1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * u_serial.c - utilities for USB gadget "serial port"/TTY support
4  *
5  * Copyright (C) 2003 Al Borchers (alborchers@steinerpoint.com)
6  * Copyright (C) 2008 David Brownell
7  * Copyright (C) 2008 by Nokia Corporation
8  *
9  * This code also borrows from usbserial.c, which is
10  * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
11  * Copyright (C) 2000 Peter Berger (pberger@brimson.com)
12  * Copyright (C) 2000 Al Borchers (alborchers@steinerpoint.com)
13  */
14 
15 /* #define VERBOSE_DEBUG */
16 
17 #include <linux/kernel.h>
18 #include <linux/sched.h>
19 #include <linux/device.h>
20 #include <linux/delay.h>
21 #include <linux/tty.h>
22 #include <linux/tty_flip.h>
23 #include <linux/slab.h>
24 #include <linux/export.h>
25 #include <linux/module.h>
26 #include <linux/console.h>
27 #include <linux/kstrtox.h>
28 #include <linux/kthread.h>
29 #include <linux/workqueue.h>
30 #include <linux/kfifo.h>
31 
32 #include "u_serial.h"
33 
34 
35 /*
36  * This component encapsulates the TTY layer glue needed to provide basic
37  * "serial port" functionality through the USB gadget stack.  Each such
38  * port is exposed through a /dev/ttyGS* node.
39  *
40  * After this module has been loaded, the individual TTY port can be requested
41  * (gserial_alloc_line()) and it will stay available until they are removed
42  * (gserial_free_line()). Each one may be connected to a USB function
43  * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
44  * host issues a config change event. Data can only flow when the port is
45  * connected to the host.
46  *
47  * A given TTY port can be made available in multiple configurations.
48  * For example, each one might expose a ttyGS0 node which provides a
49  * login application.  In one case that might use CDC ACM interface 0,
50  * while another configuration might use interface 3 for that.  The
51  * work to handle that (including descriptor management) is not part
52  * of this component.
53  *
54  * Configurations may expose more than one TTY port.  For example, if
55  * ttyGS0 provides login service, then ttyGS1 might provide dialer access
56  * for a telephone or fax link.  And ttyGS2 might be something that just
57  * needs a simple byte stream interface for some messaging protocol that
58  * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
59  *
60  *
61  * gserial is the lifecycle interface, used by USB functions
62  * gs_port is the I/O nexus, used by the tty driver
63  * tty_struct links to the tty/filesystem framework
64  *
65  * gserial <---> gs_port ... links will be null when the USB link is
66  * inactive; managed by gserial_{connect,disconnect}().  each gserial
67  * instance can wrap its own USB control protocol.
68  *	gserial->ioport == usb_ep->driver_data ... gs_port
69  *	gs_port->port_usb ... gserial
70  *
71  * gs_port <---> tty_struct ... links will be null when the TTY file
72  * isn't opened; managed by gs_open()/gs_close()
73  *	gserial->port_tty ... tty_struct
74  *	tty_struct->driver_data ... gserial
75  */
76 
77 /* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
78  * next layer of buffering.  For TX that's a circular buffer; for RX
79  * consider it a NOP.  A third layer is provided by the TTY code.
80  */
81 #define QUEUE_SIZE		16
82 #define WRITE_BUF_SIZE		8192		/* TX only */
83 #define GS_CONSOLE_BUF_SIZE	8192
84 
85 /* Prevents race conditions while accessing gser->ioport */
86 static DEFINE_SPINLOCK(serial_port_lock);
87 
88 /* console info */
89 struct gs_console {
90 	struct console		console;
91 	struct work_struct	work;
92 	spinlock_t		lock;
93 	struct usb_request	*req;
94 	struct kfifo		buf;
95 	size_t			missed;
96 };
97 
98 /*
99  * The port structure holds info for each port, one for each minor number
100  * (and thus for each /dev/ node).
101  */
102 struct gs_port {
103 	struct tty_port		port;
104 	spinlock_t		port_lock;	/* guard port_* access */
105 
106 	struct gserial		*port_usb;
107 #ifdef CONFIG_U_SERIAL_CONSOLE
108 	struct gs_console	*console;
109 #endif
110 
111 	u8			port_num;
112 
113 	struct list_head	read_pool;
114 	int read_started;
115 	int read_allocated;
116 	struct list_head	read_queue;
117 	unsigned		n_read;
118 	struct delayed_work	push;
119 
120 	struct list_head	write_pool;
121 	int write_started;
122 	int write_allocated;
123 	struct kfifo		port_write_buf;
124 	wait_queue_head_t	drain_wait;	/* wait while writes drain */
125 	bool                    write_busy;
126 	wait_queue_head_t	close_wait;
127 	bool			suspended;	/* port suspended */
128 	bool			start_delayed;	/* delay start when suspended */
129 
130 	/* REVISIT this state ... */
131 	struct usb_cdc_line_coding port_line_coding;	/* 8-N-1 etc */
132 };
133 
134 static struct portmaster {
135 	struct mutex	lock;			/* protect open/close */
136 	struct gs_port	*port;
137 } ports[MAX_U_SERIAL_PORTS];
138 
139 #define GS_CLOSE_TIMEOUT		15		/* seconds */
140 
141 
142 
143 #ifdef VERBOSE_DEBUG
144 #ifndef pr_vdebug
145 #define pr_vdebug(fmt, arg...) \
146 	pr_debug(fmt, ##arg)
147 #endif /* pr_vdebug */
148 #else
149 #ifndef pr_vdebug
150 #define pr_vdebug(fmt, arg...) \
151 	({ if (0) pr_debug(fmt, ##arg); })
152 #endif /* pr_vdebug */
153 #endif
154 
155 /*-------------------------------------------------------------------------*/
156 
157 /* I/O glue between TTY (upper) and USB function (lower) driver layers */
158 
159 /*
160  * gs_alloc_req
161  *
162  * Allocate a usb_request and its buffer.  Returns a pointer to the
163  * usb_request or NULL if there is an error.
164  */
165 struct usb_request *
166 gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
167 {
168 	struct usb_request *req;
169 
170 	req = usb_ep_alloc_request(ep, kmalloc_flags);
171 
172 	if (req != NULL) {
173 		req->length = len;
174 		req->buf = kmalloc(len, kmalloc_flags);
175 		if (req->buf == NULL) {
176 			usb_ep_free_request(ep, req);
177 			return NULL;
178 		}
179 	}
180 
181 	return req;
182 }
183 EXPORT_SYMBOL_GPL(gs_alloc_req);
184 
185 /*
186  * gs_free_req
187  *
188  * Free a usb_request and its buffer.
189  */
190 void gs_free_req(struct usb_ep *ep, struct usb_request *req)
191 {
192 	kfree(req->buf);
193 	usb_ep_free_request(ep, req);
194 }
195 EXPORT_SYMBOL_GPL(gs_free_req);
196 
197 /*
198  * gs_send_packet
199  *
200  * If there is data to send, a packet is built in the given
201  * buffer and the size is returned.  If there is no data to
202  * send, 0 is returned.
203  *
204  * Called with port_lock held.
205  */
206 static unsigned
207 gs_send_packet(struct gs_port *port, char *packet, unsigned size)
208 {
209 	unsigned len;
210 
211 	len = kfifo_len(&port->port_write_buf);
212 	if (len < size)
213 		size = len;
214 	if (size != 0)
215 		size = kfifo_out(&port->port_write_buf, packet, size);
216 	return size;
217 }
218 
219 /*
220  * gs_start_tx
221  *
222  * This function finds available write requests, calls
223  * gs_send_packet to fill these packets with data, and
224  * continues until either there are no more write requests
225  * available or no more data to send.  This function is
226  * run whenever data arrives or write requests are available.
227  *
228  * Context: caller owns port_lock; port_usb is non-null.
229  */
230 static int gs_start_tx(struct gs_port *port)
231 /*
232 __releases(&port->port_lock)
233 __acquires(&port->port_lock)
234 */
235 {
236 	struct list_head	*pool = &port->write_pool;
237 	struct usb_ep		*in;
238 	int			status = 0;
239 	bool			do_tty_wake = false;
240 
241 	if (!port->port_usb)
242 		return status;
243 
244 	in = port->port_usb->in;
245 
246 	while (!port->write_busy && !list_empty(pool)) {
247 		struct usb_request	*req;
248 		int			len;
249 
250 		if (port->write_started >= QUEUE_SIZE)
251 			break;
252 
253 		req = list_entry(pool->next, struct usb_request, list);
254 		len = gs_send_packet(port, req->buf, in->maxpacket);
255 		if (len == 0) {
256 			wake_up_interruptible(&port->drain_wait);
257 			break;
258 		}
259 		do_tty_wake = true;
260 
261 		req->length = len;
262 		list_del(&req->list);
263 		req->zero = kfifo_is_empty(&port->port_write_buf);
264 
265 		pr_vdebug("ttyGS%d: tx len=%d, %3ph ...\n", port->port_num, len, req->buf);
266 
267 		/* Drop lock while we call out of driver; completions
268 		 * could be issued while we do so.  Disconnection may
269 		 * happen too; maybe immediately before we queue this!
270 		 *
271 		 * NOTE that we may keep sending data for a while after
272 		 * the TTY closed (dev->ioport->port_tty is NULL).
273 		 */
274 		port->write_busy = true;
275 		spin_unlock(&port->port_lock);
276 		status = usb_ep_queue(in, req, GFP_ATOMIC);
277 		spin_lock(&port->port_lock);
278 		port->write_busy = false;
279 
280 		if (status) {
281 			pr_debug("%s: %s %s err %d\n",
282 					__func__, "queue", in->name, status);
283 			list_add(&req->list, pool);
284 			break;
285 		}
286 
287 		port->write_started++;
288 
289 		/* abort immediately after disconnect */
290 		if (!port->port_usb)
291 			break;
292 	}
293 
294 	if (do_tty_wake && port->port.tty)
295 		tty_wakeup(port->port.tty);
296 	return status;
297 }
298 
299 /*
300  * Context: caller owns port_lock, and port_usb is set
301  */
302 static unsigned gs_start_rx(struct gs_port *port)
303 /*
304 __releases(&port->port_lock)
305 __acquires(&port->port_lock)
306 */
307 {
308 	struct list_head	*pool = &port->read_pool;
309 	struct usb_ep		*out = port->port_usb->out;
310 
311 	while (!list_empty(pool)) {
312 		struct usb_request	*req;
313 		int			status;
314 		struct tty_struct	*tty;
315 
316 		/* no more rx if closed */
317 		tty = port->port.tty;
318 		if (!tty)
319 			break;
320 
321 		if (port->read_started >= QUEUE_SIZE)
322 			break;
323 
324 		req = list_entry(pool->next, struct usb_request, list);
325 		list_del(&req->list);
326 		req->length = out->maxpacket;
327 
328 		/* drop lock while we call out; the controller driver
329 		 * may need to call us back (e.g. for disconnect)
330 		 */
331 		spin_unlock(&port->port_lock);
332 		status = usb_ep_queue(out, req, GFP_ATOMIC);
333 		spin_lock(&port->port_lock);
334 
335 		if (status) {
336 			pr_debug("%s: %s %s err %d\n",
337 					__func__, "queue", out->name, status);
338 			list_add(&req->list, pool);
339 			break;
340 		}
341 		port->read_started++;
342 
343 		/* abort immediately after disconnect */
344 		if (!port->port_usb)
345 			break;
346 	}
347 	return port->read_started;
348 }
349 
350 /*
351  * RX work takes data out of the RX queue and hands it up to the TTY
352  * layer until it refuses to take any more data (or is throttled back).
353  * Then it issues reads for any further data.
354  *
355  * If the RX queue becomes full enough that no usb_request is queued,
356  * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
357  * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
358  * can be buffered before the TTY layer's buffers (currently 64 KB).
359  */
360 static void gs_rx_push(struct work_struct *work)
361 {
362 	struct delayed_work	*w = to_delayed_work(work);
363 	struct gs_port		*port = container_of(w, struct gs_port, push);
364 	struct tty_struct	*tty;
365 	struct list_head	*queue = &port->read_queue;
366 	bool			disconnect = false;
367 	bool			do_push = false;
368 
369 	/* hand any queued data to the tty */
370 	spin_lock_irq(&port->port_lock);
371 	tty = port->port.tty;
372 	while (!list_empty(queue)) {
373 		struct usb_request	*req;
374 
375 		req = list_first_entry(queue, struct usb_request, list);
376 
377 		/* leave data queued if tty was rx throttled */
378 		if (tty && tty_throttled(tty))
379 			break;
380 
381 		switch (req->status) {
382 		case -ESHUTDOWN:
383 			disconnect = true;
384 			pr_vdebug("ttyGS%d: shutdown\n", port->port_num);
385 			break;
386 
387 		default:
388 			/* presumably a transient fault */
389 			pr_warn("ttyGS%d: unexpected RX status %d\n",
390 				port->port_num, req->status);
391 			fallthrough;
392 		case 0:
393 			/* normal completion */
394 			break;
395 		}
396 
397 		/* push data to (open) tty */
398 		if (req->actual && tty) {
399 			char		*packet = req->buf;
400 			unsigned	size = req->actual;
401 			unsigned	n;
402 			int		count;
403 
404 			/* we may have pushed part of this packet already... */
405 			n = port->n_read;
406 			if (n) {
407 				packet += n;
408 				size -= n;
409 			}
410 
411 			count = tty_insert_flip_string(&port->port, packet,
412 					size);
413 			if (count)
414 				do_push = true;
415 			if (count != size) {
416 				/* stop pushing; TTY layer can't handle more */
417 				port->n_read += count;
418 				pr_vdebug("ttyGS%d: rx block %d/%d\n",
419 					  port->port_num, count, req->actual);
420 				break;
421 			}
422 			port->n_read = 0;
423 		}
424 
425 		list_move(&req->list, &port->read_pool);
426 		port->read_started--;
427 	}
428 
429 	/* Push from tty to ldisc; this is handled by a workqueue,
430 	 * so we won't get callbacks and can hold port_lock
431 	 */
432 	if (do_push)
433 		tty_flip_buffer_push(&port->port);
434 
435 
436 	/* We want our data queue to become empty ASAP, keeping data
437 	 * in the tty and ldisc (not here).  If we couldn't push any
438 	 * this time around, RX may be starved, so wait until next jiffy.
439 	 *
440 	 * We may leave non-empty queue only when there is a tty, and
441 	 * either it is throttled or there is no more room in flip buffer.
442 	 */
443 	if (!list_empty(queue) && !tty_throttled(tty))
444 		schedule_delayed_work(&port->push, 1);
445 
446 	/* If we're still connected, refill the USB RX queue. */
447 	if (!disconnect && port->port_usb)
448 		gs_start_rx(port);
449 
450 	spin_unlock_irq(&port->port_lock);
451 }
452 
453 static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
454 {
455 	struct gs_port	*port = ep->driver_data;
456 
457 	/* Queue all received data until the tty layer is ready for it. */
458 	spin_lock(&port->port_lock);
459 	list_add_tail(&req->list, &port->read_queue);
460 	schedule_delayed_work(&port->push, 0);
461 	spin_unlock(&port->port_lock);
462 }
463 
464 static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
465 {
466 	struct gs_port	*port = ep->driver_data;
467 
468 	spin_lock(&port->port_lock);
469 	list_add(&req->list, &port->write_pool);
470 	port->write_started--;
471 
472 	switch (req->status) {
473 	default:
474 		/* presumably a transient fault */
475 		pr_warn("%s: unexpected %s status %d\n",
476 			__func__, ep->name, req->status);
477 		fallthrough;
478 	case 0:
479 		/* normal completion */
480 		gs_start_tx(port);
481 		break;
482 
483 	case -ESHUTDOWN:
484 		/* disconnect */
485 		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
486 		break;
487 	}
488 
489 	spin_unlock(&port->port_lock);
490 }
491 
492 static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
493 							 int *allocated)
494 {
495 	struct usb_request	*req;
496 
497 	while (!list_empty(head)) {
498 		req = list_entry(head->next, struct usb_request, list);
499 		list_del(&req->list);
500 		gs_free_req(ep, req);
501 		if (allocated)
502 			(*allocated)--;
503 	}
504 }
505 
506 static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
507 		void (*fn)(struct usb_ep *, struct usb_request *),
508 		int *allocated)
509 {
510 	int			i;
511 	struct usb_request	*req;
512 	int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
513 
514 	/* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
515 	 * do quite that many this time, don't fail ... we just won't
516 	 * be as speedy as we might otherwise be.
517 	 */
518 	for (i = 0; i < n; i++) {
519 		req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
520 		if (!req)
521 			return list_empty(head) ? -ENOMEM : 0;
522 		req->complete = fn;
523 		list_add_tail(&req->list, head);
524 		if (allocated)
525 			(*allocated)++;
526 	}
527 	return 0;
528 }
529 
530 /**
531  * gs_start_io - start USB I/O streams
532  * @port: port to use
533  * Context: holding port_lock; port_tty and port_usb are non-null
534  *
535  * We only start I/O when something is connected to both sides of
536  * this port.  If nothing is listening on the host side, we may
537  * be pointlessly filling up our TX buffers and FIFO.
538  */
539 static int gs_start_io(struct gs_port *port)
540 {
541 	struct list_head	*head = &port->read_pool;
542 	struct usb_ep		*ep;
543 	int			status;
544 	unsigned		started;
545 
546 	if (!port->port_usb || !port->port.tty)
547 		return -EIO;
548 
549 	/* Allocate RX and TX I/O buffers.  We can't easily do this much
550 	 * earlier (with GFP_KERNEL) because the requests are coupled to
551 	 * endpoints, as are the packet sizes we'll be using.  Different
552 	 * configurations may use different endpoints with a given port;
553 	 * and high speed vs full speed changes packet sizes too.
554 	 */
555 	ep = port->port_usb->out;
556 	status = gs_alloc_requests(ep, head, gs_read_complete,
557 		&port->read_allocated);
558 	if (status)
559 		return status;
560 
561 	status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
562 			gs_write_complete, &port->write_allocated);
563 	if (status) {
564 		gs_free_requests(ep, head, &port->read_allocated);
565 		return status;
566 	}
567 
568 	/* queue read requests */
569 	port->n_read = 0;
570 	started = gs_start_rx(port);
571 
572 	if (started) {
573 		gs_start_tx(port);
574 		/* Unblock any pending writes into our circular buffer, in case
575 		 * we didn't in gs_start_tx() */
576 		tty_wakeup(port->port.tty);
577 	} else {
578 		gs_free_requests(ep, head, &port->read_allocated);
579 		gs_free_requests(port->port_usb->in, &port->write_pool,
580 			&port->write_allocated);
581 		status = -EIO;
582 	}
583 
584 	return status;
585 }
586 
587 /*-------------------------------------------------------------------------*/
588 
589 /* TTY Driver */
590 
591 /*
592  * gs_open sets up the link between a gs_port and its associated TTY.
593  * That link is broken *only* by TTY close(), and all driver methods
594  * know that.
595  */
596 static int gs_open(struct tty_struct *tty, struct file *file)
597 {
598 	int		port_num = tty->index;
599 	struct gs_port	*port;
600 	int		status = 0;
601 
602 	mutex_lock(&ports[port_num].lock);
603 	port = ports[port_num].port;
604 	if (!port) {
605 		status = -ENODEV;
606 		goto out;
607 	}
608 
609 	spin_lock_irq(&port->port_lock);
610 
611 	/* allocate circular buffer on first open */
612 	if (!kfifo_initialized(&port->port_write_buf)) {
613 
614 		spin_unlock_irq(&port->port_lock);
615 
616 		/*
617 		 * portmaster's mutex still protects from simultaneous open(),
618 		 * and close() can't happen, yet.
619 		 */
620 
621 		status = kfifo_alloc(&port->port_write_buf,
622 				     WRITE_BUF_SIZE, GFP_KERNEL);
623 		if (status) {
624 			pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
625 				 port_num, tty, file);
626 			goto out;
627 		}
628 
629 		spin_lock_irq(&port->port_lock);
630 	}
631 
632 	/* already open?  Great. */
633 	if (port->port.count++)
634 		goto exit_unlock_port;
635 
636 	tty->driver_data = port;
637 	port->port.tty = tty;
638 
639 	/* if connected, start the I/O stream */
640 	if (port->port_usb) {
641 		/* if port is suspended, wait resume to start I/0 stream */
642 		if (!port->suspended) {
643 			struct gserial	*gser = port->port_usb;
644 
645 			pr_debug("gs_open: start ttyGS%d\n", port->port_num);
646 			gs_start_io(port);
647 
648 			if (gser->connect)
649 				gser->connect(gser);
650 		} else {
651 			pr_debug("delay start of ttyGS%d\n", port->port_num);
652 			port->start_delayed = true;
653 		}
654 	}
655 
656 	pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
657 
658 exit_unlock_port:
659 	spin_unlock_irq(&port->port_lock);
660 out:
661 	mutex_unlock(&ports[port_num].lock);
662 	return status;
663 }
664 
665 static int gs_close_flush_done(struct gs_port *p)
666 {
667 	int cond;
668 
669 	/* return true on disconnect or empty buffer or if raced with open() */
670 	spin_lock_irq(&p->port_lock);
671 	cond = p->port_usb == NULL || !kfifo_len(&p->port_write_buf) ||
672 		p->port.count > 1;
673 	spin_unlock_irq(&p->port_lock);
674 
675 	return cond;
676 }
677 
678 static void gs_close(struct tty_struct *tty, struct file *file)
679 {
680 	struct gs_port *port = tty->driver_data;
681 	struct gserial	*gser;
682 
683 	spin_lock_irq(&port->port_lock);
684 
685 	if (port->port.count != 1) {
686 raced_with_open:
687 		if (port->port.count == 0)
688 			WARN_ON(1);
689 		else
690 			--port->port.count;
691 		goto exit;
692 	}
693 
694 	pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
695 
696 	gser = port->port_usb;
697 	if (gser && !port->suspended && gser->disconnect)
698 		gser->disconnect(gser);
699 
700 	/* wait for circular write buffer to drain, disconnect, or at
701 	 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
702 	 */
703 	if (kfifo_len(&port->port_write_buf) > 0 && gser) {
704 		spin_unlock_irq(&port->port_lock);
705 		wait_event_interruptible_timeout(port->drain_wait,
706 					gs_close_flush_done(port),
707 					GS_CLOSE_TIMEOUT * HZ);
708 		spin_lock_irq(&port->port_lock);
709 
710 		if (port->port.count != 1)
711 			goto raced_with_open;
712 
713 		gser = port->port_usb;
714 	}
715 
716 	/* Iff we're disconnected, there can be no I/O in flight so it's
717 	 * ok to free the circular buffer; else just scrub it.  And don't
718 	 * let the push async work fire again until we're re-opened.
719 	 */
720 	if (gser == NULL)
721 		kfifo_free(&port->port_write_buf);
722 	else
723 		kfifo_reset(&port->port_write_buf);
724 
725 	port->start_delayed = false;
726 	port->port.count = 0;
727 	port->port.tty = NULL;
728 
729 	pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
730 			port->port_num, tty, file);
731 
732 	wake_up(&port->close_wait);
733 exit:
734 	spin_unlock_irq(&port->port_lock);
735 }
736 
737 static ssize_t gs_write(struct tty_struct *tty, const u8 *buf, size_t count)
738 {
739 	struct gs_port	*port = tty->driver_data;
740 	unsigned long	flags;
741 
742 	pr_vdebug("gs_write: ttyGS%d (%p) writing %zu bytes\n",
743 			port->port_num, tty, count);
744 
745 	spin_lock_irqsave(&port->port_lock, flags);
746 	if (count)
747 		count = kfifo_in(&port->port_write_buf, buf, count);
748 	/* treat count == 0 as flush_chars() */
749 	if (port->port_usb)
750 		gs_start_tx(port);
751 	spin_unlock_irqrestore(&port->port_lock, flags);
752 
753 	return count;
754 }
755 
756 static int gs_put_char(struct tty_struct *tty, u8 ch)
757 {
758 	struct gs_port	*port = tty->driver_data;
759 	unsigned long	flags;
760 	int		status;
761 
762 	pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %ps\n",
763 		port->port_num, tty, ch, __builtin_return_address(0));
764 
765 	spin_lock_irqsave(&port->port_lock, flags);
766 	status = kfifo_put(&port->port_write_buf, ch);
767 	spin_unlock_irqrestore(&port->port_lock, flags);
768 
769 	return status;
770 }
771 
772 static void gs_flush_chars(struct tty_struct *tty)
773 {
774 	struct gs_port	*port = tty->driver_data;
775 	unsigned long	flags;
776 
777 	pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
778 
779 	spin_lock_irqsave(&port->port_lock, flags);
780 	if (port->port_usb)
781 		gs_start_tx(port);
782 	spin_unlock_irqrestore(&port->port_lock, flags);
783 }
784 
785 static unsigned int gs_write_room(struct tty_struct *tty)
786 {
787 	struct gs_port	*port = tty->driver_data;
788 	unsigned long	flags;
789 	unsigned int room = 0;
790 
791 	spin_lock_irqsave(&port->port_lock, flags);
792 	if (port->port_usb)
793 		room = kfifo_avail(&port->port_write_buf);
794 	spin_unlock_irqrestore(&port->port_lock, flags);
795 
796 	pr_vdebug("gs_write_room: (%d,%p) room=%u\n",
797 		port->port_num, tty, room);
798 
799 	return room;
800 }
801 
802 static unsigned int gs_chars_in_buffer(struct tty_struct *tty)
803 {
804 	struct gs_port	*port = tty->driver_data;
805 	unsigned long	flags;
806 	unsigned int	chars;
807 
808 	spin_lock_irqsave(&port->port_lock, flags);
809 	chars = kfifo_len(&port->port_write_buf);
810 	spin_unlock_irqrestore(&port->port_lock, flags);
811 
812 	pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%u\n",
813 		port->port_num, tty, chars);
814 
815 	return chars;
816 }
817 
818 /* undo side effects of setting TTY_THROTTLED */
819 static void gs_unthrottle(struct tty_struct *tty)
820 {
821 	struct gs_port		*port = tty->driver_data;
822 	unsigned long		flags;
823 
824 	spin_lock_irqsave(&port->port_lock, flags);
825 	if (port->port_usb) {
826 		/* Kickstart read queue processing.  We don't do xon/xoff,
827 		 * rts/cts, or other handshaking with the host, but if the
828 		 * read queue backs up enough we'll be NAKing OUT packets.
829 		 */
830 		pr_vdebug("ttyGS%d: unthrottle\n", port->port_num);
831 		schedule_delayed_work(&port->push, 0);
832 	}
833 	spin_unlock_irqrestore(&port->port_lock, flags);
834 }
835 
836 static int gs_break_ctl(struct tty_struct *tty, int duration)
837 {
838 	struct gs_port	*port = tty->driver_data;
839 	int		status = 0;
840 	struct gserial	*gser;
841 
842 	pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
843 			port->port_num, duration);
844 
845 	spin_lock_irq(&port->port_lock);
846 	gser = port->port_usb;
847 	if (gser && gser->send_break)
848 		status = gser->send_break(gser, duration);
849 	spin_unlock_irq(&port->port_lock);
850 
851 	return status;
852 }
853 
854 static const struct tty_operations gs_tty_ops = {
855 	.open =			gs_open,
856 	.close =		gs_close,
857 	.write =		gs_write,
858 	.put_char =		gs_put_char,
859 	.flush_chars =		gs_flush_chars,
860 	.write_room =		gs_write_room,
861 	.chars_in_buffer =	gs_chars_in_buffer,
862 	.unthrottle =		gs_unthrottle,
863 	.break_ctl =		gs_break_ctl,
864 };
865 
866 /*-------------------------------------------------------------------------*/
867 
868 static struct tty_driver *gs_tty_driver;
869 
870 #ifdef CONFIG_U_SERIAL_CONSOLE
871 
872 static void gs_console_complete_out(struct usb_ep *ep, struct usb_request *req)
873 {
874 	struct gs_console *cons = req->context;
875 
876 	switch (req->status) {
877 	default:
878 		pr_warn("%s: unexpected %s status %d\n",
879 			__func__, ep->name, req->status);
880 		fallthrough;
881 	case 0:
882 		/* normal completion */
883 		spin_lock(&cons->lock);
884 		req->length = 0;
885 		schedule_work(&cons->work);
886 		spin_unlock(&cons->lock);
887 		break;
888 	case -ECONNRESET:
889 	case -ESHUTDOWN:
890 		/* disconnect */
891 		pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
892 		break;
893 	}
894 }
895 
896 static void __gs_console_push(struct gs_console *cons)
897 {
898 	struct usb_request *req = cons->req;
899 	struct usb_ep *ep;
900 	size_t size;
901 
902 	if (!req)
903 		return;	/* disconnected */
904 
905 	if (req->length)
906 		return;	/* busy */
907 
908 	ep = cons->console.data;
909 	size = kfifo_out(&cons->buf, req->buf, ep->maxpacket);
910 	if (!size)
911 		return;
912 
913 	if (cons->missed && ep->maxpacket >= 64) {
914 		char buf[64];
915 		size_t len;
916 
917 		len = sprintf(buf, "\n[missed %zu bytes]\n", cons->missed);
918 		kfifo_in(&cons->buf, buf, len);
919 		cons->missed = 0;
920 	}
921 
922 	req->length = size;
923 
924 	spin_unlock_irq(&cons->lock);
925 	if (usb_ep_queue(ep, req, GFP_ATOMIC))
926 		req->length = 0;
927 	spin_lock_irq(&cons->lock);
928 }
929 
930 static void gs_console_work(struct work_struct *work)
931 {
932 	struct gs_console *cons = container_of(work, struct gs_console, work);
933 
934 	spin_lock_irq(&cons->lock);
935 
936 	__gs_console_push(cons);
937 
938 	spin_unlock_irq(&cons->lock);
939 }
940 
941 static void gs_console_write(struct console *co,
942 			     const char *buf, unsigned count)
943 {
944 	struct gs_console *cons = container_of(co, struct gs_console, console);
945 	unsigned long flags;
946 	size_t n;
947 
948 	spin_lock_irqsave(&cons->lock, flags);
949 
950 	n = kfifo_in(&cons->buf, buf, count);
951 	if (n < count)
952 		cons->missed += count - n;
953 
954 	if (cons->req && !cons->req->length)
955 		schedule_work(&cons->work);
956 
957 	spin_unlock_irqrestore(&cons->lock, flags);
958 }
959 
960 static struct tty_driver *gs_console_device(struct console *co, int *index)
961 {
962 	*index = co->index;
963 	return gs_tty_driver;
964 }
965 
966 static int gs_console_connect(struct gs_port *port)
967 {
968 	struct gs_console *cons = port->console;
969 	struct usb_request *req;
970 	struct usb_ep *ep;
971 
972 	if (!cons)
973 		return 0;
974 
975 	ep = port->port_usb->in;
976 	req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
977 	if (!req)
978 		return -ENOMEM;
979 	req->complete = gs_console_complete_out;
980 	req->context = cons;
981 	req->length = 0;
982 
983 	spin_lock(&cons->lock);
984 	cons->req = req;
985 	cons->console.data = ep;
986 	spin_unlock(&cons->lock);
987 
988 	pr_debug("ttyGS%d: console connected!\n", port->port_num);
989 
990 	schedule_work(&cons->work);
991 
992 	return 0;
993 }
994 
995 static void gs_console_disconnect(struct gs_port *port)
996 {
997 	struct gs_console *cons = port->console;
998 	struct usb_request *req;
999 	struct usb_ep *ep;
1000 
1001 	if (!cons)
1002 		return;
1003 
1004 	spin_lock(&cons->lock);
1005 
1006 	req = cons->req;
1007 	ep = cons->console.data;
1008 	cons->req = NULL;
1009 
1010 	spin_unlock(&cons->lock);
1011 
1012 	if (!req)
1013 		return;
1014 
1015 	usb_ep_dequeue(ep, req);
1016 	gs_free_req(ep, req);
1017 }
1018 
1019 static int gs_console_init(struct gs_port *port)
1020 {
1021 	struct gs_console *cons;
1022 	int err;
1023 
1024 	if (port->console)
1025 		return 0;
1026 
1027 	cons = kzalloc(sizeof(*port->console), GFP_KERNEL);
1028 	if (!cons)
1029 		return -ENOMEM;
1030 
1031 	strcpy(cons->console.name, "ttyGS");
1032 	cons->console.write = gs_console_write;
1033 	cons->console.device = gs_console_device;
1034 	cons->console.flags = CON_PRINTBUFFER;
1035 	cons->console.index = port->port_num;
1036 
1037 	INIT_WORK(&cons->work, gs_console_work);
1038 	spin_lock_init(&cons->lock);
1039 
1040 	err = kfifo_alloc(&cons->buf, GS_CONSOLE_BUF_SIZE, GFP_KERNEL);
1041 	if (err) {
1042 		pr_err("ttyGS%d: allocate console buffer failed\n", port->port_num);
1043 		kfree(cons);
1044 		return err;
1045 	}
1046 
1047 	port->console = cons;
1048 	register_console(&cons->console);
1049 
1050 	spin_lock_irq(&port->port_lock);
1051 	if (port->port_usb)
1052 		gs_console_connect(port);
1053 	spin_unlock_irq(&port->port_lock);
1054 
1055 	return 0;
1056 }
1057 
1058 static void gs_console_exit(struct gs_port *port)
1059 {
1060 	struct gs_console *cons = port->console;
1061 
1062 	if (!cons)
1063 		return;
1064 
1065 	unregister_console(&cons->console);
1066 
1067 	spin_lock_irq(&port->port_lock);
1068 	if (cons->req)
1069 		gs_console_disconnect(port);
1070 	spin_unlock_irq(&port->port_lock);
1071 
1072 	cancel_work_sync(&cons->work);
1073 	kfifo_free(&cons->buf);
1074 	kfree(cons);
1075 	port->console = NULL;
1076 }
1077 
1078 ssize_t gserial_set_console(unsigned char port_num, const char *page, size_t count)
1079 {
1080 	struct gs_port *port;
1081 	bool enable;
1082 	int ret;
1083 
1084 	ret = kstrtobool(page, &enable);
1085 	if (ret)
1086 		return ret;
1087 
1088 	mutex_lock(&ports[port_num].lock);
1089 	port = ports[port_num].port;
1090 
1091 	if (WARN_ON(port == NULL)) {
1092 		ret = -ENXIO;
1093 		goto out;
1094 	}
1095 
1096 	if (enable)
1097 		ret = gs_console_init(port);
1098 	else
1099 		gs_console_exit(port);
1100 out:
1101 	mutex_unlock(&ports[port_num].lock);
1102 
1103 	return ret < 0 ? ret : count;
1104 }
1105 EXPORT_SYMBOL_GPL(gserial_set_console);
1106 
1107 ssize_t gserial_get_console(unsigned char port_num, char *page)
1108 {
1109 	struct gs_port *port;
1110 	ssize_t ret;
1111 
1112 	mutex_lock(&ports[port_num].lock);
1113 	port = ports[port_num].port;
1114 
1115 	if (WARN_ON(port == NULL))
1116 		ret = -ENXIO;
1117 	else
1118 		ret = sprintf(page, "%u\n", !!port->console);
1119 
1120 	mutex_unlock(&ports[port_num].lock);
1121 
1122 	return ret;
1123 }
1124 EXPORT_SYMBOL_GPL(gserial_get_console);
1125 
1126 #else
1127 
1128 static int gs_console_connect(struct gs_port *port)
1129 {
1130 	return 0;
1131 }
1132 
1133 static void gs_console_disconnect(struct gs_port *port)
1134 {
1135 }
1136 
1137 static int gs_console_init(struct gs_port *port)
1138 {
1139 	return -ENOSYS;
1140 }
1141 
1142 static void gs_console_exit(struct gs_port *port)
1143 {
1144 }
1145 
1146 #endif
1147 
1148 static int
1149 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
1150 {
1151 	struct gs_port	*port;
1152 	int		ret = 0;
1153 
1154 	mutex_lock(&ports[port_num].lock);
1155 	if (ports[port_num].port) {
1156 		ret = -EBUSY;
1157 		goto out;
1158 	}
1159 
1160 	port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
1161 	if (port == NULL) {
1162 		ret = -ENOMEM;
1163 		goto out;
1164 	}
1165 
1166 	tty_port_init(&port->port);
1167 	spin_lock_init(&port->port_lock);
1168 	init_waitqueue_head(&port->drain_wait);
1169 	init_waitqueue_head(&port->close_wait);
1170 
1171 	INIT_DELAYED_WORK(&port->push, gs_rx_push);
1172 
1173 	INIT_LIST_HEAD(&port->read_pool);
1174 	INIT_LIST_HEAD(&port->read_queue);
1175 	INIT_LIST_HEAD(&port->write_pool);
1176 
1177 	port->port_num = port_num;
1178 	port->port_line_coding = *coding;
1179 
1180 	ports[port_num].port = port;
1181 out:
1182 	mutex_unlock(&ports[port_num].lock);
1183 	return ret;
1184 }
1185 
1186 static int gs_closed(struct gs_port *port)
1187 {
1188 	int cond;
1189 
1190 	spin_lock_irq(&port->port_lock);
1191 	cond = port->port.count == 0;
1192 	spin_unlock_irq(&port->port_lock);
1193 
1194 	return cond;
1195 }
1196 
1197 static void gserial_free_port(struct gs_port *port)
1198 {
1199 	cancel_delayed_work_sync(&port->push);
1200 	/* wait for old opens to finish */
1201 	wait_event(port->close_wait, gs_closed(port));
1202 	WARN_ON(port->port_usb != NULL);
1203 	tty_port_destroy(&port->port);
1204 	kfree(port);
1205 }
1206 
1207 void gserial_free_line(unsigned char port_num)
1208 {
1209 	struct gs_port	*port;
1210 
1211 	mutex_lock(&ports[port_num].lock);
1212 	if (!ports[port_num].port) {
1213 		mutex_unlock(&ports[port_num].lock);
1214 		return;
1215 	}
1216 	port = ports[port_num].port;
1217 	gs_console_exit(port);
1218 	ports[port_num].port = NULL;
1219 	mutex_unlock(&ports[port_num].lock);
1220 
1221 	gserial_free_port(port);
1222 	tty_unregister_device(gs_tty_driver, port_num);
1223 }
1224 EXPORT_SYMBOL_GPL(gserial_free_line);
1225 
1226 int gserial_alloc_line_no_console(unsigned char *line_num)
1227 {
1228 	struct usb_cdc_line_coding	coding;
1229 	struct gs_port			*port;
1230 	struct device			*tty_dev;
1231 	int				ret;
1232 	int				port_num;
1233 
1234 	coding.dwDTERate = cpu_to_le32(9600);
1235 	coding.bCharFormat = 8;
1236 	coding.bParityType = USB_CDC_NO_PARITY;
1237 	coding.bDataBits = USB_CDC_1_STOP_BITS;
1238 
1239 	for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
1240 		ret = gs_port_alloc(port_num, &coding);
1241 		if (ret == -EBUSY)
1242 			continue;
1243 		if (ret)
1244 			return ret;
1245 		break;
1246 	}
1247 	if (ret)
1248 		return ret;
1249 
1250 	/* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
1251 
1252 	port = ports[port_num].port;
1253 	tty_dev = tty_port_register_device(&port->port,
1254 			gs_tty_driver, port_num, NULL);
1255 	if (IS_ERR(tty_dev)) {
1256 		pr_err("%s: failed to register tty for port %d, err %ld\n",
1257 				__func__, port_num, PTR_ERR(tty_dev));
1258 
1259 		ret = PTR_ERR(tty_dev);
1260 		mutex_lock(&ports[port_num].lock);
1261 		ports[port_num].port = NULL;
1262 		mutex_unlock(&ports[port_num].lock);
1263 		gserial_free_port(port);
1264 		goto err;
1265 	}
1266 	*line_num = port_num;
1267 err:
1268 	return ret;
1269 }
1270 EXPORT_SYMBOL_GPL(gserial_alloc_line_no_console);
1271 
1272 int gserial_alloc_line(unsigned char *line_num)
1273 {
1274 	int ret = gserial_alloc_line_no_console(line_num);
1275 
1276 	if (!ret && !*line_num)
1277 		gs_console_init(ports[*line_num].port);
1278 
1279 	return ret;
1280 }
1281 EXPORT_SYMBOL_GPL(gserial_alloc_line);
1282 
1283 /**
1284  * gserial_connect - notify TTY I/O glue that USB link is active
1285  * @gser: the function, set up with endpoints and descriptors
1286  * @port_num: which port is active
1287  * Context: any (usually from irq)
1288  *
1289  * This is called activate endpoints and let the TTY layer know that
1290  * the connection is active ... not unlike "carrier detect".  It won't
1291  * necessarily start I/O queues; unless the TTY is held open by any
1292  * task, there would be no point.  However, the endpoints will be
1293  * activated so the USB host can perform I/O, subject to basic USB
1294  * hardware flow control.
1295  *
1296  * Caller needs to have set up the endpoints and USB function in @dev
1297  * before calling this, as well as the appropriate (speed-specific)
1298  * endpoint descriptors, and also have allocate @port_num by calling
1299  * @gserial_alloc_line().
1300  *
1301  * Returns negative errno or zero.
1302  * On success, ep->driver_data will be overwritten.
1303  */
1304 int gserial_connect(struct gserial *gser, u8 port_num)
1305 {
1306 	struct gs_port	*port;
1307 	unsigned long	flags;
1308 	int		status;
1309 
1310 	if (port_num >= MAX_U_SERIAL_PORTS)
1311 		return -ENXIO;
1312 
1313 	port = ports[port_num].port;
1314 	if (!port) {
1315 		pr_err("serial line %d not allocated.\n", port_num);
1316 		return -EINVAL;
1317 	}
1318 	if (port->port_usb) {
1319 		pr_err("serial line %d is in use.\n", port_num);
1320 		return -EBUSY;
1321 	}
1322 
1323 	/* activate the endpoints */
1324 	status = usb_ep_enable(gser->in);
1325 	if (status < 0)
1326 		return status;
1327 	gser->in->driver_data = port;
1328 
1329 	status = usb_ep_enable(gser->out);
1330 	if (status < 0)
1331 		goto fail_out;
1332 	gser->out->driver_data = port;
1333 
1334 	/* then tell the tty glue that I/O can work */
1335 	spin_lock_irqsave(&port->port_lock, flags);
1336 	gser->ioport = port;
1337 	port->port_usb = gser;
1338 
1339 	/* REVISIT unclear how best to handle this state...
1340 	 * we don't really couple it with the Linux TTY.
1341 	 */
1342 	gser->port_line_coding = port->port_line_coding;
1343 
1344 	/* REVISIT if waiting on "carrier detect", signal. */
1345 
1346 	/* if it's already open, start I/O ... and notify the serial
1347 	 * protocol about open/close status (connect/disconnect).
1348 	 */
1349 	if (port->port.count) {
1350 		pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
1351 		gs_start_io(port);
1352 		if (gser->connect)
1353 			gser->connect(gser);
1354 	} else {
1355 		if (gser->disconnect)
1356 			gser->disconnect(gser);
1357 	}
1358 
1359 	status = gs_console_connect(port);
1360 	spin_unlock_irqrestore(&port->port_lock, flags);
1361 
1362 	return status;
1363 
1364 fail_out:
1365 	usb_ep_disable(gser->in);
1366 	return status;
1367 }
1368 EXPORT_SYMBOL_GPL(gserial_connect);
1369 /**
1370  * gserial_disconnect - notify TTY I/O glue that USB link is inactive
1371  * @gser: the function, on which gserial_connect() was called
1372  * Context: any (usually from irq)
1373  *
1374  * This is called to deactivate endpoints and let the TTY layer know
1375  * that the connection went inactive ... not unlike "hangup".
1376  *
1377  * On return, the state is as if gserial_connect() had never been called;
1378  * there is no active USB I/O on these endpoints.
1379  */
1380 void gserial_disconnect(struct gserial *gser)
1381 {
1382 	struct gs_port	*port = gser->ioport;
1383 	unsigned long	flags;
1384 
1385 	if (!port)
1386 		return;
1387 
1388 	spin_lock_irqsave(&serial_port_lock, flags);
1389 
1390 	/* tell the TTY glue not to do I/O here any more */
1391 	spin_lock(&port->port_lock);
1392 
1393 	gs_console_disconnect(port);
1394 
1395 	/* REVISIT as above: how best to track this? */
1396 	port->port_line_coding = gser->port_line_coding;
1397 
1398 	port->port_usb = NULL;
1399 	gser->ioport = NULL;
1400 	if (port->port.count > 0) {
1401 		wake_up_interruptible(&port->drain_wait);
1402 		if (port->port.tty)
1403 			tty_hangup(port->port.tty);
1404 	}
1405 	port->suspended = false;
1406 	spin_unlock(&port->port_lock);
1407 	spin_unlock_irqrestore(&serial_port_lock, flags);
1408 
1409 	/* disable endpoints, aborting down any active I/O */
1410 	usb_ep_disable(gser->out);
1411 	usb_ep_disable(gser->in);
1412 
1413 	/* finally, free any unused/unusable I/O buffers */
1414 	spin_lock_irqsave(&port->port_lock, flags);
1415 	if (port->port.count == 0)
1416 		kfifo_free(&port->port_write_buf);
1417 	gs_free_requests(gser->out, &port->read_pool, NULL);
1418 	gs_free_requests(gser->out, &port->read_queue, NULL);
1419 	gs_free_requests(gser->in, &port->write_pool, NULL);
1420 
1421 	port->read_allocated = port->read_started =
1422 		port->write_allocated = port->write_started = 0;
1423 
1424 	spin_unlock_irqrestore(&port->port_lock, flags);
1425 }
1426 EXPORT_SYMBOL_GPL(gserial_disconnect);
1427 
1428 void gserial_suspend(struct gserial *gser)
1429 {
1430 	struct gs_port	*port;
1431 	unsigned long	flags;
1432 
1433 	spin_lock_irqsave(&serial_port_lock, flags);
1434 	port = gser->ioport;
1435 
1436 	if (!port) {
1437 		spin_unlock_irqrestore(&serial_port_lock, flags);
1438 		return;
1439 	}
1440 
1441 	spin_lock(&port->port_lock);
1442 	spin_unlock(&serial_port_lock);
1443 	port->suspended = true;
1444 	spin_unlock_irqrestore(&port->port_lock, flags);
1445 }
1446 EXPORT_SYMBOL_GPL(gserial_suspend);
1447 
1448 void gserial_resume(struct gserial *gser)
1449 {
1450 	struct gs_port *port;
1451 	unsigned long	flags;
1452 
1453 	spin_lock_irqsave(&serial_port_lock, flags);
1454 	port = gser->ioport;
1455 
1456 	if (!port) {
1457 		spin_unlock_irqrestore(&serial_port_lock, flags);
1458 		return;
1459 	}
1460 
1461 	spin_lock(&port->port_lock);
1462 	spin_unlock(&serial_port_lock);
1463 	port->suspended = false;
1464 	if (!port->start_delayed) {
1465 		spin_unlock_irqrestore(&port->port_lock, flags);
1466 		return;
1467 	}
1468 
1469 	pr_debug("delayed start ttyGS%d\n", port->port_num);
1470 	gs_start_io(port);
1471 	if (gser->connect)
1472 		gser->connect(gser);
1473 	port->start_delayed = false;
1474 	spin_unlock_irqrestore(&port->port_lock, flags);
1475 }
1476 EXPORT_SYMBOL_GPL(gserial_resume);
1477 
1478 static int __init userial_init(void)
1479 {
1480 	struct tty_driver *driver;
1481 	unsigned			i;
1482 	int				status;
1483 
1484 	driver = tty_alloc_driver(MAX_U_SERIAL_PORTS, TTY_DRIVER_REAL_RAW |
1485 			TTY_DRIVER_DYNAMIC_DEV);
1486 	if (IS_ERR(driver))
1487 		return PTR_ERR(driver);
1488 
1489 	driver->driver_name = "g_serial";
1490 	driver->name = "ttyGS";
1491 	/* uses dynamically assigned dev_t values */
1492 
1493 	driver->type = TTY_DRIVER_TYPE_SERIAL;
1494 	driver->subtype = SERIAL_TYPE_NORMAL;
1495 	driver->init_termios = tty_std_termios;
1496 
1497 	/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
1498 	 * MS-Windows.  Otherwise, most of these flags shouldn't affect
1499 	 * anything unless we were to actually hook up to a serial line.
1500 	 */
1501 	driver->init_termios.c_cflag =
1502 			B9600 | CS8 | CREAD | HUPCL | CLOCAL;
1503 	driver->init_termios.c_ispeed = 9600;
1504 	driver->init_termios.c_ospeed = 9600;
1505 
1506 	tty_set_operations(driver, &gs_tty_ops);
1507 	for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
1508 		mutex_init(&ports[i].lock);
1509 
1510 	/* export the driver ... */
1511 	status = tty_register_driver(driver);
1512 	if (status) {
1513 		pr_err("%s: cannot register, err %d\n",
1514 				__func__, status);
1515 		goto fail;
1516 	}
1517 
1518 	gs_tty_driver = driver;
1519 
1520 	pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
1521 			MAX_U_SERIAL_PORTS,
1522 			(MAX_U_SERIAL_PORTS == 1) ? "" : "s");
1523 
1524 	return status;
1525 fail:
1526 	tty_driver_kref_put(driver);
1527 	return status;
1528 }
1529 module_init(userial_init);
1530 
1531 static void __exit userial_cleanup(void)
1532 {
1533 	tty_unregister_driver(gs_tty_driver);
1534 	tty_driver_kref_put(gs_tty_driver);
1535 	gs_tty_driver = NULL;
1536 }
1537 module_exit(userial_cleanup);
1538 
1539 MODULE_LICENSE("GPL");
1540