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 <linux/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 tty_struct *, struct usb_serial_port *,
42 static void cp2101_cleanup(struct usb_serial_port *);
43 static void cp2101_close(struct tty_struct *, struct usb_serial_port *,
45 static void cp2101_get_termios(struct tty_struct *);
46 static void cp2101_set_termios(struct tty_struct *, struct usb_serial_port *,
48 static int cp2101_tiocmget(struct tty_struct *, struct file *);
49 static int cp2101_tiocmset(struct tty_struct *, struct file *,
50 unsigned int, unsigned int);
51 static void cp2101_break_ctl(struct tty_struct *, int);
52 static int cp2101_startup(struct usb_serial *);
53 static void cp2101_shutdown(struct usb_serial *);
58 static struct usb_device_id id_table [] = {
59 { USB_DEVICE(0x0489, 0xE000) }, /* Pirelli Broadband S.p.A, DP-L10 SIP/GSM Mobile */
60 { USB_DEVICE(0x08e6, 0x5501) }, /* Gemalto Prox-PU/CU contactless smartcard reader */
61 { USB_DEVICE(0x0FCF, 0x1003) }, /* Dynastream ANT development board */
62 { USB_DEVICE(0x0FCF, 0x1004) }, /* Dynastream ANT2USB */
63 { USB_DEVICE(0x0FCF, 0x1006) }, /* Dynastream ANT development board */
64 { USB_DEVICE(0x10A6, 0xAA26) }, /* Knock-off DCU-11 cable */
65 { USB_DEVICE(0x10AB, 0x10C5) }, /* Siemens MC60 Cable */
66 { USB_DEVICE(0x10B5, 0xAC70) }, /* Nokia CA-42 USB */
67 { USB_DEVICE(0x10C4, 0x800A) }, /* SPORTident BSM7-D-USB main station */
68 { USB_DEVICE(0x10C4, 0x803B) }, /* Pololu USB-serial converter */
69 { USB_DEVICE(0x10C4, 0x8053) }, /* Enfora EDG1228 */
70 { USB_DEVICE(0x10C4, 0x8066) }, /* Argussoft In-System Programmer */
71 { USB_DEVICE(0x10C4, 0x807A) }, /* Crumb128 board */
72 { USB_DEVICE(0x10C4, 0x80CA) }, /* Degree Controls Inc */
73 { USB_DEVICE(0x10C4, 0x80DD) }, /* Tracient RFID */
74 { USB_DEVICE(0x10C4, 0x80F6) }, /* Suunto sports instrument */
75 { USB_DEVICE(0x10C4, 0x813D) }, /* Burnside Telecom Deskmobile */
76 { USB_DEVICE(0x10C4, 0x814A) }, /* West Mountain Radio RIGblaster P&P */
77 { USB_DEVICE(0x10C4, 0x814B) }, /* West Mountain Radio RIGtalk */
78 { USB_DEVICE(0x10C4, 0x815E) }, /* Helicomm IP-Link 1220-DVM */
79 { USB_DEVICE(0x10C4, 0x81A6) }, /* ThinkOptics WavIt */
80 { USB_DEVICE(0x10C4, 0x81AC) }, /* MSD Dash Hawk */
81 { USB_DEVICE(0x10C4, 0x81C8) }, /* Lipowsky Industrie Elektronik GmbH, Baby-JTAG */
82 { USB_DEVICE(0x10C4, 0x81E2) }, /* Lipowsky Industrie Elektronik GmbH, Baby-LIN */
83 { USB_DEVICE(0x10C4, 0x81E7) }, /* Aerocomm Radio */
84 { USB_DEVICE(0x10C4, 0x8218) }, /* Lipowsky Industrie Elektronik GmbH, HARP-1 */
85 { USB_DEVICE(0x10c4, 0x8293) }, /* Telegesys ETRX2USB */
86 { USB_DEVICE(0x10C4, 0xEA60) }, /* Silicon Labs factory default */
87 { USB_DEVICE(0x10C4, 0xEA61) }, /* Silicon Labs factory default */
88 { USB_DEVICE(0x10C4, 0xF001) }, /* Elan Digital Systems USBscope50 */
89 { USB_DEVICE(0x10C4, 0xF002) }, /* Elan Digital Systems USBwave12 */
90 { USB_DEVICE(0x10C4, 0xF003) }, /* Elan Digital Systems USBpulse100 */
91 { USB_DEVICE(0x10C4, 0xF004) }, /* Elan Digital Systems USBcount50 */
92 { USB_DEVICE(0x10C5, 0xEA61) }, /* Silicon Labs MobiData GPRS USB Modem */
93 { USB_DEVICE(0x13AD, 0x9999) }, /* Baltech card reader */
94 { USB_DEVICE(0x166A, 0x0303) }, /* Clipsal 5500PCU C-Bus USB interface */
95 { USB_DEVICE(0x16D6, 0x0001) }, /* Jablotron serial interface */
96 { } /* Terminating Entry */
99 MODULE_DEVICE_TABLE(usb, id_table);
101 static struct usb_driver cp2101_driver = {
103 .probe = usb_serial_probe,
104 .disconnect = usb_serial_disconnect,
105 .id_table = id_table,
109 static struct usb_serial_driver cp2101_device = {
111 .owner = THIS_MODULE,
114 .usb_driver = &cp2101_driver,
115 .id_table = id_table,
118 .close = cp2101_close,
119 .break_ctl = cp2101_break_ctl,
120 .set_termios = cp2101_set_termios,
121 .tiocmget = cp2101_tiocmget,
122 .tiocmset = cp2101_tiocmset,
123 .attach = cp2101_startup,
124 .shutdown = cp2101_shutdown,
127 /* Config request types */
128 #define REQTYPE_HOST_TO_DEVICE 0x41
129 #define REQTYPE_DEVICE_TO_HOST 0xc1
131 /* Config SET requests. To GET, add 1 to the request number */
132 #define CP2101_UART 0x00 /* Enable / Disable */
133 #define CP2101_BAUDRATE 0x01 /* (BAUD_RATE_GEN_FREQ / baudrate) */
134 #define CP2101_BITS 0x03 /* 0x(0)(databits)(parity)(stopbits) */
135 #define CP2101_BREAK 0x05 /* On / Off */
136 #define CP2101_CONTROL 0x07 /* Flow control line states */
137 #define CP2101_MODEMCTL 0x13 /* Modem controls */
138 #define CP2101_CONFIG_6 0x19 /* 6 bytes of config data ??? */
141 #define UART_ENABLE 0x0001
142 #define UART_DISABLE 0x0000
144 /* CP2101_BAUDRATE */
145 #define BAUD_RATE_GEN_FREQ 0x384000
148 #define BITS_DATA_MASK 0X0f00
149 #define BITS_DATA_5 0X0500
150 #define BITS_DATA_6 0X0600
151 #define BITS_DATA_7 0X0700
152 #define BITS_DATA_8 0X0800
153 #define BITS_DATA_9 0X0900
155 #define BITS_PARITY_MASK 0x00f0
156 #define BITS_PARITY_NONE 0x0000
157 #define BITS_PARITY_ODD 0x0010
158 #define BITS_PARITY_EVEN 0x0020
159 #define BITS_PARITY_MARK 0x0030
160 #define BITS_PARITY_SPACE 0x0040
162 #define BITS_STOP_MASK 0x000f
163 #define BITS_STOP_1 0x0000
164 #define BITS_STOP_1_5 0x0001
165 #define BITS_STOP_2 0x0002
168 #define BREAK_ON 0x0000
169 #define BREAK_OFF 0x0001
172 #define CONTROL_DTR 0x0001
173 #define CONTROL_RTS 0x0002
174 #define CONTROL_CTS 0x0010
175 #define CONTROL_DSR 0x0020
176 #define CONTROL_RING 0x0040
177 #define CONTROL_DCD 0x0080
178 #define CONTROL_WRITE_DTR 0x0100
179 #define CONTROL_WRITE_RTS 0x0200
183 * Reads from the CP2101 configuration registers
184 * 'size' is specified in bytes.
185 * 'data' is a pointer to a pre-allocated array of integers large
186 * enough to hold 'size' bytes (with 4 bytes to each integer)
188 static int cp2101_get_config(struct usb_serial_port *port, u8 request,
189 unsigned int *data, int size)
191 struct usb_serial *serial = port->serial;
193 int result, i, length;
195 /* Number of integers required to contain the array */
196 length = (((size - 1) | 3) + 1)/4;
198 buf = kcalloc(length, sizeof(__le32), GFP_KERNEL);
200 dev_err(&port->dev, "%s - out of memory.\n", __func__);
204 /* For get requests, the request number must be incremented */
207 /* Issue the request, attempting to read 'size' bytes */
208 result = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
209 request, REQTYPE_DEVICE_TO_HOST, 0x0000,
212 /* Convert data into an array of integers */
213 for (i = 0; i < length; i++)
214 data[i] = le32_to_cpu(buf[i]);
218 if (result != size) {
219 dev_err(&port->dev, "%s - Unable to send config request, "
220 "request=0x%x size=%d result=%d\n",
221 __func__, request, size, result);
230 * Writes to the CP2101 configuration registers
231 * Values less than 16 bits wide are sent directly
232 * 'size' is specified in bytes.
234 static int cp2101_set_config(struct usb_serial_port *port, u8 request,
235 unsigned int *data, int size)
237 struct usb_serial *serial = port->serial;
239 int result, i, length;
241 /* Number of integers required to contain the array */
242 length = (((size - 1) | 3) + 1)/4;
244 buf = kmalloc(length * sizeof(__le32), GFP_KERNEL);
246 dev_err(&port->dev, "%s - out of memory.\n",
251 /* Array of integers into bytes */
252 for (i = 0; i < length; i++)
253 buf[i] = cpu_to_le32(data[i]);
256 result = usb_control_msg(serial->dev,
257 usb_sndctrlpipe(serial->dev, 0),
258 request, REQTYPE_HOST_TO_DEVICE, 0x0000,
261 result = usb_control_msg(serial->dev,
262 usb_sndctrlpipe(serial->dev, 0),
263 request, REQTYPE_HOST_TO_DEVICE, data[0],
269 if ((size > 2 && result != size) || result < 0) {
270 dev_err(&port->dev, "%s - Unable to send request, "
271 "request=0x%x size=%d result=%d\n",
272 __func__, request, size, result);
276 /* Single data value */
277 result = usb_control_msg(serial->dev,
278 usb_sndctrlpipe(serial->dev, 0),
279 request, REQTYPE_HOST_TO_DEVICE, data[0],
285 * cp2101_set_config_single
286 * Convenience function for calling cp2101_set_config on single data values
287 * without requiring an integer pointer
289 static inline int cp2101_set_config_single(struct usb_serial_port *port,
290 u8 request, unsigned int data)
292 return cp2101_set_config(port, request, &data, 2);
295 static int cp2101_open(struct tty_struct *tty, struct usb_serial_port *port,
298 struct usb_serial *serial = port->serial;
301 dbg("%s - port %d", __func__, port->number);
303 if (cp2101_set_config_single(port, CP2101_UART, UART_ENABLE)) {
304 dev_err(&port->dev, "%s - Unable to enable UART\n",
309 /* Start reading from the device */
310 usb_fill_bulk_urb(port->read_urb, serial->dev,
311 usb_rcvbulkpipe(serial->dev,
312 port->bulk_in_endpointAddress),
313 port->read_urb->transfer_buffer,
314 port->read_urb->transfer_buffer_length,
315 serial->type->read_bulk_callback,
317 result = usb_submit_urb(port->read_urb, GFP_KERNEL);
319 dev_err(&port->dev, "%s - failed resubmitting read urb, "
320 "error %d\n", __func__, result);
324 /* Configure the termios structure */
325 cp2101_get_termios(tty);
327 /* Set the DTR and RTS pins low */
328 cp2101_tiocmset(tty, NULL, TIOCM_DTR | TIOCM_RTS, 0);
333 static void cp2101_cleanup(struct usb_serial_port *port)
335 struct usb_serial *serial = port->serial;
337 dbg("%s - port %d", __func__, port->number);
340 /* shutdown any bulk reads that might be going on */
341 if (serial->num_bulk_out)
342 usb_kill_urb(port->write_urb);
343 if (serial->num_bulk_in)
344 usb_kill_urb(port->read_urb);
348 static void cp2101_close(struct tty_struct *tty, struct usb_serial_port *port,
351 dbg("%s - port %d", __func__, port->number);
353 /* shutdown our urbs */
354 dbg("%s - shutting down urbs", __func__);
355 usb_kill_urb(port->write_urb);
356 usb_kill_urb(port->read_urb);
358 mutex_lock(&port->serial->disc_mutex);
359 if (!port->serial->disconnected)
360 cp2101_set_config_single(port, CP2101_UART, UART_DISABLE);
361 mutex_unlock(&port->serial->disc_mutex);
366 * Reads the baud rate, data bits, parity, stop bits and flow control mode
367 * from the device, corrects any unsupported values, and configures the
368 * termios structure to reflect the state of the device
370 static void cp2101_get_termios (struct tty_struct *tty)
372 struct usb_serial_port *port = tty->driver_data;
373 unsigned int cflag, modem_ctl[4];
377 dbg("%s - port %d", __func__, port->number);
379 cp2101_get_config(port, CP2101_BAUDRATE, &baud, 2);
380 /* Convert to baudrate */
382 baud = BAUD_RATE_GEN_FREQ / baud;
384 dbg("%s - baud rate = %d", __func__, baud);
386 tty_encode_baud_rate(tty, baud, baud);
387 cflag = tty->termios->c_cflag;
389 cp2101_get_config(port, CP2101_BITS, &bits, 2);
391 switch (bits & BITS_DATA_MASK) {
393 dbg("%s - data bits = 5", __func__);
397 dbg("%s - data bits = 6", __func__);
401 dbg("%s - data bits = 7", __func__);
405 dbg("%s - data bits = 8", __func__);
409 dbg("%s - data bits = 9 (not supported, using 8 data bits)",
412 bits &= ~BITS_DATA_MASK;
414 cp2101_set_config(port, CP2101_BITS, &bits, 2);
417 dbg("%s - Unknown number of data bits, 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, disabling parity)",
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, disabling parity)",
450 bits &= ~BITS_PARITY_MASK;
451 cp2101_set_config(port, CP2101_BITS, &bits, 2);
454 dbg("%s - Unknown parity mode, disabling parity", __func__);
456 bits &= ~BITS_PARITY_MASK;
457 cp2101_set_config(port, CP2101_BITS, &bits, 2);
462 switch (bits & BITS_STOP_MASK) {
464 dbg("%s - stop bits = 1", __func__);
467 dbg("%s - stop bits = 1.5 (not supported, using 1 stop bit)",
469 bits &= ~BITS_STOP_MASK;
470 cp2101_set_config(port, CP2101_BITS, &bits, 2);
473 dbg("%s - stop bits = 2", __func__);
477 dbg("%s - Unknown number of stop bits, using 1 stop bit",
479 bits &= ~BITS_STOP_MASK;
480 cp2101_set_config(port, CP2101_BITS, &bits, 2);
484 cp2101_get_config(port, CP2101_MODEMCTL, modem_ctl, 16);
485 if (modem_ctl[0] & 0x0008) {
486 dbg("%s - flow control = CRTSCTS", __func__);
489 dbg("%s - flow control = NONE", __func__);
493 tty->termios->c_cflag = cflag;
496 static void cp2101_set_termios(struct tty_struct *tty,
497 struct usb_serial_port *port, struct ktermios *old_termios)
499 unsigned int cflag, old_cflag;
500 unsigned int baud = 0, bits;
501 unsigned int modem_ctl[4];
503 dbg("%s - port %d", __func__, port->number);
508 tty->termios->c_cflag &= ~CMSPAR;
509 cflag = tty->termios->c_cflag;
510 old_cflag = old_termios->c_cflag;
511 baud = tty_get_baud_rate(tty);
513 /* If the baud rate is to be updated*/
514 if (baud != tty_termios_baud_rate(old_termios)) {
543 dbg("%s - Setting baud rate to %d baud", __func__,
545 if (cp2101_set_config_single(port, CP2101_BAUDRATE,
546 (BAUD_RATE_GEN_FREQ / baud))) {
547 dev_err(&port->dev, "Baud rate requested not "
548 "supported by device\n");
549 baud = tty_termios_baud_rate(old_termios);
553 /* Report back the resulting baud rate */
554 tty_encode_baud_rate(tty, baud, baud);
556 /* If the number of data bits is to be updated */
557 if ((cflag & CSIZE) != (old_cflag & CSIZE)) {
558 cp2101_get_config(port, CP2101_BITS, &bits, 2);
559 bits &= ~BITS_DATA_MASK;
560 switch (cflag & CSIZE) {
563 dbg("%s - data bits = 5", __func__);
567 dbg("%s - data bits = 6", __func__);
571 dbg("%s - data bits = 7", __func__);
575 dbg("%s - data bits = 8", __func__);
579 dbg("%s - data bits = 9", __func__);
582 dev_err(&port->dev, "cp2101 driver does not "
583 "support the number of bits requested,"
584 " using 8 bit mode\n");
588 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
589 dev_err(&port->dev, "Number of data bits requested "
590 "not supported by device\n");
593 if ((cflag & (PARENB|PARODD)) != (old_cflag & (PARENB|PARODD))) {
594 cp2101_get_config(port, CP2101_BITS, &bits, 2);
595 bits &= ~BITS_PARITY_MASK;
596 if (cflag & PARENB) {
597 if (cflag & PARODD) {
598 bits |= BITS_PARITY_ODD;
599 dbg("%s - parity = ODD", __func__);
601 bits |= BITS_PARITY_EVEN;
602 dbg("%s - parity = EVEN", __func__);
605 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
606 dev_err(&port->dev, "Parity mode not supported "
610 if ((cflag & CSTOPB) != (old_cflag & CSTOPB)) {
611 cp2101_get_config(port, CP2101_BITS, &bits, 2);
612 bits &= ~BITS_STOP_MASK;
613 if (cflag & CSTOPB) {
615 dbg("%s - stop bits = 2", __func__);
618 dbg("%s - stop bits = 1", __func__);
620 if (cp2101_set_config(port, CP2101_BITS, &bits, 2))
621 dev_err(&port->dev, "Number of stop bits requested "
622 "not supported by device\n");
625 if ((cflag & CRTSCTS) != (old_cflag & CRTSCTS)) {
626 cp2101_get_config(port, CP2101_MODEMCTL, modem_ctl, 16);
627 dbg("%s - read modem controls = 0x%.4x 0x%.4x 0x%.4x 0x%.4x",
628 __func__, modem_ctl[0], modem_ctl[1],
629 modem_ctl[2], modem_ctl[3]);
631 if (cflag & CRTSCTS) {
632 modem_ctl[0] &= ~0x7B;
633 modem_ctl[0] |= 0x09;
635 dbg("%s - flow control = CRTSCTS", __func__);
637 modem_ctl[0] &= ~0x7B;
638 modem_ctl[0] |= 0x01;
639 modem_ctl[1] |= 0x40;
640 dbg("%s - flow control = NONE", __func__);
643 dbg("%s - write modem controls = 0x%.4x 0x%.4x 0x%.4x 0x%.4x",
644 __func__, modem_ctl[0], modem_ctl[1],
645 modem_ctl[2], modem_ctl[3]);
646 cp2101_set_config(port, CP2101_MODEMCTL, modem_ctl, 16);
651 static int cp2101_tiocmset (struct tty_struct *tty, struct file *file,
652 unsigned int set, unsigned int clear)
654 struct usb_serial_port *port = tty->driver_data;
655 unsigned int control = 0;
657 dbg("%s - port %d", __func__, port->number);
659 if (set & TIOCM_RTS) {
660 control |= CONTROL_RTS;
661 control |= CONTROL_WRITE_RTS;
663 if (set & TIOCM_DTR) {
664 control |= CONTROL_DTR;
665 control |= CONTROL_WRITE_DTR;
667 if (clear & TIOCM_RTS) {
668 control &= ~CONTROL_RTS;
669 control |= CONTROL_WRITE_RTS;
671 if (clear & TIOCM_DTR) {
672 control &= ~CONTROL_DTR;
673 control |= CONTROL_WRITE_DTR;
676 dbg("%s - control = 0x%.4x", __func__, control);
678 return cp2101_set_config(port, CP2101_CONTROL, &control, 2);
682 static int cp2101_tiocmget (struct tty_struct *tty, struct file *file)
684 struct usb_serial_port *port = tty->driver_data;
685 unsigned int control;
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 tty_struct *tty, int break_state)
706 struct usb_serial_port *port = tty->driver_data;
709 dbg("%s - port %d", __func__, port->number);
710 if (break_state == 0)
714 dbg("%s - turning break %s", __func__,
715 state == BREAK_OFF ? "off" : "on");
716 cp2101_set_config(port, CP2101_BREAK, &state, 2);
719 static int cp2101_startup(struct usb_serial *serial)
721 /* CP2101 buffers behave strangely unless device is reset */
722 usb_reset_device(serial->dev);
726 static void cp2101_shutdown(struct usb_serial *serial)
732 /* Stop reads and writes on all ports */
733 for (i = 0; i < serial->num_ports; ++i)
734 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");