */
	if(ld->flags & LDISC_FLAG_DEFINED)
	{
		/* If the module is being unloaded we can't use it */
		if (!try_module_get(ld->owner))
		       	ld = NULL;
		else /* lock it */
			ld->refcount++;
	}
	else
		ld = NULL;
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ld;
}

EXPORT_SYMBOL_GPL(tty_ldisc_get);

void tty_ldisc_put(int disc)
{
	struct tty_ldisc *ld;
	unsigned long flags;
	
	if (disc < N_TTY || disc >= NR_LDISCS)
		BUG();
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty_ldiscs[disc];
	if(ld->refcount == 0)
		BUG();
	ld->refcount --;
	module_put(ld->owner);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}
	
EXPORT_SYMBOL_GPL(tty_ldisc_put);

static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
{
	tty->ldisc = *ld;
	tty->ldisc.refcount = 0;
}

/**
 *	tty_ldisc_try		-	internal helper
 *	@tty: the tty
 *
 *	Make a single attempt to grab and bump the refcount on
 *	the tty ldisc. Return 0 on failure or 1 on success. This is
 *	used to implement both the waiting and non waiting versions
 *	of tty_ldisc_ref
 */

static int tty_ldisc_try(struct tty_struct *tty)
{
	unsigned long flags;
	struct tty_ldisc *ld;
	int ret = 0;
	
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	ld = &tty->ldisc;
	if(test_bit(TTY_LDISC, &tty->flags))
	{
		ld->refcount++;
		ret = 1;
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	return ret;
}

/**
 *	tty_ldisc_ref_wait	-	wait for the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a 
 *	reference to it. If the line discipline is in flux then 
 *	wait patiently until it changes.
 *
 *	Note: Must not be called from an IRQ/timer context. The caller
 *	must also be careful not to hold other locks that will deadlock
 *	against a discipline change, such as an existing ldisc reference
 *	(which we check for)
 */
 
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
{
	/* wait_event is a macro */
	wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
	if(tty->ldisc.refcount == 0)
		printk(KERN_ERR "tty_ldisc_ref_wait\n");
	return &tty->ldisc;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);

/**
 *	tty_ldisc_ref		-	get the tty ldisc
 *	@tty: tty device
 *
 *	Dereference the line discipline for the terminal and take a 
 *	reference to it. If the line discipline is in flux then 
 *	return NULL. Can be called from IRQ and timer functions.
 */
 
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
{
	if(tty_ldisc_try(tty))
		return &tty->ldisc;
	return NULL;
}

EXPORT_SYMBOL_GPL(tty_ldisc_ref);

/**
 *	tty_ldisc_deref		-	free a tty ldisc reference
 *	@ld: reference to free up
 *
 *	Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
 *	be called in IRQ context.
 */
 
void tty_ldisc_deref(struct tty_ldisc *ld)
{
	unsigned long flags;

	if(ld == NULL)
		BUG();
		
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if(ld->refcount == 0)
		printk(KERN_ERR "tty_ldisc_deref: no references.\n");
	else
		ld->refcount--;
	if(ld->refcount == 0)
		wake_up(&tty_ldisc_wait);
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
}

EXPORT_SYMBOL_GPL(tty_ldisc_deref);

/**
 *	tty_ldisc_enable	-	allow ldisc use
 *	@tty: terminal to activate ldisc on
 *
 *	Set the TTY_LDISC flag when the line discipline can be called
 *	again. Do neccessary wakeups for existing sleepers.
 *
 *	Note: nobody should set this bit except via this function. Clearing
 *	directly is allowed.
 */

static void tty_ldisc_enable(struct tty_struct *tty)
{
	set_bit(TTY_LDISC, &tty->flags);
	wake_up(&tty_ldisc_wait);
}
	
/**
 *	tty_set_ldisc		-	set line discipline
 *	@tty: the terminal to set
 *	@ldisc: the line discipline
 *
 *	Set the discipline of a tty line. Must be called from a process
 *	context.
 */
 
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
	int retval = 0;
	struct tty_ldisc o_ldisc;
	char buf[64];
	int work;
	unsigned long flags;
	struct tty_ldisc *ld;
	struct tty_struct *o_tty;

	if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
		return -EINVAL;

restart:

	ld = tty_ldisc_get(ldisc);
	/* Eduardo Blanco <ejbs@cs.cs.com.uy> */
	/* Cyrus Durgin <cider@speakeasy.org> */
	if (ld == NULL) {
		request_module("tty-ldisc-%d", ldisc);
		ld = tty_ldisc_get(ldisc);
	}
	if (ld == NULL)
		return -EINVAL;

	tty_wait_until_sent(tty, 0);

	if (tty->ldisc.num == ldisc) {
		tty_ldisc_put(ldisc);
		return 0;
	}

	o_ldisc = tty->ldisc;
	o_tty = tty->link;

	/*
	 *	Make sure we don't change while someone holds a
	 *	reference to the line discipline. The TTY_LDISC bit
	 *	prevents anyone taking a reference once it is clear.
	 *	We need the lock to avoid racing reference takers.
	 */

	spin_lock_irqsave(&tty_ldisc_lock, flags);
	if (tty->ldisc.refcount || (o_tty && o_tty->ldisc.refcount)) {
		if(tty->ldisc.refcount) {
			/* Free the new ldisc we grabbed. Must drop the lock
			   first. */
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(ldisc);
			/*
			 * There are several reasons we may be busy, including
			 * random momentary I/O traffic. We must therefore
			 * retry. We could distinguish between blocking ops
			 * and retries if we made tty_ldisc_wait() smarter. That
			 * is up for discussion.
			 */
			if (wait_event_interruptible(tty_ldisc_wait, tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
		if(o_tty && o_tty->ldisc.refcount) {
			spin_unlock_irqrestore(&tty_ldisc_lock, flags);
			tty_ldisc_put(ldisc);
			if (wait_event_interruptible(tty_ldisc_wait, o_tty->ldisc.refcount == 0) < 0)
				return -ERESTARTSYS;
			goto restart;
		}
	}

	/* if the TTY_LDISC bit is set, then we are racing against another ldisc change */

	if (!test_bit(TTY_LDISC, &tty->flags)) {
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		tty_ldisc_put(ldisc);
		ld = tty_ldisc_ref_wait(tty);
		tty_ldisc_deref(ld);
		goto restart;
	}

	clear_bit(TTY_LDISC, &tty->flags);
	clear_bit(TTY_DONT_FLIP, &tty->flags);
	if (o_tty) {
		clear_bit(TTY_LDISC, &o_tty->flags);
		clear_bit(TTY_DONT_FLIP, &o_tty->flags);
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);

	/*
	 *	From this point on we know nobody has an ldisc
	 *	usage reference, nor can they obtain one until
	 *	we say so later on.
	 */

	work = cancel_delayed_work(&tty->flip.work);
	/*
	 * Wait for ->hangup_work and ->flip.work handlers to terminate
	 */
	 
	flush_scheduled_work();
	/* Shutdown the current discipline. */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);

	/* Now set up the new line discipline. */
	tty_ldisc_assign(tty, ld);
	tty_set_termios_ldisc(tty, ldisc);
	if (tty->ldisc.open)
		retval = (tty->ldisc.open)(tty);
	if (retval < 0) {
		tty_ldisc_put(ldisc);
		/* There is an outstanding reference here so this is safe */
		tty_ldisc_assign(tty, tty_ldisc_get(o_ldisc.num));
		tty_set_termios_ldisc(tty, tty->ldisc.num);
		if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
			tty_ldisc_put(o_ldisc.num);
			/* This driver is always present */
			tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
			tty_set_termios_ldisc(tty, N_TTY);
			if (tty->ldisc.open) {
				int r = tty->ldisc.open(tty);

				if (r < 0)
					panic("Couldn't open N_TTY ldisc for "
					      "%s --- error %d.",
					      tty_name(tty, buf), r);
			}
		}
	}
	/* At this point we hold a reference to the new ldisc and a
	   a reference to the old ldisc. If we ended up flipping back
	   to the existing ldisc we have two references to it */
	
	if (tty->ldisc.num != o_ldisc.num && tty->driver->set_ldisc)
		tty->driver->set_ldisc(tty);
		
	tty_ldisc_put(o_ldisc.num);
	
	/*
	 *	Allow ldisc referencing to occur as soon as the driver
	 *	ldisc callback completes.
	 */
	 
	tty_ldisc_enable(tty);
	if (o_tty)
		tty_ldisc_enable(o_tty);
	
	/* Restart it in case no characters kick it off. Safe if
	   already running */
	if (work)
		schedule_delayed_work(&tty->flip.work, 1);
	return retval;
}

/*
 * This routine returns a tty driver structure, given a device number
 */
static struct tty_driver *get_tty_driver(dev_t device, int *index)
{
	struct tty_driver *p;

	list_for_each_entry(p, &tty_drivers, tty_drivers) {
		dev_t base = MKDEV(p->major, p->minor_start);
		if (device < base || device >= base + p->num)
			continue;
		*index = device - base;
		return p;
	}
	return NULL;
}

/*
 * If we try to write to, or set the state of, a terminal and we're
 * not in the foreground, send a SIGTTOU.  If the signal is blocked or
 * ignored, go ahead and perform the operation.  (POSIX 7.2)
 */
int tty_check_change(struct tty_struct * tty)
{
	if (current->signal->tty != tty)
		return 0;
	if (tty->pgrp <= 0) {
		printk(KERN_WARNING "tty_check_change: tty->pgrp <= 0!\n");
		return 0;
	}
	if (process_group(current) == tty->pgrp)
		return 0;
	if (is_ignored(SIGTTOU))
		return 0;
	if (is_orphaned_pgrp(process_group(current)))
		return -EIO;
	(void) kill_pg(process_group(current), SIGTTOU, 1);
	return -ERESTARTSYS;
}

EXPORT_SYMBOL(tty_check_change);

static ssize_t hung_up_tty_read(struct file * file, char __user * buf,
				size_t count, loff_t *ppos)
{
	return 0;
}

static ssize_t hung_up_tty_write(struct file * file, const char __user * buf,
				 size_t count, loff_t *ppos)
{
	return -EIO;
}

/* No kernel lock held - none needed ;) */
static unsigned int hung_up_tty_poll(struct file * filp, poll_table * wait)
{
	return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
}

static int hung_up_tty_ioctl(struct inode * inode, struct file * file,
			     unsigned int cmd, unsigned long arg)
{
	return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static struct file_operations tty_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

#ifdef CONFIG_UNIX98_PTYS
static struct file_operations ptmx_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= ptmx_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};
#endif

static struct file_operations console_fops = {
	.llseek		= no_llseek,
	.read		= tty_read,
	.write		= redirected_tty_write,
	.poll		= tty_poll,
	.ioctl		= tty_ioctl,
	.open		= tty_open,
	.release	= tty_release,
	.fasync		= tty_fasync,
};

static struct file_operations hung_up_tty_fops = {
	.llseek		= no_llseek,
	.read		= hung_up_tty_read,
	.write		= hung_up_tty_write,
	.poll		= hung_up_tty_poll,
	.ioctl		= hung_up_tty_ioctl,
	.release	= tty_release,
};

static DEFINE_SPINLOCK(redirect_lock);
static struct file *redirect;

/**
 *	tty_wakeup	-	request more data
 *	@tty: terminal
 *
 *	Internal and external helper for wakeups of tty. This function
 *	informs the line discipline if present that the driver is ready
 *	to receive more output data.
 */
 
void tty_wakeup(struct tty_struct *tty)
{
	struct tty_ldisc *ld;
	
	if (test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) {
		ld = tty_ldisc_ref(tty);
		if(ld) {
			if(ld->write_wakeup)
				ld->write_wakeup(tty);
			tty_ldisc_deref(ld);
		}
	}
	wake_up_interruptible(&tty->write_wait);
}

EXPORT_SYMBOL_GPL(tty_wakeup);

/**
 *	tty_ldisc_flush	-	flush line discipline queue
 *	@tty: tty
 *
 *	Flush the line discipline queue (if any) for this tty. If there
 *	is no line discipline active this is a no-op.
 */
 
void tty_ldisc_flush(struct tty_struct *tty)
{
	struct tty_ldisc *ld = tty_ldisc_ref(tty);
	if(ld) {
		if(ld->flush_buffer)
			ld->flush_buffer(tty);
		tty_ldisc_deref(ld);
	}
}

EXPORT_SYMBOL_GPL(tty_ldisc_flush);
	
/*
 * This can be called by the "eventd" kernel thread.  That is process synchronous,
 * but doesn't hold any locks, so we need to make sure we have the appropriate
 * locks for what we're doing..
 */
static void do_tty_hangup(void *data)
{
	struct tty_struct *tty = (struct tty_struct *) data;
	struct file * cons_filp = NULL;
	struct file *filp, *f = NULL;
	struct task_struct *p;
	struct tty_ldisc *ld;
	int    closecount = 0, n;

	if (!tty)
		return;

	/* inuse_filps is protected by the single kernel lock */
	lock_kernel();

	spin_lock(&redirect_lock);
	if (redirect && redirect->private_data == tty) {
		f = redirect;
		redirect = NULL;
	}
	spin_unlock(&redirect_lock);
	
	check_tty_count(tty, "do_tty_hangup");
	file_list_lock();
	/* This breaks for file handles being sent over AF_UNIX sockets ? */
	list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
		if (filp->f_op->write == redirected_tty_write)
			cons_filp = filp;
		if (filp->f_op->write != tty_write)
			continue;
		closecount++;
		tty_fasync(-1, filp, 0);	/* can't block */
		filp->f_op = &hung_up_tty_fops;
	}
	file_list_unlock();
	
	/* FIXME! What are the locking issues here? This may me overdoing things..
	 * this question is especially important now that we've removed the irqlock. */

	ld = tty_ldisc_ref(tty);
	if(ld != NULL)	/* We may have no line discipline at this point */
	{
		if (ld->flush_buffer)
			ld->flush_buffer(tty);
		if (tty->driver->flush_buffer)
			tty->driver->flush_buffer(tty);
		if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
		    ld->write_wakeup)
			ld->write_wakeup(tty);
		if (ld->hangup)
			ld->hangup(tty);
	}

	/* FIXME: Once we trust the LDISC code better we can wait here for
	   ldisc completion and fix the driver call race */
	   
	wake_up_interruptible(&tty->write_wait);
	wake_up_interruptible(&tty->read_wait);

	/*
	 * Shutdown the current line discipline, and reset it to
	 * N_TTY.
	 */
	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS)
	{
		down(&tty->termios_sem);
		*tty->termios = tty->driver->init_termios;
		up(&tty->termios_sem);
	}
	
	/* Defer ldisc switch */
	/* tty_deferred_ldisc_switch(N_TTY);
	
	  This should get done automatically when the port closes and
	  tty_release is called */
	
	read_lock(&tasklist_lock);
	if (tty->session > 0) {
		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
			if (p->signal->tty == tty)
				p->signal->tty = NULL;
			if (!p->signal->leader)
				continue;
			send_group_sig_info(SIGHUP, SEND_SIG_PRIV, p);
			send_group_sig_info(SIGCONT, SEND_SIG_PRIV, p);
			if (tty->pgrp > 0)
				p->signal->tty_old_pgrp = tty->pgrp;
		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
	}
	read_unlock(&tasklist_lock);

	tty->flags = 0;
	tty->session = 0;
	tty->pgrp = -1;
	tty->ctrl_status = 0;
	/*
	 *	If one of the devices matches a console pointer, we
	 *	cannot just call hangup() because that will cause
	 *	tty->count and state->count to go out of sync.
	 *	So we just call close() the right number of times.
	 */
	if (cons_filp) {
		if (tty->driver->close)
			for (n = 0; n < closecount; n++)
				tty->driver->close(tty, cons_filp);
	} else if (tty->driver->hangup)
		(tty->driver->hangup)(tty);
		
	/* We don't want to have driver/ldisc interactions beyond
	   the ones we did here. The driver layer expects no
	   calls after ->hangup() from the ldisc side. However we
	   can't yet guarantee all that */

	set_bit(TTY_HUPPED, &tty->flags);
	if (ld) {
		tty_ldisc_enable(tty);
		tty_ldisc_deref(ld);
	}
	unlock_kernel();
	if (f)
		fput(f);
}

void tty_hangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];
	
	printk(KERN_DEBUG "%s hangup...\n", tty_name(tty, buf));
#endif
	schedule_work(&tty->hangup_work);
}

EXPORT_SYMBOL(tty_hangup);

void tty_vhangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
	char	buf[64];

	printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
#endif
	do_tty_hangup((void *) tty);
}
EXPORT_SYMBOL(tty_vhangup);

int tty_hung_up_p(struct file * filp)
{
	return (filp->f_op == &hung_up_tty_fops);
}

EXPORT_SYMBOL(tty_hung_up_p);

/*
 * This function is typically called only by the session leader, when
 * it wants to disassociate itself from its controlling tty.
 *
 * It performs the following functions:
 * 	(1)  Sends a SIGHUP and SIGCONT to the foreground process group
 * 	(2)  Clears the tty from being controlling the session
 * 	(3)  Clears the controlling tty for all processes in the
 * 		session group.
 *
 * The argument on_exit is set to 1 if called when a process is
 * exiting; it is 0 if called by the ioctl TIOCNOTTY.
 */
void disassociate_ctty(int on_exit)
{
	struct tty_struct *tty;
	struct task_struct *p;
	int tty_pgrp = -1;

	lock_kernel();

	down(&tty_sem);
	tty = current->signal->tty;
	if (tty) {
		tty_pgrp = tty->pgrp;
		up(&tty_sem);
		if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
			tty_vhangup(tty);
	} else {
		if (current->signal->tty_old_pgrp) {
			kill_pg(current->signal->tty_old_pgrp, SIGHUP, on_exit);
			kill_pg(current->signal->tty_old_pgrp, SIGCONT, on_exit);
		}
		up(&tty_sem);
		unlock_kernel();	
		return;
	}
	if (tty_pgrp > 0) {
		kill_pg(tty_pgrp, SIGHUP, on_exit);
		if (!on_exit)
			kill_pg(tty_pgrp, SIGCONT, on_exit);
	}

	/* Must lock changes to tty_old_pgrp */
	down(&tty_sem);
	current->signal->tty_old_pgrp = 0;
	tty->session = 0;
	tty->pgrp = -1;

	/* Now clear signal->tty under the lock */
	read_lock(&tasklist_lock);
	do_each_task_pid(current->signal->session, PIDTYPE_SID, p) {
		p->signal->tty = NULL;
	} while_each_task_pid(current->signal->session, PIDTYPE_SID, p);
	read_unlock(&tasklist_lock);
	up(&tty_sem);
	unlock_kernel();
}

void stop_tty(struct tty_struct *tty)
{
	if (tty->stopped)
		return;
	tty->stopped = 1;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_START;
		tty->ctrl_status |= TIOCPKT_STOP;
		wake_up_interruptible(&tty->link->read_wait);
	}
	if (tty->driver->stop)
		(tty->driver->stop)(tty);
}

EXPORT_SYMBOL(stop_tty);

void start_tty(struct tty_struct *tty)
{
	if (!tty->stopped || tty->flow_stopped)
		return;
	tty->stopped = 0;
	if (tty->link && tty->link->packet) {
		tty->ctrl_status &= ~TIOCPKT_STOP;
		tty->ctrl_status |= TIOCPKT_START;
		wake_up_interruptible(&tty->link->read_wait);
	}
	if (tty->driver->start)
		(tty->driver->start)(tty);

	/* If we have a running line discipline it may need kicking */
	tty_wakeup(tty);
	wake_up_interruptible(&tty->write_wait);
}

EXPORT_SYMBOL(start_tty);

static ssize_t tty_read(struct file * file, char __user * buf, size_t count, 
			loff_t *ppos)
{
	int i;
	struct tty_struct * tty;
	struct inode *inode;
	struct tty_ldisc *ld;

	tty = (struct tty_struct *)file->private_data;
	inode = file->f_dentry->d_inode;
	if (tty_paranoia_check(tty, inode, "tty_read"))
		return -EIO;
	if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
		return -EIO;

	/* We want to wait for the line discipline to sort out in this
	   situation */
	ld = tty_ldisc_ref_wait(tty);
	lock_kernel();
	if (ld->read)
		i = (ld->read)(tty,file,buf,count);
	else
		i = -EIO;
	tty_ldisc_deref(ld);
	unlock_kernel();
	if (i > 0)
		inode->i_atime = current_fs_time(inode->i_sb);
	return i;
}

/*
 * Split writes up in sane blocksizes to avoid
 * denial-of-service type attacks
 */
static inline ssize_t do_tty_write(
	ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
	struct tty_struct *tty,
	struct file *file,
	const char __user *buf,
	size_t count)
{
	ssize_t ret = 0, written = 0;
	unsigned int chunk;
	
	if (down_interruptible(&tty->atomic_write)) {
		return -ERESTARTSYS;
	}

	/*
	 * We chunk up writes into a temporary buffer. This
	 * simplifies low-level drivers immensely, since they
	 * don't have locking issues and user mode accesses.
	 *
	 * But if TTY_NO_WRITE_SPLIT is set, we should use a
	 * big chunk-size..
	 *
	 * The default chunk-size is 2kB, because the NTTY
	 * layer has problems with bigger chunks. It will
	 * claim to be able to handle more characters than
	 * it actually does.
	 */
	chunk = 2048;
	if (test_bit(TTY_NO_WRITE_SPLIT, &tty->flags))
		chunk = 65536;
	if (count < chunk)
		chunk = count;

	/* write_buf/write_cnt is protected by the atomic_write semaphore */
	if (tty->write_cnt < chunk) {
		unsigned char *buf;

		if (chunk < 1024)
			chunk = 1024;

		buf = kmalloc(chunk, GFP_KERNEL);
		if (!buf) {
			up(&tty->atomic_write);
			return -ENOMEM;
		}
		kfree(tty->write_buf);
		tty->write_cnt = chunk;
		tty->write_buf = buf;
	}

	/* Do the write .. */
	for (;;) {
		size_t size = count;
		if (size > chunk)
			size = chunk;
		ret = -EFAULT;
		if (copy_from_user(tty->write_buf, buf, size))
			break;
		lock_kernel();
		ret = write(tty, file, tty->write_buf, size);
		unlock_kernel();
		if (ret <= 0)
			break;
		written += ret;
		buf += ret;
		count -= ret;
		if (!count)
			break;
		ret = -ERESTARTSYS;
		if (signal_pending(current))
			break;
		cond_resched();
	}
	if (written) {
		struct inode *inode = file->f_dentry->d_inode;
		inode->i_mtime = current_fs_time(inode->i_sb);
		ret = written;
	}
	up(&tty->atomic_write);
	return ret;
}


static ssize_t tty_write(struct file * file, const char __user * buf, size_t count,
			 loff_t *ppos)
{
	struct tty_struct * tty;
	struct inode *inode = file->f_dentry->d_inode;
	ssize_t ret;
	struct tty_ldisc *ld;
	
	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode, "tty_write"))
		return -EIO;
	if (!tty || !tty->driver->write || (test_bit(TTY_IO_ERROR, &tty->flags)))
		return -EIO;

	ld = tty_ldisc_ref_wait(tty);		
	if (!ld->write)
		ret = -EIO;
	else
		ret = do_tty_write(ld->write, tty, file, buf, count);
	tty_ldisc_deref(ld);
	return ret;
}

ssize_t redirected_tty_write(struct file * file, const char __user * buf, size_t count,
			 loff_t *ppos)
{
	struct file *p = NULL;

	spin_lock(&redirect_lock);
	if (redirect) {
		get_file(redirect);
		p = redirect;
	}
	spin_unlock(&redirect_lock);

	if (p) {
		ssize_t res;
		res = vfs_write(p, buf, count, &p->f_pos);
		fput(p);
		return res;
	}

	return tty_write(file, buf, count, ppos);
}

static char ptychar[] = "pqrstuvwxyzabcde";

static inline void pty_line_name(struct tty_driver *driver, int index, char *p)
{
	int i = index + driver->name_base;
	/* ->name is initialized to "ttyp", but "tty" is expected */
	sprintf(p, "%s%c%x",
			driver->subtype == PTY_TYPE_SLAVE ? "tty" : driver->name,
			ptychar[i >> 4 & 0xf], i & 0xf);
}

static inline void tty_line_name(struct tty_driver *driver, int index, char *p)
{
	sprintf(p, "%s%d", driver->name, index + driver->name_base);
}

/*
 * WSH 06/09/97: Rewritten to remove races and properly clean up after a
 * failed open.  The new code protects the open with a semaphore, so it's
 * really quite straightforward.  The semaphore locking can probably be
 * relaxed for the (most common) case of reopening a tty.
 */
static int init_dev(struct tty_driver *driver, int idx,
	struct tty_struct **ret_tty)
{
	struct tty_struct *tty, *o_tty;
	struct termios *tp, **tp_loc, *o_tp, **o_tp_loc;
	struct termios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
	int retval=0;

	/* check whether we're reopening an existing tty */
	if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
		tty = devpts_get_tty(idx);
		if (tty && driver->subtype == PTY_TYPE_MASTER)
			tty = tty->link;
	} else {
		tty = driver->ttys[idx];
	}
	if (tty) goto fast_track;

	/*
	 * First time open is complex, especially for PTY devices.
	 * This code guarantees that either everything succeeds and the
	 * TTY is ready for operation, or else the table slots are vacated
	 * and the allocated memory released.  (Except that the termios 
	 * and locked termios may be retained.)
	 */

	if (!try_module_get(driver->owner)) {
		retval = -ENODEV;
		goto end_init;
	}

	o_tty = NULL;
	tp = o_tp = NULL;
	ltp = o_ltp = NULL;

	tty = alloc_tty_struct();
	if(!tty)
		goto fail_no_mem;
	initialize_tty_struct(tty);
	tty->driver = driver;
	tty->index = idx;
	tty_line_name(driver, idx, tty->name);

	if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
		tp_loc = &tty->termios;
		ltp_loc = &tty->termios_locked;
	} else {
		tp_loc = &driver->termios[idx];
		ltp_loc = &driver->termios_locked[idx];
	}

	if (!*tp_loc) {
		tp = (struct termios *) kmalloc(sizeof(struct termios),
						GFP_KERNEL);
		if (!tp)
			goto free_mem_out;
		*tp = driver->init_termios;
	}

	if (!*ltp_loc) {
		ltp = (struct termios *) kmalloc(sizeof(struct termios),
						 GFP_KERNEL);
		if (!ltp)
			goto free_mem_out;
		memset(ltp, 0, sizeof(struct termios));
	}

	if (driver->type == TTY_DRIVER_TYPE_PTY) {
		o_tty = alloc_tty_struct();
		if (!o_tty)
			goto free_mem_out;
		initialize_tty_struct(o_tty);
		o_tty->driver = driver->other;
		o_tty->index = idx;
		tty_line_name(driver->other, idx, o_tty->name);

		if (driver->flags & TTY_DRIVER_DEVPTS_MEM) {
			o_tp_loc = &o_tty->termios;
			o_ltp_loc = &o_tty->termios_locked;
		} else {
			o_tp_loc = &driver->other->termios[idx];
			o_ltp_loc = &driver->other->termios_locked[idx];
		}

		if (!*o_tp_loc) {
			o_tp = (struct termios *)
				kmalloc(sizeof(struct termios), GFP_KERNEL);
			if (!o_tp)
				goto free_mem_out;
			*o_tp = driver->other->init_termios;
		}

		if (!*o_ltp_loc) {
			o_ltp = (struct termios *)
				kmalloc(sizeof(struct termios), GFP_KERNEL);
			if (!o_ltp)
				goto free_mem_out;
			memset(o_ltp, 0, sizeof(struct termios));
		}

		/*
		 * Everything allocated ... set up the o_tty structure.
		 */
		if (!(driver->other->flags & TTY_DRIVER_DEVPTS_MEM)) {
			driver->other->ttys[idx] = o_tty;
		}
		if (!*o_tp_loc)
			*o_tp_loc = o_tp;
		if (!*o_ltp_loc)
			*o_ltp_loc = o_ltp;
		o_tty->termios = *o_tp_loc;
		o_tty->termios_locked = *o_ltp_loc;
		driver->other->refcount++;
		if (driver->subtype == PTY_TYPE_MASTER)
			o_tty->count++;

		/* Establish the links in both directions */
		tty->link   = o_tty;
		o_tty->link = tty;
	}

	/* 
	 * All structures have been allocated, so now we install them.
	 * Failures after this point use release_mem to clean up, so 
	 * there's no need to null out the local pointers.
	 */
	if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		driver->ttys[idx] = tty;
	}
	
	if (!*tp_loc)
		*tp_loc = tp;
	if (!*ltp_loc)
		*ltp_loc = ltp;
	tty->termios = *tp_loc;
	tty->termios_locked = *ltp_loc;
	driver->refcount++;
	tty->count++;

	/* 
	 * Structures all installed ... call the ldisc open routines.
	 * If we fail here just call release_mem to clean up.  No need
	 * to decrement the use counts, as release_mem doesn't care.
	 */

	if (tty->ldisc.open) {
		retval = (tty->ldisc.open)(tty);
		if (retval)
			goto release_mem_out;
	}
	if (o_tty && o_tty->ldisc.open) {
		retval = (o_tty->ldisc.open)(o_tty);
		if (retval) {
			if (tty->ldisc.close)
				(tty->ldisc.close)(tty);
			goto release_mem_out;
		}
		tty_ldisc_enable(o_tty);
	}
	tty_ldisc_enable(tty);
	goto success;

	/*
	 * This fast open can be used if the tty is already open.
	 * No memory is allocated, and the only failures are from
	 * attempting to open a closing tty or attempting multiple
	 * opens on a pty master.
	 */
fast_track:
	if (test_bit(TTY_CLOSING, &tty->flags)) {
		retval = -EIO;
		goto end_init;
	}
	if (driver->type == TTY_DRIVER_TYPE_PTY &&
	    driver->subtype == PTY_TYPE_MASTER) {
		/*
		 * special case for PTY masters: only one open permitted, 
		 * and the slave side open count is incremented as well.
		 */
		if (tty->count) {
			retval = -EIO;
			goto end_init;
		}
		tty->link->count++;
	}
	tty->count++;
	tty->driver = driver; /* N.B. why do this every time?? */

	/* FIXME */
	if(!test_bit(TTY_LDISC, &tty->flags))
		printk(KERN_ERR "init_dev but no ldisc\n");
success:
	*ret_tty = tty;
	
	/* All paths come through here to release the semaphore */
end_init:
	return retval;

	/* Release locally allocated memory ... nothing placed in slots */
free_mem_out:
	kfree(o_tp);
	if (o_tty)
		free_tty_struct(o_tty);
	kfree(ltp);
	kfree(tp);
	free_tty_struct(tty);

fail_no_mem:
	module_put(driver->owner);
	retval = -ENOMEM;
	goto end_init;

	/* call the tty release_mem routine to clean out this slot */
release_mem_out:
	printk(KERN_INFO "init_dev: ldisc open failed, "
			 "clearing slot %d\n", idx);
	release_mem(tty, idx);
	goto end_init;
}

/*
 * Releases memory associated with a tty structure, and clears out the
 * driver table slots.
 */
static void release_mem(struct tty_struct *tty, int idx)
{
	struct tty_struct *o_tty;
	struct termios *tp;
	int devpts = tty->driver->flags & TTY_DRIVER_DEVPTS_MEM;

	if ((o_tty = tty->link) != NULL) {
		if (!devpts)
			o_tty->driver->ttys[idx] = NULL;
		if (o_tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
			tp = o_tty->termios;
			if (!devpts)
				o_tty->driver->termios[idx] = NULL;
			kfree(tp);

			tp = o_tty->termios_locked;
			if (!devpts)
				o_tty->driver->termios_locked[idx] = NULL;
			kfree(tp);
		}
		o_tty->magic = 0;
		o_tty->driver->refcount--;
		file_list_lock();
		list_del_init(&o_tty->tty_files);
		file_list_unlock();
		free_tty_struct(o_tty);
	}

	if (!devpts)
		tty->driver->ttys[idx] = NULL;
	if (tty->driver->flags & TTY_DRIVER_RESET_TERMIOS) {
		tp = tty->termios;
		if (!devpts)
			tty->driver->termios[idx] = NULL;
		kfree(tp);

		tp = tty->termios_locked;
		if (!devpts)
			tty->driver->termios_locked[idx] = NULL;
		kfree(tp);
	}

	tty->magic = 0;
	tty->driver->refcount--;
	file_list_lock();
	list_del_init(&tty->tty_files);
	file_list_unlock();
	module_put(tty->driver->owner);
	free_tty_struct(tty);
}

/*
 * Even releasing the tty structures is a tricky business.. We have
 * to be very careful that the structures are all released at the
 * same time, as interrupts might otherwise get the wrong pointers.
 *
 * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
 * lead to double frees or releasing memory still in use.
 */
static void release_dev(struct file * filp)
{
	struct tty_struct *tty, *o_tty;
	int	pty_master, tty_closing, o_tty_closing, do_sleep;
	int	devpts_master, devpts;
	int	idx;
	char	buf[64];
	unsigned long flags;
	
	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "release_dev"))
		return;

	check_tty_count(tty, "release_dev");

	tty_fasync(-1, filp, 0);

	idx = tty->index;
	pty_master = (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
		      tty->driver->subtype == PTY_TYPE_MASTER);
	devpts = (tty->driver->flags & TTY_DRIVER_DEVPTS_MEM) != 0;
	devpts_master = pty_master && devpts;
	o_tty = tty->link;

#ifdef TTY_PARANOIA_CHECK
	if (idx < 0 || idx >= tty->driver->num) {
		printk(KERN_DEBUG "release_dev: bad idx when trying to "
				  "free (%s)\n", tty->name);
		return;
	}
	if (!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		if (tty != tty->driver->ttys[idx]) {
			printk(KERN_DEBUG "release_dev: driver.table[%d] not tty "
			       "for (%s)\n", idx, tty->name);
			return;
		}
		if (tty->termios != tty->driver->termios[idx]) {
			printk(KERN_DEBUG "release_dev: driver.termios[%d] not termios "
			       "for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (tty->termios_locked != tty->driver->termios_locked[idx]) {
			printk(KERN_DEBUG "release_dev: driver.termios_locked[%d] not "
			       "termios_locked for (%s)\n",
			       idx, tty->name);
			return;
		}
	}
#endif

#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "release_dev of %s (tty count=%d)...",
	       tty_name(tty, buf), tty->count);
#endif

#ifdef TTY_PARANOIA_CHECK
	if (tty->driver->other &&
	     !(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		if (o_tty != tty->driver->other->ttys[idx]) {
			printk(KERN_DEBUG "release_dev: other->table[%d] "
					  "not o_tty for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->termios != tty->driver->other->termios[idx]) {
			printk(KERN_DEBUG "release_dev: other->termios[%d] "
					  "not o_termios for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->termios_locked != 
		      tty->driver->other->termios_locked[idx]) {
			printk(KERN_DEBUG "release_dev: other->termios_locked["
					  "%d] not o_termios_locked for (%s)\n",
			       idx, tty->name);
			return;
		}
		if (o_tty->link != tty) {
			printk(KERN_DEBUG "release_dev: bad pty pointers\n");
			return;
		}
	}
#endif
	if (tty->driver->close)
		tty->driver->close(tty, filp);

	/*
	 * Sanity check: if tty->count is going to zero, there shouldn't be
	 * any waiters on tty->read_wait or tty->write_wait.  We test the
	 * wait queues and kick everyone out _before_ actually starting to
	 * close.  This ensures that we won't block while releasing the tty
	 * structure.
	 *
	 * The test for the o_tty closing is necessary, since the master and
	 * slave sides may close in any order.  If the slave side closes out
	 * first, its count will be one, since the master side holds an open.
	 * Thus this test wouldn't be triggered at the time the slave closes,
	 * so we do it now.
	 *
	 * Note that it's possible for the tty to be opened again while we're
	 * flushing out waiters.  By recalculating the closing flags before
	 * each iteration we avoid any problems.
	 */
	while (1) {
		/* Guard against races with tty->count changes elsewhere and
		   opens on /dev/tty */
		   
		down(&tty_sem);
		tty_closing = tty->count <= 1;
		o_tty_closing = o_tty &&
			(o_tty->count <= (pty_master ? 1 : 0));
		up(&tty_sem);
		do_sleep = 0;

		if (tty_closing) {
			if (waitqueue_active(&tty->read_wait)) {
				wake_up(&tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&tty->write_wait)) {
				wake_up(&tty->write_wait);
				do_sleep++;
			}
		}
		if (o_tty_closing) {
			if (waitqueue_active(&o_tty->read_wait)) {
				wake_up(&o_tty->read_wait);
				do_sleep++;
			}
			if (waitqueue_active(&o_tty->write_wait)) {
				wake_up(&o_tty->write_wait);
				do_sleep++;
			}
		}
		if (!do_sleep)
			break;

		printk(KERN_WARNING "release_dev: %s: read/write wait queue "
				    "active!\n", tty_name(tty, buf));
		schedule();
	}	

	/*
	 * The closing flags are now consistent with the open counts on 
	 * both sides, and we've completed the last operation that could 
	 * block, so it's safe to proceed with closing.
	 */
	 
	down(&tty_sem);
	if (pty_master) {
		if (--o_tty->count < 0) {
			printk(KERN_WARNING "release_dev: bad pty slave count "
					    "(%d) for %s\n",
			       o_tty->count, tty_name(o_tty, buf));
			o_tty->count = 0;
		}
	}
	if (--tty->count < 0) {
		printk(KERN_WARNING "release_dev: bad tty->count (%d) for %s\n",
		       tty->count, tty_name(tty, buf));
		tty->count = 0;
	}
	up(&tty_sem);
	
	/*
	 * We've decremented tty->count, so we need to remove this file
	 * descriptor off the tty->tty_files list; this serves two
	 * purposes:
	 *  - check_tty_count sees the correct number of file descriptors
	 *    associated with this tty.
	 *  - do_tty_hangup no longer sees this file descriptor as
	 *    something that needs to be handled for hangups.
	 */
	file_kill(filp);
	filp->private_data = NULL;

	/*
	 * Perform some housekeeping before deciding whether to return.
	 *
	 * Set the TTY_CLOSING flag if this was the last open.  In the
	 * case of a pty we may have to wait around for the other side
	 * to close, and TTY_CLOSING makes sure we can't be reopened.
	 */
	if(tty_closing)
		set_bit(TTY_CLOSING, &tty->flags);
	if(o_tty_closing)
		set_bit(TTY_CLOSING, &o_tty->flags);

	/*
	 * If _either_ side is closing, make sure there aren't any
	 * processes that still think tty or o_tty is their controlling
	 * tty.
	 */
	if (tty_closing || o_tty_closing) {
		struct task_struct *p;

		read_lock(&tasklist_lock);
		do_each_task_pid(tty->session, PIDTYPE_SID, p) {
			p->signal->tty = NULL;
		} while_each_task_pid(tty->session, PIDTYPE_SID, p);
		if (o_tty)
			do_each_task_pid(o_tty->session, PIDTYPE_SID, p) {
				p->signal->tty = NULL;
			} while_each_task_pid(o_tty->session, PIDTYPE_SID, p);
		read_unlock(&tasklist_lock);
	}

	/* check whether both sides are closing ... */
	if (!tty_closing || (o_tty && !o_tty_closing))
		return;
	
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "freeing tty structure...");
#endif
	/*
	 * Prevent flush_to_ldisc() from rescheduling the work for later.  Then
	 * kill any delayed work. As this is the final close it does not
	 * race with the set_ldisc code path.
	 */
	clear_bit(TTY_LDISC, &tty->flags);
	clear_bit(TTY_DONT_FLIP, &tty->flags);
	cancel_delayed_work(&tty->flip.work);

	/*
	 * Wait for ->hangup_work and ->flip.work handlers to terminate
	 */
	 
	flush_scheduled_work();
	
	/*
	 * Wait for any short term users (we know they are just driver
	 * side waiters as the file is closing so user count on the file
	 * side is zero.
	 */
	spin_lock_irqsave(&tty_ldisc_lock, flags);
	while(tty->ldisc.refcount)
	{
		spin_unlock_irqrestore(&tty_ldisc_lock, flags);
		wait_event(tty_ldisc_wait, tty->ldisc.refcount == 0);
		spin_lock_irqsave(&tty_ldisc_lock, flags);
	}
	spin_unlock_irqrestore(&tty_ldisc_lock, flags);
	/*
	 * Shutdown the current line discipline, and reset it to N_TTY.
	 * N.B. why reset ldisc when we're releasing the memory??
	 *
	 * FIXME: this MUST get fixed for the new reflocking
	 */
	if (tty->ldisc.close)
		(tty->ldisc.close)(tty);
	tty_ldisc_put(tty->ldisc.num);
	
	/*
	 *	Switch the line discipline back
	 */
	tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
	tty_set_termios_ldisc(tty,N_TTY); 
	if (o_tty) {
		/* FIXME: could o_tty be in setldisc here ? */
		clear_bit(TTY_LDISC, &o_tty->flags);
		if (o_tty->ldisc.close)
			(o_tty->ldisc.close)(o_tty);
		tty_ldisc_put(o_tty->ldisc.num);
		tty_ldisc_assign(o_tty, tty_ldisc_get(N_TTY));
		tty_set_termios_ldisc(o_tty,N_TTY); 
	}
	/*
	 * The release_mem function takes care of the details of clearing
	 * the slots and preserving the termios structure.
	 */
	release_mem(tty, idx);

#ifdef CONFIG_UNIX98_PTYS
	/* Make this pty number available for reallocation */
	if (devpts) {
		down(&allocated_ptys_lock);
		idr_remove(&allocated_ptys, idx);
		up(&allocated_ptys_lock);
	}
#endif

}

/*
 * tty_open and tty_release keep up the tty count that contains the
 * number of opens done on a tty. We cannot use the inode-count, as
 * different inodes might point to the same tty.
 *
 * Open-counting is needed for pty masters, as well as for keeping
 * track of serial lines: DTR is dropped when the last close happens.
 * (This is not done solely through tty->count, now.  - Ted 1/27/92)
 *
 * The termios state of a pty is reset on first open so that
 * settings don't persist across reuse.
 */
static int tty_open(struct inode * inode, struct file * filp)
{
	struct tty_struct *tty;
	int noctty, retval;
	struct tty_driver *driver;
	int index;
	dev_t device = inode->i_rdev;
	unsigned short saved_flags = filp->f_flags;

	nonseekable_open(inode, filp);
	
retry_open:
	noctty = filp->f_flags & O_NOCTTY;
	index  = -1;
	retval = 0;
	
	down(&tty_sem);

	if (device == MKDEV(TTYAUX_MAJOR,0)) {
		if (!current->signal->tty) {
			up(&tty_sem);
			return -ENXIO;
		}
		driver = current->signal->tty->driver;
		index = current->signal->tty->index;
		filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
		/* noctty = 1; */
		goto got_driver;
	}
#ifdef CONFIG_VT
	if (device == MKDEV(TTY_MAJOR,0)) {
		extern struct tty_driver *console_driver;
		driver = console_driver;
		index = fg_console;
		noctty = 1;
		goto got_driver;
	}
#endif
	if (device == MKDEV(TTYAUX_MAJOR,1)) {
		driver = console_device(&index);
		if (driver) {
			/* Don't let /dev/console block */
			filp->f_flags |= O_NONBLOCK;
			noctty = 1;
			goto got_driver;
		}
		up(&tty_sem);
		return -ENODEV;
	}

	driver = get_tty_driver(device, &index);
	if (!driver) {
		up(&tty_sem);
		return -ENODEV;
	}
got_driver:
	retval = init_dev(driver, index, &tty);
	up(&tty_sem);
	if (retval)
		return retval;

	filp->private_data = tty;
	file_move(filp, &tty->tty_files);
	check_tty_count(tty, "tty_open");
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		noctty = 1;
#ifdef TTY_DEBUG_HANGUP
	printk(KERN_DEBUG "opening %s...", tty->name);
#endif
	if (!retval) {
		if (tty->driver->open)
			retval = tty->driver->open(tty, filp);
		else
			retval = -ENODEV;
	}
	filp->f_flags = saved_flags;

	if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) && !capable(CAP_SYS_ADMIN))
		retval = -EBUSY;

	if (retval) {
#ifdef TTY_DEBUG_HANGUP
		printk(KERN_DEBUG "error %d in opening %s...", retval,
		       tty->name);
#endif
		release_dev(filp);
		if (retval != -ERESTARTSYS)
			return retval;
		if (signal_pending(current))
			return retval;
		schedule();
		/*
		 * Need to reset f_op in case a hangup happened.
		 */
		if (filp->f_op == &hung_up_tty_fops)
			filp->f_op = &tty_fops;
		goto retry_open;
	}
	if (!noctty &&
	    current->signal->leader &&
	    !current->signal->tty &&
	    tty->session == 0) {
	    	task_lock(current);
		current->signal->tty = tty;
		task_unlock(current);
		current->signal->tty_old_pgrp = 0;
		tty->session = current->signal->session;
		tty->pgrp = process_group(current);
	}
	return 0;
}

#ifdef CONFIG_UNIX98_PTYS
static int ptmx_open(struct inode * inode, struct file * filp)
{
	struct tty_struct *tty;
	int retval;
	int index;
	int idr_ret;

	nonseekable_open(inode, filp);

	/* find a device that is not in use. */
	down(&allocated_ptys_lock);
	if (!idr_pre_get(&allocated_ptys, GFP_KERNEL)) {
		up(&allocated_ptys_lock);
		return -ENOMEM;
	}
	idr_ret = idr_get_new(&allocated_ptys, NULL, &index);
	if (idr_ret < 0) {
		up(&allocated_ptys_lock);
		if (idr_ret == -EAGAIN)
			return -ENOMEM;
		return -EIO;
	}
	if (index >= pty_limit) {
		idr_remove(&allocated_ptys, index);
		up(&allocated_ptys_lock);
		return -EIO;
	}
	up(&allocated_ptys_lock);

	down(&tty_sem);
	retval = init_dev(ptm_driver, index, &tty);
	up(&tty_sem);
	
	if (retval)
		goto out;

	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
	filp->private_data = tty;
	file_move(filp, &tty->tty_files);

	retval = -ENOMEM;
	if (devpts_pty_new(tty->link))
		goto out1;

	check_tty_count(tty, "tty_open");
	retval = ptm_driver->open(tty, filp);
	if (!retval)
		return 0;
out1:
	release_dev(filp);
out:
	down(&allocated_ptys_lock);
	idr_remove(&allocated_ptys, index);
	up(&allocated_ptys_lock);
	return retval;
}
#endif

static int tty_release(struct inode * inode, struct file * filp)
{
	lock_kernel();
	release_dev(filp);
	unlock_kernel();
	return 0;
}

/* No kernel lock held - fine */
static unsigned int tty_poll(struct file * filp, poll_table * wait)
{
	struct tty_struct * tty;
	struct tty_ldisc *ld;
	int ret = 0;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "tty_poll"))
		return 0;
		
	ld = tty_ldisc_ref_wait(tty);
	if (ld->poll)
		ret = (ld->poll)(tty, filp, wait);
	tty_ldisc_deref(ld);
	return ret;
}

static int tty_fasync(int fd, struct file * filp, int on)
{
	struct tty_struct * tty;
	int retval;

	tty = (struct tty_struct *)filp->private_data;
	if (tty_paranoia_check(tty, filp->f_dentry->d_inode, "tty_fasync"))
		return 0;
	
	retval = fasync_helper(fd, filp, on, &tty->fasync);
	if (retval <= 0)
		return retval;

	if (on) {
		if (!waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = 1;
		retval = f_setown(filp, (-tty->pgrp) ? : current->pid, 0);
		if (retval)
			return retval;
	} else {
		if (!tty->fasync && !waitqueue_active(&tty->read_wait))
			tty->minimum_to_wake = N_TTY_BUF_SIZE;
	}
	return 0;
}

static int tiocsti(struct tty_struct *tty, char __user *p)
{
	char ch, mbz = 0;
	struct tty_ldisc *ld;
	
	if ((current->signal->tty != tty) && !capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (get_user(ch, p))
		return -EFAULT;
	ld = tty_ldisc_ref_wait(tty);
	ld->receive_buf(tty, &ch, &mbz, 1);
	tty_ldisc_deref(ld);
	return 0;
}

static int tiocgwinsz(struct tty_struct *tty, struct winsize __user * arg)
{
	if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
		return -EFAULT;
	return 0;
}

static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
	struct winsize __user * arg)
{
	struct winsize tmp_ws;

	if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
		return -EFAULT;
	if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
		return 0;
#ifdef CONFIG_VT
	if (tty->driver->type == TTY_DRIVER_TYPE_CONSOLE) {
		int rc;

		acquire_console_sem();
		rc = vc_resize(tty->driver_data, tmp_ws.ws_col, tmp_ws.ws_row);
		release_console_sem();
		if (rc)
			return -ENXIO;
	}
#endif
	if (tty->pgrp > 0)
		kill_pg(tty->pgrp, SIGWINCH, 1);
	if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
		kill_pg(real_tty->pgrp, SIGWINCH, 1);
	tty->winsize = tmp_ws;
	real_tty->winsize = tmp_ws;
	return 0;
}

static int tioccons(struct file *file)
{
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (file->f_op->write == redirected_tty_write) {
		struct file *f;
		spin_lock(&redirect_lock);
		f = redirect;
		redirect = NULL;
		spin_unlock(&redirect_lock);
		if (f)
			fput(f);
		return 0;
	}
	spin_lock(&redirect_lock);
	if (redirect) {
		spin_unlock(&redirect_lock);
		return -EBUSY;
	}
	get_file(file);
	redirect = file;
	spin_unlock(&redirect_lock);
	return 0;
}


static int fionbio(struct file *file, int __user *p)
{
	int nonblock;

	if (get_user(nonblock, p))
		return -EFAULT;

	if (nonblock)
		file->f_flags |= O_NONBLOCK;
	else
		file->f_flags &= ~O_NONBLOCK;
	return 0;
}

static int tiocsctty(struct tty_struct *tty, int arg)
{
	task_t *p;

	if (current->signal->leader &&
	    (current->signal->session == tty->session))
		return 0;
	/*
	 * The process must be a session leader and
	 * not have a controlling tty already.
	 */
	if (!current->signal->leader || current->signal->tty)
		return -EPERM;
	if (tty->session > 0) {
		/*
		 * This tty is already the controlling
		 * tty for another session group!
		 */
		if ((arg == 1) && capable(CAP_SYS_ADMIN)) {
			/*
			 * Steal it away
			 */

			read_lock(&tasklist_lock);
			do_each_task_pid(tty->session, PIDTYPE_SID, p) {
				p->signal->tty = NULL;
			} while_each_task_pid(tty->session, PIDTYPE_SID, p);
			read_unlock(&tasklist_lock);
		} else
			return -EPERM;
	}
	task_lock(current);
	current->signal->tty = tty;
	task_unlock(current);
	current->signal->tty_old_pgrp = 0;
	tty->session = current->signal->session;
	tty->pgrp = process_group(current);
	return 0;
}

static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	 */
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	return put_user(real_tty->pgrp, p);
}

static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	pid_t pgrp;
	int retval = tty_check_change(real_tty);

	if (retval == -EIO)
		return -ENOTTY;
	if (retval)
		return retval;
	if (!current->signal->tty ||
	    (current->signal->tty != real_tty) ||
	    (real_tty->session != current->signal->session))
		return -ENOTTY;
	if (get_user(pgrp, p))
		return -EFAULT;
	if (pgrp < 0)
		return -EINVAL;
	if (session_of_pgrp(pgrp) != current->signal->session)
		return -EPERM;
	real_tty->pgrp = pgrp;
	return 0;
}

static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t __user *p)
{
	/*
	 * (tty == real_tty) is a cheap way of
	 * testing if the tty is NOT a master pty.
	*/
	if (tty == real_tty && current->signal->tty != real_tty)
		return -ENOTTY;
	if (real_tty->session <= 0)
		return -ENOTTY;
	return put_user(real_tty->session, p);
}

static int tiocsetd(struct tty_struct *tty, int __user *p)
{
	int ldisc;

	if (get_user(ldisc, p))
		return -EFAULT;
	return tty_set_ldisc(tty, ldisc);
}

static int send_break(struct tty_struct *tty, unsigned int duration)
{
	tty->driver->break_ctl(tty, -1);
	if (!signal_pending(current)) {
		msleep_interruptible(duration);
	}
	tty->driver->break_ctl(tty, 0);
	if (signal_pending(current))
		return -EINTR;
	return 0;
}

static int
tty_tiocmget(struct tty_struct *tty, struct file *file, int __user *p)
{
	int retval = -EINVAL;

	if (tty->driver->tiocmget) {
		retval = tty->driver->tiocmget(tty, file);

		if (retval >= 0)
			retval = put_user(retval, p);
	}
	return retval;
}

static int
tty_tiocmset(struct tty_struct *tty, struct file *file, unsigned int cmd,
	     unsigned __user *p)
{
	int retval = -EINVAL;

	if (tty->driver->tiocmset) {
		unsigned int set, clear, val;

		retval = get_user(val, p);
		if (retval)
			return retval;

		set = clear = 0;
		switch (cmd) {
		case TIOCMBIS:
			set = val;
			break;
		case TIOCMBIC:
			clear = val;
			break;
		case TIOCMSET:
			set = val;
			clear = ~val;
			break;
		}

		set &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;
		clear &= TIOCM_DTR|TIOCM_RTS|TIOCM_OUT1|TIOCM_OUT2|TIOCM_LOOP;

		retval = tty->driver->tiocmset(tty, file, set, clear);
	}
	return retval;
}

/*
 * Split this up, as gcc can choke on it otherwise..
 */
int tty_ioctl(struct inode * inode, struct file * file,
	      unsigned int cmd, unsigned long arg)
{
	struct tty_struct *tty, *real_tty;
	void __user *p = (void __user *)arg;
	int retval;
	struct tty_ldisc *ld;
	
	tty = (struct tty_struct *)file->private_data;
	if (tty_paranoia_check(tty, inode, "tty_ioctl"))
		return -EINVAL;

	real_tty = tty;
	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;

	/*
	 * Break handling by driver
	 */
	if (!tty->driver->break_ctl) {
		switch(cmd) {
		case TIOCSBRK:
		case TIOCCBRK:
			if (tty->driver->ioctl)
				return tty->driver->ioctl(tty, file, cmd, arg);
			return -EINVAL;
			
		/* These two ioctl's always return success; even if */
		/* the driver doesn't support them. */
		case TCSBRK:
		case TCSBRKP:
			if (!tty->driver->ioctl)
				return 0;
			retval = tty->driver->ioctl(tty, file, cmd, arg);
			if (retval == -ENOIOCTLCMD)
				retval = 0;
			return retval;
		}
	}

	/*
	 * Factor out some common prep work
	 */
	switch (cmd) {
	case TIOCSETD:
	case TIOCSBRK:
	case TIOCCBRK:
	case TCSBRK:
	case TCSBRKP:			
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		if (cmd != TIOCCBRK) {
			tty_wait_until_sent(tty, 0);
			if (signal_pending(current))
				return -EINTR;
		}
		break;
	}

	switch (cmd) {
		case TIOCSTI:
			return tiocsti(tty, p);
		case TIOCGWINSZ:
			return tiocgwinsz(tty, p);
		case TIOCSWINSZ:
			return tiocswinsz(tty, real_tty, p);
		case TIOCCONS:
			return real_tty!=tty ? -EINVAL : tioccons(file);
		case FIONBIO:
			return fionbio(file, p);
		case TIOCEXCL:
			set_bit(TTY_EXCLUSIVE, &tty->flags);
			return 0;
		case TIOCNXCL:
			clear_bit(TTY_EXCLUSIVE, &tty->flags);
			return 0;
		case TIOCNOTTY:
			if (current->signal->tty != tty)
				return -ENOTTY;
			if (current->signal->leader)
				disassociate_ctty(0);
			task_lock(current);
			current->signal->tty = NULL;
			task_unlock(current);
			return 0;
		case TIOCSCTTY:
			return tiocsctty(tty, arg);
		case TIOCGPGRP:
			return tiocgpgrp(tty, real_tty, p);
		case TIOCSPGRP:
			return tiocspgrp(tty, real_tty, p);
		case TIOCGSID:
			return tiocgsid(tty, real_tty, p);
		case TIOCGETD:
			/* FIXME: check this is ok */
			return put_user(tty->ldisc.num, (int __user *)p);
		case TIOCSETD:
			return tiocsetd(tty, p);
#ifdef CONFIG_VT
		case TIOCLINUX:
			return tioclinux(tty, arg);
#endif
		/*
		 * Break handling
		 */
		case TIOCSBRK:	/* Turn break on, unconditionally */
			tty->driver->break_ctl(tty, -1);
			return 0;
			
		case TIOCCBRK:	/* Turn break off, unconditionally */
			tty->driver->break_ctl(tty, 0);
			return 0;
		case TCSBRK:   /* SVID version: non-zero arg --> no break */
			/*
			 * XXX is the above comment correct, or the
			 * code below correct?  Is this ioctl used at
			 * all by anyone?
			 */
			if (!arg)
				return send_break(tty, 250);
			return 0;
		case TCSBRKP:	/* support for POSIX tcsendbreak() */	
			return send_break(tty, arg ? arg*100 : 250);

		case TIOCMGET:
			return tty_tiocmget(tty, file, p);

		case TIOCMSET:
		case TIOCMBIC:
		case TIOCMBIS:
			return tty_tiocmset(tty, file, cmd, p);
	}
	if (tty->driver->ioctl) {
		retval = (tty->driver->ioctl)(tty, file, cmd, arg);
		if (retval != -ENOIOCTLCMD)
			return retval;
	}
	ld = tty_ldisc_ref_wait(tty);
	retval = -EINVAL;
	if (ld->ioctl) {
		retval = ld->ioctl(tty, file, cmd, arg);
		if (retval == -ENOIOCTLCMD)
			retval = -EINVAL;
	}
	tty_ldisc_deref(ld);
	return retval;
}


/*
 * This implements the "Secure Attention Key" ---  the idea is to
 * prevent trojan horses by killing all processes associated with this
 * tty when the user hits the "Secure Attention Key".  Required for
 * super-paranoid applications --- see the Orange Book for more details.
 * 
 * This code could be nicer; ideally it should send a HUP, wait a few
 * seconds, then send a INT, and then a KILL signal.  But you then
 * have to coordinate with the init process, since all processes associated
 * with the current tty must be dead before the new getty is allowed
 * to spawn.
 *
 * Now, if it would be correct ;-/ The current code has a nasty hole -
 * it doesn't catch files in flight. We may send the descriptor to ourselves
 * via AF_UNIX socket, close it and later fetch from socket. FIXME.
 *
 * Nasty bug: do_SAK is being called in interrupt context.  This can
 * deadlock.  We punt it up to process context.  AKPM - 16Mar2001
 */
static void __do_SAK(void *arg)
{
#ifdef TTY_SOFT_SAK
	tty_hangup(tty);
#else
	struct tty_struct *tty = arg;
	struct task_struct *p;
	int session;
	int		i;
	struct file	*filp;
	struct tty_ldisc *disc;
	struct fdtable *fdt;
	
	if (!tty)
		return;
	session  = tty->session;
	
	/* We don't want an ldisc switch during this */
	disc = tty_ldisc_ref(tty);
	if (disc && disc->flush_buffer)
		disc->flush_buffer(tty);
	tty_ldisc_deref(disc);

	if (tty->driver->flush_buffer)
		tty->driver->flush_buffer(tty);
	
	read_lock(&tasklist_lock);
	do_each_task_pid(session, PIDTYPE_SID, p) {
		if (p->signal->tty == tty || session > 0) {
			printk(KERN_NOTICE "SAK: killed process %d"
			    " (%s): p->signal->session==tty->session\n",
			    p->pid, p->comm);
			send_sig(SIGKILL, p, 1);
			continue;
		}
		task_lock(p);
		if (p->files) {
			rcu_read_lock();
			fdt = files_fdtable(p->files);
			for (i=0; i < fdt->max_fds; i++) {
				filp = fcheck_files(p->files, i);
				if (!filp)
					continue;
				if (filp->f_op->read == tty_read &&
				    filp->private_data == tty) {
					printk(KERN_NOTICE "SAK: killed process %d"
					    " (%s): fd#%d opened to the tty\n",
					    p->pid, p->comm, i);
					send_sig(SIGKILL, p, 1);
					break;
				}
			}
			rcu_read_unlock();
		}
		task_unlock(p);
	} while_each_task_pid(session, PIDTYPE_SID, p);
	read_unlock(&tasklist_lock);
#endif
}

/*
 * The tq handling here is a little racy - tty->SAK_work may already be queued.
 * Fortunately we don't need to worry, because if ->SAK_work is already queued,
 * the values which we write to it will be identical to the values which it
 * already has. --akpm
 */
void do_SAK(struct tty_struct *tty)
{
	if (!tty)
		return;
	PREPARE_WORK(&tty->SAK_work, __do_SAK, tty);
	schedule_work(&tty->SAK_work);
}

EXPORT_SYMBOL(do_SAK);

/*
 * This routine is called out of the software interrupt to flush data
 * from the flip buffer to the line discipline. 
 */
 
static void flush_to_ldisc(void *private_)
{
	struct tty_struct *tty = (struct tty_struct *) private_;
	unsigned char	*cp;
	char		*fp;
	int		count;
	unsigned long 	flags;
	struct tty_ldisc *disc;

	disc = tty_ldisc_ref(tty);
	if (disc == NULL)	/*  !TTY_LDISC */
		return;

	if (test_bit(TTY_DONT_FLIP, &tty->flags)) {
		/*
		 * Do it after the next timer tick:
		 */
		schedule_delayed_work(&tty->flip.work, 1);
		goto out;
	}
	spin_lock_irqsave(&tty->read_lock, flags);
	if (tty->flip.buf_num) {
		cp = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
		fp = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
		tty->flip.buf_num = 0;
		tty->flip.char_buf_ptr = tty->flip.char_buf;
		tty->flip.flag_buf_ptr = tty->flip.flag_buf;
	} else {
		cp = tty->flip.char_buf;
		fp = tty->flip.flag_buf;
		tty->flip.buf_num = 1;
		tty->flip.char_buf_ptr = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
		tty->flip.flag_buf_ptr = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
	}
	count = tty->flip.count;
	tty->flip.count = 0;
	spin_unlock_irqrestore(&tty->read_lock, flags);

	disc->receive_buf(tty, cp, fp, count);
out:
	tty_ldisc_deref(disc);
}

/*
 * Routine which returns the baud rate of the tty
 *
 * Note that the baud_table needs to be kept in sync with the
 * include/asm/termbits.h file.
 */
static int baud_table[] = {
	0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
	9600, 19200, 38400, 57600, 115200, 230400, 460800,
#ifdef __sparc__
	76800, 153600, 307200, 614400, 921600
#else
	500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
	2500000, 3000000, 3500000, 4000000
#endif
};

static int n_baud_table = ARRAY_SIZE(baud_table);

/**
 *	tty_termios_baud_rate
 *	@termios: termios structure
 *
 *	Convert termios baud rate data into a speed. This should be called
 *	with the termios lock held if this termios is a terminal termios
 *	structure. May change the termios data.
 */
 
int tty_termios_baud_rate(struct termios *termios)
{
	unsigned int cbaud;
	
	cbaud = termios->c_cflag & CBAUD;

	if (cbaud & CBAUDEX) {
		cbaud &= ~CBAUDEX;

		if (cbaud < 1 || cbaud + 15 > n_baud_table)
			termios->c_cflag &= ~CBAUDEX;
		else
			cbaud += 15;
	}
	return baud_table[cbaud];
}

EXPORT_SYMBOL(tty_termios_baud_rate);

/**
 *	tty_get_baud_rate	-	get tty bit rates
 *	@tty: tty to query
 *
 *	Returns the baud rate as an integer for this terminal. The
 *	termios lock must be held by the caller and the terminal bit
 *	flags may be updated.
 */
 
int tty_get_baud_rate(struct tty_struct *tty)
{
	int baud = tty_termios_baud_rate(tty->termios);

	if (baud == 38400 && tty->alt_speed) {
		if (!tty->warned) {
			printk(KERN_WARNING "Use of setserial/setrocket to "
					    "set SPD_* flags is deprecated\n");
			tty->warned = 1;
		}
		baud = tty->alt_speed;
	}
	
	return baud;
}

EXPORT_SYMBOL(tty_get_baud_rate);

/**
 *	tty_flip_buffer_push	-	terminal
 *	@tty: tty to push
 *
 *	Queue a push of the terminal flip buffers to the line discipline. This
 *	function must not be called from IRQ context if tty->low_latency is set.
 *
 *	In the event of the queue being busy for flipping the work will be
 *	held off and retried later.
 */

void tty_flip_buffer_push(struct tty_struct *tty)
{
	if (tty->low_latency)
		flush_to_ldisc((void *) tty);
	else
		schedule_delayed_work(&tty->flip.work, 1);
}

EXPORT_SYMBOL(tty_flip_buffer_push);

/*
 * This subroutine initializes a tty structure.
 */
static void initialize_tty_struct(struct tty_struct *tty)
{
	memset(tty, 0, sizeof(struct tty_struct));
	tty->magic = TTY_MAGIC;
	tty_ldisc_assign(tty, tty_ldisc_get(N_TTY));
	tty->pgrp = -1;
	tty->overrun_time = jiffies;
	tty->flip.char_buf_ptr = tty->flip.char_buf;
	tty->flip.flag_buf_ptr = tty->flip.flag_buf;
	INIT_WORK(&tty->flip.work, flush_to_ldisc, tty);
	init_MUTEX(&tty->flip.pty_sem);
	init_MUTEX(&tty->termios_sem);
	init_waitqueue_head(&tty->write_wait);
	init_waitqueue_head(&tty->read_wait);
	INIT_WORK(&tty->hangup_work, do_tty_hangup, tty);
	sema_init(&tty->atomic_read, 1);
	sema_init(&tty->atomic_write, 1);
	spin_lock_init(&tty->read_lock);
	INIT_LIST_HEAD(&tty->tty_files);
	INIT_WORK(&tty->SAK_work, NULL, NULL);
}

/*
 * The default put_char routine if the driver did not define one.
 */
static void tty_default_put_char(struct tty_struct *tty, unsigned char ch)
{
	tty->driver->write(tty, &ch, 1);
}

static struct class *tty_class;

/**
 * tty_register_device - register a tty device
 * @driver: the tty driver that describes the tty device
 * @index: the index in the tty driver for this tty device
 * @device: a struct device that is associated with this tty device.
 *	This field is optional, if there is no known struct device for this
 *	tty device it can be set to NULL safely.
 *
 * This call is required to be made to register an individual tty device if
 * the tty driver's flags have the TTY_DRIVER_NO_DEVFS bit set.  If that
 * bit is not set, this function should not be called.
 */
void tty_register_device(struct tty_driver *driver, unsigned index,
			 struct device *device)
{
	char name[64];
	dev_t dev = MKDEV(driver->major, driver->minor_start) + index;

	if (index >= driver->num) {
		printk(KERN_ERR "Attempt to register invalid tty line number "
		       " (%d).\n", index);
		return;
	}

	devfs_mk_cdev(dev, S_IFCHR | S_IRUSR | S_IWUSR,
			"%s%d", driver->devfs_name, index + driver->name_base);

	if (driver->type == TTY_DRIVER_TYPE_PTY)
		pty_line_name(driver, index, name);
	else
		tty_line_name(driver, index, name);
	class_device_create(tty_class, NULL, dev, device, "%s", name);
}

/**
 * tty_unregister_device - unregister a tty device
 * @driver: the tty driver that describes the tty device
 * @index: the index in the tty driver for this tty device
 *
 * If a tty device is registered with a call to tty_register_device() then
 * this function must be made when the tty device is gone.
 */
void tty_unregister_device(struct tty_driver *driver, unsigned index)
{
	devfs_remove("%s%d", driver->devfs_name, index + driver->name_base);
	class_device_destroy(tty_class, MKDEV(driver->major, driver->minor_start) + index);
}

EXPORT_SYMBOL(tty_register_device);
EXPORT_SYMBOL(tty_unregister_device);

struct tty_driver *alloc_tty_driver(int lines)
{
	struct tty_driver *driver;

	driver = kmalloc(sizeof(struct tty_driver), GFP_KERNEL);
	if (driver) {
		memset(driver, 0, sizeof(struct tty_driver));
		driver->magic = TTY_DRIVER_MAGIC;
		driver->num = lines;
		/* later we'll move allocation of tables here */
	}
	return driver;
}

void put_tty_driver(struct tty_driver *driver)
{
	kfree(driver);
}

void tty_set_operations(struct tty_driver *driver, struct tty_operations *op)
{
	driver->open = op->open;
	driver->close = op->close;
	driver->write = op->write;
	driver->put_char = op->put_char;
	driver->flush_chars = op->flush_chars;
	driver->write_room = op->write_room;
	driver->chars_in_buffer = op->chars_in_buffer;
	driver->ioctl = op->ioctl;
	driver->set_termios = op->set_termios;
	driver->throttle = op->throttle;
	driver->unthrottle = op->unthrottle;
	driver->stop = op->stop;
	driver->start = op->start;
	driver->hangup = op->hangup;
	driver->break_ctl = op->break_ctl;
	driver->flush_buffer = op->flush_buffer;
	driver->set_ldisc = op->set_ldisc;
	driver->wait_until_sent = op->wait_until_sent;
	driver->send_xchar = op->send_xchar;
	driver->read_proc = op->read_proc;
	driver->write_proc = op->write_proc;
	driver->tiocmget = op->tiocmget;
	driver->tiocmset = op->tiocmset;
}


EXPORT_SYMBOL(alloc_tty_driver);
EXPORT_SYMBOL(put_tty_driver);
EXPORT_SYMBOL(tty_set_operations);

/*
 * Called by a tty driver to register itself.
 */
int tty_register_driver(struct tty_driver *driver)
{
	int error;
        int i;
	dev_t dev;
	void **p = NULL;

	if (driver->flags & TTY_DRIVER_INSTALLED)
		return 0;

	if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
		p = kmalloc(driver->num * 3 * sizeof(void *), GFP_KERNEL);
		if (!p)
			return -ENOMEM;
		memset(p, 0, driver->num * 3 * sizeof(void *));
	}

	if (!driver->major) {
		error = alloc_chrdev_region(&dev, driver->minor_start, driver->num,
						(char*)driver->name);
		if (!error) {
			driver->major = MAJOR(dev);
			driver->minor_start = MINOR(dev);
		}
	} else {
		dev = MKDEV(driver->major, driver->minor_start);
		error = register_chrdev_region(dev, driver->num,
						(char*)driver->name);
	}
	if (error < 0) {
		kfree(p);
		return error;
	}

	if (p) {
		driver->ttys = (struct tty_struct **)p;
		driver->termios = (struct termios **)(p + driver->num);
		driver->termios_locked = (struct termios **)(p + driver->num * 2);
	} else {
		driver->ttys = NULL;
		driver->termios = NULL;
		driver->termios_locked = NULL;
	}

	cdev_init(&driver->cdev, &tty_fops);
	driver->cdev.owner = driver->owner;
	error = cdev_add(&driver->cdev, dev, driver->num);
	if (error) {
		cdev_del(&driver->cdev);
		unregister_chrdev_region(dev, driver->num);
		driver->ttys = NULL;
		driver->termios = driver->termios_locked = NULL;
		kfree(p);
		return error;
	}

	if (!driver->put_char)
		driver->put_char = tty_default_put_char;
	
	list_add(&driver->tty_drivers, &tty_drivers);
	
	if ( !(driver->flags & TTY_DRIVER_NO_DEVFS) ) {
		for(i = 0; i < driver->num; i++)
		    tty_register_device(driver, i, NULL);
	}
	proc_tty_register_driver(driver);
	return 0;
}

EXPORT_SYMBOL(tty_register_driver);

/*
 * Called by a tty driver to unregister itself.
 */
int tty_unregister_driver(struct tty_driver *driver)
{
	int i;
	struct termios *tp;
	void *p;

	if (driver->refcount)
		return -EBUSY;

	unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
				driver->num);

	list_del(&driver->tty_drivers);

	/*
	 * Free the termios and termios_locked structures because
	 * we don't want to get memory leaks when modular tty
	 * drivers are removed from the kernel.
	 */
	for (i = 0; i < driver->num; i++) {
		tp = driver->termios[i];
		if (tp) {
			driver->termios[i] = NULL;
			kfree(tp);
		}
		tp = driver->termios_locked[i];
		if (tp) {
			driver->termios_locked[i] = NULL;
			kfree(tp);
		}
		if (!(driver->flags & TTY_DRIVER_NO_DEVFS))
			tty_unregister_device(driver, i);
	}
	p = driver->ttys;
	proc_tty_unregister_driver(driver);
	driver->ttys = NULL;
	driver->termios = driver->termios_locked = NULL;
	kfree(p);
	cdev_del(&driver->cdev);
	return 0;
}

EXPORT_SYMBOL(tty_unregister_driver);


/*
 * Initialize the console device. This is called *early*, so
 * we can't necessarily depend on lots of kernel help here.
 * Just do some early initializations, and do the complex setup
 * later.
 */
void __init console_init(void)
{
	initcall_t *call;

	/* Setup the default TTY line discipline. */
	(void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);

	/*
	 * set up the console device so that later boot sequences can 
	 * inform about problems etc..
	 */
#ifdef CONFIG_EARLY_PRINTK
	disable_early_printk();
#endif
	call = __con_initcall_start;
	while (call < __con_initcall_end) {
		(*call)();
		call++;
	}
}

#ifdef CONFIG_VT
extern int vty_init(void);
#endif

static int __init tty_class_init(void)
{
	tty_class = class_create(THIS_MODULE, "tty");
	if (IS_ERR(tty_class))
		return PTR_ERR(tty_class);
	return 0;
}

postcore_initcall(tty_class_init);

/* 3/2004 jmc: why do these devices exist? */

static struct cdev tty_cdev, console_cdev;
#ifdef CONFIG_UNIX98_PTYS
static struct cdev ptmx_cdev;
#endif
#ifdef CONFIG_VT
static struct cdev vc0_cdev;
#endif

/*
 * Ok, now we can initialize the rest of the tty devices and can count
 * on memory allocations, interrupts etc..
 */
static int __init tty_init(void)
{
	cdev_init(&tty_cdev, &tty_fops);
	if (cdev_add(&tty_cdev, MKDEV(TTYAUX_MAJOR, 0), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 0), 1, "/dev/tty") < 0)
		panic("Couldn't register /dev/tty driver\n");
	devfs_mk_cdev(MKDEV(TTYAUX_MAJOR, 0), S_IFCHR|S_IRUGO|S_IWUGO, "tty");
	class_device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 0), NULL, "tty");

	cdev_init(&console_cdev, &console_fops);
	if (cdev_add(&console_cdev, MKDEV(TTYAUX_MAJOR, 1), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 1), 1, "/dev/console") < 0)
		panic("Couldn't register /dev/console driver\n");
	devfs_mk_cdev(MKDEV(TTYAUX_MAJOR, 1), S_IFCHR|S_IRUSR|S_IWUSR, "console");
	class_device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 1), NULL, "console");

#ifdef CONFIG_UNIX98_PTYS
	cdev_init(&ptmx_cdev, &ptmx_fops);
	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
		panic("Couldn't register /dev/ptmx driver\n");
	devfs_mk_cdev(MKDEV(TTYAUX_MAJOR, 2), S_IFCHR|S_IRUGO|S_IWUGO, "ptmx");
	class_device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");
#endif

#ifdef CONFIG_VT
	cdev_init(&vc0_cdev, &console_fops);
	if (cdev_add(&vc0_cdev, MKDEV(TTY_MAJOR, 0), 1) ||
	    register_chrdev_region(MKDEV(TTY_MAJOR, 0), 1, "/dev/vc/0") < 0)
		panic("Couldn't register /dev/tty0 driver\n");
	devfs_mk_cdev(MKDEV(TTY_MAJOR, 0), S_IFCHR|S_IRUSR|S_IWUSR, "vc/0");
	class_device_create(tty_class, NULL, MKDEV(TTY_MAJOR, 0), NULL, "tty0");

	vty_init();
#endif
	return 0;
}
module_init(tty_init);