drivers/usb/serial/ark3116.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * Copyright (C) 2009 by Bart Hartgers (bart.hartgers+ark3116@gmail.com)
   4  * Original version:
   5  * Copyright (C) 2006
   6  *   Simon Schulz (ark3116_driver <at> auctionant.de)
   7  *
   8  * ark3116
   9  * - implements a driver for the arkmicro ark3116 chipset (vendor=0x6547,
  10  *   productid=0x0232) (used in a datacable called KQ-U8A)
  11  *
  12  * Supports full modem status lines, break, hardware flow control. Does not
  13  * support software flow control, since I do not know how to enable it in hw.
  14  *
  15  * This driver is a essentially new implementation. I initially dug
  16  * into the old ark3116.c driver and suddenly realized the ark3116 is
  17  * a 16450 with a USB interface glued to it. See comments at the
  18  * bottom of this file.
  19  */
  20
  21 #include <linux/kernel.h>
  22 #include <linux/ioctl.h>
  23 #include <linux/tty.h>
  24 #include <linux/slab.h>
  25 #include <linux/tty_flip.h>
  26 #include <linux/module.h>
  27 #include <linux/usb.h>
  28 #include <linux/usb/serial.h>
  29 #include <linux/serial.h>
  30 #include <linux/serial_reg.h>
  31 #include <linux/uaccess.h>
  32 #include <linux/mutex.h>
  33 #include <linux/spinlock.h>
  34
  35 #define DRIVER_AUTHOR "Bart Hartgers <bart.hartgers+ark3116@gmail.com>"
  36 #define DRIVER_DESC "USB ARK3116 serial/IrDA driver"
  37 #define DRIVER_DEV_DESC "ARK3116 RS232/IrDA"
  38 #define DRIVER_NAME "ark3116"
  39
  40 /* usb timeout of 1 second */
  41 #define ARK_TIMEOUT 1000
  42
  43 static const struct usb_device_id id_table[] = {
  44         { USB_DEVICE(0x6547, 0x0232) },
  45         { USB_DEVICE(0x18ec, 0x3118) },         /* USB to IrDA adapter */
  46         { },
  47 };
  48 MODULE_DEVICE_TABLE(usb, id_table);
  49
  50 static int is_irda(struct usb_serial *serial)
  51 {
  52         struct usb_device *dev = serial->dev;
  53         if (le16_to_cpu(dev->descriptor.idVendor) == 0x18ec &&
  54                         le16_to_cpu(dev->descriptor.idProduct) == 0x3118)
  55                 return 1;
  56         return 0;
  57 }
  58
  59 struct ark3116_private {
  60         int                     irda;   /* 1 for irda device */
  61
  62         /* protects hw register updates */
  63         struct mutex            hw_lock;
  64
  65         int                     quot;   /* baudrate divisor */
  66         __u32                   lcr;    /* line control register value */
  67         __u32                   hcr;    /* handshake control register (0x8)
  68                                          * value */
  69         __u32                   mcr;    /* modem control register value */
  70
  71         /* protects the status values below */
  72         spinlock_t              status_lock;
  73         __u32                   msr;    /* modem status register value */
  74         __u32                   lsr;    /* line status register value */
  75 };
  76
  77 static int ark3116_write_reg(struct usb_serial *serial,
  78                              unsigned reg, __u8 val)
  79 {
  80         int result;
  81          /* 0xfe 0x40 are magic values taken from original driver */
  82         result = usb_control_msg(serial->dev,
  83                                  usb_sndctrlpipe(serial->dev, 0),
  84                                  0xfe, 0x40, val, reg,
  85                                  NULL, 0, ARK_TIMEOUT);
  86         if (result)
  87                 return result;
  88
  89         return 0;
  90 }
  91
  92 static int ark3116_read_reg(struct usb_serial *serial,
  93                             unsigned reg, unsigned char *buf)
  94 {
  95         int result;
  96         /* 0xfe 0xc0 are magic values taken from original driver */
  97         result = usb_control_msg(serial->dev,
  98                                  usb_rcvctrlpipe(serial->dev, 0),
  99                                  0xfe, 0xc0, 0, reg,
 100                                  buf, 1, ARK_TIMEOUT);
 101         if (result < 1) {
 102                 dev_err(&serial->interface->dev,
 103                                 "failed to read register %u: %d\n",
 104                                 reg, result);
 105                 if (result >= 0)
 106                         result = -EIO;
 107
 108                 return result;
 109         }
 110
 111         return 0;
 112 }
 113
 114 static inline int calc_divisor(int bps)
 115 {
 116         /* Original ark3116 made some exceptions in rounding here
 117          * because windows did the same. Assume that is not really
 118          * necessary.
 119          * Crystal is 12MHz, probably because of USB, but we divide by 4?
 120          */
 121         return (12000000 + 2*bps) / (4*bps);
 122 }
 123
 124 static int ark3116_port_probe(struct usb_serial_port *port)
 125 {
 126         struct usb_serial *serial = port->serial;
 127         struct ark3116_private *priv;
 128
 129         priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 130         if (!priv)
 131                 return -ENOMEM;
 132
 133         mutex_init(&priv->hw_lock);
 134         spin_lock_init(&priv->status_lock);
 135
 136         priv->irda = is_irda(serial);
 137
 138         usb_set_serial_port_data(port, priv);
 139
 140         /* setup the hardware */
 141         ark3116_write_reg(serial, UART_IER, 0);
 142         /* disable DMA */
 143         ark3116_write_reg(serial, UART_FCR, 0);
 144         /* handshake control */
 145         priv->hcr = 0;
 146         ark3116_write_reg(serial, 0x8     , 0);
 147         /* modem control */
 148         priv->mcr = 0;
 149         ark3116_write_reg(serial, UART_MCR, 0);
 150
 151         if (!(priv->irda)) {
 152                 ark3116_write_reg(serial, 0xb , 0);
 153         } else {
 154                 ark3116_write_reg(serial, 0xb , 1);
 155                 ark3116_write_reg(serial, 0xc , 0);
 156                 ark3116_write_reg(serial, 0xd , 0x41);
 157                 ark3116_write_reg(serial, 0xa , 1);
 158         }
 159
 160         /* setup baudrate */
 161         ark3116_write_reg(serial, UART_LCR, UART_LCR_DLAB);
 162
 163         /* setup for 9600 8N1 */
 164         priv->quot = calc_divisor(9600);
 165         ark3116_write_reg(serial, UART_DLL, priv->quot & 0xff);
 166         ark3116_write_reg(serial, UART_DLM, (priv->quot>>8) & 0xff);
 167
 168         priv->lcr = UART_LCR_WLEN8;
 169         ark3116_write_reg(serial, UART_LCR, UART_LCR_WLEN8);
 170
 171         ark3116_write_reg(serial, 0xe, 0);
 172
 173         if (priv->irda)
 174                 ark3116_write_reg(serial, 0x9, 0);
 175
 176         dev_info(&port->dev, "using %s mode\n", priv->irda ? "IrDA" : "RS232");
 177
 178         return 0;
 179 }
 180
 181 static int ark3116_port_remove(struct usb_serial_port *port)
 182 {
 183         struct ark3116_private *priv = usb_get_serial_port_data(port);
 184
 185         /* device is closed, so URBs and DMA should be down */
 186         mutex_destroy(&priv->hw_lock);
 187         kfree(priv);
 188
 189         return 0;
 190 }
 191
 192 static void ark3116_set_termios(struct tty_struct *tty,
 193                                 struct usb_serial_port *port,
 194                                 struct ktermios *old_termios)
 195 {
 196         struct usb_serial *serial = port->serial;
 197         struct ark3116_private *priv = usb_get_serial_port_data(port);
 198         struct ktermios *termios = &tty->termios;
 199         unsigned int cflag = termios->c_cflag;
 200         int bps = tty_get_baud_rate(tty);
 201         int quot;
 202         __u8 lcr, hcr, eval;
 203
 204         /* set data bit count */
 205         switch (cflag & CSIZE) {
 206         case CS5:
 207                 lcr = UART_LCR_WLEN5;
 208                 break;
 209         case CS6:
 210                 lcr = UART_LCR_WLEN6;
 211                 break;
 212         case CS7:
 213                 lcr = UART_LCR_WLEN7;
 214                 break;
 215         default:
 216         case CS8:
 217                 lcr = UART_LCR_WLEN8;
 218                 break;
 219         }
 220         if (cflag & CSTOPB)
 221                 lcr |= UART_LCR_STOP;
 222         if (cflag & PARENB)
 223                 lcr |= UART_LCR_PARITY;
 224         if (!(cflag & PARODD))
 225                 lcr |= UART_LCR_EPAR;
 226 #ifdef CMSPAR
 227         if (cflag & CMSPAR)
 228                 lcr |= UART_LCR_SPAR;
 229 #endif
 230         /* handshake control */
 231         hcr = (cflag & CRTSCTS) ? 0x03 : 0x00;
 232
 233         /* calc baudrate */
 234         dev_dbg(&port->dev, "%s - setting bps to %d\n", __func__, bps);
 235         eval = 0;
 236         switch (bps) {
 237         case 0:
 238                 quot = calc_divisor(9600);
 239                 break;
 240         default:
 241                 if ((bps < 75) || (bps > 3000000))
 242                         bps = 9600;
 243                 quot = calc_divisor(bps);
 244                 break;
 245         case 460800:
 246                 eval = 1;
 247                 quot = calc_divisor(bps);
 248                 break;
 249         case 921600:
 250                 eval = 2;
 251                 quot = calc_divisor(bps);
 252                 break;
 253         }
 254
 255         /* Update state: synchronize */
 256         mutex_lock(&priv->hw_lock);
 257
 258         /* keep old LCR_SBC bit */
 259         lcr |= (priv->lcr & UART_LCR_SBC);
 260
 261         dev_dbg(&port->dev, "%s - setting hcr:0x%02x,lcr:0x%02x,quot:%d\n",
 262                 __func__, hcr, lcr, quot);
 263
 264         /* handshake control */
 265         if (priv->hcr != hcr) {
 266                 priv->hcr = hcr;
 267                 ark3116_write_reg(serial, 0x8, hcr);
 268         }
 269
 270         /* baudrate */
 271         if (priv->quot != quot) {
 272                 priv->quot = quot;
 273                 priv->lcr = lcr; /* need to write lcr anyway */
 274
 275                 /* disable DMA since transmit/receive is
 276                  * shadowed by UART_DLL
 277                  */
 278                 ark3116_write_reg(serial, UART_FCR, 0);
 279
 280                 ark3116_write_reg(serial, UART_LCR,
 281                                   lcr|UART_LCR_DLAB);
 282                 ark3116_write_reg(serial, UART_DLL, quot & 0xff);
 283                 ark3116_write_reg(serial, UART_DLM, (quot>>8) & 0xff);
 284
 285                 /* restore lcr */
 286                 ark3116_write_reg(serial, UART_LCR, lcr);
 287                 /* magic baudrate thingy: not sure what it does,
 288                  * but windows does this as well.
 289                  */
 290                 ark3116_write_reg(serial, 0xe, eval);
 291
 292                 /* enable DMA */
 293                 ark3116_write_reg(serial, UART_FCR, UART_FCR_DMA_SELECT);
 294         } else if (priv->lcr != lcr) {
 295                 priv->lcr = lcr;
 296                 ark3116_write_reg(serial, UART_LCR, lcr);
 297         }
 298
 299         mutex_unlock(&priv->hw_lock);
 300
 301         /* check for software flow control */
 302         if (I_IXOFF(tty) || I_IXON(tty)) {
 303                 dev_warn(&port->dev,
 304                                 "software flow control not implemented\n");
 305         }
 306
 307         /* Don't rewrite B0 */
 308         if (tty_termios_baud_rate(termios))
 309                 tty_termios_encode_baud_rate(termios, bps, bps);
 310 }
 311
 312 static void ark3116_close(struct usb_serial_port *port)
 313 {
 314         struct usb_serial *serial = port->serial;
 315
 316         /* disable DMA */
 317         ark3116_write_reg(serial, UART_FCR, 0);
 318
 319         /* deactivate interrupts */
 320         ark3116_write_reg(serial, UART_IER, 0);
 321
 322         usb_serial_generic_close(port);
 323
 324         usb_kill_urb(port->interrupt_in_urb);
 325 }
 326
 327 static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port)
 328 {
 329         struct ark3116_private *priv = usb_get_serial_port_data(port);
 330         struct usb_serial *serial = port->serial;
 331         unsigned char *buf;
 332         int result;
 333
 334         buf = kmalloc(1, GFP_KERNEL);
 335         if (buf == NULL)
 336                 return -ENOMEM;
 337
 338         result = usb_serial_generic_open(tty, port);
 339         if (result) {
 340                 dev_dbg(&port->dev,
 341                         "%s - usb_serial_generic_open failed: %d\n",
 342                         __func__, result);
 343                 goto err_free;
 344         }
 345
 346         /* remove any data still left: also clears error state */
 347         ark3116_read_reg(serial, UART_RX, buf);
 348
 349         /* read modem status */
 350         result = ark3116_read_reg(serial, UART_MSR, buf);
 351         if (result)
 352                 goto err_close;
 353         priv->msr = *buf;
 354
 355         /* read line status */
 356         result = ark3116_read_reg(serial, UART_LSR, buf);
 357         if (result)
 358                 goto err_close;
 359         priv->lsr = *buf;
 360
 361         result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 362         if (result) {
 363                 dev_err(&port->dev, "submit irq_in urb failed %d\n",
 364                         result);
 365                 goto err_close;
 366         }
 367
 368         /* activate interrupts */
 369         ark3116_write_reg(port->serial, UART_IER, UART_IER_MSI|UART_IER_RLSI);
 370
 371         /* enable DMA */
 372         ark3116_write_reg(port->serial, UART_FCR, UART_FCR_DMA_SELECT);
 373
 374         /* setup termios */
 375         if (tty)
 376                 ark3116_set_termios(tty, port, NULL);
 377
 378         kfree(buf);
 379
 380         return 0;
 381
 382 err_close:
 383         usb_serial_generic_close(port);
 384 err_free:
 385         kfree(buf);
 386
 387         return result;
 388 }
 389
 390 static int ark3116_get_serial_info(struct tty_struct *tty,
 391                         struct serial_struct *ss)
 392 {
 393         struct usb_serial_port *port = tty->driver_data;
 394
 395         ss->type = PORT_16654;
 396         ss->line = port->minor;
 397         ss->port = port->port_number;
 398         ss->baud_base = 460800;
 399         return 0;
 400 }
 401
 402 static int ark3116_tiocmget(struct tty_struct *tty)
 403 {
 404         struct usb_serial_port *port = tty->driver_data;
 405         struct ark3116_private *priv = usb_get_serial_port_data(port);
 406         __u32 status;
 407         __u32 ctrl;
 408         unsigned long flags;
 409
 410         mutex_lock(&priv->hw_lock);
 411         ctrl = priv->mcr;
 412         mutex_unlock(&priv->hw_lock);
 413
 414         spin_lock_irqsave(&priv->status_lock, flags);
 415         status = priv->msr;
 416         spin_unlock_irqrestore(&priv->status_lock, flags);
 417
 418         return  (status & UART_MSR_DSR  ? TIOCM_DSR  : 0) |
 419                 (status & UART_MSR_CTS  ? TIOCM_CTS  : 0) |
 420                 (status & UART_MSR_RI   ? TIOCM_RI   : 0) |
 421                 (status & UART_MSR_DCD  ? TIOCM_CD   : 0) |
 422                 (ctrl   & UART_MCR_DTR  ? TIOCM_DTR  : 0) |
 423                 (ctrl   & UART_MCR_RTS  ? TIOCM_RTS  : 0) |
 424                 (ctrl   & UART_MCR_OUT1 ? TIOCM_OUT1 : 0) |
 425                 (ctrl   & UART_MCR_OUT2 ? TIOCM_OUT2 : 0);
 426 }
 427
 428 static int ark3116_tiocmset(struct tty_struct *tty,
 429                         unsigned set, unsigned clr)
 430 {
 431         struct usb_serial_port *port = tty->driver_data;
 432         struct ark3116_private *priv = usb_get_serial_port_data(port);
 433
 434         /* we need to take the mutex here, to make sure that the value
 435          * in priv->mcr is actually the one that is in the hardware
 436          */
 437
 438         mutex_lock(&priv->hw_lock);
 439
 440         if (set & TIOCM_RTS)
 441                 priv->mcr |= UART_MCR_RTS;
 442         if (set & TIOCM_DTR)
 443                 priv->mcr |= UART_MCR_DTR;
 444         if (set & TIOCM_OUT1)
 445                 priv->mcr |= UART_MCR_OUT1;
 446         if (set & TIOCM_OUT2)
 447                 priv->mcr |= UART_MCR_OUT2;
 448         if (clr & TIOCM_RTS)
 449                 priv->mcr &= ~UART_MCR_RTS;
 450         if (clr & TIOCM_DTR)
 451                 priv->mcr &= ~UART_MCR_DTR;
 452         if (clr & TIOCM_OUT1)
 453                 priv->mcr &= ~UART_MCR_OUT1;
 454         if (clr & TIOCM_OUT2)
 455                 priv->mcr &= ~UART_MCR_OUT2;
 456
 457         ark3116_write_reg(port->serial, UART_MCR, priv->mcr);
 458
 459         mutex_unlock(&priv->hw_lock);
 460
 461         return 0;
 462 }
 463
 464 static void ark3116_break_ctl(struct tty_struct *tty, int break_state)
 465 {
 466         struct usb_serial_port *port = tty->driver_data;
 467         struct ark3116_private *priv = usb_get_serial_port_data(port);
 468
 469         /* LCR is also used for other things: protect access */
 470         mutex_lock(&priv->hw_lock);
 471
 472         if (break_state)
 473                 priv->lcr |= UART_LCR_SBC;
 474         else
 475                 priv->lcr &= ~UART_LCR_SBC;
 476
 477         ark3116_write_reg(port->serial, UART_LCR, priv->lcr);
 478
 479         mutex_unlock(&priv->hw_lock);
 480 }
 481
 482 static void ark3116_update_msr(struct usb_serial_port *port, __u8 msr)
 483 {
 484         struct ark3116_private *priv = usb_get_serial_port_data(port);
 485         unsigned long flags;
 486
 487         spin_lock_irqsave(&priv->status_lock, flags);
 488         priv->msr = msr;
 489         spin_unlock_irqrestore(&priv->status_lock, flags);
 490
 491         if (msr & UART_MSR_ANY_DELTA) {
 492                 /* update input line counters */
 493                 if (msr & UART_MSR_DCTS)
 494                         port->icount.cts++;
 495                 if (msr & UART_MSR_DDSR)
 496                         port->icount.dsr++;
 497                 if (msr & UART_MSR_DDCD)
 498                         port->icount.dcd++;
 499                 if (msr & UART_MSR_TERI)
 500                         port->icount.rng++;
 501                 wake_up_interruptible(&port->port.delta_msr_wait);
 502         }
 503 }
 504
 505 static void ark3116_update_lsr(struct usb_serial_port *port, __u8 lsr)
 506 {
 507         struct ark3116_private *priv = usb_get_serial_port_data(port);
 508         unsigned long flags;
 509
 510         spin_lock_irqsave(&priv->status_lock, flags);
 511         /* combine bits */
 512         priv->lsr |= lsr;
 513         spin_unlock_irqrestore(&priv->status_lock, flags);
 514
 515         if (lsr&UART_LSR_BRK_ERROR_BITS) {
 516                 if (lsr & UART_LSR_BI)
 517                         port->icount.brk++;
 518                 if (lsr & UART_LSR_FE)
 519                         port->icount.frame++;
 520                 if (lsr & UART_LSR_PE)
 521                         port->icount.parity++;
 522                 if (lsr & UART_LSR_OE)
 523                         port->icount.overrun++;
 524         }
 525 }
 526
 527 static void ark3116_read_int_callback(struct urb *urb)
 528 {
 529         struct usb_serial_port *port = urb->context;
 530         int status = urb->status;
 531         const __u8 *data = urb->transfer_buffer;
 532         int result;
 533
 534         switch (status) {
 535         case -ECONNRESET:
 536         case -ENOENT:
 537         case -ESHUTDOWN:
 538                 /* this urb is terminated, clean up */
 539                 dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
 540                         __func__, status);
 541                 return;
 542         default:
 543                 dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
 544                         __func__, status);
 545                 break;
 546         case 0: /* success */
 547                 /* discovered this by trail and error... */
 548                 if ((urb->actual_length == 4) && (data[0] == 0xe8)) {
 549                         const __u8 id = data[1]&UART_IIR_ID;
 550                         dev_dbg(&port->dev, "%s: iir=%02x\n", __func__, data[1]);
 551                         if (id == UART_IIR_MSI) {
 552                                 dev_dbg(&port->dev, "%s: msr=%02x\n",
 553                                         __func__, data[3]);
 554                                 ark3116_update_msr(port, data[3]);
 555                                 break;
 556                         } else if (id == UART_IIR_RLSI) {
 557                                 dev_dbg(&port->dev, "%s: lsr=%02x\n",
 558                                         __func__, data[2]);
 559                                 ark3116_update_lsr(port, data[2]);
 560                                 break;
 561                         }
 562                 }
 563                 /*
 564                  * Not sure what this data meant...
 565                  */
 566                 usb_serial_debug_data(&port->dev, __func__,
 567                                       urb->actual_length,
 568                                       urb->transfer_buffer);
 569                 break;
 570         }
 571
 572         result = usb_submit_urb(urb, GFP_ATOMIC);
 573         if (result)
 574                 dev_err(&port->dev, "failed to resubmit interrupt urb: %d\n",
 575                         result);
 576 }
 577
 578
 579 /* Data comes in via the bulk (data) URB, errors/interrupts via the int URB.
 580  * This means that we cannot be sure which data byte has an associated error
 581  * condition, so we report an error for all data in the next bulk read.
 582  *
 583  * Actually, there might even be a window between the bulk data leaving the
 584  * ark and reading/resetting the lsr in the read_bulk_callback where an
 585  * interrupt for the next data block could come in.
 586  * Without somekind of ordering on the ark, we would have to report the
 587  * error for the next block of data as well...
 588  * For now, let's pretend this can't happen.
 589  */
 590 static void ark3116_process_read_urb(struct urb *urb)
 591 {
 592         struct usb_serial_port *port = urb->context;
 593         struct ark3116_private *priv = usb_get_serial_port_data(port);
 594         unsigned char *data = urb->transfer_buffer;
 595         char tty_flag = TTY_NORMAL;
 596         unsigned long flags;
 597         __u32 lsr;
 598
 599         /* update line status */
 600         spin_lock_irqsave(&priv->status_lock, flags);
 601         lsr = priv->lsr;
 602         priv->lsr &= ~UART_LSR_BRK_ERROR_BITS;
 603         spin_unlock_irqrestore(&priv->status_lock, flags);
 604
 605         if (!urb->actual_length)
 606                 return;
 607
 608         if (lsr & UART_LSR_BRK_ERROR_BITS) {
 609                 if (lsr & UART_LSR_BI)
 610                         tty_flag = TTY_BREAK;
 611                 else if (lsr & UART_LSR_PE)
 612                         tty_flag = TTY_PARITY;
 613                 else if (lsr & UART_LSR_FE)
 614                         tty_flag = TTY_FRAME;
 615
 616                 /* overrun is special, not associated with a char */
 617                 if (lsr & UART_LSR_OE)
 618                         tty_insert_flip_char(&port->port, 0, TTY_OVERRUN);
 619         }
 620         tty_insert_flip_string_fixed_flag(&port->port, data, tty_flag,
 621                                                         urb->actual_length);
 622         tty_flip_buffer_push(&port->port);
 623 }
 624
 625 static struct usb_serial_driver ark3116_device = {
 626         .driver = {
 627                 .owner =        THIS_MODULE,
 628                 .name =         "ark3116",
 629         },
 630         .id_table =             id_table,
 631         .num_ports =            1,
 632         .num_bulk_in =          1,
 633         .num_bulk_out =         1,
 634         .num_interrupt_in =     1,
 635         .port_probe =           ark3116_port_probe,
 636         .port_remove =          ark3116_port_remove,
 637         .set_termios =          ark3116_set_termios,
 638         .get_serial =           ark3116_get_serial_info,
 639         .tiocmget =             ark3116_tiocmget,
 640         .tiocmset =             ark3116_tiocmset,
 641         .tiocmiwait =           usb_serial_generic_tiocmiwait,
 642         .get_icount =           usb_serial_generic_get_icount,
 643         .open =                 ark3116_open,
 644         .close =                ark3116_close,
 645         .break_ctl =            ark3116_break_ctl,
 646         .read_int_callback =    ark3116_read_int_callback,
 647         .process_read_urb =     ark3116_process_read_urb,
 648 };
 649
 650 static struct usb_serial_driver * const serial_drivers[] = {
 651         &ark3116_device, NULL
 652 };
 653
 654 module_usb_serial_driver(serial_drivers, id_table);
 655
 656 MODULE_LICENSE("GPL");
 657
 658 MODULE_AUTHOR(DRIVER_AUTHOR);
 659 MODULE_DESCRIPTION(DRIVER_DESC);
 660
 661 /*
 662  * The following describes what I learned from studying the old
 663  * ark3116.c driver, disassembling the windows driver, and some lucky
 664  * guesses. Since I do not have any datasheet or other
 665  * documentation, inaccuracies are almost guaranteed.
 666  *
 667  * Some specs for the ARK3116 can be found here:
 668  * http://web.archive.org/web/20060318000438/
 669  *   www.arkmicro.com/en/products/view.php?id=10
 670  * On that page, 2 GPIO pins are mentioned: I assume these are the
 671  * OUT1 and OUT2 pins of the UART, so I added support for those
 672  * through the MCR. Since the pins are not available on my hardware,
 673  * I could not verify this.
 674  * Also, it states there is "on-chip hardware flow control". I have
 675  * discovered how to enable that. Unfortunately, I do not know how to
 676  * enable XON/XOFF (software) flow control, which would need support
 677  * from the chip as well to work. Because of the wording on the web
 678  * page there is a real possibility the chip simply does not support
 679  * software flow control.
 680  *
 681  * I got my ark3116 as part of a mobile phone adapter cable. On the
 682  * PCB, the following numbered contacts are present:
 683  *
 684  *  1:- +5V
 685  *  2:o DTR
 686  *  3:i RX
 687  *  4:i DCD
 688  *  5:o RTS
 689  *  6:o TX
 690  *  7:i RI
 691  *  8:i DSR
 692  * 10:- 0V
 693  * 11:i CTS
 694  *
 695  * On my chip, all signals seem to be 3.3V, but 5V tolerant. But that
 696  * may be different for the one you have ;-).
 697  *
 698  * The windows driver limits the registers to 0-F, so I assume there
 699  * are actually 16 present on the device.
 700  *
 701  * On an UART interrupt, 4 bytes of data come in on the interrupt
 702  * endpoint. The bytes are 0xe8 IIR LSR MSR.
 703  *
 704  * The baudrate seems to be generated from the 12MHz crystal, using
 705  * 4-times subsampling. So quot=12e6/(4*baud). Also see description
 706  * of register E.
 707  *
 708  * Registers 0-7:
 709  * These seem to be the same as for a regular 16450. The FCR is set
 710  * to UART_FCR_DMA_SELECT (0x8), I guess to enable transfers between
 711  * the UART and the USB bridge/DMA engine.
 712  *
 713  * Register 8:
 714  * By trial and error, I found out that bit 0 enables hardware CTS,
 715  * stopping TX when CTS is +5V. Bit 1 does the same for RTS, making
 716  * RTS +5V when the 3116 cannot transfer the data to the USB bus
 717  * (verified by disabling the reading URB). Note that as far as I can
 718  * tell, the windows driver does NOT use this, so there might be some
 719  * hardware bug or something.
 720  *
 721  * According to a patch provided here
 722  * (http://lkml.org/lkml/2009/7/26/56), the ARK3116 can also be used
 723  * as an IrDA dongle. Since I do not have such a thing, I could not
 724  * investigate that aspect. However, I can speculate ;-).
 725  *
 726  * - IrDA encodes data differently than RS232. Most likely, one of
 727  *   the bits in registers 9..E enables the IR ENDEC (encoder/decoder).
 728  * - Depending on the IR transceiver, the input and output need to be
 729  *   inverted, so there are probably bits for that as well.
 730  * - IrDA is half-duplex, so there should be a bit for selecting that.
 731  *
 732  * This still leaves at least two registers unaccounted for. Perhaps
 733  * The chip can do XON/XOFF or CRC in HW?
 734  *
 735  * Register 9:
 736  * Set to 0x00 for IrDA, when the baudrate is initialised.
 737  *
 738  * Register A:
 739  * Set to 0x01 for IrDA, at init.
 740  *
 741  * Register B:
 742  * Set to 0x01 for IrDA, 0x00 for RS232, at init.
 743  *
 744  * Register C:
 745  * Set to 00 for IrDA, at init.
 746  *
 747  * Register D:
 748  * Set to 0x41 for IrDA, at init.
 749  *
 750  * Register E:
 751  * Somekind of baudrate override. The windows driver seems to set
 752  * this to 0x00 for normal baudrates, 0x01 for 460800, 0x02 for 921600.
 753  * Since 460800 and 921600 cannot be obtained by dividing 3MHz by an integer,
 754  * it could be somekind of subdivisor thingy.
 755  * However,it does not seem to do anything: selecting 921600 (divisor 3,
 756  * reg E=2), still gets 1 MHz. I also checked if registers 9, C or F would
 757  * work, but they don't.
 758  *
 759  * Register F: unknown
 760  */