2 * Silicon Laboratories CP2101/CP2102 USB to RS232 serial adaptor driver
4 * Copyright (C) 2005 Craig Shelley (craig@microtron.org.uk)
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License version
8 * 2 as published by the Free Software Foundation.
10 * Support to set flow control line levels using TIOCMGET and TIOCMSET
11 * thanks to Karl Hiramoto karl@hiramoto.org. RTSCTS hardware flow
12 * control thanks to Munir Nassar nassarmu@real-time.com
15 * Buffers are not flushed when the port is opened.
16 * Multiple calls to write() may fail with "Resource temporarily unavailable"
20 #include <linux/kernel.h>
21 #include <linux/errno.h>
22 #include <linux/slab.h>
23 #include <linux/tty.h>
24 #include <linux/tty_flip.h>
25 #include <linux/module.h>
26 #include <linux/moduleparam.h>
27 #include <linux/usb.h>
28 #include <asm/uaccess.h>
29 #include <linux/usb/serial.h>
34 #define DRIVER_VERSION "v0.07"
35 #define DRIVER_DESC "Silicon Labs CP2101/CP2102 RS232 serial adaptor driver"
40 static int cp2101_open(struct usb_serial_port*, struct file*);
41 static void cp2101_cleanup(struct usb_serial_port*);
42 static void cp2101_close(struct usb_serial_port*, struct file*);
43 static void cp2101_get_termios(struct usb_serial_port*);
44 static void cp2101_set_termios(struct usb_serial_port*, struct ktermios*);
45 static int cp2101_tiocmget (struct usb_serial_port *, struct file *);
46 static int cp2101_tiocmset (struct usb_serial_port *, struct file *,
47 unsigned int, unsigned int);
48 static void cp2101_break_ctl(struct usb_serial_port*, int);
49 static int cp2101_startup (struct usb_serial *);
50 static void cp2101_shutdown(struct usb_serial*);
55 static struct usb_device_id id_table [] = {
56 { USB_DEVICE(0x0489, 0xE000) }, /* Pirelli Broadband S.p.A, DP-L10 SIP/GSM Mobile */
57 { USB_DEVICE(0x08e6, 0x5501) }, /* Gemalto Prox-PU/CU contactless smartcard reader */
58 { USB_DEVICE(0x0FCF, 0x1003) }, /* Dynastream ANT development board */
59 { USB_DEVICE(0x0FCF, 0x1004) }, /* Dynastream ANT2USB */
60 { USB_DEVICE(0x0FCF, 0x1006) }, /* Dynastream ANT development board */
61 { USB_DEVICE(0x10A6, 0xAA26) }, /* Knock-off DCU-11 cable */
62 { USB_DEVICE(0x10AB, 0x10C5) }, /* Siemens MC60 Cable */
63 { USB_DEVICE(0x10B5, 0xAC70) }, /* Nokia CA-42 USB */
64 { USB_DEVICE(0x10C4, 0x800A) }, /* SPORTident BSM7-D-USB main station */
65 { USB_DEVICE(0x10C4, 0x803B) }, /* Pololu USB-serial converter */
66 { USB_DEVICE(0x10C4, 0x8053) }, /* Enfora EDG1228 */
67 { USB_DEVICE(0x10C4, 0x8066) }, /* Argussoft In-System Programmer */
68 { USB_DEVICE(0x10C4, 0x807A) }, /* Crumb128 board */
69 { USB_DEVICE(0x10C4, 0x80CA) }, /* Degree Controls Inc */
70 { USB_DEVICE(0x10C4, 0x80DD) }, /* Tracient RFID */
71 { USB_DEVICE(0x10C4, 0x80F6) }, /* Suunto sports instrument */
72 { USB_DEVICE(0x10C4, 0x813D) }, /* Burnside Telecom Deskmobile */
73 { USB_DEVICE(0x10C4, 0x814A) }, /* West Mountain Radio RIGblaster P&P */
74 { USB_DEVICE(0x10C4, 0x814B) }, /* West Mountain Radio RIGtalk */
75 { USB_DEVICE(0x10C4, 0x815E) }, /* Helicomm IP-Link 1220-DVM */
76 { USB_DEVICE(0x10C4, 0x81A6) }, /* ThinkOptics WavIt */
77 { USB_DEVICE(0x10C4, 0x81AC) }, /* MSD Dash Hawk */
78 { USB_DEVICE(0x10C4, 0x81C8) }, /* Lipowsky Industrie Elektronik GmbH, Baby-JTAG */
79 { USB_DEVICE(0x10C4, 0x81E2) }, /* Lipowsky Industrie Elektronik GmbH, Baby-LIN */
80 { USB_DEVICE(0x10C4, 0x81E7) }, /* Aerocomm Radio */
81 { USB_DEVICE(0x10C4, 0x8218) }, /* Lipowsky Industrie Elektronik GmbH, HARP-1 */
82 { USB_DEVICE(0x10c4, 0x8293) }, /* Telegesys ETRX2USB */
83 { USB_DEVICE(0x10C4, 0xEA60) }, /* Silicon Labs factory default */
84 { USB_DEVICE(0x10C4, 0xEA61) }, /* Silicon Labs factory default */
85 { USB_DEVICE(0x10C4, 0xF001) }, /* Elan Digital Systems USBscope50 */
86 { USB_DEVICE(0x10C4, 0xF002) }, /* Elan Digital Systems USBwave12 */
87 { USB_DEVICE(0x10C4, 0xF003) }, /* Elan Digital Systems USBpulse100 */
88 { USB_DEVICE(0x10C4, 0xF004) }, /* Elan Digital Systems USBcount50 */
89 { USB_DEVICE(0x10C5, 0xEA61) }, /* Silicon Labs MobiData GPRS USB Modem */
90 { USB_DEVICE(0x13AD, 0x9999) }, /* Baltech card reader */
91 { USB_DEVICE(0x166A, 0x0303) }, /* Clipsal 5500PCU C-Bus USB interface */
92 { USB_DEVICE(0x16D6, 0x0001) }, /* Jablotron serial interface */
93 { } /* Terminating Entry */
96 MODULE_DEVICE_TABLE (usb, id_table);
98 static struct usb_driver cp2101_driver = {
100 .probe = usb_serial_probe,
101 .disconnect = usb_serial_disconnect,
102 .id_table = id_table,
106 static struct usb_serial_driver cp2101_device = {
108 .owner = THIS_MODULE,
111 .usb_driver = &cp2101_driver,
112 .id_table = id_table,
115 .close = cp2101_close,
116 .break_ctl = cp2101_break_ctl,
117 .set_termios = cp2101_set_termios,
118 .tiocmget = cp2101_tiocmget,
119 .tiocmset = cp2101_tiocmset,
120 .attach = cp2101_startup,
121 .shutdown = cp2101_shutdown,
124 /* Config request types */
125 #define REQTYPE_HOST_TO_DEVICE 0x41
126 #define REQTYPE_DEVICE_TO_HOST 0xc1
128 /* Config SET requests. To GET, add 1 to the request number */
129 #define CP2101_UART 0x00 /* Enable / Disable */
130 #define CP2101_BAUDRATE 0x01 /* (BAUD_RATE_GEN_FREQ / baudrate) */
131 #define CP2101_BITS 0x03 /* 0x(0)(databits)(parity)(stopbits) */
132 #define CP2101_BREAK 0x05 /* On / Off */
133 #define CP2101_CONTROL 0x07 /* Flow control line states */
134 #define CP2101_MODEMCTL 0x13 /* Modem controls */
135 #define CP2101_CONFIG_6 0x19 /* 6 bytes of config data ??? */
138 #define UART_ENABLE 0x0001
139 #define UART_DISABLE 0x0000
141 /* CP2101_BAUDRATE */
142 #define BAUD_RATE_GEN_FREQ 0x384000
145 #define BITS_DATA_MASK 0X0f00
146 #define BITS_DATA_5 0X0500
147 #define BITS_DATA_6 0X0600
148 #define BITS_DATA_7 0X0700
149 #define BITS_DATA_8 0X0800
150 #define BITS_DATA_9 0X0900
152 #define BITS_PARITY_MASK 0x00f0
153 #define BITS_PARITY_NONE 0x0000
154 #define BITS_PARITY_ODD 0x0010
155 #define BITS_PARITY_EVEN 0x0020
156 #define BITS_PARITY_MARK 0x0030
157 #define BITS_PARITY_SPACE 0x0040
159 #define BITS_STOP_MASK 0x000f
160 #define BITS_STOP_1 0x0000
161 #define BITS_STOP_1_5 0x0001
162 #define BITS_STOP_2 0x0002
165 #define BREAK_ON 0x0000
166 #define BREAK_OFF 0x0001
169 #define CONTROL_DTR 0x0001
170 #define CONTROL_RTS 0x0002
171 #define CONTROL_CTS 0x0010
172 #define CONTROL_DSR 0x0020
173 #define CONTROL_RING 0x0040
174 #define CONTROL_DCD 0x0080
175 #define CONTROL_WRITE_DTR 0x0100
176 #define CONTROL_WRITE_RTS 0x0200
180 * Reads from the CP2101 configuration registers
181 * 'size' is specified in bytes.
182 * 'data' is a pointer to a pre-allocated array of integers large
183 * enough to hold 'size' bytes (with 4 bytes to each integer)
185 static int cp2101_get_config(struct usb_serial_port* port, u8 request,
186 unsigned int *data, int size)
188 struct usb_serial *serial = port->serial;
190 int result, i, length;
192 /* Number of integers required to contain the array */
193 length = (((size - 1) | 3) + 1)/4;
195 buf = kcalloc(length, sizeof(__le32), GFP_KERNEL);
197 dev_err(&port->dev, "%s - out of memory.\n", __func__);
201 /* For get requests, the request number must be incremented */
204 /* Issue the request, attempting to read 'size' bytes */
205 result = usb_control_msg (serial->dev,usb_rcvctrlpipe (serial->dev, 0),
206 request, REQTYPE_DEVICE_TO_HOST, 0x0000,
209 /* Convert data into an array of integers */
210 for (i=0; i<length; i++)
211 data[i] = le32_to_cpu(buf[i]);
215 if (result != size) {
216 dev_err(&port->dev, "%s - Unable to send config request, "
217 "request=0x%x size=%d result=%d\n",
218 __func__, request, size, result);
227 * Writes to the CP2101 configuration registers
228 * Values less than 16 bits wide are sent directly
229 * 'size' is specified in bytes.
231 static int cp2101_set_config(struct usb_serial_port* port, u8 request,
232 unsigned int *data, int size)
234 struct usb_serial *serial = port->serial;
236 int result, i, length;
238 /* Number of integers required to contain the array */
239 length = (((size - 1) | 3) + 1)/4;
241 buf = kmalloc(length * sizeof(__le32), GFP_KERNEL);
243 dev_err(&port->dev, "%s - out of memory.\n",
248 /* Array of integers into bytes */
249 for (i = 0; i < length; i++)
250 buf[i] = cpu_to_le32(data[i]);
253 result = usb_control_msg (serial->dev,
254 usb_sndctrlpipe(serial->dev, 0),
255 request, REQTYPE_HOST_TO_DEVICE, 0x0000,
258 result = usb_control_msg (serial->dev,
259 usb_sndctrlpipe(serial->dev, 0),
260 request, REQTYPE_HOST_TO_DEVICE, data[0],
266 if ((size > 2 && result != size) || result < 0) {
267 dev_err(&port->dev, "%s - Unable to send request, "
268 "request=0x%x size=%d result=%d\n",
269 __func__, request, size, result);
273 /* Single data value */
274 result = usb_control_msg (serial->dev,
275 usb_sndctrlpipe(serial->dev, 0),
276 request, REQTYPE_HOST_TO_DEVICE, data[0],
282 * cp2101_set_config_single
283 * Convenience function for calling cp2101_set_config on single data values
284 * without requiring an integer pointer
286 static inline int cp2101_set_config_single(struct usb_serial_port* port,
287 u8 request, unsigned int data)
289 return cp2101_set_config(port, request, &data, 2);
292 static int cp2101_open (struct usb_serial_port *port, struct file *filp)
294 struct usb_serial *serial = port->serial;
297 dbg("%s - port %d", __func__, port->number);
299 if (cp2101_set_config_single(port, CP2101_UART, UART_ENABLE)) {
300 dev_err(&port->dev, "%s - Unable to enable UART\n",
305 /* Start reading from the device */
306 usb_fill_bulk_urb (port->read_urb, serial->dev,
307 usb_rcvbulkpipe(serial->dev,
308 port->bulk_in_endpointAddress),
309 port->read_urb->transfer_buffer,
310 port->read_urb->transfer_buffer_length,
311 serial->type->read_bulk_callback,
313 result = usb_submit_urb(port->read_urb, GFP_KERNEL);
315 dev_err(&port->dev, "%s - failed resubmitting read urb, "
316 "error %d\n", __func__, result);
320 /* Configure the termios structure */
321 cp2101_get_termios(port);
323 /* Set the DTR and RTS pins low */
324 cp2101_tiocmset(port, NULL, TIOCM_DTR | TIOCM_RTS, 0);
329 static void cp2101_cleanup (struct usb_serial_port *port)
331 struct usb_serial *serial = port->serial;
333 dbg("%s - port %d", __func__, port->number);
336 /* shutdown any bulk reads that might be going on */
337 if (serial->num_bulk_out)
338 usb_kill_urb(port->write_urb);
339 if (serial->num_bulk_in)
340 usb_kill_urb(port->read_urb);
344 static void cp2101_close (struct usb_serial_port *port, struct file * filp)
346 dbg("%s - port %d", __func__, port->number);
348 /* shutdown our urbs */
349 dbg("%s - shutting down urbs", __func__);
350 usb_kill_urb(port->write_urb);
351 usb_kill_urb(port->read_urb);
353 mutex_lock(&port->serial->disc_mutex);
354 if (!port->serial->disconnected)
355 cp2101_set_config_single(port, CP2101_UART, UART_DISABLE);
356 mutex_unlock(&port->serial->disc_mutex);
361 * Reads the baud rate, data bits, parity, stop bits and flow control mode
362 * from the device, corrects any unsupported values, and configures the
363 * termios structure to reflect the state of the device
365 static void cp2101_get_termios (struct usb_serial_port *port)
367 unsigned int cflag, modem_ctl[4];
371 dbg("%s - port %d", __func__, port->number);
373 if (!port->tty || !port->tty->termios) {
374 dbg("%s - no tty structures", __func__);
378 cp2101_get_config(port, CP2101_BAUDRATE, &baud, 2);
379 /* Convert to baudrate */
381 baud = BAUD_RATE_GEN_FREQ / baud;
383 dbg("%s - baud rate = %d", __func__, baud);
385 tty_encode_baud_rate(port->tty, baud, baud);
386 cflag = port->tty->termios->c_cflag;
388 cp2101_get_config(port, CP2101_BITS, &bits, 2);
390 switch(bits & BITS_DATA_MASK) {
392 dbg("%s - data bits = 5", __func__);
396 dbg("%s - data bits = 6", __func__);
400 dbg("%s - data bits = 7", __func__);
404 dbg("%s - data bits = 8", __func__);
408 dbg("%s - data bits = 9 (not supported, "
409 "using 8 data bits)", __func__);
411 bits &= ~BITS_DATA_MASK;
413 cp2101_set_config(port, CP2101_BITS, &bits, 2);
416 dbg("%s - Unknown number of data bits, "
417 "using 8", __func__);
419 bits &= ~BITS_DATA_MASK;
421 cp2101_set_config(port, CP2101_BITS, &bits, 2);
425 switch(bits & BITS_PARITY_MASK) {
426 case BITS_PARITY_NONE:
427 dbg("%s - parity = NONE", __func__);
430 case BITS_PARITY_ODD:
431 dbg("%s - parity = ODD", __func__);
432 cflag |= (PARENB|PARODD);
434 case BITS_PARITY_EVEN:
435 dbg("%s - parity = EVEN", __func__);
439 case BITS_PARITY_MARK:
440 dbg("%s - parity = MARK (not supported, "
441 "disabling parity)", __func__);
443 bits &= ~BITS_PARITY_MASK;
444 cp2101_set_config(port, CP2101_BITS, &bits, 2);
446 case BITS_PARITY_SPACE:
447 dbg("%s - parity = SPACE (not supported, "
448 "disabling parity)", __func__);
450 bits &= ~BITS_PARITY_MASK;
451 cp2101_set_config(port, CP2101_BITS, &bits, 2);
454 dbg("%s - Unknown parity mode, "
455 "disabling parity", __func__);
457 bits &= ~BITS_PARITY_MASK;
458 cp2101_set_config(port, CP2101_BITS, &bits, 2);
463 switch(bits & BITS_STOP_MASK) {
465 dbg("%s - stop bits = 1", __func__);
468 dbg("%s - stop bits = 1.5 (not supported, "
469 "using 1 stop bit)", __func__);
470 bits &= ~BITS_STOP_MASK;
471 cp2101_set_config(port, CP2101_BITS, &bits, 2);
474 dbg("%s - stop bits = 2", __func__);
478 dbg("%s - Unknown number of stop bits, "
479 "using 1 stop bit", __func__);
480 bits &= ~BITS_STOP_MASK;
481 cp2101_set_config(port, CP2101_BITS, &bits, 2);
485 cp2101_get_config(port, CP2101_MODEMCTL, modem_ctl, 16);
486 if (modem_ctl[0] & 0x0008) {
487 dbg("%s - flow control = CRTSCTS", __func__);
490 dbg("%s - flow control = NONE", __func__);
494 port->tty->termios->c_cflag = cflag;
497 static void cp2101_set_termios (struct usb_serial_port *port,
498 struct ktermios *old_termios)
500 unsigned int cflag, old_cflag;
502 unsigned int modem_ctl[4];
504 dbg("%s - port %d", __func__, port->number);
506 if (!port->tty || !port->tty->termios) {
507 dbg("%s - no tty structures", __func__);
510 port->tty->termios->c_cflag &= ~CMSPAR;
512 cflag = port->tty->termios->c_cflag;
513 old_cflag = old_termios->c_cflag;
514 baud = tty_get_baud_rate(port->tty);
516 /* If the baud rate is to be updated*/
517 if (baud != tty_termios_baud_rate(old_termios)) {
546 dbg("%s - Setting baud rate to %d baud", __func__,
548 if (cp2101_set_config_single(port, CP2101_BAUDRATE,
549 (BAUD_RATE_GEN_FREQ / baud))) {
550 dev_err(&port->dev, "Baud rate requested not "
551 "supported by device\n");
552 baud = tty_termios_baud_rate(old_termios);
556 /* Report back the resulting baud rate */
557 tty_encode_baud_rate(port->tty, baud, baud);
559 /* If the number of data bits is to be updated */
560 if ((cflag & CSIZE) != (old_cflag & CSIZE)) {
561 cp2101_get_config(port, CP2101_BITS, &bits, 2);
562 bits &= ~BITS_DATA_MASK;
563 switch (cflag & CSIZE) {
566 dbg("%s - data bits = 5", __func__);
570 dbg("%s - data bits = 6", __func__);
574 dbg("%s - data bits = 7", __func__);
578 dbg("%s - data bits = 8", __func__);
582 dbg("%s - data bits = 9", __func__);
585 dev_err(&port->dev, "cp2101 driver does not "
586 "support the number of bits requested,"
587 " using 8 bit mode\n");
591 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
592 dev_err(&port->dev, "Number of data bits requested "
593 "not supported by device\n");
596 if ((cflag & (PARENB|PARODD)) != (old_cflag & (PARENB|PARODD))) {
597 cp2101_get_config(port, CP2101_BITS, &bits, 2);
598 bits &= ~BITS_PARITY_MASK;
599 if (cflag & PARENB) {
600 if (cflag & PARODD) {
601 bits |= BITS_PARITY_ODD;
602 dbg("%s - parity = ODD", __func__);
604 bits |= BITS_PARITY_EVEN;
605 dbg("%s - parity = EVEN", __func__);
608 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
609 dev_err(&port->dev, "Parity mode not supported "
613 if ((cflag & CSTOPB) != (old_cflag & CSTOPB)) {
614 cp2101_get_config(port, CP2101_BITS, &bits, 2);
615 bits &= ~BITS_STOP_MASK;
616 if (cflag & CSTOPB) {
618 dbg("%s - stop bits = 2", __func__);
621 dbg("%s - stop bits = 1", __func__);
623 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
624 dev_err(&port->dev, "Number of stop bits requested "
625 "not supported by device\n");
628 if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
629 cp2101_get_config(port, CP2101_MODEMCTL, modem_ctl, 16);
630 dbg("%s - read modem controls = 0x%.4x 0x%.4x 0x%.4x 0x%.4x",
631 __func__, modem_ctl[0], modem_ctl[1],
632 modem_ctl[2], modem_ctl[3]);
634 if (cflag & CRTSCTS) {
635 modem_ctl[0] &= ~0x7B;
636 modem_ctl[0] |= 0x09;
638 dbg("%s - flow control = CRTSCTS", __func__);
640 modem_ctl[0] &= ~0x7B;
641 modem_ctl[0] |= 0x01;
642 modem_ctl[1] |= 0x40;
643 dbg("%s - flow control = NONE", __func__);
646 dbg("%s - write modem controls = 0x%.4x 0x%.4x 0x%.4x 0x%.4x",
647 __func__, modem_ctl[0], modem_ctl[1],
648 modem_ctl[2], modem_ctl[3]);
649 cp2101_set_config(port, CP2101_MODEMCTL, modem_ctl, 16);
654 static int cp2101_tiocmset (struct usb_serial_port *port, struct file *file,
655 unsigned int set, unsigned int clear)
659 dbg("%s - port %d", __func__, port->number);
661 if (set & TIOCM_RTS) {
662 control |= CONTROL_RTS;
663 control |= CONTROL_WRITE_RTS;
665 if (set & TIOCM_DTR) {
666 control |= CONTROL_DTR;
667 control |= CONTROL_WRITE_DTR;
669 if (clear & TIOCM_RTS) {
670 control &= ~CONTROL_RTS;
671 control |= CONTROL_WRITE_RTS;
673 if (clear & TIOCM_DTR) {
674 control &= ~CONTROL_DTR;
675 control |= CONTROL_WRITE_DTR;
678 dbg("%s - control = 0x%.4x", __func__, control);
680 return cp2101_set_config(port, CP2101_CONTROL, &control, 2);
684 static int cp2101_tiocmget (struct usb_serial_port *port, struct file *file)
688 dbg("%s - port %d", __func__, port->number);
690 cp2101_get_config(port, CP2101_CONTROL, &control, 1);
692 result = ((control & CONTROL_DTR) ? TIOCM_DTR : 0)
693 |((control & CONTROL_RTS) ? TIOCM_RTS : 0)
694 |((control & CONTROL_CTS) ? TIOCM_CTS : 0)
695 |((control & CONTROL_DSR) ? TIOCM_DSR : 0)
696 |((control & CONTROL_RING)? TIOCM_RI : 0)
697 |((control & CONTROL_DCD) ? TIOCM_CD : 0);
699 dbg("%s - control = 0x%.2x", __func__, control);
704 static void cp2101_break_ctl (struct usb_serial_port *port, int break_state)
708 dbg("%s - port %d", __func__, port->number);
709 if (break_state == 0)
713 dbg("%s - turning break %s", __func__,
714 state==BREAK_OFF ? "off" : "on");
715 cp2101_set_config(port, CP2101_BREAK, &state, 2);
718 static int cp2101_startup (struct usb_serial *serial)
720 /* CP2101 buffers behave strangely unless device is reset */
721 usb_reset_device(serial->dev);
725 static void cp2101_shutdown (struct usb_serial *serial)
731 /* Stop reads and writes on all ports */
732 for (i=0; i < serial->num_ports; ++i) {
733 cp2101_cleanup(serial->port[i]);
737 static int __init cp2101_init (void)
741 retval = usb_serial_register(&cp2101_device);
743 return retval; /* Failed to register */
745 retval = usb_register(&cp2101_driver);
747 /* Failed to register */
748 usb_serial_deregister(&cp2101_device);
753 info(DRIVER_DESC " " DRIVER_VERSION);
757 static void __exit cp2101_exit (void)
759 usb_deregister (&cp2101_driver);
760 usb_serial_deregister (&cp2101_device);
763 module_init(cp2101_init);
764 module_exit(cp2101_exit);
766 MODULE_DESCRIPTION(DRIVER_DESC);
767 MODULE_VERSION(DRIVER_VERSION);
768 MODULE_LICENSE("GPL");
770 module_param(debug, bool, S_IRUGO | S_IWUSR);
771 MODULE_PARM_DESC(debug, "Enable verbose debugging messages");