xref: /openbmc/linux/drivers/usb/serial/cypress_m8.c (revision 2cf1c348)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * USB Cypress M8 driver
4  *
5  * 	Copyright (C) 2004
6  * 	    Lonnie Mendez (dignome@gmail.com)
7  *	Copyright (C) 2003,2004
8  *	    Neil Whelchel (koyama@firstlight.net)
9  *
10  * See Documentation/usb/usb-serial.rst for more information on using this
11  * driver
12  *
13  * See http://geocities.com/i0xox0i for information on this driver and the
14  * earthmate usb device.
15  */
16 
17 /* Thanks to Neil Whelchel for writing the first cypress m8 implementation
18    for linux. */
19 /* Thanks to cypress for providing references for the hid reports. */
20 /* Thanks to Jiang Zhang for providing links and for general help. */
21 /* Code originates and was built up from ftdi_sio, belkin, pl2303 and others.*/
22 
23 
24 #include <linux/kernel.h>
25 #include <linux/errno.h>
26 #include <linux/slab.h>
27 #include <linux/tty.h>
28 #include <linux/tty_driver.h>
29 #include <linux/tty_flip.h>
30 #include <linux/module.h>
31 #include <linux/moduleparam.h>
32 #include <linux/spinlock.h>
33 #include <linux/usb.h>
34 #include <linux/usb/serial.h>
35 #include <linux/serial.h>
36 #include <linux/kfifo.h>
37 #include <linux/delay.h>
38 #include <linux/uaccess.h>
39 #include <asm/unaligned.h>
40 
41 #include "cypress_m8.h"
42 
43 
44 static bool stats;
45 static int interval;
46 static bool unstable_bauds;
47 
48 #define DRIVER_AUTHOR "Lonnie Mendez <dignome@gmail.com>, Neil Whelchel <koyama@firstlight.net>"
49 #define DRIVER_DESC "Cypress USB to Serial Driver"
50 
51 /* write buffer size defines */
52 #define CYPRESS_BUF_SIZE	1024
53 
54 static const struct usb_device_id id_table_earthmate[] = {
55 	{ USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB) },
56 	{ USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB_LT20) },
57 	{ }						/* Terminating entry */
58 };
59 
60 static const struct usb_device_id id_table_cyphidcomrs232[] = {
61 	{ USB_DEVICE(VENDOR_ID_CYPRESS, PRODUCT_ID_CYPHIDCOM) },
62 	{ USB_DEVICE(VENDOR_ID_SAI, PRODUCT_ID_CYPHIDCOM) },
63 	{ USB_DEVICE(VENDOR_ID_POWERCOM, PRODUCT_ID_UPS) },
64 	{ USB_DEVICE(VENDOR_ID_FRWD, PRODUCT_ID_CYPHIDCOM_FRWD) },
65 	{ }						/* Terminating entry */
66 };
67 
68 static const struct usb_device_id id_table_nokiaca42v2[] = {
69 	{ USB_DEVICE(VENDOR_ID_DAZZLE, PRODUCT_ID_CA42) },
70 	{ }						/* Terminating entry */
71 };
72 
73 static const struct usb_device_id id_table_combined[] = {
74 	{ USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB) },
75 	{ USB_DEVICE(VENDOR_ID_DELORME, PRODUCT_ID_EARTHMATEUSB_LT20) },
76 	{ USB_DEVICE(VENDOR_ID_CYPRESS, PRODUCT_ID_CYPHIDCOM) },
77 	{ USB_DEVICE(VENDOR_ID_SAI, PRODUCT_ID_CYPHIDCOM) },
78 	{ USB_DEVICE(VENDOR_ID_POWERCOM, PRODUCT_ID_UPS) },
79 	{ USB_DEVICE(VENDOR_ID_FRWD, PRODUCT_ID_CYPHIDCOM_FRWD) },
80 	{ USB_DEVICE(VENDOR_ID_DAZZLE, PRODUCT_ID_CA42) },
81 	{ }						/* Terminating entry */
82 };
83 
84 MODULE_DEVICE_TABLE(usb, id_table_combined);
85 
86 enum packet_format {
87 	packet_format_1,  /* b0:status, b1:payload count */
88 	packet_format_2   /* b0[7:3]:status, b0[2:0]:payload count */
89 };
90 
91 struct cypress_private {
92 	spinlock_t lock;		   /* private lock */
93 	int chiptype;			   /* identifier of device, for quirks/etc */
94 	int bytes_in;			   /* used for statistics */
95 	int bytes_out;			   /* used for statistics */
96 	int cmd_count;			   /* used for statistics */
97 	int cmd_ctrl;			   /* always set this to 1 before issuing a command */
98 	struct kfifo write_fifo;	   /* write fifo */
99 	int write_urb_in_use;		   /* write urb in use indicator */
100 	int write_urb_interval;            /* interval to use for write urb */
101 	int read_urb_interval;             /* interval to use for read urb */
102 	int comm_is_ok;                    /* true if communication is (still) ok */
103 	__u8 line_control;	   	   /* holds dtr / rts value */
104 	__u8 current_status;	   	   /* received from last read - info on dsr,cts,cd,ri,etc */
105 	__u8 current_config;	   	   /* stores the current configuration byte */
106 	__u8 rx_flags;			   /* throttling - used from whiteheat/ftdi_sio */
107 	enum packet_format pkt_fmt;	   /* format to use for packet send / receive */
108 	int get_cfg_unsafe;		   /* If true, the CYPRESS_GET_CONFIG is unsafe */
109 	int baud_rate;			   /* stores current baud rate in
110 					      integer form */
111 	char prev_status;		   /* used for TIOCMIWAIT */
112 };
113 
114 /* function prototypes for the Cypress USB to serial device */
115 static int  cypress_earthmate_port_probe(struct usb_serial_port *port);
116 static int  cypress_hidcom_port_probe(struct usb_serial_port *port);
117 static int  cypress_ca42v2_port_probe(struct usb_serial_port *port);
118 static void cypress_port_remove(struct usb_serial_port *port);
119 static int  cypress_open(struct tty_struct *tty, struct usb_serial_port *port);
120 static void cypress_close(struct usb_serial_port *port);
121 static void cypress_dtr_rts(struct usb_serial_port *port, int on);
122 static int  cypress_write(struct tty_struct *tty, struct usb_serial_port *port,
123 			const unsigned char *buf, int count);
124 static void cypress_send(struct usb_serial_port *port);
125 static unsigned int cypress_write_room(struct tty_struct *tty);
126 static void cypress_earthmate_init_termios(struct tty_struct *tty);
127 static void cypress_set_termios(struct tty_struct *tty,
128 			struct usb_serial_port *port, struct ktermios *old);
129 static int  cypress_tiocmget(struct tty_struct *tty);
130 static int  cypress_tiocmset(struct tty_struct *tty,
131 			unsigned int set, unsigned int clear);
132 static unsigned int cypress_chars_in_buffer(struct tty_struct *tty);
133 static void cypress_throttle(struct tty_struct *tty);
134 static void cypress_unthrottle(struct tty_struct *tty);
135 static void cypress_set_dead(struct usb_serial_port *port);
136 static void cypress_read_int_callback(struct urb *urb);
137 static void cypress_write_int_callback(struct urb *urb);
138 
139 static struct usb_serial_driver cypress_earthmate_device = {
140 	.driver = {
141 		.owner =		THIS_MODULE,
142 		.name =			"earthmate",
143 	},
144 	.description =			"DeLorme Earthmate USB",
145 	.id_table =			id_table_earthmate,
146 	.num_ports =			1,
147 	.port_probe =			cypress_earthmate_port_probe,
148 	.port_remove =			cypress_port_remove,
149 	.open =				cypress_open,
150 	.close =			cypress_close,
151 	.dtr_rts =			cypress_dtr_rts,
152 	.write =			cypress_write,
153 	.write_room =			cypress_write_room,
154 	.init_termios =			cypress_earthmate_init_termios,
155 	.set_termios =			cypress_set_termios,
156 	.tiocmget =			cypress_tiocmget,
157 	.tiocmset =			cypress_tiocmset,
158 	.tiocmiwait =			usb_serial_generic_tiocmiwait,
159 	.chars_in_buffer =		cypress_chars_in_buffer,
160 	.throttle =		 	cypress_throttle,
161 	.unthrottle =			cypress_unthrottle,
162 	.read_int_callback =		cypress_read_int_callback,
163 	.write_int_callback =		cypress_write_int_callback,
164 };
165 
166 static struct usb_serial_driver cypress_hidcom_device = {
167 	.driver = {
168 		.owner =		THIS_MODULE,
169 		.name =			"cyphidcom",
170 	},
171 	.description =			"HID->COM RS232 Adapter",
172 	.id_table =			id_table_cyphidcomrs232,
173 	.num_ports =			1,
174 	.port_probe =			cypress_hidcom_port_probe,
175 	.port_remove =			cypress_port_remove,
176 	.open =				cypress_open,
177 	.close =			cypress_close,
178 	.dtr_rts =			cypress_dtr_rts,
179 	.write =			cypress_write,
180 	.write_room =			cypress_write_room,
181 	.set_termios =			cypress_set_termios,
182 	.tiocmget =			cypress_tiocmget,
183 	.tiocmset =			cypress_tiocmset,
184 	.tiocmiwait =			usb_serial_generic_tiocmiwait,
185 	.chars_in_buffer =		cypress_chars_in_buffer,
186 	.throttle =			cypress_throttle,
187 	.unthrottle =			cypress_unthrottle,
188 	.read_int_callback =		cypress_read_int_callback,
189 	.write_int_callback =		cypress_write_int_callback,
190 };
191 
192 static struct usb_serial_driver cypress_ca42v2_device = {
193 	.driver = {
194 		.owner =		THIS_MODULE,
195 		.name =			"nokiaca42v2",
196 	},
197 	.description =			"Nokia CA-42 V2 Adapter",
198 	.id_table =			id_table_nokiaca42v2,
199 	.num_ports =			1,
200 	.port_probe =			cypress_ca42v2_port_probe,
201 	.port_remove =			cypress_port_remove,
202 	.open =				cypress_open,
203 	.close =			cypress_close,
204 	.dtr_rts =			cypress_dtr_rts,
205 	.write =			cypress_write,
206 	.write_room =			cypress_write_room,
207 	.set_termios =			cypress_set_termios,
208 	.tiocmget =			cypress_tiocmget,
209 	.tiocmset =			cypress_tiocmset,
210 	.tiocmiwait =			usb_serial_generic_tiocmiwait,
211 	.chars_in_buffer =		cypress_chars_in_buffer,
212 	.throttle =			cypress_throttle,
213 	.unthrottle =			cypress_unthrottle,
214 	.read_int_callback =		cypress_read_int_callback,
215 	.write_int_callback =		cypress_write_int_callback,
216 };
217 
218 static struct usb_serial_driver * const serial_drivers[] = {
219 	&cypress_earthmate_device, &cypress_hidcom_device,
220 	&cypress_ca42v2_device, NULL
221 };
222 
223 /*****************************************************************************
224  * Cypress serial helper functions
225  *****************************************************************************/
226 
227 /* FRWD Dongle hidcom needs to skip reset and speed checks */
228 static inline bool is_frwd(struct usb_device *dev)
229 {
230 	return ((le16_to_cpu(dev->descriptor.idVendor) == VENDOR_ID_FRWD) &&
231 		(le16_to_cpu(dev->descriptor.idProduct) == PRODUCT_ID_CYPHIDCOM_FRWD));
232 }
233 
234 static int analyze_baud_rate(struct usb_serial_port *port, speed_t new_rate)
235 {
236 	struct cypress_private *priv;
237 	priv = usb_get_serial_port_data(port);
238 
239 	if (unstable_bauds)
240 		return new_rate;
241 
242 	/* FRWD Dongle uses 115200 bps */
243 	if (is_frwd(port->serial->dev))
244 		return new_rate;
245 
246 	/*
247 	 * The general purpose firmware for the Cypress M8 allows for
248 	 * a maximum speed of 57600bps (I have no idea whether DeLorme
249 	 * chose to use the general purpose firmware or not), if you
250 	 * need to modify this speed setting for your own project
251 	 * please add your own chiptype and modify the code likewise.
252 	 * The Cypress HID->COM device will work successfully up to
253 	 * 115200bps (but the actual throughput is around 3kBps).
254 	 */
255 	if (port->serial->dev->speed == USB_SPEED_LOW) {
256 		/*
257 		 * Mike Isely <isely@pobox.com> 2-Feb-2008: The
258 		 * Cypress app note that describes this mechanism
259 		 * states the the low-speed part can't handle more
260 		 * than 800 bytes/sec, in which case 4800 baud is the
261 		 * safest speed for a part like that.
262 		 */
263 		if (new_rate > 4800) {
264 			dev_dbg(&port->dev,
265 				"%s - failed setting baud rate, device incapable speed %d\n",
266 				__func__, new_rate);
267 			return -1;
268 		}
269 	}
270 	switch (priv->chiptype) {
271 	case CT_EARTHMATE:
272 		if (new_rate <= 600) {
273 			/* 300 and 600 baud rates are supported under
274 			 * the generic firmware, but are not used with
275 			 * NMEA and SiRF protocols */
276 			dev_dbg(&port->dev,
277 				"%s - failed setting baud rate, unsupported speed of %d on Earthmate GPS\n",
278 				__func__, new_rate);
279 			return -1;
280 		}
281 		break;
282 	default:
283 		break;
284 	}
285 	return new_rate;
286 }
287 
288 
289 /* This function can either set or retrieve the current serial line settings */
290 static int cypress_serial_control(struct tty_struct *tty,
291 	struct usb_serial_port *port, speed_t baud_rate, int data_bits,
292 	int stop_bits, int parity_enable, int parity_type, int reset,
293 	int cypress_request_type)
294 {
295 	int new_baudrate = 0, retval = 0, tries = 0;
296 	struct cypress_private *priv;
297 	struct device *dev = &port->dev;
298 	u8 *feature_buffer;
299 	const unsigned int feature_len = 5;
300 	unsigned long flags;
301 
302 	priv = usb_get_serial_port_data(port);
303 
304 	if (!priv->comm_is_ok)
305 		return -ENODEV;
306 
307 	feature_buffer = kcalloc(feature_len, sizeof(u8), GFP_KERNEL);
308 	if (!feature_buffer)
309 		return -ENOMEM;
310 
311 	switch (cypress_request_type) {
312 	case CYPRESS_SET_CONFIG:
313 		/* 0 means 'Hang up' so doesn't change the true bit rate */
314 		new_baudrate = priv->baud_rate;
315 		if (baud_rate && baud_rate != priv->baud_rate) {
316 			dev_dbg(dev, "%s - baud rate is changing\n", __func__);
317 			retval = analyze_baud_rate(port, baud_rate);
318 			if (retval >= 0) {
319 				new_baudrate = retval;
320 				dev_dbg(dev, "%s - New baud rate set to %d\n",
321 					__func__, new_baudrate);
322 			}
323 		}
324 		dev_dbg(dev, "%s - baud rate is being sent as %d\n", __func__,
325 			new_baudrate);
326 
327 		/* fill the feature_buffer with new configuration */
328 		put_unaligned_le32(new_baudrate, feature_buffer);
329 		feature_buffer[4] |= data_bits - 5;   /* assign data bits in 2 bit space ( max 3 ) */
330 		/* 1 bit gap */
331 		feature_buffer[4] |= (stop_bits << 3);   /* assign stop bits in 1 bit space */
332 		feature_buffer[4] |= (parity_enable << 4);   /* assign parity flag in 1 bit space */
333 		feature_buffer[4] |= (parity_type << 5);   /* assign parity type in 1 bit space */
334 		/* 1 bit gap */
335 		feature_buffer[4] |= (reset << 7);   /* assign reset at end of byte, 1 bit space */
336 
337 		dev_dbg(dev, "%s - device is being sent this feature report:\n", __func__);
338 		dev_dbg(dev, "%s - %02X - %02X - %02X - %02X - %02X\n", __func__,
339 			feature_buffer[0], feature_buffer[1],
340 			feature_buffer[2], feature_buffer[3],
341 			feature_buffer[4]);
342 
343 		do {
344 			retval = usb_control_msg(port->serial->dev,
345 					usb_sndctrlpipe(port->serial->dev, 0),
346 					HID_REQ_SET_REPORT,
347 					USB_DIR_OUT | USB_RECIP_INTERFACE | USB_TYPE_CLASS,
348 					0x0300, 0, feature_buffer,
349 					feature_len, 500);
350 
351 			if (tries++ >= 3)
352 				break;
353 
354 		} while (retval != feature_len &&
355 			 retval != -ENODEV);
356 
357 		if (retval != feature_len) {
358 			dev_err(dev, "%s - failed sending serial line settings - %d\n",
359 				__func__, retval);
360 			cypress_set_dead(port);
361 		} else {
362 			spin_lock_irqsave(&priv->lock, flags);
363 			priv->baud_rate = new_baudrate;
364 			priv->current_config = feature_buffer[4];
365 			spin_unlock_irqrestore(&priv->lock, flags);
366 			/* If we asked for a speed change encode it */
367 			if (baud_rate)
368 				tty_encode_baud_rate(tty,
369 					new_baudrate, new_baudrate);
370 		}
371 	break;
372 	case CYPRESS_GET_CONFIG:
373 		if (priv->get_cfg_unsafe) {
374 			/* Not implemented for this device,
375 			   and if we try to do it we're likely
376 			   to crash the hardware. */
377 			retval = -ENOTTY;
378 			goto out;
379 		}
380 		dev_dbg(dev, "%s - retrieving serial line settings\n", __func__);
381 		do {
382 			retval = usb_control_msg(port->serial->dev,
383 					usb_rcvctrlpipe(port->serial->dev, 0),
384 					HID_REQ_GET_REPORT,
385 					USB_DIR_IN | USB_RECIP_INTERFACE | USB_TYPE_CLASS,
386 					0x0300, 0, feature_buffer,
387 					feature_len, 500);
388 
389 			if (tries++ >= 3)
390 				break;
391 		} while (retval != feature_len
392 						&& retval != -ENODEV);
393 
394 		if (retval != feature_len) {
395 			dev_err(dev, "%s - failed to retrieve serial line settings - %d\n",
396 				__func__, retval);
397 			cypress_set_dead(port);
398 			goto out;
399 		} else {
400 			spin_lock_irqsave(&priv->lock, flags);
401 			/* store the config in one byte, and later
402 			   use bit masks to check values */
403 			priv->current_config = feature_buffer[4];
404 			priv->baud_rate = get_unaligned_le32(feature_buffer);
405 			spin_unlock_irqrestore(&priv->lock, flags);
406 		}
407 	}
408 	spin_lock_irqsave(&priv->lock, flags);
409 	++priv->cmd_count;
410 	spin_unlock_irqrestore(&priv->lock, flags);
411 out:
412 	kfree(feature_buffer);
413 	return retval;
414 } /* cypress_serial_control */
415 
416 
417 static void cypress_set_dead(struct usb_serial_port *port)
418 {
419 	struct cypress_private *priv = usb_get_serial_port_data(port);
420 	unsigned long flags;
421 
422 	spin_lock_irqsave(&priv->lock, flags);
423 	if (!priv->comm_is_ok) {
424 		spin_unlock_irqrestore(&priv->lock, flags);
425 		return;
426 	}
427 	priv->comm_is_ok = 0;
428 	spin_unlock_irqrestore(&priv->lock, flags);
429 
430 	dev_err(&port->dev, "cypress_m8 suspending failing port %d - "
431 		"interval might be too short\n", port->port_number);
432 }
433 
434 
435 /*****************************************************************************
436  * Cypress serial driver functions
437  *****************************************************************************/
438 
439 
440 static int cypress_generic_port_probe(struct usb_serial_port *port)
441 {
442 	struct usb_serial *serial = port->serial;
443 	struct cypress_private *priv;
444 
445 	if (!port->interrupt_out_urb || !port->interrupt_in_urb) {
446 		dev_err(&port->dev, "required endpoint is missing\n");
447 		return -ENODEV;
448 	}
449 
450 	priv = kzalloc(sizeof(struct cypress_private), GFP_KERNEL);
451 	if (!priv)
452 		return -ENOMEM;
453 
454 	priv->comm_is_ok = !0;
455 	spin_lock_init(&priv->lock);
456 	if (kfifo_alloc(&priv->write_fifo, CYPRESS_BUF_SIZE, GFP_KERNEL)) {
457 		kfree(priv);
458 		return -ENOMEM;
459 	}
460 
461 	/* Skip reset for FRWD device. It is a workaound:
462 	   device hangs if it receives SET_CONFIGURE in Configured
463 	   state. */
464 	if (!is_frwd(serial->dev))
465 		usb_reset_configuration(serial->dev);
466 
467 	priv->cmd_ctrl = 0;
468 	priv->line_control = 0;
469 	priv->rx_flags = 0;
470 	/* Default packet format setting is determined by packet size.
471 	   Anything with a size larger then 9 must have a separate
472 	   count field since the 3 bit count field is otherwise too
473 	   small.  Otherwise we can use the slightly more compact
474 	   format.  This is in accordance with the cypress_m8 serial
475 	   converter app note. */
476 	if (port->interrupt_out_size > 9)
477 		priv->pkt_fmt = packet_format_1;
478 	else
479 		priv->pkt_fmt = packet_format_2;
480 
481 	if (interval > 0) {
482 		priv->write_urb_interval = interval;
483 		priv->read_urb_interval = interval;
484 		dev_dbg(&port->dev, "%s - read & write intervals forced to %d\n",
485 			__func__, interval);
486 	} else {
487 		priv->write_urb_interval = port->interrupt_out_urb->interval;
488 		priv->read_urb_interval = port->interrupt_in_urb->interval;
489 		dev_dbg(&port->dev, "%s - intervals: read=%d write=%d\n",
490 			__func__, priv->read_urb_interval,
491 			priv->write_urb_interval);
492 	}
493 	usb_set_serial_port_data(port, priv);
494 
495 	port->port.drain_delay = 256;
496 
497 	return 0;
498 }
499 
500 
501 static int cypress_earthmate_port_probe(struct usb_serial_port *port)
502 {
503 	struct usb_serial *serial = port->serial;
504 	struct cypress_private *priv;
505 	int ret;
506 
507 	ret = cypress_generic_port_probe(port);
508 	if (ret) {
509 		dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
510 		return ret;
511 	}
512 
513 	priv = usb_get_serial_port_data(port);
514 	priv->chiptype = CT_EARTHMATE;
515 	/* All Earthmate devices use the separated-count packet
516 	   format!  Idiotic. */
517 	priv->pkt_fmt = packet_format_1;
518 	if (serial->dev->descriptor.idProduct !=
519 				cpu_to_le16(PRODUCT_ID_EARTHMATEUSB)) {
520 		/* The old original USB Earthmate seemed able to
521 		   handle GET_CONFIG requests; everything they've
522 		   produced since that time crashes if this command is
523 		   attempted :-( */
524 		dev_dbg(&port->dev,
525 			"%s - Marking this device as unsafe for GET_CONFIG commands\n",
526 			__func__);
527 		priv->get_cfg_unsafe = !0;
528 	}
529 
530 	return 0;
531 }
532 
533 static int cypress_hidcom_port_probe(struct usb_serial_port *port)
534 {
535 	struct cypress_private *priv;
536 	int ret;
537 
538 	ret = cypress_generic_port_probe(port);
539 	if (ret) {
540 		dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
541 		return ret;
542 	}
543 
544 	priv = usb_get_serial_port_data(port);
545 	priv->chiptype = CT_CYPHIDCOM;
546 
547 	return 0;
548 }
549 
550 static int cypress_ca42v2_port_probe(struct usb_serial_port *port)
551 {
552 	struct cypress_private *priv;
553 	int ret;
554 
555 	ret = cypress_generic_port_probe(port);
556 	if (ret) {
557 		dev_dbg(&port->dev, "%s - Failed setting up port\n", __func__);
558 		return ret;
559 	}
560 
561 	priv = usb_get_serial_port_data(port);
562 	priv->chiptype = CT_CA42V2;
563 
564 	return 0;
565 }
566 
567 static void cypress_port_remove(struct usb_serial_port *port)
568 {
569 	struct cypress_private *priv;
570 
571 	priv = usb_get_serial_port_data(port);
572 
573 	kfifo_free(&priv->write_fifo);
574 	kfree(priv);
575 }
576 
577 static int cypress_open(struct tty_struct *tty, struct usb_serial_port *port)
578 {
579 	struct cypress_private *priv = usb_get_serial_port_data(port);
580 	struct usb_serial *serial = port->serial;
581 	unsigned long flags;
582 	int result = 0;
583 
584 	if (!priv->comm_is_ok)
585 		return -EIO;
586 
587 	/* clear halts before open */
588 	usb_clear_halt(serial->dev, 0x81);
589 	usb_clear_halt(serial->dev, 0x02);
590 
591 	spin_lock_irqsave(&priv->lock, flags);
592 	/* reset read/write statistics */
593 	priv->bytes_in = 0;
594 	priv->bytes_out = 0;
595 	priv->cmd_count = 0;
596 	priv->rx_flags = 0;
597 	spin_unlock_irqrestore(&priv->lock, flags);
598 
599 	/* Set termios */
600 	cypress_send(port);
601 
602 	if (tty)
603 		cypress_set_termios(tty, port, NULL);
604 
605 	/* setup the port and start reading from the device */
606 	usb_fill_int_urb(port->interrupt_in_urb, serial->dev,
607 		usb_rcvintpipe(serial->dev, port->interrupt_in_endpointAddress),
608 		port->interrupt_in_urb->transfer_buffer,
609 		port->interrupt_in_urb->transfer_buffer_length,
610 		cypress_read_int_callback, port, priv->read_urb_interval);
611 	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
612 
613 	if (result) {
614 		dev_err(&port->dev,
615 			"%s - failed submitting read urb, error %d\n",
616 							__func__, result);
617 		cypress_set_dead(port);
618 	}
619 
620 	return result;
621 } /* cypress_open */
622 
623 static void cypress_dtr_rts(struct usb_serial_port *port, int on)
624 {
625 	struct cypress_private *priv = usb_get_serial_port_data(port);
626 	/* drop dtr and rts */
627 	spin_lock_irq(&priv->lock);
628 	if (on == 0)
629 		priv->line_control = 0;
630 	else
631 		priv->line_control = CONTROL_DTR | CONTROL_RTS;
632 	priv->cmd_ctrl = 1;
633 	spin_unlock_irq(&priv->lock);
634 	cypress_write(NULL, port, NULL, 0);
635 }
636 
637 static void cypress_close(struct usb_serial_port *port)
638 {
639 	struct cypress_private *priv = usb_get_serial_port_data(port);
640 	unsigned long flags;
641 
642 	spin_lock_irqsave(&priv->lock, flags);
643 	kfifo_reset_out(&priv->write_fifo);
644 	spin_unlock_irqrestore(&priv->lock, flags);
645 
646 	dev_dbg(&port->dev, "%s - stopping urbs\n", __func__);
647 	usb_kill_urb(port->interrupt_in_urb);
648 	usb_kill_urb(port->interrupt_out_urb);
649 
650 	if (stats)
651 		dev_info(&port->dev, "Statistics: %d Bytes In | %d Bytes Out | %d Commands Issued\n",
652 			priv->bytes_in, priv->bytes_out, priv->cmd_count);
653 } /* cypress_close */
654 
655 
656 static int cypress_write(struct tty_struct *tty, struct usb_serial_port *port,
657 					const unsigned char *buf, int count)
658 {
659 	struct cypress_private *priv = usb_get_serial_port_data(port);
660 
661 	dev_dbg(&port->dev, "%s - %d bytes\n", __func__, count);
662 
663 	/* line control commands, which need to be executed immediately,
664 	   are not put into the buffer for obvious reasons.
665 	 */
666 	if (priv->cmd_ctrl) {
667 		count = 0;
668 		goto finish;
669 	}
670 
671 	if (!count)
672 		return count;
673 
674 	count = kfifo_in_locked(&priv->write_fifo, buf, count, &priv->lock);
675 
676 finish:
677 	cypress_send(port);
678 
679 	return count;
680 } /* cypress_write */
681 
682 
683 static void cypress_send(struct usb_serial_port *port)
684 {
685 	int count = 0, result, offset, actual_size;
686 	struct cypress_private *priv = usb_get_serial_port_data(port);
687 	struct device *dev = &port->dev;
688 	unsigned long flags;
689 
690 	if (!priv->comm_is_ok)
691 		return;
692 
693 	dev_dbg(dev, "%s - interrupt out size is %d\n", __func__,
694 		port->interrupt_out_size);
695 
696 	spin_lock_irqsave(&priv->lock, flags);
697 	if (priv->write_urb_in_use) {
698 		dev_dbg(dev, "%s - can't write, urb in use\n", __func__);
699 		spin_unlock_irqrestore(&priv->lock, flags);
700 		return;
701 	}
702 	spin_unlock_irqrestore(&priv->lock, flags);
703 
704 	/* clear buffer */
705 	memset(port->interrupt_out_urb->transfer_buffer, 0,
706 						port->interrupt_out_size);
707 
708 	spin_lock_irqsave(&priv->lock, flags);
709 	switch (priv->pkt_fmt) {
710 	default:
711 	case packet_format_1:
712 		/* this is for the CY7C64013... */
713 		offset = 2;
714 		port->interrupt_out_buffer[0] = priv->line_control;
715 		break;
716 	case packet_format_2:
717 		/* this is for the CY7C63743... */
718 		offset = 1;
719 		port->interrupt_out_buffer[0] = priv->line_control;
720 		break;
721 	}
722 
723 	if (priv->line_control & CONTROL_RESET)
724 		priv->line_control &= ~CONTROL_RESET;
725 
726 	if (priv->cmd_ctrl) {
727 		priv->cmd_count++;
728 		dev_dbg(dev, "%s - line control command being issued\n", __func__);
729 		spin_unlock_irqrestore(&priv->lock, flags);
730 		goto send;
731 	} else
732 		spin_unlock_irqrestore(&priv->lock, flags);
733 
734 	count = kfifo_out_locked(&priv->write_fifo,
735 					&port->interrupt_out_buffer[offset],
736 					port->interrupt_out_size - offset,
737 					&priv->lock);
738 	if (count == 0)
739 		return;
740 
741 	switch (priv->pkt_fmt) {
742 	default:
743 	case packet_format_1:
744 		port->interrupt_out_buffer[1] = count;
745 		break;
746 	case packet_format_2:
747 		port->interrupt_out_buffer[0] |= count;
748 	}
749 
750 	dev_dbg(dev, "%s - count is %d\n", __func__, count);
751 
752 send:
753 	spin_lock_irqsave(&priv->lock, flags);
754 	priv->write_urb_in_use = 1;
755 	spin_unlock_irqrestore(&priv->lock, flags);
756 
757 	if (priv->cmd_ctrl)
758 		actual_size = 1;
759 	else
760 		actual_size = count +
761 			      (priv->pkt_fmt == packet_format_1 ? 2 : 1);
762 
763 	usb_serial_debug_data(dev, __func__, port->interrupt_out_size,
764 			      port->interrupt_out_urb->transfer_buffer);
765 
766 	usb_fill_int_urb(port->interrupt_out_urb, port->serial->dev,
767 		usb_sndintpipe(port->serial->dev, port->interrupt_out_endpointAddress),
768 		port->interrupt_out_buffer, actual_size,
769 		cypress_write_int_callback, port, priv->write_urb_interval);
770 	result = usb_submit_urb(port->interrupt_out_urb, GFP_ATOMIC);
771 	if (result) {
772 		dev_err_console(port,
773 				"%s - failed submitting write urb, error %d\n",
774 							__func__, result);
775 		priv->write_urb_in_use = 0;
776 		cypress_set_dead(port);
777 	}
778 
779 	spin_lock_irqsave(&priv->lock, flags);
780 	if (priv->cmd_ctrl)
781 		priv->cmd_ctrl = 0;
782 
783 	/* do not count the line control and size bytes */
784 	priv->bytes_out += count;
785 	spin_unlock_irqrestore(&priv->lock, flags);
786 
787 	usb_serial_port_softint(port);
788 } /* cypress_send */
789 
790 
791 /* returns how much space is available in the soft buffer */
792 static unsigned int cypress_write_room(struct tty_struct *tty)
793 {
794 	struct usb_serial_port *port = tty->driver_data;
795 	struct cypress_private *priv = usb_get_serial_port_data(port);
796 	unsigned int room;
797 	unsigned long flags;
798 
799 	spin_lock_irqsave(&priv->lock, flags);
800 	room = kfifo_avail(&priv->write_fifo);
801 	spin_unlock_irqrestore(&priv->lock, flags);
802 
803 	dev_dbg(&port->dev, "%s - returns %u\n", __func__, room);
804 	return room;
805 }
806 
807 
808 static int cypress_tiocmget(struct tty_struct *tty)
809 {
810 	struct usb_serial_port *port = tty->driver_data;
811 	struct cypress_private *priv = usb_get_serial_port_data(port);
812 	__u8 status, control;
813 	unsigned int result = 0;
814 	unsigned long flags;
815 
816 	spin_lock_irqsave(&priv->lock, flags);
817 	control = priv->line_control;
818 	status = priv->current_status;
819 	spin_unlock_irqrestore(&priv->lock, flags);
820 
821 	result = ((control & CONTROL_DTR)        ? TIOCM_DTR : 0)
822 		| ((control & CONTROL_RTS)       ? TIOCM_RTS : 0)
823 		| ((status & UART_CTS)        ? TIOCM_CTS : 0)
824 		| ((status & UART_DSR)        ? TIOCM_DSR : 0)
825 		| ((status & UART_RI)         ? TIOCM_RI  : 0)
826 		| ((status & UART_CD)         ? TIOCM_CD  : 0);
827 
828 	dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
829 
830 	return result;
831 }
832 
833 
834 static int cypress_tiocmset(struct tty_struct *tty,
835 			       unsigned int set, unsigned int clear)
836 {
837 	struct usb_serial_port *port = tty->driver_data;
838 	struct cypress_private *priv = usb_get_serial_port_data(port);
839 	unsigned long flags;
840 
841 	spin_lock_irqsave(&priv->lock, flags);
842 	if (set & TIOCM_RTS)
843 		priv->line_control |= CONTROL_RTS;
844 	if (set & TIOCM_DTR)
845 		priv->line_control |= CONTROL_DTR;
846 	if (clear & TIOCM_RTS)
847 		priv->line_control &= ~CONTROL_RTS;
848 	if (clear & TIOCM_DTR)
849 		priv->line_control &= ~CONTROL_DTR;
850 	priv->cmd_ctrl = 1;
851 	spin_unlock_irqrestore(&priv->lock, flags);
852 
853 	return cypress_write(tty, port, NULL, 0);
854 }
855 
856 static void cypress_earthmate_init_termios(struct tty_struct *tty)
857 {
858 	tty_encode_baud_rate(tty, 4800, 4800);
859 }
860 
861 static void cypress_set_termios(struct tty_struct *tty,
862 	struct usb_serial_port *port, struct ktermios *old_termios)
863 {
864 	struct cypress_private *priv = usb_get_serial_port_data(port);
865 	struct device *dev = &port->dev;
866 	int data_bits, stop_bits, parity_type, parity_enable;
867 	unsigned int cflag;
868 	unsigned long flags;
869 	__u8 oldlines;
870 	int linechange = 0;
871 
872 	/* Unsupported features need clearing */
873 	tty->termios.c_cflag &= ~(CMSPAR|CRTSCTS);
874 
875 	cflag = tty->termios.c_cflag;
876 
877 	/* set number of data bits, parity, stop bits */
878 	/* when parity is disabled the parity type bit is ignored */
879 
880 	/* 1 means 2 stop bits, 0 means 1 stop bit */
881 	stop_bits = cflag & CSTOPB ? 1 : 0;
882 
883 	if (cflag & PARENB) {
884 		parity_enable = 1;
885 		/* 1 means odd parity, 0 means even parity */
886 		parity_type = cflag & PARODD ? 1 : 0;
887 	} else
888 		parity_enable = parity_type = 0;
889 
890 	data_bits = tty_get_char_size(cflag);
891 
892 	spin_lock_irqsave(&priv->lock, flags);
893 	oldlines = priv->line_control;
894 	if ((cflag & CBAUD) == B0) {
895 		/* drop dtr and rts */
896 		dev_dbg(dev, "%s - dropping the lines, baud rate 0bps\n", __func__);
897 		priv->line_control &= ~(CONTROL_DTR | CONTROL_RTS);
898 	} else
899 		priv->line_control = (CONTROL_DTR | CONTROL_RTS);
900 	spin_unlock_irqrestore(&priv->lock, flags);
901 
902 	dev_dbg(dev, "%s - sending %d stop_bits, %d parity_enable, %d parity_type, %d data_bits (+5)\n",
903 		__func__, stop_bits, parity_enable, parity_type, data_bits);
904 
905 	cypress_serial_control(tty, port, tty_get_baud_rate(tty),
906 			data_bits, stop_bits,
907 			parity_enable, parity_type,
908 			0, CYPRESS_SET_CONFIG);
909 
910 	/* we perform a CYPRESS_GET_CONFIG so that the current settings are
911 	 * filled into the private structure this should confirm that all is
912 	 * working if it returns what we just set */
913 	cypress_serial_control(tty, port, 0, 0, 0, 0, 0, 0, CYPRESS_GET_CONFIG);
914 
915 	/* Here we can define custom tty settings for devices; the main tty
916 	 * termios flag base comes from empeg.c */
917 
918 	spin_lock_irqsave(&priv->lock, flags);
919 	if (priv->chiptype == CT_EARTHMATE && priv->baud_rate == 4800) {
920 		dev_dbg(dev, "Using custom termios settings for a baud rate of 4800bps.\n");
921 		/* define custom termios settings for NMEA protocol */
922 
923 		tty->termios.c_iflag /* input modes - */
924 			&= ~(IGNBRK  /* disable ignore break */
925 			| BRKINT     /* disable break causes interrupt */
926 			| PARMRK     /* disable mark parity errors */
927 			| ISTRIP     /* disable clear high bit of input char */
928 			| INLCR      /* disable translate NL to CR */
929 			| IGNCR      /* disable ignore CR */
930 			| ICRNL      /* disable translate CR to NL */
931 			| IXON);     /* disable enable XON/XOFF flow control */
932 
933 		tty->termios.c_oflag /* output modes */
934 			&= ~OPOST;    /* disable postprocess output char */
935 
936 		tty->termios.c_lflag /* line discipline modes */
937 			&= ~(ECHO     /* disable echo input characters */
938 			| ECHONL      /* disable echo new line */
939 			| ICANON      /* disable erase, kill, werase, and rprnt
940 					 special characters */
941 			| ISIG        /* disable interrupt, quit, and suspend
942 					 special characters */
943 			| IEXTEN);    /* disable non-POSIX special characters */
944 	} /* CT_CYPHIDCOM: Application should handle this for device */
945 
946 	linechange = (priv->line_control != oldlines);
947 	spin_unlock_irqrestore(&priv->lock, flags);
948 
949 	/* if necessary, set lines */
950 	if (linechange) {
951 		priv->cmd_ctrl = 1;
952 		cypress_write(tty, port, NULL, 0);
953 	}
954 } /* cypress_set_termios */
955 
956 
957 /* returns amount of data still left in soft buffer */
958 static unsigned int cypress_chars_in_buffer(struct tty_struct *tty)
959 {
960 	struct usb_serial_port *port = tty->driver_data;
961 	struct cypress_private *priv = usb_get_serial_port_data(port);
962 	unsigned int chars;
963 	unsigned long flags;
964 
965 	spin_lock_irqsave(&priv->lock, flags);
966 	chars = kfifo_len(&priv->write_fifo);
967 	spin_unlock_irqrestore(&priv->lock, flags);
968 
969 	dev_dbg(&port->dev, "%s - returns %u\n", __func__, chars);
970 	return chars;
971 }
972 
973 
974 static void cypress_throttle(struct tty_struct *tty)
975 {
976 	struct usb_serial_port *port = tty->driver_data;
977 	struct cypress_private *priv = usb_get_serial_port_data(port);
978 
979 	spin_lock_irq(&priv->lock);
980 	priv->rx_flags = THROTTLED;
981 	spin_unlock_irq(&priv->lock);
982 }
983 
984 
985 static void cypress_unthrottle(struct tty_struct *tty)
986 {
987 	struct usb_serial_port *port = tty->driver_data;
988 	struct cypress_private *priv = usb_get_serial_port_data(port);
989 	int actually_throttled, result;
990 
991 	spin_lock_irq(&priv->lock);
992 	actually_throttled = priv->rx_flags & ACTUALLY_THROTTLED;
993 	priv->rx_flags = 0;
994 	spin_unlock_irq(&priv->lock);
995 
996 	if (!priv->comm_is_ok)
997 		return;
998 
999 	if (actually_throttled) {
1000 		result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
1001 		if (result) {
1002 			dev_err(&port->dev, "%s - failed submitting read urb, "
1003 					"error %d\n", __func__, result);
1004 			cypress_set_dead(port);
1005 		}
1006 	}
1007 }
1008 
1009 
1010 static void cypress_read_int_callback(struct urb *urb)
1011 {
1012 	struct usb_serial_port *port = urb->context;
1013 	struct cypress_private *priv = usb_get_serial_port_data(port);
1014 	struct device *dev = &urb->dev->dev;
1015 	struct tty_struct *tty;
1016 	unsigned char *data = urb->transfer_buffer;
1017 	unsigned long flags;
1018 	char tty_flag = TTY_NORMAL;
1019 	int bytes = 0;
1020 	int result;
1021 	int i = 0;
1022 	int status = urb->status;
1023 
1024 	switch (status) {
1025 	case 0: /* success */
1026 		break;
1027 	case -ECONNRESET:
1028 	case -ENOENT:
1029 	case -ESHUTDOWN:
1030 		/* precursor to disconnect so just go away */
1031 		return;
1032 	case -EPIPE:
1033 		/* Can't call usb_clear_halt while in_interrupt */
1034 		fallthrough;
1035 	default:
1036 		/* something ugly is going on... */
1037 		dev_err(dev, "%s - unexpected nonzero read status received: %d\n",
1038 			__func__, status);
1039 		cypress_set_dead(port);
1040 		return;
1041 	}
1042 
1043 	spin_lock_irqsave(&priv->lock, flags);
1044 	if (priv->rx_flags & THROTTLED) {
1045 		dev_dbg(dev, "%s - now throttling\n", __func__);
1046 		priv->rx_flags |= ACTUALLY_THROTTLED;
1047 		spin_unlock_irqrestore(&priv->lock, flags);
1048 		return;
1049 	}
1050 	spin_unlock_irqrestore(&priv->lock, flags);
1051 
1052 	tty = tty_port_tty_get(&port->port);
1053 	if (!tty) {
1054 		dev_dbg(dev, "%s - bad tty pointer - exiting\n", __func__);
1055 		return;
1056 	}
1057 
1058 	spin_lock_irqsave(&priv->lock, flags);
1059 	result = urb->actual_length;
1060 	switch (priv->pkt_fmt) {
1061 	default:
1062 	case packet_format_1:
1063 		/* This is for the CY7C64013... */
1064 		priv->current_status = data[0] & 0xF8;
1065 		bytes = data[1] + 2;
1066 		i = 2;
1067 		break;
1068 	case packet_format_2:
1069 		/* This is for the CY7C63743... */
1070 		priv->current_status = data[0] & 0xF8;
1071 		bytes = (data[0] & 0x07) + 1;
1072 		i = 1;
1073 		break;
1074 	}
1075 	spin_unlock_irqrestore(&priv->lock, flags);
1076 	if (result < bytes) {
1077 		dev_dbg(dev,
1078 			"%s - wrong packet size - received %d bytes but packet said %d bytes\n",
1079 			__func__, result, bytes);
1080 		goto continue_read;
1081 	}
1082 
1083 	usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
1084 
1085 	spin_lock_irqsave(&priv->lock, flags);
1086 	/* check to see if status has changed */
1087 	if (priv->current_status != priv->prev_status) {
1088 		u8 delta = priv->current_status ^ priv->prev_status;
1089 
1090 		if (delta & UART_MSR_MASK) {
1091 			if (delta & UART_CTS)
1092 				port->icount.cts++;
1093 			if (delta & UART_DSR)
1094 				port->icount.dsr++;
1095 			if (delta & UART_RI)
1096 				port->icount.rng++;
1097 			if (delta & UART_CD)
1098 				port->icount.dcd++;
1099 
1100 			wake_up_interruptible(&port->port.delta_msr_wait);
1101 		}
1102 
1103 		priv->prev_status = priv->current_status;
1104 	}
1105 	spin_unlock_irqrestore(&priv->lock, flags);
1106 
1107 	/* hangup, as defined in acm.c... this might be a bad place for it
1108 	 * though */
1109 	if (tty && !C_CLOCAL(tty) && !(priv->current_status & UART_CD)) {
1110 		dev_dbg(dev, "%s - calling hangup\n", __func__);
1111 		tty_hangup(tty);
1112 		goto continue_read;
1113 	}
1114 
1115 	/* There is one error bit... I'm assuming it is a parity error
1116 	 * indicator as the generic firmware will set this bit to 1 if a
1117 	 * parity error occurs.
1118 	 * I can not find reference to any other error events. */
1119 	spin_lock_irqsave(&priv->lock, flags);
1120 	if (priv->current_status & CYP_ERROR) {
1121 		spin_unlock_irqrestore(&priv->lock, flags);
1122 		tty_flag = TTY_PARITY;
1123 		dev_dbg(dev, "%s - Parity Error detected\n", __func__);
1124 	} else
1125 		spin_unlock_irqrestore(&priv->lock, flags);
1126 
1127 	/* process read if there is data other than line status */
1128 	if (bytes > i) {
1129 		tty_insert_flip_string_fixed_flag(&port->port, data + i,
1130 				tty_flag, bytes - i);
1131 		tty_flip_buffer_push(&port->port);
1132 	}
1133 
1134 	spin_lock_irqsave(&priv->lock, flags);
1135 	/* control and status byte(s) are also counted */
1136 	priv->bytes_in += bytes;
1137 	spin_unlock_irqrestore(&priv->lock, flags);
1138 
1139 continue_read:
1140 	tty_kref_put(tty);
1141 
1142 	/* Continue trying to always read */
1143 
1144 	if (priv->comm_is_ok) {
1145 		usb_fill_int_urb(port->interrupt_in_urb, port->serial->dev,
1146 				usb_rcvintpipe(port->serial->dev,
1147 					port->interrupt_in_endpointAddress),
1148 				port->interrupt_in_urb->transfer_buffer,
1149 				port->interrupt_in_urb->transfer_buffer_length,
1150 				cypress_read_int_callback, port,
1151 				priv->read_urb_interval);
1152 		result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
1153 		if (result && result != -EPERM) {
1154 			dev_err(dev, "%s - failed resubmitting read urb, error %d\n",
1155 				__func__, result);
1156 			cypress_set_dead(port);
1157 		}
1158 	}
1159 } /* cypress_read_int_callback */
1160 
1161 
1162 static void cypress_write_int_callback(struct urb *urb)
1163 {
1164 	struct usb_serial_port *port = urb->context;
1165 	struct cypress_private *priv = usb_get_serial_port_data(port);
1166 	struct device *dev = &urb->dev->dev;
1167 	int status = urb->status;
1168 
1169 	switch (status) {
1170 	case 0:
1171 		/* success */
1172 		break;
1173 	case -ECONNRESET:
1174 	case -ENOENT:
1175 	case -ESHUTDOWN:
1176 		/* this urb is terminated, clean up */
1177 		dev_dbg(dev, "%s - urb shutting down with status: %d\n",
1178 			__func__, status);
1179 		priv->write_urb_in_use = 0;
1180 		return;
1181 	case -EPIPE:
1182 		/* Cannot call usb_clear_halt while in_interrupt */
1183 		fallthrough;
1184 	default:
1185 		dev_err(dev, "%s - unexpected nonzero write status received: %d\n",
1186 			__func__, status);
1187 		cypress_set_dead(port);
1188 		break;
1189 	}
1190 	priv->write_urb_in_use = 0;
1191 
1192 	/* send any buffered data */
1193 	cypress_send(port);
1194 }
1195 
1196 module_usb_serial_driver(serial_drivers, id_table_combined);
1197 
1198 MODULE_AUTHOR(DRIVER_AUTHOR);
1199 MODULE_DESCRIPTION(DRIVER_DESC);
1200 MODULE_LICENSE("GPL");
1201 
1202 module_param(stats, bool, 0644);
1203 MODULE_PARM_DESC(stats, "Enable statistics or not");
1204 module_param(interval, int, 0644);
1205 MODULE_PARM_DESC(interval, "Overrides interrupt interval");
1206 module_param(unstable_bauds, bool, 0644);
1207 MODULE_PARM_DESC(unstable_bauds, "Allow unstable baud rates");
1208