summaryrefslogtreecommitdiffstats
path: root/fs/devfs/base.c
blob: 8b679b67e5e0f78e18dbd25015f7990cfa6f1f5a (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
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
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
/*  devfs (Device FileSystem) driver.

    Copyright (C) 1998-2002  Richard Gooch

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

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

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

    Richard Gooch may be reached by email at  rgooch@atnf.csiro.au
    The postal address is:
      Richard Gooch, c/o ATNF, P. O. Box 76, Epping, N.S.W., 2121, Australia.

    ChangeLog

    19980110   Richard Gooch <rgooch@atnf.csiro.au>
               Original version.
  v0.1
    19980111   Richard Gooch <rgooch@atnf.csiro.au>
               Created per-fs inode table rather than using inode->u.generic_ip
  v0.2
    19980111   Richard Gooch <rgooch@atnf.csiro.au>
               Created .epoch inode which has a ctime of 0.
	       Fixed loss of named pipes when dentries lost.
	       Fixed loss of inode data when devfs_register() follows mknod().
  v0.3
    19980111   Richard Gooch <rgooch@atnf.csiro.au>
               Fix for when compiling with CONFIG_KERNELD.
    19980112   Richard Gooch <rgooch@atnf.csiro.au>
               Fix for readdir() which sometimes didn't show entries.
	       Added <<tolerant>> option to <devfs_register>.
  v0.4
    19980113   Richard Gooch <rgooch@atnf.csiro.au>
               Created <devfs_fill_file> function.
  v0.5
    19980115   Richard Gooch <rgooch@atnf.csiro.au>
               Added subdirectory support. Major restructuring.
    19980116   Richard Gooch <rgooch@atnf.csiro.au>
               Fixed <find_by_dev> to not search major=0,minor=0.
	       Added symlink support.
  v0.6
    19980120   Richard Gooch <rgooch@atnf.csiro.au>
               Created <devfs_mk_dir> function and support directory unregister
    19980120   Richard Gooch <rgooch@atnf.csiro.au>
               Auto-ownership uses real uid/gid rather than effective uid/gid.
  v0.7
    19980121   Richard Gooch <rgooch@atnf.csiro.au>
               Supported creation of sockets.
  v0.8
    19980122   Richard Gooch <rgooch@atnf.csiro.au>
               Added DEVFS_FL_HIDE_UNREG flag.
	       Interface change to <devfs_mk_symlink>.
               Created <devfs_symlink> to support symlink(2).
  v0.9
    19980123   Richard Gooch <rgooch@atnf.csiro.au>
               Added check to <devfs_fill_file> to check inode is in devfs.
	       Added optional traversal of symlinks.
  v0.10
    19980124   Richard Gooch <rgooch@atnf.csiro.au>
               Created <devfs_get_flags> and <devfs_set_flags>.
  v0.11
    19980125   C. Scott Ananian <cananian@alumni.princeton.edu>
               Created <devfs_find_handle>.
    19980125   Richard Gooch <rgooch@atnf.csiro.au>
               Allow removal of symlinks.
  v0.12
    19980125   Richard Gooch <rgooch@atnf.csiro.au>
               Created <devfs_set_symlink_destination>.
    19980126   Richard Gooch <rgooch@atnf.csiro.au>
               Moved DEVFS_SUPER_MAGIC into header file.
	       Added DEVFS_FL_HIDE flag.
	       Created <devfs_get_maj_min>.
	       Created <devfs_get_handle_from_inode>.
	       Fixed minor bug in <find_by_dev>.
    19980127   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed interface to <find_by_dev>, <find_entry>,
	       <devfs_unregister>, <devfs_fill_file> and <devfs_find_handle>.
	       Fixed inode times when symlink created with symlink(2).
  v0.13
    19980129   C. Scott Ananian <cananian@alumni.princeton.edu>
               Exported <devfs_set_symlink_destination>, <devfs_get_maj_min>
	       and <devfs_get_handle_from_inode>.
    19980129   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_unlink> to support unlink(2).
  v0.14
    19980129   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed kerneld support for entries in devfs subdirectories.
    19980130   Richard Gooch <rgooch@atnf.csiro.au>
	       Bugfixes in <call_kerneld>.
  v0.15
    19980207   Richard Gooch <rgooch@atnf.csiro.au>
	       Call kerneld when looking up unregistered entries.
  v0.16
    19980326   Richard Gooch <rgooch@atnf.csiro.au>
	       Modified interface to <devfs_find_handle> for symlink traversal.
  v0.17
    19980331   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed persistence bug with device numbers for manually created
	       device files.
	       Fixed problem with recreating symlinks with different content.
  v0.18
    19980401   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed to CONFIG_KMOD.
	       Hide entries which are manually unlinked.
	       Always invalidate devfs dentry cache when registering entries.
	       Created <devfs_rmdir> to support rmdir(2).
	       Ensure directories created by <devfs_mk_dir> are visible.
  v0.19
    19980402   Richard Gooch <rgooch@atnf.csiro.au>
	       Invalidate devfs dentry cache when making directories.
	       Invalidate devfs dentry cache when removing entries.
	       Fixed persistence bug with fifos.
  v0.20
    19980421   Richard Gooch <rgooch@atnf.csiro.au>
	       Print process command when debugging kerneld/kmod.
	       Added debugging for register/unregister/change operations.
    19980422   Richard Gooch <rgooch@atnf.csiro.au>
	       Added "devfs=" boot options.
  v0.21
    19980426   Richard Gooch <rgooch@atnf.csiro.au>
	       No longer lock/unlock superblock in <devfs_put_super>.
	       Drop negative dentries when they are released.
	       Manage dcache more efficiently.
  v0.22
    19980427   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFS_FL_AUTO_DEVNUM flag.
  v0.23
    19980430   Richard Gooch <rgooch@atnf.csiro.au>
	       No longer set unnecessary methods.
  v0.24
    19980504   Richard Gooch <rgooch@atnf.csiro.au>
	       Added PID display to <call_kerneld> debugging message.
	       Added "after" debugging message to <call_kerneld>.
    19980519   Richard Gooch <rgooch@atnf.csiro.au>
	       Added "diread" and "diwrite" boot options.
    19980520   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed persistence problem with permissions.
  v0.25
    19980602   Richard Gooch <rgooch@atnf.csiro.au>
	       Support legacy device nodes.
	       Fixed bug where recreated inodes were hidden.
  v0.26
    19980602   Richard Gooch <rgooch@atnf.csiro.au>
	       Improved debugging in <get_vfs_inode>.
    19980607   Richard Gooch <rgooch@atnf.csiro.au>
	       No longer free old dentries in <devfs_mk_dir>.
	       Free all dentries for a given entry when deleting inodes.
  v0.27
    19980627   Richard Gooch <rgooch@atnf.csiro.au>
	       Limit auto-device numbering to majors 128 to 239.
  v0.28
    19980629   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed inode times persistence problem.
  v0.29
    19980704   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed spelling in <devfs_readlink> debug.
	       Fixed bug in <devfs_setup> parsing "dilookup".
  v0.30
    19980705   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed devfs inode leak when manually recreating inodes.
	       Fixed permission persistence problem when recreating inodes.
  v0.31
    19980727   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed harmless "unused variable" compiler warning.
	       Fixed modes for manually recreated device nodes.
  v0.32
    19980728   Richard Gooch <rgooch@atnf.csiro.au>
	       Added NULL devfs inode warning in <devfs_read_inode>.
	       Force all inode nlink values to 1.
  v0.33
    19980730   Richard Gooch <rgooch@atnf.csiro.au>
	       Added "dimknod" boot option.
	       Set inode nlink to 0 when freeing dentries.
	       Fixed modes for manually recreated symlinks.
  v0.34
    19980802   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bugs in recreated directories and symlinks.
  v0.35
    19980806   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bugs in recreated device nodes.
    19980807   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bug in currently unused <devfs_get_handle_from_inode>.
	       Defined new <devfs_handle_t> type.
	       Improved debugging when getting entries.
	       Fixed bug where directories could be emptied.
  v0.36
    19980809   Richard Gooch <rgooch@atnf.csiro.au>
	       Replaced dummy .epoch inode with .devfsd character device.
    19980810   Richard Gooch <rgooch@atnf.csiro.au>
	       Implemented devfsd protocol revision 0.
  v0.37
    19980819   Richard Gooch <rgooch@atnf.csiro.au>
	       Added soothing message to warning in <devfs_d_iput>.
  v0.38
    19980829   Richard Gooch <rgooch@atnf.csiro.au>
	       Use GCC extensions for structure initialisations.
	       Implemented async open notification.
	       Incremented devfsd protocol revision to 1.
  v0.39
    19980908   Richard Gooch <rgooch@atnf.csiro.au>
	       Moved async open notification to end of <devfs_open>.
  v0.40
    19980910   Richard Gooch <rgooch@atnf.csiro.au>
	       Prepended "/dev/" to module load request.
	       Renamed <call_kerneld> to <call_kmod>.
  v0.41
    19980910   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed typo "AYSNC" -> "ASYNC".
  v0.42
    19980910   Richard Gooch <rgooch@atnf.csiro.au>
	       Added open flag for files.
  v0.43
    19980927   Richard Gooch <rgooch@atnf.csiro.au>
	       Set i_blocks=0 and i_blksize=1024 in <devfs_read_inode>.
  v0.44
    19981005   Richard Gooch <rgooch@atnf.csiro.au>
	       Added test for empty <<name>> in <devfs_find_handle>.
	       Renamed <generate_path> to <devfs_generate_path> and published.
  v0.45
    19981006   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_get_fops>.
  v0.46
    19981007   Richard Gooch <rgooch@atnf.csiro.au>
	       Limit auto-device numbering to majors 144 to 239.
  v0.47
    19981010   Richard Gooch <rgooch@atnf.csiro.au>
	       Updated <devfs_follow_link> for VFS change in 2.1.125.
  v0.48
    19981022   Richard Gooch <rgooch@atnf.csiro.au>
	       Created DEVFS_ FL_COMPAT flag.
  v0.49
    19981023   Richard Gooch <rgooch@atnf.csiro.au>
	       Created "nocompat" boot option.
  v0.50
    19981025   Richard Gooch <rgooch@atnf.csiro.au>
	       Replaced "mount" boot option with "nomount".
  v0.51
    19981110   Richard Gooch <rgooch@atnf.csiro.au>
	       Created "only" boot option.
  v0.52
    19981112   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFS_FL_REMOVABLE flag.
  v0.53
    19981114   Richard Gooch <rgooch@atnf.csiro.au>
	       Only call <scan_dir_for_removable> on first call to
	       <devfs_readdir>.
  v0.54
    19981205   Richard Gooch <rgooch@atnf.csiro.au>
	       Updated <devfs_rmdir> for VFS change in 2.1.131.
  v0.55
    19981218   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_mk_compat>.
    19981220   Richard Gooch <rgooch@atnf.csiro.au>
	       Check for partitions on removable media in <devfs_lookup>.
  v0.56
    19990118   Richard Gooch <rgooch@atnf.csiro.au>
	       Added support for registering regular files.
	       Created <devfs_set_file_size>.
	       Update devfs inodes from entries if not changed through FS.
  v0.57
    19990124   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed <devfs_fill_file> to only initialise temporary inodes.
	       Trap for NULL fops in <devfs_register>.
	       Return -ENODEV in <devfs_fill_file> for non-driver inodes.
  v0.58
    19990126   Richard Gooch <rgooch@atnf.csiro.au>
	       Switched from PATH_MAX to DEVFS_PATHLEN.
  v0.59
    19990127   Richard Gooch <rgooch@atnf.csiro.au>
	       Created "nottycompat" boot option.
  v0.60
    19990318   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed <devfsd_read> to not overrun event buffer.
  v0.61
    19990329   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_auto_unregister>.
  v0.62
    19990330   Richard Gooch <rgooch@atnf.csiro.au>
	       Don't return unregistred entries in <devfs_find_handle>.
	       Panic in <devfs_unregister> if entry unregistered.
    19990401   Richard Gooch <rgooch@atnf.csiro.au>
	       Don't panic in <devfs_auto_unregister> for duplicates.
  v0.63
    19990402   Richard Gooch <rgooch@atnf.csiro.au>
	       Don't unregister already unregistered entries in <unregister>.
  v0.64
    19990510   Richard Gooch <rgooch@atnf.csiro.au>
	       Disable warning messages when unable to read partition table for
	       removable media.
  v0.65
    19990512   Richard Gooch <rgooch@atnf.csiro.au>
	       Updated <devfs_lookup> for VFS change in 2.3.1-pre1.
	       Created "oops-on-panic" boot option.
	       Improved debugging in <devfs_register> and <devfs_unregister>.
  v0.66
    19990519   Richard Gooch <rgooch@atnf.csiro.au>
	       Added documentation for some functions.
    19990525   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed "oops-on-panic" boot option: now always Oops.
  v0.67
    19990531   Richard Gooch <rgooch@atnf.csiro.au>
	       Improved debugging in <devfs_register>.
  v0.68
    19990604   Richard Gooch <rgooch@atnf.csiro.au>
	       Added "diunlink" and "nokmod" boot options.
	       Removed superfluous warning message in <devfs_d_iput>.
  v0.69
    19990611   Richard Gooch <rgooch@atnf.csiro.au>
	       Took account of change to <d_alloc_root>.
  v0.70
    19990614   Richard Gooch <rgooch@atnf.csiro.au>
	       Created separate event queue for each mounted devfs.
	       Removed <devfs_invalidate_dcache>.
	       Created new ioctl()s.
	       Incremented devfsd protocol revision to 3.
	       Fixed bug when re-creating directories: contents were lost.
	       Block access to inodes until devfsd updates permissions.
    19990615   Richard Gooch <rgooch@atnf.csiro.au>
	       Support 2.2.x kernels.
  v0.71
    19990623   Richard Gooch <rgooch@atnf.csiro.au>
	       Switched to sending process uid/gid to devfsd.
	       Renamed <call_kmod> to <try_modload>.
	       Added DEVFSD_NOTIFY_LOOKUP event.
    19990624   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFSD_NOTIFY_CHANGE event.
	       Incremented devfsd protocol revision to 4.
  v0.72
    19990713   Richard Gooch <rgooch@atnf.csiro.au>
	       Return EISDIR rather than EINVAL for read(2) on directories.
  v0.73
    19990809   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed <devfs_setup> to new __init scheme.
  v0.74
    19990901   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed remaining function declarations to new __init scheme.
  v0.75
    19991013   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_get_info>, <devfs_set_info>,
	       <devfs_get_first_child> and <devfs_get_next_sibling>.
	       Added <<dir>> parameter to <devfs_register>, <devfs_mk_compat>,
	       <devfs_mk_dir> and <devfs_find_handle>.
	       Work sponsored by SGI.
  v0.76
    19991017   Richard Gooch <rgooch@atnf.csiro.au>
	       Allow multiple unregistrations.
	       Work sponsored by SGI.
  v0.77
    19991026   Richard Gooch <rgooch@atnf.csiro.au>
	       Added major and minor number to devfsd protocol.
	       Incremented devfsd protocol revision to 5.
	       Work sponsored by SGI.
  v0.78
    19991030   Richard Gooch <rgooch@atnf.csiro.au>
	       Support info pointer for all devfs entry types.
	       Added <<info>> parameter to <devfs_mk_dir> and
	       <devfs_mk_symlink>.
	       Work sponsored by SGI.
  v0.79
    19991031   Richard Gooch <rgooch@atnf.csiro.au>
	       Support "../" when searching devfs namespace.
	       Work sponsored by SGI.
  v0.80
    19991101   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_get_unregister_slave>.
	       Work sponsored by SGI.
  v0.81
    19991103   Richard Gooch <rgooch@atnf.csiro.au>
	       Exported <devfs_get_parent>.
	       Work sponsored by SGI.
  v0.82
    19991104   Richard Gooch <rgooch@atnf.csiro.au>
               Removed unused <devfs_set_symlink_destination>.
    19991105   Richard Gooch <rgooch@atnf.csiro.au>
               Do not hide entries from devfsd or children.
	       Removed DEVFS_ FL_TTY_COMPAT flag.
	       Removed "nottycompat" boot option.
	       Removed <devfs_mk_compat>.
	       Work sponsored by SGI.
  v0.83
    19991107   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFS_FL_WAIT flag.
	       Work sponsored by SGI.
  v0.84
    19991107   Richard Gooch <rgooch@atnf.csiro.au>
	       Support new "disc" naming scheme in <get_removable_partition>.
	       Allow NULL fops in <devfs_register>.
	       Work sponsored by SGI.
  v0.85
    19991110   Richard Gooch <rgooch@atnf.csiro.au>
	       Fall back to major table if NULL fops given to <devfs_register>.
	       Work sponsored by SGI.
  v0.86
    19991204   Richard Gooch <rgooch@atnf.csiro.au>
	       Support fifos when unregistering.
	       Work sponsored by SGI.
  v0.87
    19991209   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed obsolete DEVFS_ FL_COMPAT and DEVFS_ FL_TOLERANT flags.
	       Work sponsored by SGI.
  v0.88
    19991214   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed kmod support.
	       Work sponsored by SGI.
  v0.89
    19991216   Richard Gooch <rgooch@atnf.csiro.au>
	       Improved debugging in <get_vfs_inode>.
	       Ensure dentries created by devfsd will be cleaned up.
	       Work sponsored by SGI.
  v0.90
    19991223   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_get_name>.
	       Work sponsored by SGI.
  v0.91
    20000203   Richard Gooch <rgooch@atnf.csiro.au>
	       Ported to kernel 2.3.42.
	       Removed <devfs_fill_file>.
	       Work sponsored by SGI.
  v0.92
    20000306   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFS_ FL_NO_PERSISTENCE flag.
	       Removed unnecessary call to <update_devfs_inode_from_entry> in
	       <devfs_readdir>.
	       Work sponsored by SGI.
  v0.93
    20000413   Richard Gooch <rgooch@atnf.csiro.au>
	       Set inode->i_size to correct size for symlinks.
    20000414   Richard Gooch <rgooch@atnf.csiro.au>
	       Only give lookup() method to directories to comply with new VFS
	       assumptions.
	       Work sponsored by SGI.
    20000415   Richard Gooch <rgooch@atnf.csiro.au>
	       Remove unnecessary tests in symlink methods.
	       Don't kill existing block ops in <devfs_read_inode>.
	       Work sponsored by SGI.
  v0.94
    20000424   Richard Gooch <rgooch@atnf.csiro.au>
	       Don't create missing directories in <devfs_find_handle>.
	       Work sponsored by SGI.
  v0.95
    20000430   Richard Gooch <rgooch@atnf.csiro.au>
	       Added CONFIG_DEVFS_MOUNT.
	       Work sponsored by SGI.
  v0.96
    20000608   Richard Gooch <rgooch@atnf.csiro.au>
	       Disabled multi-mount capability (use VFS bindings instead).
	       Work sponsored by SGI.
  v0.97
    20000610   Richard Gooch <rgooch@atnf.csiro.au>
	       Switched to FS_SINGLE to disable multi-mounts.
    20000612   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed module support.
	       Removed multi-mount code.
	       Removed compatibility macros: VFS has changed too much.
	       Work sponsored by SGI.
  v0.98
    20000614   Richard Gooch <rgooch@atnf.csiro.au>
	       Merged devfs inode into devfs entry.
	       Work sponsored by SGI.
  v0.99
    20000619   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed dead code in <devfs_register> which used to call
	       <free_dentries>.
	       Work sponsored by SGI.
  v0.100
    20000621   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed interface to <devfs_register>.
	       Work sponsored by SGI.
  v0.101
    20000622   Richard Gooch <rgooch@atnf.csiro.au>
	       Simplified interface to <devfs_mk_symlink> and <devfs_mk_dir>.
	       Simplified interface to <devfs_find_handle>.
	       Work sponsored by SGI.
  v0.102
    20010519   Richard Gooch <rgooch@atnf.csiro.au>
	       Ensure <devfs_generate_path> terminates string for root entry.
	       Exported <devfs_get_name> to modules.
    20010520   Richard Gooch <rgooch@atnf.csiro.au>
	       Make <devfs_mk_symlink> send events to devfsd.
	       Cleaned up option processing in <devfs_setup>.
    20010521   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bugs in handling symlinks: could leak or cause Oops.
    20010522   Richard Gooch <rgooch@atnf.csiro.au>
	       Cleaned up directory handling by separating fops.
  v0.103
    20010601   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed handling of inverted options in <devfs_setup>.
  v0.104
    20010604   Richard Gooch <rgooch@atnf.csiro.au>
	       Adjusted <try_modload> to account for <devfs_generate_path> fix.
  v0.105
    20010617   Richard Gooch <rgooch@atnf.csiro.au>
	       Answered question posed by Al Viro and removed his comments.
	       Moved setting of registered flag after other fields are changed.
	       Fixed race between <devfsd_close> and <devfsd_notify_one>.
	       Global VFS changes added bogus BKL to <devfsd_close>: removed.
	       Widened locking in <devfs_readlink> and <devfs_follow_link>.
	       Replaced <devfsd_read> stack usage with <devfsd_ioctl> kmalloc.
	       Simplified locking in <devfsd_ioctl> and fixed memory leak.
  v0.106
    20010709   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed broken devnum allocation and use <devfs_alloc_devnum>.
	       Fixed old devnum leak by calling new <devfs_dealloc_devnum>.
  v0.107
    20010712   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bug in <devfs_setup> which could hang boot process.
  v0.108
    20010730   Richard Gooch <rgooch@atnf.csiro.au>
	       Added DEVFSD_NOTIFY_DELETE event.
    20010801   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed #include <asm/segment.h>.
  v0.109
    20010807   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed inode table races by removing it and using
	       inode->u.generic_ip instead.
	       Moved <devfs_read_inode> into <get_vfs_inode>.
	       Moved <devfs_write_inode> into <devfs_notify_change>.
  v0.110
    20010808   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed race in <devfs_do_symlink> for uni-processor.
  v0.111
    20010818   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed remnant of multi-mount support in <devfs_mknod>.
               Removed unused DEVFS_FL_SHOW_UNREG flag.
  v0.112
    20010820   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed nlink field from struct devfs_inode.
  v0.113
    20010823   Richard Gooch <rgooch@atnf.csiro.au>
	       Replaced BKL with global rwsem to protect symlink data (quick
	       and dirty hack).
  v0.114
    20010827   Richard Gooch <rgooch@atnf.csiro.au>
	       Replaced global rwsem for symlink with per-link refcount.
  v0.115
    20010919   Richard Gooch <rgooch@atnf.csiro.au>
	       Set inode->i_mapping->a_ops for block nodes in <get_vfs_inode>.
  v0.116
    20011008   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed overrun in <devfs_link> by removing function (not needed).
    20011009   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed buffer underrun in <try_modload>.
    20011029   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed race in <devfsd_ioctl> when setting event mask.
    20011114   Richard Gooch <rgooch@atnf.csiro.au>
	       First release of new locking code.
  v1.0
    20011117   Richard Gooch <rgooch@atnf.csiro.au>
	       Discard temporary buffer, now use "%s" for dentry names.
    20011118   Richard Gooch <rgooch@atnf.csiro.au>
	       Don't generate path in <try_modload>: use fake entry instead.
	       Use "existing" directory in <_devfs_make_parent_for_leaf>.
    20011122   Richard Gooch <rgooch@atnf.csiro.au>
	       Use slab cache rather than fixed buffer for devfsd events.
  v1.1
    20011125   Richard Gooch <rgooch@atnf.csiro.au>
	       Send DEVFSD_NOTIFY_REGISTERED events in <devfs_mk_dir>.
    20011127   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed locking bug in <devfs_d_revalidate_wait> due to typo.
	       Do not send CREATE, CHANGE, ASYNC_OPEN or DELETE events from
	       devfsd or children.
  v1.2
    20011202   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bug in <devfsd_read>: was dereferencing freed pointer.
  v1.3
    20011203   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed bug in <devfsd_close>: was dereferencing freed pointer.
	       Added process group check for devfsd privileges.
  v1.4
    20011204   Richard Gooch <rgooch@atnf.csiro.au>
	       Use SLAB_ATOMIC in <devfsd_notify_de> from <devfs_d_delete>.
  v1.5
    20011211   Richard Gooch <rgooch@atnf.csiro.au>
	       Return old entry in <devfs_mk_dir> for 2.4.x kernels.
    20011212   Richard Gooch <rgooch@atnf.csiro.au>
	       Increment refcount on module in <check_disc_changed>.
    20011215   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_get_handle> and exported <devfs_put>.
	       Increment refcount on module in <devfs_get_ops>.
	       Created <devfs_put_ops>.
  v1.6
    20011216   Richard Gooch <rgooch@atnf.csiro.au>
	       Added poisoning to <devfs_put>.
	       Improved debugging messages.
  v1.7
    20011221   Richard Gooch <rgooch@atnf.csiro.au>
	       Corrected (made useful) debugging message in <unregister>.
	       Moved <kmem_cache_create> in <mount_devfs_fs> to <init_devfs_fs>
    20011224   Richard Gooch <rgooch@atnf.csiro.au>
	       Added magic number to guard against scribbling drivers.
    20011226   Richard Gooch <rgooch@atnf.csiro.au>
	       Only return old entry in <devfs_mk_dir> if a directory.
	       Defined macros for error and debug messages.
  v1.8
    20020113   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed (rare, old) race in <devfs_lookup>.
  v1.9
    20020120   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed deadlock bug in <devfs_d_revalidate_wait>.
	       Tag VFS deletable in <devfs_mk_symlink> if handle ignored.
  v1.10
    20020129   Richard Gooch <rgooch@atnf.csiro.au>
	       Added KERN_* to remaining messages.
	       Cleaned up declaration of <stat_read>.
  v1.11
    20020219   Richard Gooch <rgooch@atnf.csiro.au>
	       Changed <devfs_rmdir> to allow later additions if not yet empty.
  v1.12
    20020406   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed silently introduced calls to lock_kernel() and
	       unlock_kernel() due to recent VFS locking changes. BKL isn't
	       required in devfs.
  v1.13
    20020428   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed 2.4.x compatibility code.
  v1.14
    20020510   Richard Gooch <rgooch@atnf.csiro.au>
	       Added BKL to <devfs_open> because drivers still need it.
  v1.15
    20020512   Richard Gooch <rgooch@atnf.csiro.au>
	       Protected <scan_dir_for_removable> and <get_removable_partition>
	       from changing directory contents.
  v1.16
    20020514   Richard Gooch <rgooch@atnf.csiro.au>
	       Minor cleanup of <scan_dir_for_removable>.
  v1.17
    20020721   Richard Gooch <rgooch@atnf.csiro.au>
	       Switched to ISO C structure field initialisers.
	       Switch to set_current_state() and move before add_wait_queue().
    20020722   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed devfs entry leak in <devfs_readdir> when *readdir fails.
  v1.18
    20020725   Richard Gooch <rgooch@atnf.csiro.au>
	       Created <devfs_find_and_unregister>.
  v1.19
    20020728   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed deprecated <devfs_find_handle>.
  v1.20
    20020820   Richard Gooch <rgooch@atnf.csiro.au>
	       Fixed module unload race in <devfs_open>.
  v1.21
    20021013   Richard Gooch <rgooch@atnf.csiro.au>
	       Removed DEVFS_ FL_AUTO_OWNER.
	       Switched lingering structure field initialiser to ISO C.
	       Added locking when updating FCB flags.
  v1.22
*/
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/time.h>
#include <linux/tty.h>
#include <linux/timer.h>
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/wait.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/ioport.h>
#include <linux/delay.h>
#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/devfs_fs.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/smp_lock.h>
#include <linux/smp.h>
#include <linux/rwsem.h>
#include <linux/sched.h>
#include <linux/namei.h>
#include <linux/bitops.h>

#include <asm/uaccess.h>
#include <asm/io.h>
#include <asm/processor.h>
#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/atomic.h>

#define DEVFS_VERSION            "2004-01-31"

#define DEVFS_NAME "devfs"

#define FIRST_INODE 1

#define STRING_LENGTH 256
#define FAKE_BLOCK_SIZE 1024
#define POISON_PTR ( *(void **) poison_array )
#define MAGIC_VALUE 0x327db823

#ifndef TRUE
#  define TRUE 1
#  define FALSE 0
#endif

#define MODE_DIR (S_IFDIR | S_IWUSR | S_IRUGO | S_IXUGO)

#define DEBUG_NONE         0x0000000
#define DEBUG_MODULE_LOAD  0x0000001
#define DEBUG_REGISTER     0x0000002
#define DEBUG_UNREGISTER   0x0000004
#define DEBUG_FREE         0x0000008
#define DEBUG_SET_FLAGS    0x0000010
#define DEBUG_S_READ       0x0000100	/*  Break  */
#define DEBUG_I_LOOKUP     0x0001000	/*  Break  */
#define DEBUG_I_CREATE     0x0002000
#define DEBUG_I_GET        0x0004000
#define DEBUG_I_CHANGE     0x0008000
#define DEBUG_I_UNLINK     0x0010000
#define DEBUG_I_RLINK      0x0020000
#define DEBUG_I_FLINK      0x0040000
#define DEBUG_I_MKNOD      0x0080000
#define DEBUG_F_READDIR    0x0100000	/*  Break  */
#define DEBUG_D_DELETE     0x1000000	/*  Break  */
#define DEBUG_D_RELEASE    0x2000000
#define DEBUG_D_IPUT       0x4000000
#define DEBUG_ALL          0xfffffff
#define DEBUG_DISABLED     DEBUG_NONE

#define OPTION_NONE             0x00
#define OPTION_MOUNT            0x01

#define PRINTK(format, args...) \
   {printk (KERN_ERR "%s" format, __FUNCTION__ , ## args);}

#define OOPS(format, args...) \
   {printk (KERN_CRIT "%s" format, __FUNCTION__ , ## args); \
    printk ("Forcing Oops\n"); \
    BUG();}

#ifdef CONFIG_DEVFS_DEBUG
#  define VERIFY_ENTRY(de) \
   {if ((de) && (de)->magic_number != MAGIC_VALUE) \
        OOPS ("(%p): bad magic value: %x\n", (de), (de)->magic_number);}
#  define WRITE_ENTRY_MAGIC(de,magic) (de)->magic_number = (magic)
#  define DPRINTK(flag, format, args...) \
   {if (devfs_debug & flag) \
	printk (KERN_INFO "%s" format, __FUNCTION__ , ## args);}
#else
#  define VERIFY_ENTRY(de)
#  define WRITE_ENTRY_MAGIC(de,magic)
#  define DPRINTK(flag, format, args...)
#endif

typedef struct devfs_entry *devfs_handle_t;

struct directory_type {
	rwlock_t lock;		/*  Lock for searching(R)/updating(W)   */
	struct devfs_entry *first;
	struct devfs_entry *last;
	unsigned char no_more_additions:1;
};

struct symlink_type {
	unsigned int length;	/*  Not including the NULL-termimator       */
	char *linkname;		/*  This is NULL-terminated                 */
};

struct devfs_inode {		/*  This structure is for "persistent" inode storage  */
	struct dentry *dentry;
	struct timespec atime;
	struct timespec mtime;
	struct timespec ctime;
	unsigned int ino;	/*  Inode number as seen in the VFS         */
	uid_t uid;
	gid_t gid;
};

struct devfs_entry {
#ifdef CONFIG_DEVFS_DEBUG
	unsigned int magic_number;
#endif
	void *info;
	atomic_t refcount;	/*  When this drops to zero, it's unused    */
	union {
		struct directory_type dir;
		dev_t dev;
		struct symlink_type symlink;
		const char *name;	/*  Only used for (mode == 0)               */
	} u;
	struct devfs_entry *prev;	/*  Previous entry in the parent directory  */
	struct devfs_entry *next;	/*  Next entry in the parent directory      */
	struct devfs_entry *parent;	/*  The parent directory                    */
	struct devfs_inode inode;
	umode_t mode;
	unsigned short namelen;	/*  I think 64k+ filenames are a way off... */
	unsigned char vfs:1;	/*  Whether the VFS may delete the entry   */
	char name[1];		/*  This is just a dummy: the allocated array
				   is bigger. This is NULL-terminated      */
};

/*  The root of the device tree  */
static struct devfs_entry *root_entry;

struct devfsd_buf_entry {
	struct devfs_entry *de;	/*  The name is generated with this         */
	unsigned short type;	/*  The type of event                       */
	umode_t mode;
	uid_t uid;
	gid_t gid;
	struct devfsd_buf_entry *next;
};

struct fs_info {		/*  This structure is for the mounted devfs  */
	struct super_block *sb;
	spinlock_t devfsd_buffer_lock;	/*  Lock when inserting/deleting events  */
	struct devfsd_buf_entry *devfsd_first_event;
	struct devfsd_buf_entry *devfsd_last_event;
	volatile int devfsd_sleeping;
	volatile struct task_struct *devfsd_task;
	volatile pid_t devfsd_pgrp;
	volatile struct file *devfsd_file;
	struct devfsd_notify_struct *devfsd_info;
	volatile unsigned long devfsd_event_mask;
	atomic_t devfsd_overrun_count;
	wait_queue_head_t devfsd_wait_queue;	/*  Wake devfsd on input       */
	wait_queue_head_t revalidate_wait_queue;	/*  Wake when devfsd sleeps    */
};

static struct fs_info fs_info = {.devfsd_buffer_lock = SPIN_LOCK_UNLOCKED };
static kmem_cache_t *devfsd_buf_cache;
#ifdef CONFIG_DEVFS_DEBUG
static unsigned int devfs_debug_init __initdata = DEBUG_NONE;
static unsigned int devfs_debug = DEBUG_NONE;
static DEFINE_SPINLOCK(stat_lock);
static unsigned int stat_num_entries;
static unsigned int stat_num_bytes;
#endif
static unsigned char poison_array[8] =
    { 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a, 0x5a };

#ifdef CONFIG_DEVFS_MOUNT
static unsigned int boot_options = OPTION_MOUNT;
#else
static unsigned int boot_options = OPTION_NONE;
#endif

/*  Forward function declarations  */
static devfs_handle_t _devfs_walk_path(struct devfs_entry *dir,
				       const char *name, int namelen,
				       int traverse_symlink);
static ssize_t devfsd_read(struct file *file, char __user *buf, size_t len,
			   loff_t * ppos);
static int devfsd_ioctl(struct inode *inode, struct file *file,
			unsigned int cmd, unsigned long arg);
static int devfsd_close(struct inode *inode, struct file *file);
#ifdef CONFIG_DEVFS_DEBUG
static ssize_t stat_read(struct file *file, char __user *buf, size_t len,
			 loff_t * ppos);
static struct file_operations stat_fops = {
	.open = nonseekable_open,
	.read = stat_read,
};
#endif

/*  Devfs daemon file operations  */
static struct file_operations devfsd_fops = {
	.open = nonseekable_open,
	.read = devfsd_read,
	.ioctl = devfsd_ioctl,
	.release = devfsd_close,
};

/*  Support functions follow  */

/**
 *	devfs_get - Get a reference to a devfs entry.
 *	@de:  The devfs entry.
 */

static struct devfs_entry *devfs_get(struct devfs_entry *de)
{
	VERIFY_ENTRY(de);
	if (de)
		atomic_inc(&de->refcount);
	return de;
}				/*  End Function devfs_get  */

/**
 *	devfs_put - Put (release) a reference to a devfs entry.
 *	@de:  The handle to the devfs entry.
 */

static void devfs_put(devfs_handle_t de)
{
	if (!de)
		return;
	VERIFY_ENTRY(de);
	if (de->info == POISON_PTR)
		OOPS("(%p): poisoned pointer\n", de);
	if (!atomic_dec_and_test(&de->refcount))
		return;
	if (de == root_entry)
		OOPS("(%p): root entry being freed\n", de);
	DPRINTK(DEBUG_FREE, "(%s): de: %p, parent: %p \"%s\"\n",
		de->name, de, de->parent,
		de->parent ? de->parent->name : "no parent");
	if (S_ISLNK(de->mode))
		kfree(de->u.symlink.linkname);
	WRITE_ENTRY_MAGIC(de, 0);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	--stat_num_entries;
	stat_num_bytes -= sizeof *de + de->namelen;
	if (S_ISLNK(de->mode))
		stat_num_bytes -= de->u.symlink.length + 1;
	spin_unlock(&stat_lock);
#endif
	de->info = POISON_PTR;
	kfree(de);
}				/*  End Function devfs_put  */

/**
 *	_devfs_search_dir - Search for a devfs entry in a directory.
 *	@dir:  The directory to search.
 *	@name:  The name of the entry to search for.
 *	@namelen:  The number of characters in @name.
 *
 *  Search for a devfs entry in a directory and returns a pointer to the entry
 *   on success, else %NULL. The directory must be locked already.
 *   An implicit devfs_get() is performed on the returned entry.
 */

static struct devfs_entry *_devfs_search_dir(struct devfs_entry *dir,
					     const char *name,
					     unsigned int namelen)
{
	struct devfs_entry *curr;

	if (!S_ISDIR(dir->mode)) {
		PRINTK("(%s): not a directory\n", dir->name);
		return NULL;
	}
	for (curr = dir->u.dir.first; curr != NULL; curr = curr->next) {
		if (curr->namelen != namelen)
			continue;
		if (memcmp(curr->name, name, namelen) == 0)
			break;
		/*  Not found: try the next one  */
	}
	return devfs_get(curr);
}				/*  End Function _devfs_search_dir  */

/**
 *	_devfs_alloc_entry - Allocate a devfs entry.
 *	@name:     the name of the entry
 *	@namelen:  the number of characters in @name
 *      @mode:     the mode for the entry
 *
 *  Allocate a devfs entry and returns a pointer to the entry on success, else
 *   %NULL.
 */

static struct devfs_entry *_devfs_alloc_entry(const char *name,
					      unsigned int namelen,
					      umode_t mode)
{
	struct devfs_entry *new;
	static unsigned long inode_counter = FIRST_INODE;
	static DEFINE_SPINLOCK(counter_lock);

	if (name && (namelen < 1))
		namelen = strlen(name);
	if ((new = kmalloc(sizeof *new + namelen, GFP_KERNEL)) == NULL)
		return NULL;
	memset(new, 0, sizeof *new + namelen);	/*  Will set '\0' on name  */
	new->mode = mode;
	if (S_ISDIR(mode))
		rwlock_init(&new->u.dir.lock);
	atomic_set(&new->refcount, 1);
	spin_lock(&counter_lock);
	new->inode.ino = inode_counter++;
	spin_unlock(&counter_lock);
	if (name)
		memcpy(new->name, name, namelen);
	new->namelen = namelen;
	WRITE_ENTRY_MAGIC(new, MAGIC_VALUE);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	++stat_num_entries;
	stat_num_bytes += sizeof *new + namelen;
	spin_unlock(&stat_lock);
#endif
	return new;
}				/*  End Function _devfs_alloc_entry  */

/**
 *	_devfs_append_entry - Append a devfs entry to a directory's child list.
 *	@dir:  The directory to add to.
 *	@de:  The devfs entry to append.
 *	@old_de: If an existing entry exists, it will be written here. This may
 *		 be %NULL. An implicit devfs_get() is performed on this entry.
 *
 *  Append a devfs entry to a directory's list of children, checking first to
 *   see if an entry of the same name exists. The directory will be locked.
 *   The value 0 is returned on success, else a negative error code.
 *   On failure, an implicit devfs_put() is performed on %de.
 */

static int _devfs_append_entry(devfs_handle_t dir, devfs_handle_t de,
			       devfs_handle_t * old_de)
{
	int retval;

	if (old_de)
		*old_de = NULL;
	if (!S_ISDIR(dir->mode)) {
		PRINTK("(%s): dir: \"%s\" is not a directory\n", de->name,
		       dir->name);
		devfs_put(de);
		return -ENOTDIR;
	}
	write_lock(&dir->u.dir.lock);
	if (dir->u.dir.no_more_additions)
		retval = -ENOENT;
	else {
		struct devfs_entry *old;

		old = _devfs_search_dir(dir, de->name, de->namelen);
		if (old_de)
			*old_de = old;
		else
			devfs_put(old);
		if (old == NULL) {
			de->parent = dir;
			de->prev = dir->u.dir.last;
			/*  Append to the directory's list of children  */
			if (dir->u.dir.first == NULL)
				dir->u.dir.first = de;
			else
				dir->u.dir.last->next = de;
			dir->u.dir.last = de;
			retval = 0;
		} else
			retval = -EEXIST;
	}
	write_unlock(&dir->u.dir.lock);
	if (retval)
		devfs_put(de);
	return retval;
}				/*  End Function _devfs_append_entry  */

/**
 *	_devfs_get_root_entry - Get the root devfs entry.
 *
 *	Returns the root devfs entry on success, else %NULL.
 *
 *	TODO it must be called asynchronously due to the fact
 *	that devfs is initialized relatively late. Proper way
 *	is to remove module_init from init_devfs_fs and manually
 *	call it early enough during system init
 */

static struct devfs_entry *_devfs_get_root_entry(void)
{
	struct devfs_entry *new;
	static DEFINE_SPINLOCK(root_lock);

	if (root_entry)
		return root_entry;

	new = _devfs_alloc_entry(NULL, 0, MODE_DIR);
	if (new == NULL)
		return NULL;

	spin_lock(&root_lock);
	if (root_entry) {
		spin_unlock(&root_lock);
		devfs_put(new);
		return root_entry;
	}
	root_entry = new;
	spin_unlock(&root_lock);

	return root_entry;
}				/*  End Function _devfs_get_root_entry  */

/**
 *	_devfs_descend - Descend down a tree using the next component name.
 *	@dir:  The directory to search.
 *	@name:  The component name to search for.
 *	@namelen:  The length of %name.
 *	@next_pos:  The position of the next '/' or '\0' is written here.
 *
 *  Descend into a directory, searching for a component. This function forms
 *   the core of a tree-walking algorithm. The directory will be locked.
 *   The devfs entry corresponding to the component is returned. If there is
 *   no matching entry, %NULL is returned.
 *   An implicit devfs_get() is performed on the returned entry.
 */

static struct devfs_entry *_devfs_descend(struct devfs_entry *dir,
					  const char *name, int namelen,
					  int *next_pos)
{
	const char *stop, *ptr;
	struct devfs_entry *entry;

	if ((namelen >= 3) && (strncmp(name, "../", 3) == 0)) {	/*  Special-case going to parent directory  */
		*next_pos = 3;
		return devfs_get(dir->parent);
	}
	stop = name + namelen;
	/*  Search for a possible '/'  */
	for (ptr = name; (ptr < stop) && (*ptr != '/'); ++ptr) ;
	*next_pos = ptr - name;
	read_lock(&dir->u.dir.lock);
	entry = _devfs_search_dir(dir, name, *next_pos);
	read_unlock(&dir->u.dir.lock);
	return entry;
}				/*  End Function _devfs_descend  */

static devfs_handle_t _devfs_make_parent_for_leaf(struct devfs_entry *dir,
						  const char *name,
						  int namelen, int *leaf_pos)
{
	int next_pos = 0;

	if (dir == NULL)
		dir = _devfs_get_root_entry();
	if (dir == NULL)
		return NULL;
	devfs_get(dir);
	/*  Search for possible trailing component and ignore it  */
	for (--namelen; (namelen > 0) && (name[namelen] != '/'); --namelen) ;
	*leaf_pos = (name[namelen] == '/') ? (namelen + 1) : 0;
	for (; namelen > 0; name += next_pos, namelen -= next_pos) {
		struct devfs_entry *de, *old = NULL;

		if ((de =
		     _devfs_descend(dir, name, namelen, &next_pos)) == NULL) {
			de = _devfs_alloc_entry(name, next_pos, MODE_DIR);
			devfs_get(de);
			if (!de || _devfs_append_entry(dir, de, &old)) {
				devfs_put(de);
				if (!old || !S_ISDIR(old->mode)) {
					devfs_put(old);
					devfs_put(dir);
					return NULL;
				}
				de = old;	/*  Use the existing directory  */
			}
		}
		if (de == dir->parent) {
			devfs_put(dir);
			devfs_put(de);
			return NULL;
		}
		devfs_put(dir);
		dir = de;
		if (name[next_pos] == '/')
			++next_pos;
	}
	return dir;
}				/*  End Function _devfs_make_parent_for_leaf  */

static devfs_handle_t _devfs_prepare_leaf(devfs_handle_t * dir,
					  const char *name, umode_t mode)
{
	int namelen, leaf_pos;
	struct devfs_entry *de;

	namelen = strlen(name);
	if ((*dir = _devfs_make_parent_for_leaf(*dir, name, namelen,
						&leaf_pos)) == NULL) {
		PRINTK("(%s): could not create parent path\n", name);
		return NULL;
	}
	if ((de = _devfs_alloc_entry(name + leaf_pos, namelen - leaf_pos, mode))
	    == NULL) {
		PRINTK("(%s): could not allocate entry\n", name);
		devfs_put(*dir);
		return NULL;
	}
	return de;
}				/*  End Function _devfs_prepare_leaf  */

static devfs_handle_t _devfs_walk_path(struct devfs_entry *dir,
				       const char *name, int namelen,
				       int traverse_symlink)
{
	int next_pos = 0;

	if (dir == NULL)
		dir = _devfs_get_root_entry();
	if (dir == NULL)
		return NULL;
	devfs_get(dir);
	for (; namelen > 0; name += next_pos, namelen -= next_pos) {
		struct devfs_entry *de, *link;

		if (!S_ISDIR(dir->mode)) {
			devfs_put(dir);
			return NULL;
		}

		if ((de =
		     _devfs_descend(dir, name, namelen, &next_pos)) == NULL) {
			devfs_put(dir);
			return NULL;
		}
		if (S_ISLNK(de->mode) && traverse_symlink) {	/*  Need to follow the link: this is a stack chomper  */
			/* FIXME what if it puts outside of mounted tree? */
			link = _devfs_walk_path(dir, de->u.symlink.linkname,
						de->u.symlink.length, TRUE);
			devfs_put(de);
			if (!link) {
				devfs_put(dir);
				return NULL;
			}
			de = link;
		}
		devfs_put(dir);
		dir = de;
		if (name[next_pos] == '/')
			++next_pos;
	}
	return dir;
}				/*  End Function _devfs_walk_path  */

/**
 *	_devfs_find_entry - Find a devfs entry.
 *	@dir: The handle to the parent devfs directory entry. If this is %NULL the
 *		name is relative to the root of the devfs.
 *	@name: The name of the entry. This may be %NULL.
 *	@traverse_symlink: If %TRUE then symbolic links are traversed.
 *
 *	Returns the devfs_entry pointer on success, else %NULL. An implicit
 *	devfs_get() is performed.
 */

static struct devfs_entry *_devfs_find_entry(devfs_handle_t dir,
					     const char *name,
					     int traverse_symlink)
{
	unsigned int namelen = strlen(name);

	if (name[0] == '/') {
		/*  Skip leading pathname component  */
		if (namelen < 2) {
			PRINTK("(%s): too short\n", name);
			return NULL;
		}
		for (++name, --namelen; (*name != '/') && (namelen > 0);
		     ++name, --namelen) ;
		if (namelen < 2) {
			PRINTK("(%s): too short\n", name);
			return NULL;
		}
		++name;
		--namelen;
	}
	return _devfs_walk_path(dir, name, namelen, traverse_symlink);
}				/*  End Function _devfs_find_entry  */

static struct devfs_entry *get_devfs_entry_from_vfs_inode(struct inode *inode)
{
	if (inode == NULL)
		return NULL;
	VERIFY_ENTRY((struct devfs_entry *)inode->u.generic_ip);
	return inode->u.generic_ip;
}				/*  End Function get_devfs_entry_from_vfs_inode  */

/**
 *	free_dentry - Free the dentry for a device entry and invalidate inode.
 *	@de: The entry.
 *
 *	This must only be called after the entry has been unhooked from its
 *	 parent directory.
 */

static void free_dentry(struct devfs_entry *de)
{
	struct dentry *dentry = de->inode.dentry;

	if (!dentry)
		return;
	spin_lock(&dcache_lock);
	dget_locked(dentry);
	spin_unlock(&dcache_lock);
	/*  Forcefully remove the inode  */
	if (dentry->d_inode != NULL)
		dentry->d_inode->i_nlink = 0;
	d_drop(dentry);
	dput(dentry);
}				/*  End Function free_dentry  */

/**
 *	is_devfsd_or_child - Test if the current process is devfsd or one of its children.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if devfsd or child, else %FALSE.
 */

static int is_devfsd_or_child(struct fs_info *fs_info)
{
	struct task_struct *p = current;

	if (p == fs_info->devfsd_task)
		return (TRUE);
	if (process_group(p) == fs_info->devfsd_pgrp)
		return (TRUE);
	read_lock(&tasklist_lock);
	for (; p != &init_task; p = p->real_parent) {
		if (p == fs_info->devfsd_task) {
			read_unlock(&tasklist_lock);
			return (TRUE);
		}
	}
	read_unlock(&tasklist_lock);
	return (FALSE);
}				/*  End Function is_devfsd_or_child  */

/**
 *	devfsd_queue_empty - Test if devfsd has work pending in its event queue.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if the queue is empty, else %FALSE.
 */

static inline int devfsd_queue_empty(struct fs_info *fs_info)
{
	return (fs_info->devfsd_last_event) ? FALSE : TRUE;
}				/*  End Function devfsd_queue_empty  */

/**
 *	wait_for_devfsd_finished - Wait for devfsd to finish processing its event queue.
 *	@fs_info: The filesystem information.
 *
 *	Returns %TRUE if no more waiting will be required, else %FALSE.
 */

static int wait_for_devfsd_finished(struct fs_info *fs_info)
{
	DECLARE_WAITQUEUE(wait, current);

	if (fs_info->devfsd_task == NULL)
		return (TRUE);
	if (devfsd_queue_empty(fs_info) && fs_info->devfsd_sleeping)
		return TRUE;
	if (is_devfsd_or_child(fs_info))
		return (FALSE);
	set_current_state(TASK_UNINTERRUPTIBLE);
	add_wait_queue(&fs_info->revalidate_wait_queue, &wait);
	if (!devfsd_queue_empty(fs_info) || !fs_info->devfsd_sleeping)
		if (fs_info->devfsd_task)
			schedule();
	remove_wait_queue(&fs_info->revalidate_wait_queue, &wait);
	__set_current_state(TASK_RUNNING);
	return (TRUE);
}				/*  End Function wait_for_devfsd_finished  */

/**
 *	devfsd_notify_de - Notify the devfsd daemon of a change.
 *	@de: The devfs entry that has changed. This and all parent entries will
 *            have their reference counts incremented if the event was queued.
 *	@type: The type of change.
 *	@mode: The mode of the entry.
 *	@uid: The user ID.
 *	@gid: The group ID.
 *	@fs_info: The filesystem info.
 *
 *	Returns %TRUE if an event was queued and devfsd woken up, else %FALSE.
 */

static int devfsd_notify_de(struct devfs_entry *de,
			    unsigned short type, umode_t mode,
			    uid_t uid, gid_t gid, struct fs_info *fs_info)
{
	struct devfsd_buf_entry *entry;
	struct devfs_entry *curr;

	if (!(fs_info->devfsd_event_mask & (1 << type)))
		return (FALSE);
	if ((entry = kmem_cache_alloc(devfsd_buf_cache, SLAB_KERNEL)) == NULL) {
		atomic_inc(&fs_info->devfsd_overrun_count);
		return (FALSE);
	}
	for (curr = de; curr != NULL; curr = curr->parent)
		devfs_get(curr);
	entry->de = de;
	entry->type = type;
	entry->mode = mode;
	entry->uid = uid;
	entry->gid = gid;
	entry->next = NULL;
	spin_lock(&fs_info->devfsd_buffer_lock);
	if (!fs_info->devfsd_first_event)
		fs_info->devfsd_first_event = entry;
	if (fs_info->devfsd_last_event)
		fs_info->devfsd_last_event->next = entry;
	fs_info->devfsd_last_event = entry;
	spin_unlock(&fs_info->devfsd_buffer_lock);
	wake_up_interruptible(&fs_info->devfsd_wait_queue);
	return (TRUE);
}				/*  End Function devfsd_notify_de  */

/**
 *	devfsd_notify - Notify the devfsd daemon of a change.
 *	@de: The devfs entry that has changed.
 *	@type: The type of change event.
 *	@wait: If TRUE, the function waits for the daemon to finish processing
 *		the event.
 */

static void devfsd_notify(struct devfs_entry *de, unsigned short type)
{
	devfsd_notify_de(de, type, de->mode, current->euid,
			 current->egid, &fs_info);
}

static int devfs_mk_dev(dev_t dev, umode_t mode, const char *fmt, va_list args)
{
	struct devfs_entry *dir = NULL, *de;
	char buf[64];
	int error, n;

	n = vsnprintf(buf, sizeof(buf), fmt, args);
	if (n >= sizeof(buf) || !buf[0]) {
		printk(KERN_WARNING "%s: invalid format string %s\n",
		       __FUNCTION__, fmt);
		return -EINVAL;
	}

	de = _devfs_prepare_leaf(&dir, buf, mode);
	if (!de) {
		printk(KERN_WARNING "%s: could not prepare leaf for %s\n",
		       __FUNCTION__, buf);
		return -ENOMEM;	/* could be more accurate... */
	}

	de->u.dev = dev;

	error = _devfs_append_entry(dir, de, NULL);
	if (error) {
		printk(KERN_WARNING "%s: could not append to parent for %s\n",
		       __FUNCTION__, buf);
		goto out;
	}

	devfsd_notify(de, DEVFSD_NOTIFY_REGISTERED);
      out:
	devfs_put(dir);
	return error;
}

int devfs_mk_bdev(dev_t dev, umode_t mode, const char *fmt, ...)
{
	va_list args;

	if (!S_ISBLK(mode)) {
		printk(KERN_WARNING "%s: invalide mode (%u) for %s\n",
		       __FUNCTION__, mode, fmt);
		return -EINVAL;
	}

	va_start(args, fmt);
	return devfs_mk_dev(dev, mode, fmt, args);
}

EXPORT_SYMBOL(devfs_mk_bdev);

int devfs_mk_cdev(dev_t dev, umode_t mode, const char *fmt, ...)
{
	va_list args;

	if (!S_ISCHR(mode)) {
		printk(KERN_WARNING "%s: invalide mode (%u) for %s\n",
		       __FUNCTION__, mode, fmt);
		return -EINVAL;
	}

	va_start(args, fmt);
	return devfs_mk_dev(dev, mode, fmt, args);
}

EXPORT_SYMBOL(devfs_mk_cdev);

/**
 *	_devfs_unhook - Unhook a device entry from its parents list
 *	@de: The entry to unhook.
 *
 *	Returns %TRUE if the entry was unhooked, else %FALSE if it was
 *		previously unhooked.
 *	The caller must have a write lock on the parent directory.
 */

static int _devfs_unhook(struct devfs_entry *de)
{
	struct devfs_entry *parent;

	if (!de || (de->prev == de))
		return FALSE;
	parent = de->parent;
	if (de->prev == NULL)
		parent->u.dir.first = de->next;
	else
		de->prev->next = de->next;
	if (de->next == NULL)
		parent->u.dir.last = de->prev;
	else
		de->next->prev = de->prev;
	de->prev = de;		/*  Indicate we're unhooked                      */
	de->next = NULL;	/*  Force early termination for <devfs_readdir>  */
	return TRUE;
}				/*  End Function _devfs_unhook  */

/**
 *	_devfs_unregister - Unregister a device entry from its parent.
 *	@dir: The parent directory.
 *	@de: The entry to unregister.
 *
 *	The caller must have a write lock on the parent directory, which is
 *	unlocked by this function.
 */

static void _devfs_unregister(struct devfs_entry *dir, struct devfs_entry *de)
{
	int unhooked = _devfs_unhook(de);

	write_unlock(&dir->u.dir.lock);
	if (!unhooked)
		return;
	devfs_get(dir);
	devfsd_notify(de, DEVFSD_NOTIFY_UNREGISTERED);
	free_dentry(de);
	devfs_put(dir);
	if (!S_ISDIR(de->mode))
		return;
	while (TRUE) {		/*  Recursively unregister: this is a stack chomper  */
		struct devfs_entry *child;

		write_lock(&de->u.dir.lock);
		de->u.dir.no_more_additions = TRUE;
		child = de->u.dir.first;
		VERIFY_ENTRY(child);
		_devfs_unregister(de, child);
		if (!child)
			break;
		DPRINTK(DEBUG_UNREGISTER, "(%s): child: %p  refcount: %d\n",
			child->name, child, atomic_read(&child->refcount));
		devfs_put(child);
	}
}				/*  End Function _devfs_unregister  */

static int devfs_do_symlink(devfs_handle_t dir, const char *name,
			    const char *link, devfs_handle_t * handle)
{
	int err;
	unsigned int linklength;
	char *newlink;
	struct devfs_entry *de;

	if (handle != NULL)
		*handle = NULL;
	if (name == NULL) {
		PRINTK("(): NULL name pointer\n");
		return -EINVAL;
	}
	if (link == NULL) {
		PRINTK("(%s): NULL link pointer\n", name);
		return -EINVAL;
	}
	linklength = strlen(link);
	if ((newlink = kmalloc(linklength + 1, GFP_KERNEL)) == NULL)
		return -ENOMEM;
	memcpy(newlink, link, linklength);
	newlink[linklength] = '\0';
	if ((de = _devfs_prepare_leaf(&dir, name, S_IFLNK | S_IRUGO | S_IXUGO))
	    == NULL) {
		PRINTK("(%s): could not prepare leaf\n", name);
		kfree(newlink);
		return -ENOTDIR;
	}
	de->info = NULL;
	de->u.symlink.linkname = newlink;
	de->u.symlink.length = linklength;
	if ((err = _devfs_append_entry(dir, de, NULL)) != 0) {
		PRINTK("(%s): could not append to parent, err: %d\n", name,
		       err);
		devfs_put(dir);
		return err;
	}
	devfs_put(dir);
#ifdef CONFIG_DEVFS_DEBUG
	spin_lock(&stat_lock);
	stat_num_bytes += linklength + 1;
	spin_unlock(&stat_lock);
#endif
	if (handle != NULL)
		*handle = de;
	return 0;
}				/*  End Function devfs_do_symlink  */

/**
 *	devfs_mk_symlink Create a symbolic link in the devfs namespace.
 *	@from: The name of the entry.
 *	@to: Name of the destination
 *
 *	Returns 0 on success, else a negative error code is returned.
 */

int devfs_mk_symlink(const char *from, const char *to)
{
	devfs_handle_t de;
	int err;

	err = devfs_do_symlink(NULL, from, to, &de);
	if (!err) {
		de->vfs = TRUE;
		devfsd_notify(de, DEVFSD_NOTIFY_REGISTERED);
	}

	return err;
}

/**
 *	devfs_mk_dir - Create a directory in the devfs namespace.
 *		new name is relative to the root of the devfs.
 *	@fmt: The name of the entry.
 *
 *	Use of this function is optional. The devfs_register() function
 *	will automatically create intermediate directories as needed. This function
 *	is provided for efficiency reasons, as it provides a handle to a directory.
 *	On failure %NULL is returned.
 */

int devfs_mk_dir(const char *fmt, ...)
{
	struct devfs_entry *dir = NULL, *de = NULL, *old;
	char buf[64];
	va_list args;
	int error, n;

	va_start(args, fmt);
	n = vsnprintf(buf, 64, fmt, args);
	if (n >= 64 || !buf[0]) {
		printk(KERN_WARNING "%s: invalid argument.", __FUNCTION__);
		return -EINVAL;
	}

	de = _devfs_prepare_leaf(&dir, buf, MODE_DIR);
	if (!de) {
		PRINTK("(%s): could not prepare leaf\n", buf);
		return -EINVAL;
	}

	error = _devfs_append_entry(dir, de, &old);
	if (error == -EEXIST && S_ISDIR(old->mode)) {
		/*
		 * devfs_mk_dir() of an already-existing directory will
		 * return success.
		 */
		error = 0;
		goto out_put;
	} else if (error) {
		PRINTK("(%s): could not append to dir: %p \"%s\"\n",
		       buf, dir, dir->name);
		devfs_put(old);
		goto out_put;
	}

	devfsd_notify(de, DEVFSD_NOTIFY_REGISTERED);

      out_put:
	devfs_put(dir);
	return error;
}

void devfs_remove(const char *fmt, ...)
{
	char buf[64];
	va_list args;
	int n;

	va_start(args, fmt);
	n = vsnprintf(buf, sizeof(buf), fmt, args);
	if (n < sizeof(buf) && buf[0]) {
		devfs_handle_t de = _devfs_find_entry(NULL, buf, 0);

		if (!de) {
			printk(KERN_ERR "%s: %s not found, cannot remove\n",
			       __FUNCTION__, buf);
			dump_stack();
			return;
		}

		write_lock(&de->parent->u.dir.lock);
		_devfs_unregister(de->parent, de);
		devfs_put(de);
		devfs_put(de);
	}
}

/**
 *	devfs_generate_path - Generate a pathname for an entry, relative to the devfs root.
 *	@de: The devfs entry.
 *	@path: The buffer to write the pathname to. The pathname and '\0'
 *		terminator will be written at the end of the buffer.
 *	@buflen: The length of the buffer.
 *
 *	Returns the offset in the buffer where the pathname starts on success,
 *	else a negative error code.
 */

static int devfs_generate_path(devfs_handle_t de, char *path, int buflen)
{
	int pos;
#define NAMEOF(de) ( (de)->mode ? (de)->name : (de)->u.name )

	if (de == NULL)
		return -EINVAL;
	VERIFY_ENTRY(de);
	if (de->namelen >= buflen)
		return -ENAMETOOLONG;	/*  Must be first       */
	path[buflen - 1] = '\0';
	if (de->parent == NULL)
		return buflen - 1;	/*  Don't prepend root  */
	pos = buflen - de->namelen - 1;
	memcpy(path + pos, NAMEOF(de), de->namelen);
	for (de = de->parent; de->parent != NULL; de = de->parent) {
		if (pos - de->namelen - 1 < 0)
			return -ENAMETOOLONG;
		path[--pos] = '/';
		pos -= de->namelen;
		memcpy(path + pos, NAMEOF(de), de->namelen);
	}
	return pos;
}				/*  End Function devfs_generate_path  */

/**
 *	devfs_setup - Process kernel boot options.
 *	@str: The boot options after the "devfs=".
 */

static int __init devfs_setup(char *str)
{
	static struct {
		char *name;
		unsigned int mask;
		unsigned int *opt;
	} devfs_options_tab[] __initdata = {
#ifdef CONFIG_DEVFS_DEBUG
		{
		"dall", DEBUG_ALL, &devfs_debug_init}, {
		"dmod", DEBUG_MODULE_LOAD, &devfs_debug_init}, {
		"dreg", DEBUG_REGISTER, &devfs_debug_init}, {
		"dunreg", DEBUG_UNREGISTER, &devfs_debug_init}, {
		"dfree", DEBUG_FREE, &devfs_debug_init}, {
		"diget", DEBUG_I_GET, &devfs_debug_init}, {
		"dchange", DEBUG_SET_FLAGS, &devfs_debug_init}, {
		"dsread", DEBUG_S_READ, &devfs_debug_init}, {
		"dichange", DEBUG_I_CHANGE, &devfs_debug_init}, {
		"dimknod", DEBUG_I_MKNOD, &devfs_debug_init}, {
		"dilookup", DEBUG_I_LOOKUP, &devfs_debug_init}, {
		"diunlink", DEBUG_I_UNLINK, &devfs_debug_init},
#endif				/*  CONFIG_DEVFS_DEBUG  */
		{
		"mount", OPTION_MOUNT, &boot_options}, {
		NULL, 0, NULL}
	};

	while ((*str != '\0') && !isspace(*str)) {
		int i, found = 0, invert = 0;

		if (strncmp(str, "no", 2) == 0) {
			invert = 1;
			str += 2;
		}
		for (i = 0; devfs_options_tab[i].name != NULL; i++) {
			int len = strlen(devfs_options_tab[i].name);

			if (strncmp(str, devfs_options_tab[i].name, len) == 0) {
				if (invert)
					*devfs_options_tab[i].opt &=
					    ~devfs_options_tab[i].mask;
				else
					*devfs_options_tab[i].opt |=
					    devfs_options_tab[i].mask;
				str += len;
				found = 1;
				break;
			}
		}
		if (!found)
			return 0;	/*  No match         */
		if (*str != ',')
			return 0;	/*  No more options  */
		++str;
	}
	return 1;
}				/*  End Function devfs_setup  */

__setup("devfs=", devfs_setup);

EXPORT_SYMBOL(devfs_mk_dir);
EXPORT_SYMBOL(devfs_remove);

/**
 *	try_modload - Notify devfsd of an inode lookup by a non-devfsd process.
 *	@parent: The parent devfs entry.
 *	@fs_info: The filesystem info.
 *	@name: The device name.
 *	@namelen: The number of characters in @name.
 *	@buf: A working area that will be used. This must not go out of scope
 *            until devfsd is idle again.
 *
 *	Returns 0 on success (event was queued), else a negative error code.
 */

static int try_modload(struct devfs_entry *parent, struct fs_info *fs_info,
		       const char *name, unsigned namelen,
		       struct devfs_entry *buf)
{
	if (!(fs_info->devfsd_event_mask & (1 << DEVFSD_NOTIFY_LOOKUP)))
		return -ENOENT;
	if (is_devfsd_or_child(fs_info))
		return -ENOENT;
	memset(buf, 0, sizeof *buf);
	atomic_set(&buf->refcount, 1);
	buf->parent = parent;
	buf->namelen = namelen;
	buf->u.name = name;
	WRITE_ENTRY_MAGIC(buf, MAGIC_VALUE);
	if (!devfsd_notify_de(buf, DEVFSD_NOTIFY_LOOKUP, 0,
			      current->euid, current->egid, fs_info))
		return -ENOENT;
	/*  Possible success: event has been queued  */
	return 0;
}				/*  End Function try_modload  */

/*  Superblock operations follow  */

static struct inode_operations devfs_iops;
static struct inode_operations devfs_dir_iops;
static struct file_operations devfs_fops;
static struct file_operations devfs_dir_fops;
static struct inode_operations devfs_symlink_iops;

static int devfs_notify_change(struct dentry *dentry, struct iattr *iattr)
{
	int retval;
	struct devfs_entry *de;
	struct inode *inode = dentry->d_inode;
	struct fs_info *fs_info = inode->i_sb->s_fs_info;

	de = get_devfs_entry_from_vfs_inode(inode);
	if (de == NULL)
		return -ENODEV;
	retval = inode_change_ok(inode, iattr);
	if (retval != 0)
		return retval;
	retval = inode_setattr(inode, iattr);
	if (retval != 0)
		return retval;
	DPRINTK(DEBUG_I_CHANGE, "(%d): VFS inode: %p  devfs_entry: %p\n",
		(int)inode->i_ino, inode, de);
	DPRINTK(DEBUG_I_CHANGE, "():   mode: 0%o  uid: %d  gid: %d\n",
		(int)inode->i_mode, (int)inode->i_uid, (int)inode->i_gid);
	/*  Inode is not on hash chains, thus must save permissions here rather
	   than in a write_inode() method  */
	de->mode = inode->i_mode;
	de->inode.uid = inode->i_uid;
	de->inode.gid = inode->i_gid;
	de->inode.atime = inode->i_atime;
	de->inode.mtime = inode->i_mtime;
	de->inode.ctime = inode->i_ctime;
	if ((iattr->ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) &&
	    !is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_CHANGE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	return 0;
}				/*  End Function devfs_notify_change  */

static struct super_operations devfs_sops = {
	.drop_inode = generic_delete_inode,
	.statfs = simple_statfs,
};

/**
 *	_devfs_get_vfs_inode - Get a VFS inode.
 *	@sb: The super block.
 *	@de: The devfs inode.
 *	@dentry: The dentry to register with the devfs inode.
 *
 *	Returns the inode on success, else %NULL. An implicit devfs_get() is
 *       performed if the inode is created.
 */

static struct inode *_devfs_get_vfs_inode(struct super_block *sb,
					  struct devfs_entry *de,
					  struct dentry *dentry)
{
	struct inode *inode;

	if (de->prev == de)
		return NULL;	/*  Quick check to see if unhooked  */
	if ((inode = new_inode(sb)) == NULL) {
		PRINTK("(%s): new_inode() failed, de: %p\n", de->name, de);
		return NULL;
	}
	if (de->parent) {
		read_lock(&de->parent->u.dir.lock);
		if (de->prev != de)
			de->inode.dentry = dentry;	/*      Not unhooked  */
		read_unlock(&de->parent->u.dir.lock);
	} else
		de->inode.dentry = dentry;	/*  Root: no locking needed  */
	if (de->inode.dentry != dentry) {	/*  Must have been unhooked  */
		iput(inode);
		return NULL;
	}
	/* FIXME where is devfs_put? */
	inode->u.generic_ip = devfs_get(de);
	inode->i_ino = de->inode.ino;
	DPRINTK(DEBUG_I_GET, "(%d): VFS inode: %p  devfs_entry: %p\n",
		(int)inode->i_ino, inode, de);
	inode->i_blocks = 0;
	inode->i_blksize = FAKE_BLOCK_SIZE;
	inode->i_op = &devfs_iops;
	inode->i_mode = de->mode;
	if (S_ISDIR(de->mode)) {
		inode->i_op = &devfs_dir_iops;
		inode->i_fop = &devfs_dir_fops;
	} else if (S_ISLNK(de->mode)) {
		inode->i_op = &devfs_symlink_iops;
		inode->i_size = de->u.symlink.length;
	} else if (S_ISCHR(de->mode) || S_ISBLK(de->mode)) {
		init_special_inode(inode, de->mode, de->u.dev);
	} else if (S_ISFIFO(de->mode) || S_ISSOCK(de->mode)) {
		init_special_inode(inode, de->mode, 0);
	} else {
		PRINTK("(%s): unknown mode %o de: %p\n",
		       de->name, de->mode, de);
		iput(inode);
		devfs_put(de);
		return NULL;
	}

	inode->i_uid = de->inode.uid;
	inode->i_gid = de->inode.gid;
	inode->i_atime = de->inode.atime;
	inode->i_mtime = de->inode.mtime;
	inode->i_ctime = de->inode.ctime;
	DPRINTK(DEBUG_I_GET, "():   mode: 0%o  uid: %d  gid: %d\n",
		(int)inode->i_mode, (int)inode->i_uid, (int)inode->i_gid);
	return inode;
}				/*  End Function _devfs_get_vfs_inode  */

/*  File operations for device entries follow  */

static int devfs_readdir(struct file *file, void *dirent, filldir_t filldir)
{
	int err, count;
	int stored = 0;
	struct fs_info *fs_info;
	struct devfs_entry *parent, *de, *next = NULL;
	struct inode *inode = file->f_dentry->d_inode;

	fs_info = inode->i_sb->s_fs_info;
	parent = get_devfs_entry_from_vfs_inode(file->f_dentry->d_inode);
	if ((long)file->f_pos < 0)
		return -EINVAL;
	DPRINTK(DEBUG_F_READDIR, "(%s): fs_info: %p  pos: %ld\n",
		parent->name, fs_info, (long)file->f_pos);
	switch ((long)file->f_pos) {
	case 0:
		err = (*filldir) (dirent, "..", 2, file->f_pos,
				  parent_ino(file->f_dentry), DT_DIR);
		if (err == -EINVAL)
			break;
		if (err < 0)
			return err;
		file->f_pos++;
		++stored;
		/*  Fall through  */
	case 1:
		err =
		    (*filldir) (dirent, ".", 1, file->f_pos, inode->i_ino,
				DT_DIR);
		if (err == -EINVAL)
			break;
		if (err < 0)
			return err;
		file->f_pos++;
		++stored;
		/*  Fall through  */
	default:
		/*  Skip entries  */
		count = file->f_pos - 2;
		read_lock(&parent->u.dir.lock);
		for (de = parent->u.dir.first; de && (count > 0); de = de->next)
			--count;
		devfs_get(de);
		read_unlock(&parent->u.dir.lock);
		/*  Now add all remaining entries  */
		while (de) {
			err = (*filldir) (dirent, de->name, de->namelen,
					  file->f_pos, de->inode.ino,
					  de->mode >> 12);
			if (err < 0)
				devfs_put(de);
			else {
				file->f_pos++;
				++stored;
			}
			if (err == -EINVAL)
				break;
			if (err < 0)
				return err;
			read_lock(&parent->u.dir.lock);
			next = devfs_get(de->next);
			read_unlock(&parent->u.dir.lock);
			devfs_put(de);
			de = next;
		}
		break;
	}
	return stored;
}				/*  End Function devfs_readdir  */

/* Open devfs specific special files */
static int devfs_open(struct inode *inode, struct file *file)
{
	int err;
	int minor = MINOR(inode->i_rdev);
	struct file_operations *old_fops, *new_fops;

	switch (minor) {
	case 0:		/* /dev/.devfsd */
		new_fops = fops_get(&devfsd_fops);
		break;
#ifdef CONFIG_DEVFS_DEBUG
	case 1:		/* /dev/.stat */
		new_fops = fops_get(&stat_fops);
		break;
#endif
	default:
		return -ENODEV;
	}

	if (new_fops == NULL)
		return -ENODEV;
	old_fops = file->f_op;
	file->f_op = new_fops;
	err = new_fops->open ? new_fops->open(inode, file) : 0;
	if (err) {
		file->f_op = old_fops;
		fops_put(new_fops);
	} else
		fops_put(old_fops);
	return err;
}				/*  End Function devfs_open  */

static struct file_operations devfs_fops = {
	.open = devfs_open,
};

static struct file_operations devfs_dir_fops = {
	.read = generic_read_dir,
	.readdir = devfs_readdir,
};

/*  Dentry operations for device entries follow  */

/**
 *	devfs_d_release - Callback for when a dentry is freed.
 *	@dentry: The dentry.
 */

static void devfs_d_release(struct dentry *dentry)
{
	DPRINTK(DEBUG_D_RELEASE, "(%p): inode: %p\n", dentry, dentry->d_inode);
}				/*  End Function devfs_d_release  */

/**
 *	devfs_d_iput - Callback for when a dentry loses its inode.
 *	@dentry: The dentry.
 *	@inode:	The inode.
 */

static void devfs_d_iput(struct dentry *dentry, struct inode *inode)
{
	struct devfs_entry *de;

	de = get_devfs_entry_from_vfs_inode(inode);
	DPRINTK(DEBUG_D_IPUT,
		"(%s): dentry: %p inode: %p de: %p de->dentry: %p\n", de->name,
		dentry, inode, de, de->inode.dentry);
	if (de->inode.dentry && (de->inode.dentry != dentry))
		OOPS("(%s): de: %p dentry: %p de->dentry: %p\n",
		     de->name, de, dentry, de->inode.dentry);
	de->inode.dentry = NULL;
	iput(inode);
	devfs_put(de);
}				/*  End Function devfs_d_iput  */

static int devfs_d_delete(struct dentry *dentry);

static struct dentry_operations devfs_dops = {
	.d_delete = devfs_d_delete,
	.d_release = devfs_d_release,
	.d_iput = devfs_d_iput,
};

static int devfs_d_revalidate_wait(struct dentry *dentry, struct nameidata *);

static struct dentry_operations devfs_wait_dops = {
	.d_delete = devfs_d_delete,
	.d_release = devfs_d_release,
	.d_iput = devfs_d_iput,
	.d_revalidate = devfs_d_revalidate_wait,
};

/**
 *	devfs_d_delete - Callback for when all files for a dentry are closed.
 *	@dentry: The dentry.
 */

static int devfs_d_delete(struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;

	if (dentry->d_op == &devfs_wait_dops)
		dentry->d_op = &devfs_dops;
	/*  Unhash dentry if negative (has no inode)  */
	if (inode == NULL) {
		DPRINTK(DEBUG_D_DELETE, "(%p): dropping negative dentry\n",
			dentry);
		return 1;
	}
	return 0;
}				/*  End Function devfs_d_delete  */

struct devfs_lookup_struct {
	devfs_handle_t de;
	wait_queue_head_t wait_queue;
};

/* XXX: this doesn't handle the case where we got a negative dentry
        but a devfs entry has been registered in the meanwhile */
static int devfs_d_revalidate_wait(struct dentry *dentry, struct nameidata *nd)
{
	struct inode *dir = dentry->d_parent->d_inode;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	devfs_handle_t parent = get_devfs_entry_from_vfs_inode(dir);
	struct devfs_lookup_struct *lookup_info = dentry->d_fsdata;
	DECLARE_WAITQUEUE(wait, current);
	int need_lock;

	/*
	 * FIXME HACK
	 *
	 * make sure that
	 *   d_instantiate always runs under lock
	 *   we release i_sem lock before going to sleep
	 *
	 * unfortunately sometimes d_revalidate is called with
	 * and sometimes without i_sem lock held. The following checks
	 * attempt to deduce when we need to add (and drop resp.) lock
	 * here. This relies on current (2.6.2) calling coventions:
	 *
	 *   lookup_hash is always run under i_sem and is passing NULL
	 *   as nd
	 *
	 *   open(...,O_CREATE,...) calls _lookup_hash under i_sem
	 *   and sets flags to LOOKUP_OPEN|LOOKUP_CREATE
	 *
	 *   all other invocations of ->d_revalidate seem to happen
	 *   outside of i_sem
	 */
	need_lock = nd &&
	    (!(nd->flags & LOOKUP_CREATE) || (nd->flags & LOOKUP_PARENT));

	if (need_lock)
		down(&dir->i_sem);

	if (is_devfsd_or_child(fs_info)) {
		devfs_handle_t de = lookup_info->de;
		struct inode *inode;

		DPRINTK(DEBUG_I_LOOKUP,
			"(%s): dentry: %p inode: %p de: %p by: \"%s\"\n",
			dentry->d_name.name, dentry, dentry->d_inode, de,
			current->comm);
		if (dentry->d_inode)
			goto out;
		if (de == NULL) {
			read_lock(&parent->u.dir.lock);
			de = _devfs_search_dir(parent, dentry->d_name.name,
					       dentry->d_name.len);
			read_unlock(&parent->u.dir.lock);
			if (de == NULL)
				goto out;
			lookup_info->de = de;
		}
		/*  Create an inode, now that the driver information is available  */
		inode = _devfs_get_vfs_inode(dir->i_sb, de, dentry);
		if (!inode)
			goto out;
		DPRINTK(DEBUG_I_LOOKUP,
			"(%s): new VFS inode(%u): %p de: %p by: \"%s\"\n",
			de->name, de->inode.ino, inode, de, current->comm);
		d_instantiate(dentry, inode);
		goto out;
	}
	if (lookup_info == NULL)
		goto out;	/*  Early termination  */
	read_lock(&parent->u.dir.lock);
	if (dentry->d_fsdata) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		add_wait_queue(&lookup_info->wait_queue, &wait);
		read_unlock(&parent->u.dir.lock);
		/* at this point it is always (hopefully) locked */
		up(&dir->i_sem);
		schedule();
		down(&dir->i_sem);
		/*
		 * This does not need nor should remove wait from wait_queue.
		 * Wait queue head is never reused - nothing is ever added to it
		 * after all waiters have been waked up and head itself disappears
		 * very soon after it. Moreover it is local variable on stack that
		 * is likely to have already disappeared so any reference to it
		 * at this point is buggy.
		 */

	} else
		read_unlock(&parent->u.dir.lock);

      out:
	if (need_lock)
		up(&dir->i_sem);
	return 1;
}				/*  End Function devfs_d_revalidate_wait  */

/*  Inode operations for device entries follow  */

static struct dentry *devfs_lookup(struct inode *dir, struct dentry *dentry,
				   struct nameidata *nd)
{
	struct devfs_entry tmp;	/*  Must stay in scope until devfsd idle again  */
	struct devfs_lookup_struct lookup_info;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	struct devfs_entry *parent, *de;
	struct inode *inode;
	struct dentry *retval = NULL;

	/*  Set up the dentry operations before anything else, to ensure cleaning
	   up on any error  */
	dentry->d_op = &devfs_dops;
	/*  First try to get the devfs entry for this directory  */
	parent = get_devfs_entry_from_vfs_inode(dir);
	DPRINTK(DEBUG_I_LOOKUP, "(%s): dentry: %p parent: %p by: \"%s\"\n",
		dentry->d_name.name, dentry, parent, current->comm);
	if (parent == NULL)
		return ERR_PTR(-ENOENT);
	read_lock(&parent->u.dir.lock);
	de = _devfs_search_dir(parent, dentry->d_name.name, dentry->d_name.len);
	read_unlock(&parent->u.dir.lock);
	lookup_info.de = de;
	init_waitqueue_head(&lookup_info.wait_queue);
	dentry->d_fsdata = &lookup_info;
	if (de == NULL) {	/*  Try with devfsd. For any kind of failure, leave a negative dentry
				   so someone else can deal with it (in the case where the sysadmin
				   does a mknod()). It's important to do this before hashing the
				   dentry, so that the devfsd queue is filled before revalidates
				   can start  */
		if (try_modload(parent, fs_info, dentry->d_name.name, dentry->d_name.len, &tmp) < 0) {	/*  Lookup event was not queued to devfsd  */
			d_add(dentry, NULL);
			return NULL;
		}
	}
	dentry->d_op = &devfs_wait_dops;
	d_add(dentry, NULL);	/*  Open the floodgates  */
	/*  Unlock directory semaphore, which will release any waiters. They
	   will get the hashed dentry, and may be forced to wait for
	   revalidation  */
	up(&dir->i_sem);
	wait_for_devfsd_finished(fs_info);	/*  If I'm not devfsd, must wait  */
	down(&dir->i_sem);	/*  Grab it again because them's the rules  */
	de = lookup_info.de;
	/*  If someone else has been so kind as to make the inode, we go home
	   early  */
	if (dentry->d_inode)
		goto out;
	if (de == NULL) {
		read_lock(&parent->u.dir.lock);
		de = _devfs_search_dir(parent, dentry->d_name.name,
				       dentry->d_name.len);
		read_unlock(&parent->u.dir.lock);
		if (de == NULL)
			goto out;
		/*  OK, there's an entry now, but no VFS inode yet  */
	}
	/*  Create an inode, now that the driver information is available  */
	inode = _devfs_get_vfs_inode(dir->i_sb, de, dentry);
	if (!inode) {
		retval = ERR_PTR(-ENOMEM);
		goto out;
	}
	DPRINTK(DEBUG_I_LOOKUP,
		"(%s): new VFS inode(%u): %p de: %p by: \"%s\"\n", de->name,
		de->inode.ino, inode, de, current->comm);
	d_instantiate(dentry, inode);
      out:
	write_lock(&parent->u.dir.lock);
	dentry->d_op = &devfs_dops;
	dentry->d_fsdata = NULL;
	wake_up(&lookup_info.wait_queue);
	write_unlock(&parent->u.dir.lock);
	devfs_put(de);
	return retval;
}				/*  End Function devfs_lookup  */

static int devfs_unlink(struct inode *dir, struct dentry *dentry)
{
	int unhooked;
	struct devfs_entry *de;
	struct inode *inode = dentry->d_inode;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;

	de = get_devfs_entry_from_vfs_inode(inode);
	DPRINTK(DEBUG_I_UNLINK, "(%s): de: %p\n", dentry->d_name.name, de);
	if (de == NULL)
		return -ENOENT;
	if (!de->vfs)
		return -EPERM;
	write_lock(&de->parent->u.dir.lock);
	unhooked = _devfs_unhook(de);
	write_unlock(&de->parent->u.dir.lock);
	if (!unhooked)
		return -ENOENT;
	if (!is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_DELETE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	free_dentry(de);
	devfs_put(de);
	return 0;
}				/*  End Function devfs_unlink  */

static int devfs_symlink(struct inode *dir, struct dentry *dentry,
			 const char *symname)
{
	int err;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	struct devfs_entry *parent, *de;
	struct inode *inode;

	/*  First try to get the devfs entry for this directory  */
	parent = get_devfs_entry_from_vfs_inode(dir);
	if (parent == NULL)
		return -ENOENT;
	err = devfs_do_symlink(parent, dentry->d_name.name, symname, &de);
	DPRINTK(DEBUG_DISABLED, "(%s): errcode from <devfs_do_symlink>: %d\n",
		dentry->d_name.name, err);
	if (err < 0)
		return err;
	de->vfs = TRUE;
	de->inode.uid = current->euid;
	de->inode.gid = current->egid;
	de->inode.atime = CURRENT_TIME;
	de->inode.mtime = CURRENT_TIME;
	de->inode.ctime = CURRENT_TIME;
	if ((inode = _devfs_get_vfs_inode(dir->i_sb, de, dentry)) == NULL)
		return -ENOMEM;
	DPRINTK(DEBUG_DISABLED, "(%s): new VFS inode(%u): %p  dentry: %p\n",
		dentry->d_name.name, de->inode.ino, inode, dentry);
	d_instantiate(dentry, inode);
	if (!is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_CREATE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	return 0;
}				/*  End Function devfs_symlink  */

static int devfs_mkdir(struct inode *dir, struct dentry *dentry, int mode)
{
	int err;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	struct devfs_entry *parent, *de;
	struct inode *inode;

	mode = (mode & ~S_IFMT) | S_IFDIR;	/*  VFS doesn't pass S_IFMT part  */
	parent = get_devfs_entry_from_vfs_inode(dir);
	if (parent == NULL)
		return -ENOENT;
	de = _devfs_alloc_entry(dentry->d_name.name, dentry->d_name.len, mode);
	if (!de)
		return -ENOMEM;
	de->vfs = TRUE;
	if ((err = _devfs_append_entry(parent, de, NULL)) != 0)
		return err;
	de->inode.uid = current->euid;
	de->inode.gid = current->egid;
	de->inode.atime = CURRENT_TIME;
	de->inode.mtime = CURRENT_TIME;
	de->inode.ctime = CURRENT_TIME;
	if ((inode = _devfs_get_vfs_inode(dir->i_sb, de, dentry)) == NULL)
		return -ENOMEM;
	DPRINTK(DEBUG_DISABLED, "(%s): new VFS inode(%u): %p  dentry: %p\n",
		dentry->d_name.name, de->inode.ino, inode, dentry);
	d_instantiate(dentry, inode);
	if (!is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_CREATE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	return 0;
}				/*  End Function devfs_mkdir  */

static int devfs_rmdir(struct inode *dir, struct dentry *dentry)
{
	int err = 0;
	struct devfs_entry *de;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	struct inode *inode = dentry->d_inode;

	if (dir->i_sb->s_fs_info != inode->i_sb->s_fs_info)
		return -EINVAL;
	de = get_devfs_entry_from_vfs_inode(inode);
	if (de == NULL)
		return -ENOENT;
	if (!S_ISDIR(de->mode))
		return -ENOTDIR;
	if (!de->vfs)
		return -EPERM;
	/*  First ensure the directory is empty and will stay that way  */
	write_lock(&de->u.dir.lock);
	if (de->u.dir.first)
		err = -ENOTEMPTY;
	else
		de->u.dir.no_more_additions = TRUE;
	write_unlock(&de->u.dir.lock);
	if (err)
		return err;
	/*  Now unhook the directory from its parent  */
	write_lock(&de->parent->u.dir.lock);
	if (!_devfs_unhook(de))
		err = -ENOENT;
	write_unlock(&de->parent->u.dir.lock);
	if (err)
		return err;
	if (!is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_DELETE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	free_dentry(de);
	devfs_put(de);
	return 0;
}				/*  End Function devfs_rmdir  */

static int devfs_mknod(struct inode *dir, struct dentry *dentry, int mode,
		       dev_t rdev)
{
	int err;
	struct fs_info *fs_info = dir->i_sb->s_fs_info;
	struct devfs_entry *parent, *de;
	struct inode *inode;

	DPRINTK(DEBUG_I_MKNOD, "(%s): mode: 0%o  dev: %u:%u\n",
		dentry->d_name.name, mode, MAJOR(rdev), MINOR(rdev));
	parent = get_devfs_entry_from_vfs_inode(dir);
	if (parent == NULL)
		return -ENOENT;
	de = _devfs_alloc_entry(dentry->d_name.name, dentry->d_name.len, mode);
	if (!de)
		return -ENOMEM;
	de->vfs = TRUE;
	if (S_ISCHR(mode) || S_ISBLK(mode))
		de->u.dev = rdev;
	if ((err = _devfs_append_entry(parent, de, NULL)) != 0)
		return err;
	de->inode.uid = current->euid;
	de->inode.gid = current->egid;
	de->inode.atime = CURRENT_TIME;
	de->inode.mtime = CURRENT_TIME;
	de->inode.ctime = CURRENT_TIME;
	if ((inode = _devfs_get_vfs_inode(dir->i_sb, de, dentry)) == NULL)
		return -ENOMEM;
	DPRINTK(DEBUG_I_MKNOD, ":   new VFS inode(%u): %p  dentry: %p\n",
		de->inode.ino, inode, dentry);
	d_instantiate(dentry, inode);
	if (!is_devfsd_or_child(fs_info))
		devfsd_notify_de(de, DEVFSD_NOTIFY_CREATE, inode->i_mode,
				 inode->i_uid, inode->i_gid, fs_info);
	return 0;
}				/*  End Function devfs_mknod  */

static void *devfs_follow_link(struct dentry *dentry, struct nameidata *nd)
{
	struct devfs_entry *p = get_devfs_entry_from_vfs_inode(dentry->d_inode);
	nd_set_link(nd, p ? p->u.symlink.linkname : ERR_PTR(-ENODEV));
	return NULL;
}				/*  End Function devfs_follow_link  */

static struct inode_operations devfs_iops = {
	.setattr = devfs_notify_change,
};

static struct inode_operations devfs_dir_iops = {
	.lookup = devfs_lookup,
	.unlink = devfs_unlink,
	.symlink = devfs_symlink,
	.mkdir = devfs_mkdir,
	.rmdir = devfs_rmdir,
	.mknod = devfs_mknod,
	.setattr = devfs_notify_change,
};

static struct inode_operations devfs_symlink_iops = {
	.readlink = generic_readlink,
	.follow_link = devfs_follow_link,
	.setattr = devfs_notify_change,
};

static int devfs_fill_super(struct super_block *sb, void *data, int silent)
{
	struct inode *root_inode = NULL;

	if (_devfs_get_root_entry() == NULL)
		goto out_no_root;
	atomic_set(&fs_info.devfsd_overrun_count, 0);
	init_waitqueue_head(&fs_info.devfsd_wait_queue);
	init_waitqueue_head(&fs_info.revalidate_wait_queue);
	fs_info.sb = sb;
	sb->s_fs_info = &fs_info;
	sb->s_blocksize = 1024;
	sb->s_blocksize_bits = 10;
	sb->s_magic = DEVFS_SUPER_MAGIC;
	sb->s_op = &devfs_sops;
	sb->s_time_gran = 1;
	if ((root_inode = _devfs_get_vfs_inode(sb, root_entry, NULL)) == NULL)
		goto out_no_root;
	sb->s_root = d_alloc_root(root_inode);
	if (!sb->s_root)
		goto out_no_root;
	DPRINTK(DEBUG_S_READ, "(): made devfs ptr: %p\n", sb->s_fs_info);
	return 0;

      out_no_root:
	PRINTK("(): get root inode failed\n");
	if (root_inode)
		iput(root_inode);
	return -EINVAL;
}				/*  End Function devfs_fill_super  */

static struct super_block *devfs_get_sb(struct file_system_type *fs_type,
					int flags, const char *dev_name,
					void *data)
{
	return get_sb_single(fs_type, flags, data, devfs_fill_super);
}

static struct file_system_type devfs_fs_type = {
	.name = DEVFS_NAME,
	.get_sb = devfs_get_sb,
	.kill_sb = kill_anon_super,
};

/*  File operations for devfsd follow  */

static ssize_t devfsd_read(struct file *file, char __user *buf, size_t len,
			   loff_t * ppos)
{
	int done = FALSE;
	int ival;
	loff_t pos, devname_offset, tlen, rpos;
	devfs_handle_t de;
	struct devfsd_buf_entry *entry;
	struct fs_info *fs_info = file->f_dentry->d_inode->i_sb->s_fs_info;
	struct devfsd_notify_struct *info = fs_info->devfsd_info;
	DECLARE_WAITQUEUE(wait, current);

	/*  Verify the task has grabbed the queue  */
	if (fs_info->devfsd_task != current)
		return -EPERM;
	info->major = 0;
	info->minor = 0;
	/*  Block for a new entry  */
	set_current_state(TASK_INTERRUPTIBLE);
	add_wait_queue(&fs_info->devfsd_wait_queue, &wait);
	while (devfsd_queue_empty(fs_info)) {
		fs_info->devfsd_sleeping = TRUE;
		wake_up(&fs_info->revalidate_wait_queue);
		schedule();
		fs_info->devfsd_sleeping = FALSE;
		if (signal_pending(current)) {
			remove_wait_queue(&fs_info->devfsd_wait_queue, &wait);
			__set_current_state(TASK_RUNNING);
			return -EINTR;
		}
		set_current_state(TASK_INTERRUPTIBLE);
	}
	remove_wait_queue(&fs_info->devfsd_wait_queue, &wait);
	__set_current_state(TASK_RUNNING);
	/*  Now play with the data  */
	ival = atomic_read(&fs_info->devfsd_overrun_count);
	info->overrun_count = ival;
	entry = fs_info->devfsd_first_event;
	info->type = entry->type;
	info->mode = entry->mode;
	info->uid = entry->uid;
	info->gid = entry->gid;
	de = entry->de;
	if (S_ISCHR(de->mode) || S_ISBLK(de->mode)) {
		info->major = MAJOR(de->u.dev);
		info->minor = MINOR(de->u.dev);
	}
	pos = devfs_generate_path(de, info->devname, DEVFS_PATHLEN);
	if (pos < 0)
		return pos;
	info->namelen = DEVFS_PATHLEN - pos - 1;
	if (info->mode == 0)
		info->mode = de->mode;
	devname_offset = info->devname - (char *)info;
	rpos = *ppos;
	if (rpos < devname_offset) {
		/*  Copy parts of the header  */
		tlen = devname_offset - rpos;
		if (tlen > len)
			tlen = len;
		if (copy_to_user(buf, (char *)info + rpos, tlen)) {
			return -EFAULT;
		}
		rpos += tlen;
		buf += tlen;
		len -= tlen;
	}
	if ((rpos >= devname_offset) && (len > 0)) {
		/*  Copy the name  */
		tlen = info->namelen + 1;
		if (tlen > len)
			tlen = len;
		else
			done = TRUE;
		if (copy_to_user
		    (buf, info->devname + pos + rpos - devname_offset, tlen)) {
			return -EFAULT;
		}
		rpos += tlen;
	}
	tlen = rpos - *ppos;
	if (done) {
		devfs_handle_t parent;

		spin_lock(&fs_info->devfsd_buffer_lock);
		fs_info->devfsd_first_event = entry->next;
		if (entry->next == NULL)
			fs_info->devfsd_last_event = NULL;
		spin_unlock(&fs_info->devfsd_buffer_lock);
		for (; de != NULL; de = parent) {
			parent = de->parent;
			devfs_put(de);
		}
		kmem_cache_free(devfsd_buf_cache, entry);
		if (ival > 0)
			atomic_sub(ival, &fs_info->devfsd_overrun_count);
		*ppos = 0;
	} else
		*ppos = rpos;
	return tlen;
}				/*  End Function devfsd_read  */

static int devfsd_ioctl(struct inode *inode, struct file *file,
			unsigned int cmd, unsigned long arg)
{
	int ival;
	struct fs_info *fs_info = inode->i_sb->s_fs_info;

	switch (cmd) {
	case DEVFSDIOC_GET_PROTO_REV:
		ival = DEVFSD_PROTOCOL_REVISION_KERNEL;
		if (copy_to_user((void __user *)arg, &ival, sizeof ival))
			return -EFAULT;
		break;
	case DEVFSDIOC_SET_EVENT_MASK:
		/*  Ensure only one reader has access to the queue. This scheme will
		   work even if the global kernel lock were to be removed, because it
		   doesn't matter who gets in first, as long as only one gets it  */
		if (fs_info->devfsd_task == NULL) {
			static DEFINE_SPINLOCK(lock);

			if (!spin_trylock(&lock))
				return -EBUSY;
			if (fs_info->devfsd_task != NULL) {	/*  We lost the race...  */
				spin_unlock(&lock);
				return -EBUSY;
			}
			fs_info->devfsd_task = current;
			spin_unlock(&lock);
			fs_info->devfsd_pgrp =
			    (process_group(current) ==
			     current->pid) ? process_group(current) : 0;
			fs_info->devfsd_file = file;
			fs_info->devfsd_info =
			    kmalloc(sizeof *fs_info->devfsd_info, GFP_KERNEL);
			if (!fs_info->devfsd_info) {
				devfsd_close(inode, file);
				return -ENOMEM;
			}
		} else if (fs_info->devfsd_task != current)
			return -EBUSY;
		fs_info->devfsd_event_mask = arg;	/*  Let the masses come forth  */
		break;
	case DEVFSDIOC_RELEASE_EVENT_QUEUE:
		if (fs_info->devfsd_file != file)
			return -EPERM;
		return devfsd_close(inode, file);
		/*break; */
#ifdef CONFIG_DEVFS_DEBUG
	case DEVFSDIOC_SET_DEBUG_MASK:
		if (copy_from_user(&ival, (void __user *)arg, sizeof ival))
			return -EFAULT;
		devfs_debug = ival;
		break;
#endif
	default:
		return -ENOIOCTLCMD;
	}
	return 0;
}				/*  End Function devfsd_ioctl  */

static int devfsd_close(struct inode *inode, struct file *file)
{
	struct devfsd_buf_entry *entry, *next;
	struct fs_info *fs_info = inode->i_sb->s_fs_info;

	if (fs_info->devfsd_file != file)
		return 0;
	fs_info->devfsd_event_mask = 0;
	fs_info->devfsd_file = NULL;
	spin_lock(&fs_info->devfsd_buffer_lock);
	entry = fs_info->devfsd_first_event;
	fs_info->devfsd_first_event = NULL;
	fs_info->devfsd_last_event = NULL;
	if (fs_info->devfsd_info) {
		kfree(fs_info->devfsd_info);
		fs_info->devfsd_info = NULL;
	}
	spin_unlock(&fs_info->devfsd_buffer_lock);
	fs_info->devfsd_pgrp = 0;
	fs_info->devfsd_task = NULL;
	wake_up(&fs_info->revalidate_wait_queue);
	for (; entry; entry = next) {
		next = entry->next;
		kmem_cache_free(devfsd_buf_cache, entry);
	}
	return 0;
}				/*  End Function devfsd_close  */

#ifdef CONFIG_DEVFS_DEBUG
static ssize_t stat_read(struct file *file, char __user *buf, size_t len,
			 loff_t * ppos)
{
	ssize_t num;
	char txt[80];

	num = sprintf(txt, "Number of entries: %u  number of bytes: %u\n",
		      stat_num_entries, stat_num_bytes) + 1;
	if (*ppos >= num)
		return 0;
	if (*ppos + len > num)
		len = num - *ppos;
	if (copy_to_user(buf, txt + *ppos, len))
		return -EFAULT;
	*ppos += len;
	return len;
}				/*  End Function stat_read  */
#endif

static int __init init_devfs_fs(void)
{
	int err;
	int major;
	struct devfs_entry *devfsd;
#ifdef CONFIG_DEVFS_DEBUG
	struct devfs_entry *stat;
#endif

	if (_devfs_get_root_entry() == NULL)
		return -ENOMEM;

	printk(KERN_INFO "%s: %s Richard Gooch (rgooch@atnf.csiro.au)\n",
	       DEVFS_NAME, DEVFS_VERSION);
	devfsd_buf_cache = kmem_cache_create("devfsd_event",
					     sizeof(struct devfsd_buf_entry),
					     0, 0, NULL, NULL);
	if (!devfsd_buf_cache)
		OOPS("(): unable to allocate event slab\n");
#ifdef CONFIG_DEVFS_DEBUG
	devfs_debug = devfs_debug_init;
	printk(KERN_INFO "%s: devfs_debug: 0x%0x\n", DEVFS_NAME, devfs_debug);
#endif
	printk(KERN_INFO "%s: boot_options: 0x%0x\n", DEVFS_NAME, boot_options);

	/* register special device for devfsd communication */
	major = register_chrdev(0, "devfs", &devfs_fops);
	if (major < 0)
		return major;

	/*  And create the entry for ".devfsd"  */
	devfsd = _devfs_alloc_entry(".devfsd", 0, S_IFCHR | S_IRUSR | S_IWUSR);
	if (devfsd == NULL)
		return -ENOMEM;
	devfsd->u.dev = MKDEV(major, 0);
	_devfs_append_entry(root_entry, devfsd, NULL);

#ifdef CONFIG_DEVFS_DEBUG
	stat = _devfs_alloc_entry(".stat", 0, S_IFCHR | S_IRUGO);
	if (stat == NULL)
		return -ENOMEM;
	stat->u.dev = MKDEV(major, 1);
	_devfs_append_entry(root_entry, stat, NULL);
#endif

	err = register_filesystem(&devfs_fs_type);
	return err;
}				/*  End Function init_devfs_fs  */

void __init mount_devfs_fs(void)
{
	int err;

	if (!(boot_options & OPTION_MOUNT))
		return;
	err = do_mount("none", "/dev", "devfs", 0, NULL);
	if (err == 0)
		printk(KERN_INFO "Mounted devfs on /dev\n");
	else
		PRINTK("(): unable to mount devfs, err: %d\n", err);
}				/*  End Function mount_devfs_fs  */

module_init(init_devfs_fs)