aboutsummaryrefslogblamecommitdiff
path: root/nuttx/drivers/usbdev/cdcacm.c
blob: cb867997664cb8869b98d00e8dbdd622885079ca (plain) (tree)
1
2
3
4
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
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


                                                                             
                                                               

























































































































































































                                                                                         





                                                                      






















                                                                               



                                     

                                     
      




































































































































































































































































































































































                                                                                       







                                                                         
































































































































































                                                                              
 


                   

                                      
                        






                                                                      























































































                                                                                     
 












































































































                                                                                     
 


































































































































































































































































































































































































































































































































































































































































                                                                                               


                                                                          

                    





                                       

                           
                                                          














                                                                             








































































                                                                              
































































































































































































































































































































































































































































                                                                                           










                                                      
































































































                                                                                
                                                                     




























































                                                                               
/****************************************************************************
 * drivers/usbdev/cdcacm.c
 *
 *   Copyright (C) 2011-2013 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <semaphore.h>
#include <string.h>
#include <errno.h>
#include <queue.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/arch.h>
#include <nuttx/serial/serial.h>

#include <nuttx/usb/usb.h>
#include <nuttx/usb/cdc.h>
#include <nuttx/usb/usbdev.h>
#include <nuttx/usb/cdcacm.h>
#include <nuttx/usb/usbdev_trace.h>

#include "cdcacm.h"

#ifdef CONFIG_USBMSC_COMPOSITE
#  include <nuttx/usb/composite.h>
#  include "composite.h"
#endif

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/****************************************************************************
 * Private Types
 ****************************************************************************/

/* Container to support a list of requests */

struct cdcacm_req_s
{
  FAR struct cdcacm_req_s *flink;      /* Implements a singly linked list */
  FAR struct usbdev_req_s *req;        /* The contained request */
};

/* This structure describes the internal state of the driver */

struct cdcacm_dev_s
{
  FAR struct uart_dev_s    serdev;     /* Serial device structure */
  FAR struct usbdev_s     *usbdev;     /* usbdev driver pointer */

  uint8_t config;                      /* Configuration number */
  uint8_t nwrq;                        /* Number of queue write requests (in reqlist)*/
  uint8_t nrdq;                        /* Number of queue read requests (in epbulkout) */
  uint8_t minor;                       /* The device minor number */
  bool    rxenabled;                   /* true: UART RX "interrupts" enabled */
  int16_t rxhead;                      /* Working head; used when rx int disabled */

  uint8_t                  ctrlline;   /* Buffered control line state */
  struct cdc_linecoding_s  linecoding; /* Buffered line status */
  cdcacm_callback_t        callback;   /* Serial event callback function */

  FAR struct usbdev_ep_s  *epintin;    /* Interrupt IN endpoint structure */
  FAR struct usbdev_ep_s  *epbulkin;   /* Bulk IN endpoint structure */
  FAR struct usbdev_ep_s  *epbulkout;  /* Bulk OUT endpoint structure */
  FAR struct usbdev_req_s *ctrlreq;    /* Allocoated control request */
  struct sq_queue_s        reqlist;    /* List of write request containers */

  /* Pre-allocated write request containers.  The write requests will
   * be linked in a free list (reqlist), and used to send requests to
   * EPBULKIN; Read requests will be queued in the EBULKOUT.
   */

  struct cdcacm_req_s wrreqs[CONFIG_CDCACM_NWRREQS];
  struct cdcacm_req_s rdreqs[CONFIG_CDCACM_NWRREQS];

  /* Serial I/O buffers */

  char rxbuffer[CONFIG_CDCACM_RXBUFSIZE];
  char txbuffer[CONFIG_CDCACM_TXBUFSIZE];
};

/* The internal version of the class driver */

struct cdcacm_driver_s
{
  struct usbdevclass_driver_s drvr;
  FAR struct cdcacm_dev_s     *dev;
};

/* This is what is allocated */

struct cdcacm_alloc_s
{
  struct cdcacm_dev_s    dev;
  struct cdcacm_driver_s drvr;
};

/****************************************************************************
 * Private Function Prototypes
 ****************************************************************************/

/* Transfer helpers *********************************************************/

static uint16_t cdcacm_fillrequest(FAR struct cdcacm_dev_s *priv,
                 uint8_t *reqbuf, uint16_t reqlen);
static int     cdcacm_sndpacket(FAR struct cdcacm_dev_s *priv);
static inline int cdcacm_recvpacket(FAR struct cdcacm_dev_s *priv,
                 uint8_t *reqbuf, uint16_t reqlen);

/* Request helpers *********************************************************/

static struct usbdev_req_s *cdcacm_allocreq(FAR struct usbdev_ep_s *ep,
                 uint16_t len);
static void    cdcacm_freereq(FAR struct usbdev_ep_s *ep,
                 FAR struct usbdev_req_s *req);

/* Configuration ***********************************************************/

static void    cdcacm_resetconfig(FAR struct cdcacm_dev_s *priv);
#ifdef CONFIG_USBDEV_DUALSPEED
static int     cdcacm_epconfigure(FAR struct usbdev_ep_s *ep,
                 enum cdcacm_epdesc_e epid, uint16_t mxpacket, bool last);
#endif
static int     cdcacm_setconfig(FAR struct cdcacm_dev_s *priv,
                 uint8_t config);

/* Completion event handlers ***********************************************/

static void    cdcacm_ep0incomplete(FAR struct usbdev_ep_s *ep,
                 FAR struct usbdev_req_s *req);
static void    cdcacm_rdcomplete(FAR struct usbdev_ep_s *ep,
                 FAR struct usbdev_req_s *req);
static void    cdcacm_wrcomplete(FAR struct usbdev_ep_s *ep,
                 FAR struct usbdev_req_s *req);

/* USB class device ********************************************************/

static int     cdcacm_bind(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev);
static void    cdcacm_unbind(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev);
static int     cdcacm_setup(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev,
                 FAR const struct usb_ctrlreq_s *ctrl, FAR uint8_t *dataout,
                 size_t outlen);
static void    cdcacm_disconnect(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev);
#ifdef CONFIG_SERIAL_REMOVABLE
static void    cdcacm_suspend(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev);
static void    cdcacm_resume(FAR struct usbdevclass_driver_s *driver,
                 FAR struct usbdev_s *dev);
#endif

/* UART Operations **********************************************************/

static int     cdcuart_setup(FAR struct uart_dev_s *dev);
static void    cdcuart_shutdown(FAR struct uart_dev_s *dev);
static int     cdcuart_attach(FAR struct uart_dev_s *dev);
static void    cdcuart_detach(FAR struct uart_dev_s *dev);
static int     cdcuart_ioctl(FAR struct file *filep,int cmd,unsigned long arg);
static void    cdcuart_rxint(FAR struct uart_dev_s *dev, bool enable);
static void    cdcuart_txint(FAR struct uart_dev_s *dev, bool enable);
static bool    cdcuart_txempty(FAR struct uart_dev_s *dev);

/****************************************************************************
 * Private Variables
 ****************************************************************************/
/* USB class device *********************************************************/

static const struct usbdevclass_driverops_s g_driverops =
{
  cdcacm_bind,          /* bind */
  cdcacm_unbind,        /* unbind */
  cdcacm_setup,         /* setup */
  cdcacm_disconnect,    /* disconnect */
#ifdef CONFIG_SERIAL_REMOVABLE
  cdcacm_suspend,       /* suspend */
  cdcacm_resume,        /* resume */
#else
  NULL,                 /* suspend */
  NULL,                 /* resume */
#endif
};

/* Serial port **************************************************************/

static const struct uart_ops_s g_uartops =
{
  cdcuart_setup,        /* setup */
  cdcuart_shutdown,     /* shutdown */
  cdcuart_attach,       /* attach */
  cdcuart_detach,       /* detach */
  cdcuart_ioctl,        /* ioctl */
  NULL,                 /* receive */
  cdcuart_rxint,        /* rxinit */
  NULL,                 /* rxavailable */
  NULL,                 /* send */
  cdcuart_txint,        /* txinit */
  NULL,                 /* txready */
  cdcuart_txempty       /* txempty */
};

/****************************************************************************
 * Private Functions
 ****************************************************************************/

/****************************************************************************
 * Name: cdcacm_fillrequest
 *
 * Description:
 *   If there is data to send it is copied to the given buffer.  Called
 *   either to initiate the first write operation, or from the completion
 *   interrupt handler service consecutive write operations.
 *
 * NOTE: The USB serial driver does not use the serial drivers
 *   uart_xmitchars() API.  That logic is essentially duplicated here because
 *   unlike UART hardware, we need to be able to handle writes not byte-by-byte,
 *   but packet-by-packet. Unfortunately, that decision also exposes some
 *   internals of the serial driver in the following.
 *
 ****************************************************************************/

static uint16_t cdcacm_fillrequest(FAR struct cdcacm_dev_s *priv, uint8_t *reqbuf,
                                   uint16_t reqlen)
{
  FAR uart_dev_t *serdev = &priv->serdev;
  FAR struct uart_buffer_s *xmit = &serdev->xmit;
  irqstate_t flags;
  uint16_t nbytes = 0;

  /* Disable interrupts */

  flags = irqsave();

  /* Transfer bytes while we have bytes available and there is room in the request */

  while (xmit->head != xmit->tail && nbytes < reqlen)
    {
      *reqbuf++ = xmit->buffer[xmit->tail];
      nbytes++;

      /* Increment the tail pointer */

      if (++(xmit->tail) >= xmit->size)
        {
          xmit->tail = 0;
        }
    }

  /* When all of the characters have been sent from the buffer
   * disable the "TX interrupt".
   */

  if (xmit->head == xmit->tail)
    {
      uart_disabletxint(serdev);
    }

  /* If any bytes were removed from the buffer, inform any waiters
   * there there is space available.
   */

  if (nbytes)
    {
      uart_datasent(serdev);
    }

  irqrestore(flags);
  return nbytes;
}

/****************************************************************************
 * Name: cdcacm_sndpacket
 *
 * Description:
 *   This function obtains write requests, transfers the TX data into the
 *   request, and submits the requests to the USB controller.  This continues
 *   untils either (1) there are no further packets available, or (2) thre is
 *   no further data to send.
 *
 ****************************************************************************/

static int cdcacm_sndpacket(FAR struct cdcacm_dev_s *priv)
{
  FAR struct usbdev_ep_s *ep;
  FAR struct usbdev_req_s *req;
  FAR struct cdcacm_req_s *reqcontainer;
  uint16_t reqlen;
  irqstate_t flags;
  int len;
  int ret = OK;

#ifdef CONFIG_DEBUG
  if (priv == NULL)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return -ENODEV;
    }
#endif

  flags = irqsave();

  /* Use our IN endpoint for the transfer */

  ep = priv->epbulkin;

  /* Loop until either (1) we run out or write requests, or (2) cdcacm_fillrequest()
   * is unable to fill the request with data (i.e., until there is no more data
   * to be sent).
   */

  uvdbg("head=%d tail=%d nwrq=%d empty=%d\n",
        priv->serdev.xmit.head, priv->serdev.xmit.tail,
        priv->nwrq, sq_empty(&priv->reqlist));

  /* Get the maximum number of bytes that will fit into one bulk IN request */

#ifdef CONFIG_CDCACM_BULKREQLEN
  reqlen = MAX(CONFIG_CDCACM_BULKREQLEN, ep->maxpacket);
#else
  reqlen = ep->maxpacket;
#endif

  while (!sq_empty(&priv->reqlist))
    {
      /* Peek at the request in the container at the head of the list */

      reqcontainer = (struct cdcacm_req_s *)sq_peek(&priv->reqlist);
      req          = reqcontainer->req;

      /* Fill the request with serial TX data */

      len = cdcacm_fillrequest(priv, req->buf, reqlen);
      if (len > 0)
        {
          /* Remove the empty container from the request list */

          (void)sq_remfirst(&priv->reqlist);
          priv->nwrq--;

          /* Then submit the request to the endpoint */

          req->len     = len;
          req->priv    = reqcontainer;
          req->flags   = USBDEV_REQFLAGS_NULLPKT;
          ret          = EP_SUBMIT(ep, req);
          if (ret != OK)
            {
              usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_SUBMITFAIL), (uint16_t)-ret);
              break;
            }
        }
      else
        {
          break;
        }
    }

  irqrestore(flags);
  return ret;
}

/****************************************************************************
 * Name: cdcacm_recvpacket
 *
 * Description:
 *   A normal completion event was received by the read completion handler
 *   at the interrupt level (with interrupts disabled).  This function handles
 *   the USB packet and provides the received data to the uart RX buffer.
 *
 * Assumptions:
 *   Called from the USB interrupt handler with interrupts disabled.
 *
 ****************************************************************************/

static inline int cdcacm_recvpacket(FAR struct cdcacm_dev_s *priv,
                                    uint8_t *reqbuf, uint16_t reqlen)
{
  FAR uart_dev_t *serdev = &priv->serdev;
  FAR struct uart_buffer_s *recv = &serdev->recv;
  uint16_t currhead;
  uint16_t nexthead;
  uint16_t nbytes = 0;

  uvdbg("head=%d tail=%d nrdq=%d reqlen=%d\n",
        priv->serdev.recv.head, priv->serdev.recv.tail, priv->nrdq, reqlen);

  /* Get the next head index. During the time that RX interrupts are disabled, the
   * the serial driver will be extracting data from the circular buffer and modifying
   * recv.tail.  During this time, we should avoid modifying recv.head; Instead we will
   * use a shadow copy of the index.  When interrupts are restored, the real recv.head
   * will be updated with this indes.
   */

  if (priv->rxenabled)
    {
      currhead = recv->head;
    }
  else
    {
      currhead = priv->rxhead;
    }

  /* Pre-calculate the head index and check for wrap around.  We need to do this
   * so that we can determine if the circular buffer will overrun BEFORE we
   * overrun the buffer!
   */

  nexthead = currhead + 1;
  if (nexthead >= recv->size)
    {
      nexthead = 0;
    }

  /* Then copy data into the RX buffer until either: (1) all of the data has been
   * copied, or (2) the RX buffer is full.  NOTE:  If the RX buffer becomes full,
   * then we have overrun the serial driver and data will be lost.
   */

  while (nexthead != recv->tail && nbytes < reqlen)
    {
      /* Copy one byte to the head of the circular RX buffer */

      recv->buffer[currhead] = *reqbuf++;

      /* Update counts and indices */

      currhead = nexthead;
      nbytes++;

      /* Increment the head index and check for wrap around */

      nexthead = currhead + 1;
      if (nexthead >= recv->size)
        {
          nexthead = 0;
        }
    }

  /* Write back the head pointer using the shadow index if RX "interrupts"
   * are disabled.
   */

  if (priv->rxenabled)
    {
      recv->head = currhead;
    }
  else
    {
      priv->rxhead = currhead;
    }

  /* If data was added to the incoming serial buffer, then wake up any
   * threads is waiting for incoming data. If we are running in an interrupt
   * handler, then the serial driver will not run until the interrupt handler
   * returns.
   */

  if (priv->rxenabled && nbytes > 0)
    {
      uart_datareceived(serdev);
    }

  /* Return an error if the entire packet could not be transferred */

  if (nbytes < reqlen)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RXOVERRUN), 0);
      return -ENOSPC;
    }
  return OK;
}

/****************************************************************************
 * Name: cdcacm_allocreq
 *
 * Description:
 *   Allocate a request instance along with its buffer
 *
 ****************************************************************************/

static struct usbdev_req_s *cdcacm_allocreq(FAR struct usbdev_ep_s *ep,
                                            uint16_t len)
{
  FAR struct usbdev_req_s *req;

  req = EP_ALLOCREQ(ep);
  if (req != NULL)
    {
      req->len = len;
      req->buf = EP_ALLOCBUFFER(ep, len);
      if (!req->buf)
        {
          EP_FREEREQ(ep, req);
          req = NULL;
        }
    }
  return req;
}

/****************************************************************************
 * Name: cdcacm_freereq
 *
 * Description:
 *   Free a request instance along with its buffer
 *
 ****************************************************************************/

static void cdcacm_freereq(FAR struct usbdev_ep_s *ep,
                           FAR struct usbdev_req_s *req)
{
  if (ep != NULL && req != NULL)
    {
      if (req->buf != NULL)
        {
          EP_FREEBUFFER(ep, req->buf);
        }
      EP_FREEREQ(ep, req);
    }
}

/****************************************************************************
 * Name: cdcacm_resetconfig
 *
 * Description:
 *   Mark the device as not configured and disable all endpoints.
 *
 ****************************************************************************/

static void cdcacm_resetconfig(FAR struct cdcacm_dev_s *priv)
{
  /* Are we configured? */

  if (priv->config != CDCACM_CONFIGIDNONE)
    {
      /* Yes.. but not anymore */

      priv->config = CDCACM_CONFIGIDNONE;

      /* Inform the "upper half" driver that there is no (functional) USB
       * connection.
       */

#ifdef CONFIG_SERIAL_REMOVABLE
      uart_connected(&priv->serdev, false);
#endif

      /* Disable endpoints.  This should force completion of all pending
       * transfers.
       */

      EP_DISABLE(priv->epintin);
      EP_DISABLE(priv->epbulkin);
      EP_DISABLE(priv->epbulkout);
    }
}

/****************************************************************************
 * Name: cdcacm_epconfigure
 *
 * Description:
 *   Configure one endpoint.
 *
 ****************************************************************************/

#ifdef CONFIG_USBDEV_DUALSPEED
static int cdcacm_epconfigure(FAR struct usbdev_ep_s *ep,
                              enum cdcacm_epdesc_e epid, uint16_t mxpacket,
                              bool last)
{
  struct usb_epdesc_s epdesc;
  cdcacm_mkepdesc(epid, mxpacket, &epdesc);
  return EP_CONFIGURE(ep, &epdesc, last);
}
#endif

/****************************************************************************
 * Name: cdcacm_setconfig
 *
 * Description:
 *   Set the device configuration by allocating and configuring endpoints and
 *   by allocating and queue read and write requests.
 *
 ****************************************************************************/

static int cdcacm_setconfig(FAR struct cdcacm_dev_s *priv, uint8_t config)
{
  FAR struct usbdev_req_s *req;
  int i;
  int ret = 0;

#if CONFIG_DEBUG
  if (priv == NULL)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return -EIO;
    }
#endif

  if (config == priv->config)
    {
      /* Already configured -- Do nothing */

      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_ALREADYCONFIGURED), 0);
      return 0;
    }

  /* Discard the previous configuration data */

  cdcacm_resetconfig(priv);

  /* Was this a request to simply discard the current configuration? */

  if (config == CDCACM_CONFIGIDNONE)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_CONFIGNONE), 0);
      return 0;
    }

  /* We only accept one configuration */

  if (config != CDCACM_CONFIGID)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_CONFIGIDBAD), 0);
      return -EINVAL;
    }

  /* Configure the IN interrupt endpoint */

#ifdef CONFIG_USBDEV_DUALSPEED
  if (priv->usbdev->speed == USB_SPEED_HIGH)
    {
      ret = cdcacm_epconfigure(priv->epintin, CDCACM_EPINTIN,
                               CONFIG_CDCACM_EPINTIN_HSSIZE, false);
    }
  else
#endif
    {
      ret = EP_CONFIGURE(priv->epintin,
                         cdcacm_getepdesc(CDCACM_EPINTIN), false);
    }

  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPINTINCONFIGFAIL), 0);
      goto errout;
    }
  priv->epintin->priv = priv;

  /* Configure the IN bulk endpoint */

#ifdef CONFIG_USBDEV_DUALSPEED
  if (priv->usbdev->speed == USB_SPEED_HIGH)
    {
      ret = cdcacm_epconfigure(priv->epbulkin, CDCACM_EPBULKIN,
                               CONFIG_CDCACM_EPBULKIN_HSSIZE, false);
    }
  else
#endif
    {
      ret = EP_CONFIGURE(priv->epbulkin,
                         cdcacm_getepdesc(CDCACM_EPBULKIN), false);
    }

  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPBULKINCONFIGFAIL), 0);
      goto errout;
    }

  priv->epbulkin->priv = priv;

  /* Configure the OUT bulk endpoint */

#ifdef CONFIG_USBDEV_DUALSPEED
  if (priv->usbdev->speed == USB_SPEED_HIGH)
    {
      ret = cdcacm_epconfigure(priv->epbulkout, CDCACM_EPBULKOUT,
                               CONFIG_CDCACM_EPBULKOUT_HSSIZE, true);
    }
  else
#endif
    {
      ret = EP_CONFIGURE(priv->epbulkout,
                         cdcacm_getepdesc(CDCACM_EPBULKOUT), true);
    }

  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPBULKOUTCONFIGFAIL), 0);
      goto errout;
    }

  priv->epbulkout->priv = priv;

  /* Queue read requests in the bulk OUT endpoint */

  DEBUGASSERT(priv->nrdq == 0);
  for (i = 0; i < CONFIG_CDCACM_NRDREQS; i++)
    {
      req           = priv->rdreqs[i].req;
      req->callback = cdcacm_rdcomplete;
      ret           = EP_SUBMIT(priv->epbulkout, req);
      if (ret != OK)
        {
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RDSUBMIT), (uint16_t)-ret);
          goto errout;
        }

      priv->nrdq++;
    }

  /* We are successfully configured */

  priv->config = config;

  /* Inform the "upper half" driver that we are "open for business" */

#ifdef CONFIG_SERIAL_REMOVABLE
  uart_connected(&priv->serdev, true);
#endif

  return OK;

errout:
  cdcacm_resetconfig(priv);
  return ret;
}

/****************************************************************************
 * Name: cdcacm_ep0incomplete
 *
 * Description:
 *   Handle completion of EP0 control operations
 *
 ****************************************************************************/

static void cdcacm_ep0incomplete(FAR struct usbdev_ep_s *ep,
                                 FAR struct usbdev_req_s *req)
{
  if (req->result || req->xfrd != req->len)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_REQRESULT), (uint16_t)-req->result);
    }
}

/****************************************************************************
 * Name: cdcacm_rdcomplete
 *
 * Description:
 *   Handle completion of read request on the bulk OUT endpoint.  This
 *   is handled like the receipt of serial data on the "UART"
 *
 ****************************************************************************/

static void cdcacm_rdcomplete(FAR struct usbdev_ep_s *ep,
                              FAR struct usbdev_req_s *req)
{
  FAR struct cdcacm_dev_s *priv;
  irqstate_t flags;
  int ret;

  /* Sanity check */

#ifdef CONFIG_DEBUG
  if (!ep || !ep->priv || !req)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract references to private data */

  priv = (FAR struct cdcacm_dev_s*)ep->priv;

  /* Process the received data unless this is some unusual condition */

  flags = irqsave();
  switch (req->result)
    {
    case 0: /* Normal completion */
      usbtrace(TRACE_CLASSRDCOMPLETE, priv->nrdq);
      cdcacm_recvpacket(priv, req->buf, req->xfrd);
      break;

    case -ESHUTDOWN: /* Disconnection */
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RDSHUTDOWN), 0);
      priv->nrdq--;
      irqrestore(flags);
      return;

    default: /* Some other error occurred */
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RDUNEXPECTED), (uint16_t)-req->result);
      break;
    };

  /* Requeue the read request */

#ifdef CONFIG_CDCACM_BULKREQLEN
  req->len = MAX(CONFIG_CDCACM_BULKREQLEN, ep->maxpacket);
#else
  req->len = ep->maxpacket;
#endif

  ret      = EP_SUBMIT(ep, req);
  if (ret != OK)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RDSUBMIT), (uint16_t)-req->result);
    }

  irqrestore(flags);
}

/****************************************************************************
 * Name: cdcacm_wrcomplete
 *
 * Description:
 *   Handle completion of write request.  This function probably executes
 *   in the context of an interrupt handler.
 *
 ****************************************************************************/

static void cdcacm_wrcomplete(FAR struct usbdev_ep_s *ep,
                              FAR struct usbdev_req_s *req)
{
  FAR struct cdcacm_dev_s *priv;
  FAR struct cdcacm_req_s *reqcontainer;
  irqstate_t flags;

  /* Sanity check */

#ifdef CONFIG_DEBUG
  if (!ep || !ep->priv || !req || !req->priv)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract references to our private data */

  priv         = (FAR struct cdcacm_dev_s *)ep->priv;
  reqcontainer = (FAR struct cdcacm_req_s *)req->priv;

  /* Return the write request to the free list */

  flags = irqsave();
  sq_addlast((sq_entry_t*)reqcontainer, &priv->reqlist);
  priv->nwrq++;
  irqrestore(flags);

  /* Send the next packet unless this was some unusual termination
   * condition
   */

  switch (req->result)
    {
    case OK: /* Normal completion */
      usbtrace(TRACE_CLASSWRCOMPLETE, priv->nwrq);
      cdcacm_sndpacket(priv);
      break;

    case -ESHUTDOWN: /* Disconnection */
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_WRSHUTDOWN), priv->nwrq);
      break;

    default: /* Some other error occurred */
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_WRUNEXPECTED), (uint16_t)-req->result);
      break;
    }
}

/****************************************************************************
 * USB Class Driver Methods
 ****************************************************************************/

/****************************************************************************
 * Name: cdcacm_bind
 *
 * Description:
 *   Invoked when the driver is bound to a USB device driver
 *
 ****************************************************************************/

static int cdcacm_bind(FAR struct usbdevclass_driver_s *driver,
                       FAR struct usbdev_s *dev)
{
  FAR struct cdcacm_dev_s *priv = ((FAR struct cdcacm_driver_s*)driver)->dev;
  FAR struct cdcacm_req_s *reqcontainer;
  irqstate_t flags;
  uint16_t reqlen;
  int ret;
  int i;

  usbtrace(TRACE_CLASSBIND, 0);

  /* Bind the structures */

  priv->usbdev   = dev;

  /* Save the reference to our private data structure in EP0 so that it
   * can be recovered in ep0 completion events (Unless we are part of 
   * a composite device and, in that case, the composite device owns
   * EP0).
   */

#ifndef CONFIG_USBMSC_COMPOSITE
  dev->ep0->priv = priv;
#endif

  /* Preallocate control request */

  priv->ctrlreq = cdcacm_allocreq(dev->ep0, CDCACM_MXDESCLEN);
  if (priv->ctrlreq == NULL)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_ALLOCCTRLREQ), 0);
      ret = -ENOMEM;
      goto errout;
    }

  priv->ctrlreq->callback = cdcacm_ep0incomplete;

  /* Pre-allocate all endpoints... the endpoints will not be functional
   * until the SET CONFIGURATION request is processed in cdcacm_setconfig.
   * This is done here because there may be calls to kmalloc and the SET
   * CONFIGURATION processing probably occurrs within interrupt handling
   * logic where kmalloc calls will fail.
   */

  /* Pre-allocate the IN interrupt endpoint */

  priv->epintin = DEV_ALLOCEP(dev, CDCACM_EPINTIN_ADDR, true, USB_EP_ATTR_XFER_INT);
  if (!priv->epintin)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPINTINALLOCFAIL), 0);
      ret = -ENODEV;
      goto errout;
    }
  priv->epintin->priv = priv;

  /* Pre-allocate the IN bulk endpoint */

  priv->epbulkin = DEV_ALLOCEP(dev, CDCACM_EPINBULK_ADDR, true, USB_EP_ATTR_XFER_BULK);
  if (!priv->epbulkin)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPBULKINALLOCFAIL), 0);
      ret = -ENODEV;
      goto errout;
    }
  priv->epbulkin->priv = priv;

  /* Pre-allocate the OUT bulk endpoint */

  priv->epbulkout = DEV_ALLOCEP(dev, CDCACM_EPOUTBULK_ADDR, false, USB_EP_ATTR_XFER_BULK);
  if (!priv->epbulkout)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPBULKOUTALLOCFAIL), 0);
      ret = -ENODEV;
      goto errout;
    }
  priv->epbulkout->priv = priv;

  /* Pre-allocate read requests */

#ifdef CONFIG_CDCACM_BULKREQLEN
  reqlen = MAX(CONFIG_CDCACM_BULKREQLEN, priv->epbulkout->maxpacket);
#else
  reqlen = priv->epbulkout->maxpacket;
#endif

  for (i = 0; i < CONFIG_CDCACM_NRDREQS; i++)
    {
      reqcontainer      = &priv->rdreqs[i];
      reqcontainer->req = cdcacm_allocreq(priv->epbulkout, reqlen);
      if (reqcontainer->req == NULL)
        {
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_RDALLOCREQ), -ENOMEM);
          ret = -ENOMEM;
          goto errout;
        }
      reqcontainer->req->priv     = reqcontainer;
      reqcontainer->req->callback = cdcacm_rdcomplete;
    }

  /* Pre-allocate write request containers and put in a free list */

#ifdef CONFIG_CDCACM_BULKREQLEN
  reqlen = MAX(CONFIG_CDCACM_BULKREQLEN, priv->epbulkin->maxpacket);
#else
  reqlen = priv->epbulkin->maxpacket;
#endif

  for (i = 0; i < CONFIG_CDCACM_NWRREQS; i++)
    {
      reqcontainer      = &priv->wrreqs[i];
      reqcontainer->req = cdcacm_allocreq(priv->epbulkin, reqlen);
      if (reqcontainer->req == NULL)
        {
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_WRALLOCREQ), -ENOMEM);
          ret = -ENOMEM;
          goto errout;
        }
      reqcontainer->req->priv     = reqcontainer;
      reqcontainer->req->callback = cdcacm_wrcomplete;

      flags = irqsave();
      sq_addlast((sq_entry_t*)reqcontainer, &priv->reqlist);
      priv->nwrq++;     /* Count of write requests available */
      irqrestore(flags);
    }

  /* Report if we are selfpowered (unless we are part of a composite device) */

#ifndef CONFIG_CDCACM_COMPOSITE
#ifdef CONFIG_USBDEV_SELFPOWERED
  DEV_SETSELFPOWERED(dev);
#endif

  /* And pull-up the data line for the soft connect function (unless we are
   * part of a composite device)
   */

  DEV_CONNECT(dev);
#endif
  return OK;

errout:
  cdcacm_unbind(driver, dev);
  return ret;
}

/****************************************************************************
 * Name: cdcacm_unbind
 *
 * Description:
 *    Invoked when the driver is unbound from a USB device driver
 *
 ****************************************************************************/

static void cdcacm_unbind(FAR struct usbdevclass_driver_s *driver,
                          FAR struct usbdev_s *dev)
{
  FAR struct cdcacm_dev_s *priv;
  FAR struct cdcacm_req_s *reqcontainer;
  irqstate_t flags;
  int i;

  usbtrace(TRACE_CLASSUNBIND, 0);

#ifdef CONFIG_DEBUG
  if (!driver || !dev)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract reference to private data */

  priv = ((FAR struct cdcacm_driver_s*)driver)->dev;

#ifdef CONFIG_DEBUG
  if (!priv)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EP0NOTBOUND), 0);
      return;
    }
#endif

  /* Make sure that we are not already unbound */

  if (priv != NULL)
    {
      /* Make sure that the endpoints have been unconfigured.  If
       * we were terminated gracefully, then the configuration should
       * already have been reset.  If not, then calling cdcacm_resetconfig
       * should cause the endpoints to immediately terminate all
       * transfers and return the requests to us (with result == -ESHUTDOWN)
       */

      cdcacm_resetconfig(priv);
      up_mdelay(50);

      /* Free the interrupt IN endpoint */

      if (priv->epintin)
        {
          DEV_FREEEP(dev, priv->epintin);
          priv->epintin = NULL;
        }

      /* Free the bulk IN endpoint */

      if (priv->epbulkin)
        {
          DEV_FREEEP(dev, priv->epbulkin);
          priv->epbulkin = NULL;
        }

      /* Free the pre-allocated control request */

      if (priv->ctrlreq != NULL)
        {
          cdcacm_freereq(dev->ep0, priv->ctrlreq);
          priv->ctrlreq = NULL;
        }

      /* Free pre-allocated read requests (which should all have
       * been returned to the free list at this time -- we don't check)
       */

      DEBUGASSERT(priv->nrdq == 0);
      for (i = 0; i < CONFIG_CDCACM_NRDREQS; i++)
        {
          reqcontainer = &priv->rdreqs[i];
          if (reqcontainer->req)
            {
              cdcacm_freereq(priv->epbulkout, reqcontainer->req);
              reqcontainer->req = NULL;
            }
        }

      /* Free the bulk OUT endpoint */

      if (priv->epbulkout)
        {
          DEV_FREEEP(dev, priv->epbulkout);
          priv->epbulkout = NULL;
        }

      /* Free write requests that are not in use (which should be all
       * of them)
       */

      flags = irqsave();
      DEBUGASSERT(priv->nwrq == CONFIG_CDCACM_NWRREQS);
      while (!sq_empty(&priv->reqlist))
        {
          reqcontainer = (struct cdcacm_req_s *)sq_remfirst(&priv->reqlist);
          if (reqcontainer->req != NULL)
            {
              cdcacm_freereq(priv->epbulkin, reqcontainer->req);
              priv->nwrq--;     /* Number of write requests queued */
            }
        }
      DEBUGASSERT(priv->nwrq == 0);
      irqrestore(flags);
    }

  /* Clear out all data in the circular buffer */

  priv->serdev.xmit.head = 0;
  priv->serdev.xmit.tail = 0;
}

/****************************************************************************
 * Name: cdcacm_setup
 *
 * Description:
 *   Invoked for ep0 control requests.  This function probably executes
 *   in the context of an interrupt handler.
 *
 ****************************************************************************/

static int cdcacm_setup(FAR struct usbdevclass_driver_s *driver,
                        FAR struct usbdev_s *dev,
                        FAR const struct usb_ctrlreq_s *ctrl,
                        FAR uint8_t *dataout, size_t outlen)
{
  FAR struct cdcacm_dev_s *priv;
  FAR struct usbdev_req_s *ctrlreq;
  uint16_t value;
  uint16_t index;
  uint16_t len;
  int ret = -EOPNOTSUPP;

#ifdef CONFIG_DEBUG
  if (!driver || !dev || !ctrl)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return -EIO;
     }
#endif

  /* Extract reference to private data */

  usbtrace(TRACE_CLASSSETUP, ctrl->req);
  priv = ((FAR struct cdcacm_driver_s*)driver)->dev;

#ifdef CONFIG_DEBUG
  if (!priv || !priv->ctrlreq)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EP0NOTBOUND), 0);
      return -ENODEV;
    }
#endif
  ctrlreq = priv->ctrlreq;

  /* Extract the little-endian 16-bit values to host order */

  value = GETUINT16(ctrl->value);
  index = GETUINT16(ctrl->index);
  len   = GETUINT16(ctrl->len);

  uvdbg("type=%02x req=%02x value=%04x index=%04x len=%04x\n",
        ctrl->type, ctrl->req, value, index, len);

  if ((ctrl->type & USB_REQ_TYPE_MASK) == USB_REQ_TYPE_STANDARD)
    {
      /***********************************************************************
       * Standard Requests
       ***********************************************************************/

      switch (ctrl->req)
        {
        case USB_REQ_GETDESCRIPTOR:
          {
            /* The value field specifies the descriptor type in the MS byte and the
             * descriptor index in the LS byte (order is little endian)
             */

            switch (ctrl->value[1])
              {
              /* If the serial device is used in as part of a composite device,
               * then the device descriptor is provided by logic in the composite
               * device implementation.
               */

#ifndef CONFIG_CDCACM_COMPOSITE
              case USB_DESC_TYPE_DEVICE:
                {
                  ret = USB_SIZEOF_DEVDESC;
                  memcpy(ctrlreq->buf, cdcacm_getdevdesc(), ret);
                }
                break;
#endif

              /* If the serial device is used in as part of a composite device,
               * then the device qualifier descriptor is provided by logic in the
               * composite device implementation.
               */

#if !defined(CONFIG_CDCACM_COMPOSITE) && defined(CONFIG_USBDEV_DUALSPEED)
              case USB_DESC_TYPE_DEVICEQUALIFIER:
                {
                  ret = USB_SIZEOF_QUALDESC;
                  memcpy(ctrlreq->buf, cdcacm_getqualdesc(), ret);
                }
                break;

              case USB_DESC_TYPE_OTHERSPEEDCONFIG:
#endif

              /* If the serial device is used in as part of a composite device,
               * then the configuration descriptor is provided by logic in the
               * composite device implementation.
               */

#ifndef CONFIG_CDCACM_COMPOSITE
              case USB_DESC_TYPE_CONFIG:
                {
#ifdef CONFIG_USBDEV_DUALSPEED
                  ret = cdcacm_mkcfgdesc(ctrlreq->buf, dev->speed, ctrl->req);
#else
                  ret = cdcacm_mkcfgdesc(ctrlreq->buf);
#endif
                }
                break;
#endif

              /* If the serial device is used in as part of a composite device,
               * then the language string descriptor is provided by logic in the
               * composite device implementation.
               */

#ifndef CONFIG_CDCACM_COMPOSITE
              case USB_DESC_TYPE_STRING:
                {
                  /* index == language code. */

                  ret = cdcacm_mkstrdesc(ctrl->value[0], (struct usb_strdesc_s *)ctrlreq->buf);
                }
                break;
#endif

              default:
                {
                  usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_GETUNKNOWNDESC), value);
                }
                break;
              }
          }
          break;

        case USB_REQ_SETCONFIGURATION:
          {
            if (ctrl->type == 0)
              {
                ret = cdcacm_setconfig(priv, value);
              }
          }
          break;

        /* If the serial device is used in as part of a composite device,
         * then the overall composite class configuration is managed by logic
         * in the composite device implementation.
         */

#ifndef CONFIG_CDCACM_COMPOSITE
        case USB_REQ_GETCONFIGURATION:
          {
            if (ctrl->type == USB_DIR_IN)
              {
                *(uint8_t*)ctrlreq->buf = priv->config;
                ret = 1;
              }
          }
          break;
#endif

        case USB_REQ_SETINTERFACE:
          {
            if (ctrl->type == USB_REQ_RECIPIENT_INTERFACE &&
                priv->config == CDCACM_CONFIGID)
              {
                if ((index == CDCACM_NOTIFID && value == CDCACM_NOTALTIFID) ||
                    (index == CDCACM_DATAIFID && value == CDCACM_DATAALTIFID))
                  {
                    cdcacm_resetconfig(priv);
                    cdcacm_setconfig(priv, priv->config);
                    ret = 0;
                  }
              }
          }
          break;

        case USB_REQ_GETINTERFACE:
          {
            if (ctrl->type == (USB_DIR_IN|USB_REQ_RECIPIENT_INTERFACE) &&
                priv->config == CDCACM_CONFIGIDNONE)
              {
                if ((index == CDCACM_NOTIFID && value == CDCACM_NOTALTIFID) ||
                    (index == CDCACM_DATAIFID && value == CDCACM_DATAALTIFID))
                   {
                    *(uint8_t*) ctrlreq->buf = value;
                    ret = 1;
                  }
                else
                  {
                    ret = -EDOM;
                  }
              }
           }
           break;

        default:
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDSTDREQ), ctrl->req);
          break;
        }
    }

  else if ((ctrl->type & USB_REQ_TYPE_MASK) == USB_REQ_TYPE_CLASS)
    {
      /***********************************************************************
       * CDC ACM-Specific Requests
       ***********************************************************************/

      switch (ctrl->req)
        {
        /* ACM_GET_LINE_CODING requests current DTE rate, stop-bits, parity, and
         * number-of-character bits. (Optional)
         */

        case ACM_GET_LINE_CODING:
          {
            if (ctrl->type == (USB_DIR_IN|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE) &&
            index == CDCACM_NOTIFID)
              {
                /* Return the current line status from the private data structure */

                memcpy(ctrlreq->buf, &priv->linecoding, SIZEOF_CDC_LINECODING);
                ret = SIZEOF_CDC_LINECODING;
              }
            else
              {
                usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDCLASSREQ), ctrl->type);
              }
          }
          break;

        /* ACM_SET_LINE_CODING configures DTE rate, stop-bits, parity, and
         * number-of-character bits. (Optional)
         */

        case ACM_SET_LINE_CODING:
          {
            if (ctrl->type == (USB_DIR_OUT|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE) &&
                len == SIZEOF_CDC_LINECODING && /* dataout && len == outlen && */
                index == CDCACM_NOTIFID)
              {
                /* Save the new line coding in the private data structure.  NOTE:
                 * that this is conditional now because not all device controller
                 * drivers supported provisioni of EP0 OUT data with the setup
                 * command.
                 */

                if (dataout && len <= SIZEOF_CDC_LINECODING) /* REVISIT */
                  {
                    memcpy(&priv->linecoding, dataout, SIZEOF_CDC_LINECODING);
                  }
                ret = 0;

                /* If there is a registered callback to receive line status info, then
                 * callout now.
                 */

                if (priv->callback)
                  {
                    priv->callback(CDCACM_EVENT_LINECODING);
                  }
              }
            else
              {
                usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDCLASSREQ), ctrl->type);
              }
          }
          break;

        /* ACM_SET_CTRL_LINE_STATE: RS-232 signal used to tell the DCE device the
         * DTE device is now present. (Optional)
         */

        case ACM_SET_CTRL_LINE_STATE:
          {
            if (ctrl->type == (USB_DIR_OUT|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE) &&
                index == CDCACM_NOTIFID)
              {
                /* Save the control line state in the private data structure. Only bits
                 * 0 and 1 have meaning.
                 */

                priv->ctrlline = value & 3;
                ret = 0;

                /* If there is a registered callback to receive control line status info,
                 * then callout now.
                 */

                if (priv->callback)
                  {
                    priv->callback(CDCACM_EVENT_CTRLLINE);
                  }
              }
            else
              {
                usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDCLASSREQ), ctrl->type);
              }
          }
          break;

        /*  Sends special carrier*/

        case ACM_SEND_BREAK:
          {
            if (ctrl->type == (USB_DIR_OUT|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE) &&
                index == CDCACM_NOTIFID)
              {
                /* If there is a registered callback to handle the SendBreak request,
                 * then callout now.
                 */

                ret = 0;
                if (priv->callback)
                  {
                    priv->callback(CDCACM_EVENT_SENDBREAK);
                  }
              }
            else
              {
                usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDCLASSREQ), ctrl->type);
              }
          }
          break;

        default:
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDCLASSREQ), ctrl->req);
          break;
        }
    }
  else
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UNSUPPORTEDTYPE), ctrl->type);
    }

  /* Respond to the setup command if data was returned.  On an error return
   * value (ret < 0), the USB driver will stall.
   */

  if (ret >= 0)
    {
      /* Configure the response */

      ctrlreq->len   = MIN(len, ret);
      ctrlreq->flags = USBDEV_REQFLAGS_NULLPKT;

      /* Send the response -- either directly to the USB controller or
       * indirectly in the case where this class is a member of a composite
       * device.
       */

#ifndef CONFIG_CDCACM_COMPOSITE
      ret = EP_SUBMIT(dev->ep0, ctrlreq);
#else
      ret = composite_ep0submit(driver, dev, ctrlreq);
#endif
      if (ret < 0)
        {
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EPRESPQ), (uint16_t)-ret);
          ctrlreq->result = OK;
          cdcacm_ep0incomplete(dev->ep0, ctrlreq);
        }
    }
  return ret;
}

/****************************************************************************
 * Name: cdcacm_disconnect
 *
 * Description:
 *   Invoked after all transfers have been stopped, when the host is
 *   disconnected.  This function is probably called from the context of an
 *   interrupt handler.
 *
 ****************************************************************************/

static void cdcacm_disconnect(FAR struct usbdevclass_driver_s *driver,
                              FAR struct usbdev_s *dev)
{
  FAR struct cdcacm_dev_s *priv;
  irqstate_t flags;

  usbtrace(TRACE_CLASSDISCONNECT, 0);

#ifdef CONFIG_DEBUG
  if (!driver || !dev || !dev->ep0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract reference to private data */

  priv = ((FAR struct cdcacm_driver_s*)driver)->dev;

#ifdef CONFIG_DEBUG
  if (!priv)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_EP0NOTBOUND), 0);
      return;
    }
#endif

  /* Inform the "upper half serial driver that we have lost the USB serial
   * connection.
   */

  flags = irqsave();
#ifdef CONFIG_SERIAL_REMOVABLE
  uart_connected(&priv->serdev, false);
#endif

  /* Reset the configuration */

  cdcacm_resetconfig(priv);

  /* Clear out all outgoing data in the circular buffer */

  priv->serdev.xmit.head = 0;
  priv->serdev.xmit.tail = 0;
  irqrestore(flags);

  /* Perform the soft connect function so that we will we can be
   * re-enumerated (unless we are part of a composite device)
   */

#ifndef CONFIG_CDCACM_COMPOSITE
  DEV_CONNECT(dev);
#endif
}

/****************************************************************************
 * Name: cdcacm_suspend
 *
 * Description:
 *   Handle the USB suspend event.
 *
 ****************************************************************************/

#ifdef CONFIG_SERIAL_REMOVABLE
static void cdcacm_suspend(FAR struct usbdevclass_driver_s *driver,
                           FAR struct usbdev_s *dev)
{
  FAR struct cdcacm_dev_s *priv;

  usbtrace(TRACE_CLASSSUSPEND, 0);

#ifdef CONFIG_DEBUG
  if (!driver || !dev)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract reference to private data */

  priv = ((FAR struct cdcacm_driver_s*)driver)->dev;

  /* And let the "upper half" driver now that we are suspended */

  uart_connected(&priv->serdev, false);
}
#endif

/****************************************************************************
 * Name: cdcacm_resume
 *
 * Description:
 *   Handle the USB resume event.
 *
 ****************************************************************************/

#ifdef CONFIG_SERIAL_REMOVABLE
static void cdcacm_resume(FAR struct usbdevclass_driver_s *driver,
                          FAR struct usbdev_s *dev)
{
  FAR struct cdcacm_dev_s *priv;

  usbtrace(TRACE_CLASSRESUME, 0);

#ifdef CONFIG_DEBUG
  if (!driver || !dev)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return;
     }
#endif

  /* Extract reference to private data */

  priv = ((FAR struct cdcacm_driver_s*)driver)->dev;

  /* Are we still configured? */

  if (priv->config != CDCACM_CONFIGIDNONE)
    {
      /* Yes.. let the "upper half" know that have resumed */

      uart_connected(&priv->serdev, true);
    }
}
#endif

/****************************************************************************
 * Serial Device Methods
 ****************************************************************************/

/****************************************************************************
 * Name: cdcuart_setup
 *
 * Description:
 *   This method is called the first time that the serial port is opened.
 *
 ****************************************************************************/

static int cdcuart_setup(FAR struct uart_dev_s *dev)
{
  FAR struct cdcacm_dev_s *priv;

  usbtrace(CDCACM_CLASSAPI_SETUP, 0);

  /* Sanity check */

#if CONFIG_DEBUG
  if (!dev || !dev->priv)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return -EIO;
    }
#endif

  /* Extract reference to private data */

  priv = (FAR struct cdcacm_dev_s*)dev->priv;

  /* Check if we have been configured */

  if (priv->config == CDCACM_CONFIGIDNONE)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_SETUPNOTCONNECTED), 0);
      return -ENOTCONN;
    }

  return OK;
}

/****************************************************************************
 * Name: cdcuart_shutdown
 *
 * Description:
 *   This method is called when the serial port is closed.  This operation
 *   is very simple for the USB serial backend because the serial driver
 *   has already assured that the TX data has full drained -- it calls
 *   cdcuart_txempty() until that function returns true before calling this
 *   function.
 *
 ****************************************************************************/

static void cdcuart_shutdown(FAR struct uart_dev_s *dev)
{
  usbtrace(CDCACM_CLASSAPI_SHUTDOWN, 0);

  /* Sanity check */

#if CONFIG_DEBUG
  if (!dev || !dev->priv)
    {
       usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
    }
#endif
}

/****************************************************************************
 * Name: cdcuart_attach
 *
 * Description:
 *   Does not apply to the USB serial class device
 *
 ****************************************************************************/

static int cdcuart_attach(FAR struct uart_dev_s *dev)
{
  usbtrace(CDCACM_CLASSAPI_ATTACH, 0);
  return OK;
}

/****************************************************************************
 * Name: cdcuart_detach
 *
 * Description:
*   Does not apply to the USB serial class device
  *
 ****************************************************************************/

static void cdcuart_detach(FAR struct uart_dev_s *dev)
{
  usbtrace(CDCACM_CLASSAPI_DETACH, 0);
}

/****************************************************************************
 * Name: cdcuart_ioctl
 *
 * Description:
 *   All ioctl calls will be routed through this method
 *
 ****************************************************************************/

static int cdcuart_ioctl(FAR struct file *filep,int cmd,unsigned long arg)
{
  struct inode        *inode = filep->f_inode;
  struct cdcacm_dev_s *priv  = inode->i_private;
  int                  ret   = OK;

  switch (cmd)
    {
    /* CAICO_REGISTERCB
     *   Register a callback for serial event notification. Argument:
     *   cdcacm_callback_t.  See cdcacm_callback_t type definition below.
     *   NOTE:  The callback will most likely invoked at the interrupt level.
     *   The called back function should, therefore, limit its operations to
     *   invoking some kind of IPC to handle the serial event in some normal
     *   task environment.
     */

    case CAIOC_REGISTERCB:
      {
        /* Save the new callback function */

        priv->callback = (cdcacm_callback_t)((uintptr_t)arg);
      }
      break;

    /* CAIOC_GETLINECODING
     *   Get current line coding.  Argument: struct cdc_linecoding_s*.
     *   See include/nuttx/usb/cdc.h for structure definition.  This IOCTL
     *   should be called to get the data associated with the
     *   CDCACM_EVENT_LINECODING event).
     */

    case CAIOC_GETLINECODING:
      {
        FAR struct cdc_linecoding_s *ptr = (FAR struct cdc_linecoding_s *)((uintptr_t)arg);
        if (ptr)
          {
            memcpy(ptr, &priv->linecoding, sizeof(struct cdc_linecoding_s));
          }
        else
          {
            ret = -EINVAL;
          }
      }
      break;

    /* CAIOC_GETCTRLLINE
     *   Get control line status bits. Argument FAR int*.  See
     *   include/nuttx/usb/cdc.h for bit definitions.  This IOCTL should be
     *   called to get the data associated CDCACM_EVENT_CTRLLINE event.
     */

   case CAIOC_GETCTRLLINE:
      {
        FAR int *ptr = (FAR int *)((uintptr_t)arg);
        if (ptr)
          {
            *ptr = priv->ctrlline;
          }
        else
          {
            ret = -EINVAL;
          }
      }
      break;

    /* CAIOC_NOTIFY
     *   Send a serial state to the host via the Interrupt IN endpoint.
     *   Argument: int.  This includes the current state of the carrier detect,
     *   DSR, break, and ring signal.  See "Table 69: UART State Bitmap Values"
     *   and CDC_UART_definitions in include/nuttx/usb/cdc.h.
     */

    case CAIOC_NOTIFY:
      {
        /* Not yet implemented.  I probably won't bother to implement until
         * I comr up with a usage model that needs it.
         *
         * Here is what the needs to be done:
         *
         * 1. Format and send a request header with:
         *
         *   bmRequestType:
         *    USB_REQ_DIR_IN|USB_REQ_TYPE_CLASS|USB_REQ_RECIPIENT_INTERFACE
         *   bRequest: ACM_SERIAL_STATE
         *   wValue: 0
         *   wIndex: 0
         *   wLength: Length of data
         *
         * 2. Followed by the notification data (in a separate packet)
         */

        ret = -ENOSYS;
      }
      break;

    default:
      ret = -ENOTTY;
      break;
    }

  return ret;
}

/****************************************************************************
 * Name: cdcuart_rxint
 *
 * Description:
 *   Called by the serial driver to enable or disable RX interrupts.  We, of
 *   course, have no RX interrupts but must behave consistently.  This method
 *   is called under the conditions:
 *
 *   1. With enable==true when the port is opened (just after cdcuart_setup
 *      and cdcuart_attach are called called)
 *   2. With enable==false while transferring data from the RX buffer
 *   2. With enable==true while waiting for more incoming data
 *   3. With enable==false when the port is closed (just before cdcuart_detach
 *      and cdcuart_shutdown are called).
 *
 ****************************************************************************/

static void cdcuart_rxint(FAR struct uart_dev_s *dev, bool enable)
{
  FAR struct cdcacm_dev_s *priv;
  FAR uart_dev_t *serdev;
  irqstate_t flags;

  usbtrace(CDCACM_CLASSAPI_RXINT, (uint16_t)enable);

  /* Sanity check */

#if CONFIG_DEBUG
  if (!dev || !dev->priv)
    {
       usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
       return;
    }
#endif

  /* Extract reference to private data */

  priv   = (FAR struct cdcacm_dev_s*)dev->priv;
  serdev = &priv->serdev;

  /* We need exclusive access to the RX buffer and private structure
   * in the following.
   */

  flags = irqsave();
  if (enable)
    {
       /* RX "interrupts" are enabled.  Is this a transition from disabled
        * to enabled state?
        */

       if (!priv->rxenabled)
         {
           /* Yes.  During the time that RX interrupts are disabled, the
            * the serial driver will be extracting data from the circular
            * buffer and modifying recv.tail.  During this time, we
            * should avoid modifying recv.head; When interrupts are restored,
            * we can update the head pointer for all of the data that we
            * put into cicular buffer while "interrupts" were disabled.
            */

          if (priv->rxhead != serdev->recv.head)
            {
              serdev->recv.head = priv->rxhead;

              /* Yes... signal the availability of new data */

              uart_datareceived(serdev);
            }

          /* RX "interrupts are no longer disabled */

          priv->rxenabled = true;
        }
    }

  /* RX "interrupts" are disabled.  Is this a transition from enabled
   * to disabled state?
   */

  else if (priv->rxenabled)
    {
      /* Yes.  During the time that RX interrupts are disabled, the
       * the serial driver will be extracting data from the circular
       * buffer and modifying recv.tail.  During this time, we
       * should avoid modifying recv.head; When interrupts are disabled,
       * we use a shadow index and continue adding data to the circular
       * buffer.
       */

      priv->rxhead    = serdev->recv.head;
      priv->rxenabled = false;
    }
  irqrestore(flags);
}

/****************************************************************************
 * Name: cdcuart_txint
 *
 * Description:
 *   Called by the serial driver to enable or disable TX interrupts.  We, of
 *   course, have no TX interrupts but must behave consistently.  Initially,
 *   TX interrupts are disabled.  This method is called under the conditions:
 *
 *   1. With enable==false while transferring data into the TX buffer
 *   2. With enable==true when data may be taken from the buffer.
 *   3. With enable==false when the TX buffer is empty
 *
 ****************************************************************************/

static void cdcuart_txint(FAR struct uart_dev_s *dev, bool enable)
{
  FAR struct cdcacm_dev_s *priv;

  usbtrace(CDCACM_CLASSAPI_TXINT, (uint16_t)enable);

  /* Sanity checks */

#if CONFIG_DEBUG
  if (!dev || !dev->priv)
    {
       usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
       return;
    }
#endif

 /* Extract references to private data */

  priv = (FAR struct cdcacm_dev_s*)dev->priv;

  /* If the new state is enabled and if there is data in the XMIT buffer,
   * send the next packet now.
   */

  uvdbg("enable=%d head=%d tail=%d\n",
        enable, priv->serdev.xmit.head, priv->serdev.xmit.tail);

  if (enable && priv->serdev.xmit.head != priv->serdev.xmit.tail)
    {
      cdcacm_sndpacket(priv);
    }
}

/****************************************************************************
 * Name: cdcuart_txempty
 *
 * Description:
 *   Return true when all data has been sent.  This is called from the
 *   serial driver when the driver is closed.  It will call this API
 *   periodically until it reports true.  NOTE that the serial driver takes all
 *   responsibility for flushing TX data through the hardware so we can be
 *   a bit sloppy about that.
 *
 ****************************************************************************/

static bool cdcuart_txempty(FAR struct uart_dev_s *dev)
{
  FAR struct cdcacm_dev_s *priv = (FAR struct cdcacm_dev_s*)dev->priv;

  usbtrace(CDCACM_CLASSAPI_TXEMPTY, 0);

#if CONFIG_DEBUG
  if (!priv)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_INVALIDARG), 0);
      return true;
    }
#endif

  /* When all of the allocated write requests have been returned to the
   * reqlist, then there is no longer any TX data in flight.
   */

  return priv->nwrq >= CONFIG_CDCACM_NWRREQS;
}

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: cdcacm_classobject
 *
 * Description:
 *   Register USB serial port (and USB serial console if so configured) and
 *   return the class object.
 *
 * Input Parameter:
 *   minor - Device minor number.  E.g., minor 0 would correspond to
 *     /dev/ttyACM0.
 *   classdev - The location to return the CDC serial class' device
 *     instance.
 *
 * Returned Value:
 *   A pointer to the allocated class object (NULL on failure).
 *
 ****************************************************************************/

#ifndef CONFIG_CDCACM_COMPOSITE
static
#endif
int cdcacm_classobject(int minor, FAR struct usbdevclass_driver_s **classdev)
{
  FAR struct cdcacm_alloc_s *alloc;
  FAR struct cdcacm_dev_s *priv;
  FAR struct cdcacm_driver_s *drvr;
  char devname[CDCACM_DEVNAME_SIZE];
  int ret;

  /* Allocate the structures needed */

  alloc = (FAR struct cdcacm_alloc_s*)kmalloc(sizeof(struct cdcacm_alloc_s));
  if (!alloc)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_ALLOCDEVSTRUCT), 0);
      return -ENOMEM;
    }

  /* Convenience pointers into the allocated blob */

  priv = &alloc->dev;
  drvr = &alloc->drvr;

  /* Initialize the USB serial driver structure */

  memset(priv, 0, sizeof(struct cdcacm_dev_s));
  sq_init(&priv->reqlist);

  priv->minor              = minor;

  /* Fake line status */

  priv->linecoding.baud[0] = (115200) & 0xff;       /* Baud=115200 */
  priv->linecoding.baud[1] = (115200 >> 8) & 0xff;
  priv->linecoding.baud[2] = (115200 >> 16) & 0xff;
  priv->linecoding.baud[3] = (115200 >> 24) & 0xff;
  priv->linecoding.stop    = CDC_CHFMT_STOP1;       /* One stop bit */
  priv->linecoding.parity  = CDC_PARITY_NONE;       /* No parity */
  priv->linecoding.nbits   = 8;                     /* 8 data bits */

  /* Initialize the serial driver sub-structure */

      /* The initial state is disconnected */

#ifdef CONFIG_SERIAL_REMOVABLE
  priv->serdev.disconnected = true;
#endif
  priv->serdev.recv.size    = CONFIG_CDCACM_RXBUFSIZE;
  priv->serdev.recv.buffer  = priv->rxbuffer;
  priv->serdev.xmit.size    = CONFIG_CDCACM_TXBUFSIZE;
  priv->serdev.xmit.buffer  = priv->txbuffer;
  priv->serdev.ops          = &g_uartops;
  priv->serdev.priv         = priv;

  /* Initialize the USB class driver structure */

#ifdef CONFIG_USBDEV_DUALSPEED
  drvr->drvr.speed         = USB_SPEED_HIGH;
#else
  drvr->drvr.speed         = USB_SPEED_FULL;
#endif
  drvr->drvr.ops           = &g_driverops;
  drvr->dev                = priv;

  /* Register the USB serial console */

#ifdef CONFIG_CDCACM_CONSOLE
  priv->serdev.isconsole = true;
  ret = uart_register("/dev/console", &priv->serdev);
  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_CONSOLEREGISTER), (uint16_t)-ret);
      goto errout_with_class;
    }
#endif

  /* Register the CDC/ACM TTY device */

  sprintf(devname, CDCACM_DEVNAME_FORMAT, minor);
  ret = uart_register(devname, &priv->serdev);
  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UARTREGISTER), (uint16_t)-ret);
      goto errout_with_class;
    }

  *classdev = &drvr->drvr;
  return OK;

errout_with_class:
  kfree(alloc);
  return ret;
}

/****************************************************************************
 * Name: cdcacm_initialize
 *
 * Description:
 *   Register USB serial port (and USB serial console if so configured).
 *
 * Input Parameter:
 *   minor - Device minor number.  E.g., minor 0 would correspond to
 *     /dev/ttyACM0.
 *   handle - An optional opaque reference to the CDC/ACM class object that
 *     may subsequently be used with cdcacm_uninitialize().
 *
 * Returned Value:
 *   Zero (OK) means that the driver was successfully registered.  On any
 *   failure, a negated errno value is retured.
 *
 ****************************************************************************/

#ifndef CONFIG_CDCACM_COMPOSITE
int cdcacm_initialize(int minor, FAR void **handle)
{
  FAR struct usbdevclass_driver_s *drvr = NULL;
  int ret;

  /* Get an instance of the serial driver class object */

  ret = cdcacm_classobject(minor, &drvr);
  if (ret == OK)
    {
      /* Register the USB serial class driver */

      ret = usbdev_register(drvr);
      if (ret < 0)
        {
          usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_DEVREGISTER), (uint16_t)-ret);
        }
    }

  /* Return the driver instance (if any) if the caller has requested it
   * by provided a pointer to the location to return it.
   */

  if (handle)
    {
      *handle = (FAR void*)drvr;
    }

  return ret;
}
#endif

/****************************************************************************
 * Name: cdcacm_uninitialize
 *
 * Description:
 *   Un-initialize the USB storage class driver.  This function is used
 *   internally by the USB composite driver to unitialize the CDC/ACM
 *   driver.  This same interface is available (with an untyped input
 *   parameter) when the CDC/ACM driver is used standalone.
 *
 * Input Parameters:
 *   There is one parameter, it differs in typing depending upon whether the
 *   CDC/ACM driver is an internal part of a composite device, or a standalone
 *   USB driver:
 *
 *     classdev - The class object returned by board_cdcclassobject() or
 *       cdcacm_classobject()
 *     handle - The opaque handle represetning the class object returned by
 *       a previous call to cdcacm_initialize().
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

#ifdef CONFIG_CDCACM_COMPOSITE
void cdcacm_uninitialize(FAR struct usbdevclass_driver_s *classdev)
#else
void cdcacm_uninitialize(FAR void *handle)
#endif
{
#ifdef CONFIG_CDCACM_COMPOSITE
  FAR struct cdcacm_driver_s *drvr = (FAR struct cdcacm_driver_s *)classdev;
#else
  FAR struct cdcacm_driver_s *drvr = (FAR struct cdcacm_driver_s *)handle;
#endif
  FAR struct cdcacm_dev_s    *priv = drvr->dev;
  char devname[CDCACM_DEVNAME_SIZE];
  int ret;

  /* Un-register the CDC/ACM TTY device */

  sprintf(devname, CDCACM_DEVNAME_FORMAT, priv->minor);
  ret = unregister_driver(devname);
  if (ret < 0)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_UARTUNREGISTER), (uint16_t)-ret);
    }

  /* Unregister the driver (unless we are a part of a composite device).  The
   * device unregister logic will (1) return all of the requests to us then
   * (2) all the unbind method.
   *
   * The same thing will happen in the composite case except that: (1) the
   * composite driver will call usbdev_unregister() which will (2) return the
   * requests for all members of the composite, and (3) call the unbind
   * method in the composite device which will (4) call the unbind method
   * for this device.
   */

#ifndef CONFIG_CDCACM_COMPOSITE
  usbdev_unregister(&drvr->drvr);
#endif

  /* And free the driver structure */

  kfree(priv);
}