drivers/usb/serial/ch341.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
   4  * Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
   5  * Copyright 2009, Boris Hajduk <boris@hajduk.org>
   6  *
   7  * ch341.c implements a serial port driver for the Winchiphead CH341.
   8  *
   9  * The CH341 device can be used to implement an RS232 asynchronous
  10  * serial port, an IEEE-1284 parallel printer port or a memory-like
  11  * interface. In all cases the CH341 supports an I2C interface as well.
  12  * This driver only supports the asynchronous serial interface.
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/tty.h>
  17 #include <linux/module.h>
  18 #include <linux/slab.h>
  19 #include <linux/usb.h>
  20 #include <linux/usb/serial.h>
  21 #include <linux/serial.h>
  22 #include <asm/unaligned.h>
  23
  24 #define DEFAULT_BAUD_RATE 9600
  25 #define DEFAULT_TIMEOUT   1000
  26
  27 /* flags for IO-Bits */
  28 #define CH341_BIT_RTS (1 << 6)
  29 #define CH341_BIT_DTR (1 << 5)
  30
  31 /******************************/
  32 /* interrupt pipe definitions */
  33 /******************************/
  34 /* always 4 interrupt bytes */
  35 /* first irq byte normally 0x08 */
  36 /* second irq byte base 0x7d + below */
  37 /* third irq byte base 0x94 + below */
  38 /* fourth irq byte normally 0xee */
  39
  40 /* second interrupt byte */
  41 #define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
  42
  43 /* status returned in third interrupt answer byte, inverted in data
  44    from irq */
  45 #define CH341_BIT_CTS 0x01
  46 #define CH341_BIT_DSR 0x02
  47 #define CH341_BIT_RI  0x04
  48 #define CH341_BIT_DCD 0x08
  49 #define CH341_BITS_MODEM_STAT 0x0f /* all bits */
  50
  51 /*******************************/
  52 /* baudrate calculation factor */
  53 /*******************************/
  54 #define CH341_BAUDBASE_FACTOR 1532620800
  55 #define CH341_BAUDBASE_DIVMAX 3
  56
  57 /* Break support - the information used to implement this was gleaned from
  58  * the Net/FreeBSD uchcom.c driver by Takanori Watanabe.  Domo arigato.
  59  */
  60
  61 #define CH341_REQ_READ_VERSION 0x5F
  62 #define CH341_REQ_WRITE_REG    0x9A
  63 #define CH341_REQ_READ_REG     0x95
  64 #define CH341_REQ_SERIAL_INIT  0xA1
  65 #define CH341_REQ_MODEM_CTRL   0xA4
  66
  67 #define CH341_REG_BREAK        0x05
  68 #define CH341_REG_LCR          0x18
  69 #define CH341_NBREAK_BITS      0x01
  70
  71 #define CH341_LCR_ENABLE_RX    0x80
  72 #define CH341_LCR_ENABLE_TX    0x40
  73 #define CH341_LCR_MARK_SPACE   0x20
  74 #define CH341_LCR_PAR_EVEN     0x10
  75 #define CH341_LCR_ENABLE_PAR   0x08
  76 #define CH341_LCR_STOP_BITS_2  0x04
  77 #define CH341_LCR_CS8          0x03
  78 #define CH341_LCR_CS7          0x02
  79 #define CH341_LCR_CS6          0x01
  80 #define CH341_LCR_CS5          0x00
  81
  82 static const struct usb_device_id id_table[] = {
  83         { USB_DEVICE(0x4348, 0x5523) },
  84         { USB_DEVICE(0x1a86, 0x7523) },
  85         { USB_DEVICE(0x1a86, 0x5523) },
  86         { },
  87 };
  88 MODULE_DEVICE_TABLE(usb, id_table);
  89
  90 struct ch341_private {
  91         spinlock_t lock; /* access lock */
  92         unsigned baud_rate; /* set baud rate */
  93         u8 mcr;
  94         u8 msr;
  95         u8 lcr;
  96 };
  97
  98 static void ch341_set_termios(struct tty_struct *tty,
  99                               struct usb_serial_port *port,
 100                               struct ktermios *old_termios);
 101
 102 static int ch341_control_out(struct usb_device *dev, u8 request,
 103                              u16 value, u16 index)
 104 {
 105         int r;
 106
 107         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
 108                 request, value, index);
 109
 110         r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
 111                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
 112                             value, index, NULL, 0, DEFAULT_TIMEOUT);
 113         if (r < 0)
 114                 dev_err(&dev->dev, "failed to send control message: %d\n", r);
 115
 116         return r;
 117 }
 118
 119 static int ch341_control_in(struct usb_device *dev,
 120                             u8 request, u16 value, u16 index,
 121                             char *buf, unsigned bufsize)
 122 {
 123         int r;
 124
 125         dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
 126                 request, value, index, bufsize);
 127
 128         r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
 129                             USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
 130                             value, index, buf, bufsize, DEFAULT_TIMEOUT);
 131         if (r < bufsize) {
 132                 if (r >= 0) {
 133                         dev_err(&dev->dev,
 134                                 "short control message received (%d < %u)\n",
 135                                 r, bufsize);
 136                         r = -EIO;
 137                 }
 138
 139                 dev_err(&dev->dev, "failed to receive control message: %d\n",
 140                         r);
 141                 return r;
 142         }
 143
 144         return 0;
 145 }
 146
 147 static int ch341_set_baudrate_lcr(struct usb_device *dev,
 148                                   struct ch341_private *priv, u8 lcr)
 149 {
 150         short a;
 151         int r;
 152         unsigned long factor;
 153         short divisor;
 154
 155         if (!priv->baud_rate)
 156                 return -EINVAL;
 157         factor = (CH341_BAUDBASE_FACTOR / priv->baud_rate);
 158         divisor = CH341_BAUDBASE_DIVMAX;
 159
 160         while ((factor > 0xfff0) && divisor) {
 161                 factor >>= 3;
 162                 divisor--;
 163         }
 164
 165         if (factor > 0xfff0)
 166                 return -EINVAL;
 167
 168         factor = 0x10000 - factor;
 169         a = (factor & 0xff00) | divisor;
 170
 171         /*
 172          * CH341A buffers data until a full endpoint-size packet (32 bytes)
 173          * has been received unless bit 7 is set.
 174          */
 175         a |= BIT(7);
 176
 177         r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x1312, a);
 178         if (r)
 179                 return r;
 180
 181         r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, lcr);
 182         if (r)
 183                 return r;
 184
 185         return r;
 186 }
 187
 188 static int ch341_set_handshake(struct usb_device *dev, u8 control)
 189 {
 190         return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
 191 }
 192
 193 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
 194 {
 195         const unsigned int size = 2;
 196         char *buffer;
 197         int r;
 198         unsigned long flags;
 199
 200         buffer = kmalloc(size, GFP_KERNEL);
 201         if (!buffer)
 202                 return -ENOMEM;
 203
 204         r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
 205         if (r < 0)
 206                 goto out;
 207
 208         spin_lock_irqsave(&priv->lock, flags);
 209         priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
 210         spin_unlock_irqrestore(&priv->lock, flags);
 211
 212 out:    kfree(buffer);
 213         return r;
 214 }
 215
 216 /* -------------------------------------------------------------------------- */
 217
 218 static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
 219 {
 220         const unsigned int size = 2;
 221         char *buffer;
 222         int r;
 223
 224         buffer = kmalloc(size, GFP_KERNEL);
 225         if (!buffer)
 226                 return -ENOMEM;
 227
 228         /* expect two bytes 0x27 0x00 */
 229         r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
 230         if (r < 0)
 231                 goto out;
 232         dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
 233
 234         r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
 235         if (r < 0)
 236                 goto out;
 237
 238         r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
 239         if (r < 0)
 240                 goto out;
 241
 242         r = ch341_set_handshake(dev, priv->mcr);
 243
 244 out:    kfree(buffer);
 245         return r;
 246 }
 247
 248 static int ch341_port_probe(struct usb_serial_port *port)
 249 {
 250         struct ch341_private *priv;
 251         int r;
 252
 253         priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
 254         if (!priv)
 255                 return -ENOMEM;
 256
 257         spin_lock_init(&priv->lock);
 258         priv->baud_rate = DEFAULT_BAUD_RATE;
 259         /*
 260          * Some CH340 devices appear unable to change the initial LCR
 261          * settings, so set a sane 8N1 default.
 262          */
 263         priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
 264
 265         r = ch341_configure(port->serial->dev, priv);
 266         if (r < 0)
 267                 goto error;
 268
 269         usb_set_serial_port_data(port, priv);
 270         return 0;
 271
 272 error:  kfree(priv);
 273         return r;
 274 }
 275
 276 static int ch341_port_remove(struct usb_serial_port *port)
 277 {
 278         struct ch341_private *priv;
 279
 280         priv = usb_get_serial_port_data(port);
 281         kfree(priv);
 282
 283         return 0;
 284 }
 285
 286 static int ch341_carrier_raised(struct usb_serial_port *port)
 287 {
 288         struct ch341_private *priv = usb_get_serial_port_data(port);
 289         if (priv->msr & CH341_BIT_DCD)
 290                 return 1;
 291         return 0;
 292 }
 293
 294 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
 295 {
 296         struct ch341_private *priv = usb_get_serial_port_data(port);
 297         unsigned long flags;
 298
 299         /* drop DTR and RTS */
 300         spin_lock_irqsave(&priv->lock, flags);
 301         if (on)
 302                 priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
 303         else
 304                 priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
 305         spin_unlock_irqrestore(&priv->lock, flags);
 306         ch341_set_handshake(port->serial->dev, priv->mcr);
 307 }
 308
 309 static void ch341_close(struct usb_serial_port *port)
 310 {
 311         usb_serial_generic_close(port);
 312         usb_kill_urb(port->interrupt_in_urb);
 313 }
 314
 315
 316 /* open this device, set default parameters */
 317 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 318 {
 319         struct ch341_private *priv = usb_get_serial_port_data(port);
 320         int r;
 321
 322         if (tty)
 323                 ch341_set_termios(tty, port, NULL);
 324
 325         dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
 326         r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 327         if (r) {
 328                 dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
 329                         __func__, r);
 330                 return r;
 331         }
 332
 333         r = ch341_get_status(port->serial->dev, priv);
 334         if (r < 0) {
 335                 dev_err(&port->dev, "failed to read modem status: %d\n", r);
 336                 goto err_kill_interrupt_urb;
 337         }
 338
 339         r = usb_serial_generic_open(tty, port);
 340         if (r)
 341                 goto err_kill_interrupt_urb;
 342
 343         return 0;
 344
 345 err_kill_interrupt_urb:
 346         usb_kill_urb(port->interrupt_in_urb);
 347
 348         return r;
 349 }
 350
 351 /* Old_termios contains the original termios settings and
 352  * tty->termios contains the new setting to be used.
 353  */
 354 static void ch341_set_termios(struct tty_struct *tty,
 355                 struct usb_serial_port *port, struct ktermios *old_termios)
 356 {
 357         struct ch341_private *priv = usb_get_serial_port_data(port);
 358         unsigned baud_rate;
 359         unsigned long flags;
 360         u8 lcr;
 361         int r;
 362
 363         /* redundant changes may cause the chip to lose bytes */
 364         if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
 365                 return;
 366
 367         baud_rate = tty_get_baud_rate(tty);
 368
 369         lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
 370
 371         switch (C_CSIZE(tty)) {
 372         case CS5:
 373                 lcr |= CH341_LCR_CS5;
 374                 break;
 375         case CS6:
 376                 lcr |= CH341_LCR_CS6;
 377                 break;
 378         case CS7:
 379                 lcr |= CH341_LCR_CS7;
 380                 break;
 381         case CS8:
 382                 lcr |= CH341_LCR_CS8;
 383                 break;
 384         }
 385
 386         if (C_PARENB(tty)) {
 387                 lcr |= CH341_LCR_ENABLE_PAR;
 388                 if (C_PARODD(tty) == 0)
 389                         lcr |= CH341_LCR_PAR_EVEN;
 390                 if (C_CMSPAR(tty))
 391                         lcr |= CH341_LCR_MARK_SPACE;
 392         }
 393
 394         if (C_CSTOPB(tty))
 395                 lcr |= CH341_LCR_STOP_BITS_2;
 396
 397         if (baud_rate) {
 398                 priv->baud_rate = baud_rate;
 399
 400                 r = ch341_set_baudrate_lcr(port->serial->dev, priv, lcr);
 401                 if (r < 0 && old_termios) {
 402                         priv->baud_rate = tty_termios_baud_rate(old_termios);
 403                         tty_termios_copy_hw(&tty->termios, old_termios);
 404                 } else if (r == 0) {
 405                         priv->lcr = lcr;
 406                 }
 407         }
 408
 409         spin_lock_irqsave(&priv->lock, flags);
 410         if (C_BAUD(tty) == B0)
 411                 priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
 412         else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
 413                 priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
 414         spin_unlock_irqrestore(&priv->lock, flags);
 415
 416         ch341_set_handshake(port->serial->dev, priv->mcr);
 417 }
 418
 419 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
 420 {
 421         const uint16_t ch341_break_reg =
 422                         ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
 423         struct usb_serial_port *port = tty->driver_data;
 424         int r;
 425         uint16_t reg_contents;
 426         uint8_t *break_reg;
 427
 428         break_reg = kmalloc(2, GFP_KERNEL);
 429         if (!break_reg)
 430                 return;
 431
 432         r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
 433                         ch341_break_reg, 0, break_reg, 2);
 434         if (r < 0) {
 435                 dev_err(&port->dev, "%s - USB control read error (%d)\n",
 436                                 __func__, r);
 437                 goto out;
 438         }
 439         dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
 440                 __func__, break_reg[0], break_reg[1]);
 441         if (break_state != 0) {
 442                 dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
 443                 break_reg[0] &= ~CH341_NBREAK_BITS;
 444                 break_reg[1] &= ~CH341_LCR_ENABLE_TX;
 445         } else {
 446                 dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
 447                 break_reg[0] |= CH341_NBREAK_BITS;
 448                 break_reg[1] |= CH341_LCR_ENABLE_TX;
 449         }
 450         dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
 451                 __func__, break_reg[0], break_reg[1]);
 452         reg_contents = get_unaligned_le16(break_reg);
 453         r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
 454                         ch341_break_reg, reg_contents);
 455         if (r < 0)
 456                 dev_err(&port->dev, "%s - USB control write error (%d)\n",
 457                                 __func__, r);
 458 out:
 459         kfree(break_reg);
 460 }
 461
 462 static int ch341_tiocmset(struct tty_struct *tty,
 463                           unsigned int set, unsigned int clear)
 464 {
 465         struct usb_serial_port *port = tty->driver_data;
 466         struct ch341_private *priv = usb_get_serial_port_data(port);
 467         unsigned long flags;
 468         u8 control;
 469
 470         spin_lock_irqsave(&priv->lock, flags);
 471         if (set & TIOCM_RTS)
 472                 priv->mcr |= CH341_BIT_RTS;
 473         if (set & TIOCM_DTR)
 474                 priv->mcr |= CH341_BIT_DTR;
 475         if (clear & TIOCM_RTS)
 476                 priv->mcr &= ~CH341_BIT_RTS;
 477         if (clear & TIOCM_DTR)
 478                 priv->mcr &= ~CH341_BIT_DTR;
 479         control = priv->mcr;
 480         spin_unlock_irqrestore(&priv->lock, flags);
 481
 482         return ch341_set_handshake(port->serial->dev, control);
 483 }
 484
 485 static void ch341_update_status(struct usb_serial_port *port,
 486                                         unsigned char *data, size_t len)
 487 {
 488         struct ch341_private *priv = usb_get_serial_port_data(port);
 489         struct tty_struct *tty;
 490         unsigned long flags;
 491         u8 status;
 492         u8 delta;
 493
 494         if (len < 4)
 495                 return;
 496
 497         status = ~data[2] & CH341_BITS_MODEM_STAT;
 498
 499         spin_lock_irqsave(&priv->lock, flags);
 500         delta = status ^ priv->msr;
 501         priv->msr = status;
 502         spin_unlock_irqrestore(&priv->lock, flags);
 503
 504         if (data[1] & CH341_MULT_STAT)
 505                 dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
 506
 507         if (!delta)
 508                 return;
 509
 510         if (delta & CH341_BIT_CTS)
 511                 port->icount.cts++;
 512         if (delta & CH341_BIT_DSR)
 513                 port->icount.dsr++;
 514         if (delta & CH341_BIT_RI)
 515                 port->icount.rng++;
 516         if (delta & CH341_BIT_DCD) {
 517                 port->icount.dcd++;
 518                 tty = tty_port_tty_get(&port->port);
 519                 if (tty) {
 520                         usb_serial_handle_dcd_change(port, tty,
 521                                                 status & CH341_BIT_DCD);
 522                         tty_kref_put(tty);
 523                 }
 524         }
 525
 526         wake_up_interruptible(&port->port.delta_msr_wait);
 527 }
 528
 529 static void ch341_read_int_callback(struct urb *urb)
 530 {
 531         struct usb_serial_port *port = urb->context;
 532         unsigned char *data = urb->transfer_buffer;
 533         unsigned int len = urb->actual_length;
 534         int status;
 535
 536         switch (urb->status) {
 537         case 0:
 538                 /* success */
 539                 break;
 540         case -ECONNRESET:
 541         case -ENOENT:
 542         case -ESHUTDOWN:
 543                 /* this urb is terminated, clean up */
 544                 dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
 545                         __func__, urb->status);
 546                 return;
 547         default:
 548                 dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
 549                         __func__, urb->status);
 550                 goto exit;
 551         }
 552
 553         usb_serial_debug_data(&port->dev, __func__, len, data);
 554         ch341_update_status(port, data, len);
 555 exit:
 556         status = usb_submit_urb(urb, GFP_ATOMIC);
 557         if (status) {
 558                 dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
 559                         __func__, status);
 560         }
 561 }
 562
 563 static int ch341_tiocmget(struct tty_struct *tty)
 564 {
 565         struct usb_serial_port *port = tty->driver_data;
 566         struct ch341_private *priv = usb_get_serial_port_data(port);
 567         unsigned long flags;
 568         u8 mcr;
 569         u8 status;
 570         unsigned int result;
 571
 572         spin_lock_irqsave(&priv->lock, flags);
 573         mcr = priv->mcr;
 574         status = priv->msr;
 575         spin_unlock_irqrestore(&priv->lock, flags);
 576
 577         result = ((mcr & CH341_BIT_DTR)         ? TIOCM_DTR : 0)
 578                   | ((mcr & CH341_BIT_RTS)      ? TIOCM_RTS : 0)
 579                   | ((status & CH341_BIT_CTS)   ? TIOCM_CTS : 0)
 580                   | ((status & CH341_BIT_DSR)   ? TIOCM_DSR : 0)
 581                   | ((status & CH341_BIT_RI)    ? TIOCM_RI  : 0)
 582                   | ((status & CH341_BIT_DCD)   ? TIOCM_CD  : 0);
 583
 584         dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
 585
 586         return result;
 587 }
 588
 589 static int ch341_reset_resume(struct usb_serial *serial)
 590 {
 591         struct usb_serial_port *port = serial->port[0];
 592         struct ch341_private *priv = usb_get_serial_port_data(port);
 593         int ret;
 594
 595         /* reconfigure ch341 serial port after bus-reset */
 596         ch341_configure(serial->dev, priv);
 597
 598         if (tty_port_initialized(&port->port)) {
 599                 ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
 600                 if (ret) {
 601                         dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
 602                                 ret);
 603                         return ret;
 604                 }
 605
 606                 ret = ch341_get_status(port->serial->dev, priv);
 607                 if (ret < 0) {
 608                         dev_err(&port->dev, "failed to read modem status: %d\n",
 609                                 ret);
 610                 }
 611         }
 612
 613         return usb_serial_generic_resume(serial);
 614 }
 615
 616 static struct usb_serial_driver ch341_device = {
 617         .driver = {
 618                 .owner  = THIS_MODULE,
 619                 .name   = "ch341-uart",
 620         },
 621         .id_table          = id_table,
 622         .num_ports         = 1,
 623         .open              = ch341_open,
 624         .dtr_rts           = ch341_dtr_rts,
 625         .carrier_raised    = ch341_carrier_raised,
 626         .close             = ch341_close,
 627         .set_termios       = ch341_set_termios,
 628         .break_ctl         = ch341_break_ctl,
 629         .tiocmget          = ch341_tiocmget,
 630         .tiocmset          = ch341_tiocmset,
 631         .tiocmiwait        = usb_serial_generic_tiocmiwait,
 632         .read_int_callback = ch341_read_int_callback,
 633         .port_probe        = ch341_port_probe,
 634         .port_remove       = ch341_port_remove,
 635         .reset_resume      = ch341_reset_resume,
 636 };
 637
 638 static struct usb_serial_driver * const serial_drivers[] = {
 639         &ch341_device, NULL
 640 };
 641
 642 module_usb_serial_driver(serial_drivers, id_table);
 643
 644 MODULE_LICENSE("GPL v2");