Loading...
Note: File does not exist in v6.8.
1/*
2 * u_serial.c - utilities for USB gadget "serial port"/TTY support
3 *
4 * Copyright (C) 2003 Al Borchers (alborchers@steinerpoint.com)
5 * Copyright (C) 2008 David Brownell
6 * Copyright (C) 2008 by Nokia Corporation
7 *
8 * This code also borrows from usbserial.c, which is
9 * Copyright (C) 1999 - 2002 Greg Kroah-Hartman (greg@kroah.com)
10 * Copyright (C) 2000 Peter Berger (pberger@brimson.com)
11 * Copyright (C) 2000 Al Borchers (alborchers@steinerpoint.com)
12 *
13 * This software is distributed under the terms of the GNU General
14 * Public License ("GPL") as published by the Free Software Foundation,
15 * either version 2 of that License or (at your option) any later version.
16 */
17
18/* #define VERBOSE_DEBUG */
19
20#include <linux/kernel.h>
21#include <linux/sched.h>
22#include <linux/interrupt.h>
23#include <linux/device.h>
24#include <linux/delay.h>
25#include <linux/tty.h>
26#include <linux/tty_flip.h>
27#include <linux/slab.h>
28#include <linux/export.h>
29
30#include "u_serial.h"
31
32
33/*
34 * This component encapsulates the TTY layer glue needed to provide basic
35 * "serial port" functionality through the USB gadget stack. Each such
36 * port is exposed through a /dev/ttyGS* node.
37 *
38 * After initialization (gserial_setup), these TTY port devices stay
39 * available until they are removed (gserial_cleanup). Each one may be
40 * connected to a USB function (gserial_connect), or disconnected (with
41 * gserial_disconnect) when the USB host issues a config change event.
42 * Data can only flow when the port is connected to the host.
43 *
44 * A given TTY port can be made available in multiple configurations.
45 * For example, each one might expose a ttyGS0 node which provides a
46 * login application. In one case that might use CDC ACM interface 0,
47 * while another configuration might use interface 3 for that. The
48 * work to handle that (including descriptor management) is not part
49 * of this component.
50 *
51 * Configurations may expose more than one TTY port. For example, if
52 * ttyGS0 provides login service, then ttyGS1 might provide dialer access
53 * for a telephone or fax link. And ttyGS2 might be something that just
54 * needs a simple byte stream interface for some messaging protocol that
55 * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
56 */
57
58#define PREFIX "ttyGS"
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
84/* circular buffer */
85struct gs_buf {
86 unsigned buf_size;
87 char *buf_buf;
88 char *buf_get;
89 char *buf_put;
90};
91
92/*
93 * The port structure holds info for each port, one for each minor number
94 * (and thus for each /dev/ node).
95 */
96struct gs_port {
97 struct tty_port port;
98 spinlock_t port_lock; /* guard port_* access */
99
100 struct gserial *port_usb;
101
102 bool openclose; /* open/close in progress */
103 u8 port_num;
104
105 struct list_head read_pool;
106 int read_started;
107 int read_allocated;
108 struct list_head read_queue;
109 unsigned n_read;
110 struct tasklet_struct push;
111
112 struct list_head write_pool;
113 int write_started;
114 int write_allocated;
115 struct gs_buf port_write_buf;
116 wait_queue_head_t drain_wait; /* wait while writes drain */
117
118 /* REVISIT this state ... */
119 struct usb_cdc_line_coding port_line_coding; /* 8-N-1 etc */
120};
121
122/* increase N_PORTS if you need more */
123#define N_PORTS 4
124static struct portmaster {
125 struct mutex lock; /* protect open/close */
126 struct gs_port *port;
127} ports[N_PORTS];
128static unsigned n_ports;
129
130#define GS_CLOSE_TIMEOUT 15 /* seconds */
131
132
133
134#ifdef VERBOSE_DEBUG
135#define pr_vdebug(fmt, arg...) \
136 pr_debug(fmt, ##arg)
137#else
138#define pr_vdebug(fmt, arg...) \
139 ({ if (0) pr_debug(fmt, ##arg); })
140#endif
141
142/*-------------------------------------------------------------------------*/
143
144/* Circular Buffer */
145
146/*
147 * gs_buf_alloc
148 *
149 * Allocate a circular buffer and all associated memory.
150 */
151static int gs_buf_alloc(struct gs_buf *gb, unsigned size)
152{
153 gb->buf_buf = kmalloc(size, GFP_KERNEL);
154 if (gb->buf_buf == NULL)
155 return -ENOMEM;
156
157 gb->buf_size = size;
158 gb->buf_put = gb->buf_buf;
159 gb->buf_get = gb->buf_buf;
160
161 return 0;
162}
163
164/*
165 * gs_buf_free
166 *
167 * Free the buffer and all associated memory.
168 */
169static void gs_buf_free(struct gs_buf *gb)
170{
171 kfree(gb->buf_buf);
172 gb->buf_buf = NULL;
173}
174
175/*
176 * gs_buf_clear
177 *
178 * Clear out all data in the circular buffer.
179 */
180static void gs_buf_clear(struct gs_buf *gb)
181{
182 gb->buf_get = gb->buf_put;
183 /* equivalent to a get of all data available */
184}
185
186/*
187 * gs_buf_data_avail
188 *
189 * Return the number of bytes of data written into the circular
190 * buffer.
191 */
192static unsigned gs_buf_data_avail(struct gs_buf *gb)
193{
194 return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
195}
196
197/*
198 * gs_buf_space_avail
199 *
200 * Return the number of bytes of space available in the circular
201 * buffer.
202 */
203static unsigned gs_buf_space_avail(struct gs_buf *gb)
204{
205 return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
206}
207
208/*
209 * gs_buf_put
210 *
211 * Copy data data from a user buffer and put it into the circular buffer.
212 * Restrict to the amount of space available.
213 *
214 * Return the number of bytes copied.
215 */
216static unsigned
217gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
218{
219 unsigned len;
220
221 len = gs_buf_space_avail(gb);
222 if (count > len)
223 count = len;
224
225 if (count == 0)
226 return 0;
227
228 len = gb->buf_buf + gb->buf_size - gb->buf_put;
229 if (count > len) {
230 memcpy(gb->buf_put, buf, len);
231 memcpy(gb->buf_buf, buf+len, count - len);
232 gb->buf_put = gb->buf_buf + count - len;
233 } else {
234 memcpy(gb->buf_put, buf, count);
235 if (count < len)
236 gb->buf_put += count;
237 else /* count == len */
238 gb->buf_put = gb->buf_buf;
239 }
240
241 return count;
242}
243
244/*
245 * gs_buf_get
246 *
247 * Get data from the circular buffer and copy to the given buffer.
248 * Restrict to the amount of data available.
249 *
250 * Return the number of bytes copied.
251 */
252static unsigned
253gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
254{
255 unsigned len;
256
257 len = gs_buf_data_avail(gb);
258 if (count > len)
259 count = len;
260
261 if (count == 0)
262 return 0;
263
264 len = gb->buf_buf + gb->buf_size - gb->buf_get;
265 if (count > len) {
266 memcpy(buf, gb->buf_get, len);
267 memcpy(buf+len, gb->buf_buf, count - len);
268 gb->buf_get = gb->buf_buf + count - len;
269 } else {
270 memcpy(buf, gb->buf_get, count);
271 if (count < len)
272 gb->buf_get += count;
273 else /* count == len */
274 gb->buf_get = gb->buf_buf;
275 }
276
277 return count;
278}
279
280/*-------------------------------------------------------------------------*/
281
282/* I/O glue between TTY (upper) and USB function (lower) driver layers */
283
284/*
285 * gs_alloc_req
286 *
287 * Allocate a usb_request and its buffer. Returns a pointer to the
288 * usb_request or NULL if there is an error.
289 */
290struct usb_request *
291gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
292{
293 struct usb_request *req;
294
295 req = usb_ep_alloc_request(ep, kmalloc_flags);
296
297 if (req != NULL) {
298 req->length = len;
299 req->buf = kmalloc(len, kmalloc_flags);
300 if (req->buf == NULL) {
301 usb_ep_free_request(ep, req);
302 return NULL;
303 }
304 }
305
306 return req;
307}
308
309/*
310 * gs_free_req
311 *
312 * Free a usb_request and its buffer.
313 */
314void gs_free_req(struct usb_ep *ep, struct usb_request *req)
315{
316 kfree(req->buf);
317 usb_ep_free_request(ep, req);
318}
319
320/*
321 * gs_send_packet
322 *
323 * If there is data to send, a packet is built in the given
324 * buffer and the size is returned. If there is no data to
325 * send, 0 is returned.
326 *
327 * Called with port_lock held.
328 */
329static unsigned
330gs_send_packet(struct gs_port *port, char *packet, unsigned size)
331{
332 unsigned len;
333
334 len = gs_buf_data_avail(&port->port_write_buf);
335 if (len < size)
336 size = len;
337 if (size != 0)
338 size = gs_buf_get(&port->port_write_buf, packet, size);
339 return size;
340}
341
342/*
343 * gs_start_tx
344 *
345 * This function finds available write requests, calls
346 * gs_send_packet to fill these packets with data, and
347 * continues until either there are no more write requests
348 * available or no more data to send. This function is
349 * run whenever data arrives or write requests are available.
350 *
351 * Context: caller owns port_lock; port_usb is non-null.
352 */
353static int gs_start_tx(struct gs_port *port)
354/*
355__releases(&port->port_lock)
356__acquires(&port->port_lock)
357*/
358{
359 struct list_head *pool = &port->write_pool;
360 struct usb_ep *in = port->port_usb->in;
361 int status = 0;
362 bool do_tty_wake = false;
363
364 while (!list_empty(pool)) {
365 struct usb_request *req;
366 int len;
367
368 if (port->write_started >= QUEUE_SIZE)
369 break;
370
371 req = list_entry(pool->next, struct usb_request, list);
372 len = gs_send_packet(port, req->buf, in->maxpacket);
373 if (len == 0) {
374 wake_up_interruptible(&port->drain_wait);
375 break;
376 }
377 do_tty_wake = true;
378
379 req->length = len;
380 list_del(&req->list);
381 req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
382
383 pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
384 port->port_num, len, *((u8 *)req->buf),
385 *((u8 *)req->buf+1), *((u8 *)req->buf+2));
386
387 /* Drop lock while we call out of driver; completions
388 * could be issued while we do so. Disconnection may
389 * happen too; maybe immediately before we queue this!
390 *
391 * NOTE that we may keep sending data for a while after
392 * the TTY closed (dev->ioport->port_tty is NULL).
393 */
394 spin_unlock(&port->port_lock);
395 status = usb_ep_queue(in, req, GFP_ATOMIC);
396 spin_lock(&port->port_lock);
397
398 if (status) {
399 pr_debug("%s: %s %s err %d\n",
400 __func__, "queue", in->name, status);
401 list_add(&req->list, pool);
402 break;
403 }
404
405 port->write_started++;
406
407 /* abort immediately after disconnect */
408 if (!port->port_usb)
409 break;
410 }
411
412 if (do_tty_wake && port->port.tty)
413 tty_wakeup(port->port.tty);
414 return status;
415}
416
417/*
418 * Context: caller owns port_lock, and port_usb is set
419 */
420static unsigned gs_start_rx(struct gs_port *port)
421/*
422__releases(&port->port_lock)
423__acquires(&port->port_lock)
424*/
425{
426 struct list_head *pool = &port->read_pool;
427 struct usb_ep *out = port->port_usb->out;
428
429 while (!list_empty(pool)) {
430 struct usb_request *req;
431 int status;
432 struct tty_struct *tty;
433
434 /* no more rx if closed */
435 tty = port->port.tty;
436 if (!tty)
437 break;
438
439 if (port->read_started >= QUEUE_SIZE)
440 break;
441
442 req = list_entry(pool->next, struct usb_request, list);
443 list_del(&req->list);
444 req->length = out->maxpacket;
445
446 /* drop lock while we call out; the controller driver
447 * may need to call us back (e.g. for disconnect)
448 */
449 spin_unlock(&port->port_lock);
450 status = usb_ep_queue(out, req, GFP_ATOMIC);
451 spin_lock(&port->port_lock);
452
453 if (status) {
454 pr_debug("%s: %s %s err %d\n",
455 __func__, "queue", out->name, status);
456 list_add(&req->list, pool);
457 break;
458 }
459 port->read_started++;
460
461 /* abort immediately after disconnect */
462 if (!port->port_usb)
463 break;
464 }
465 return port->read_started;
466}
467
468/*
469 * RX tasklet takes data out of the RX queue and hands it up to the TTY
470 * layer until it refuses to take any more data (or is throttled back).
471 * Then it issues reads for any further data.
472 *
473 * If the RX queue becomes full enough that no usb_request is queued,
474 * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
475 * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
476 * can be buffered before the TTY layer's buffers (currently 64 KB).
477 */
478static void gs_rx_push(unsigned long _port)
479{
480 struct gs_port *port = (void *)_port;
481 struct tty_struct *tty;
482 struct list_head *queue = &port->read_queue;
483 bool disconnect = false;
484 bool do_push = false;
485
486 /* hand any queued data to the tty */
487 spin_lock_irq(&port->port_lock);
488 tty = port->port.tty;
489 while (!list_empty(queue)) {
490 struct usb_request *req;
491
492 req = list_first_entry(queue, struct usb_request, list);
493
494 /* discard data if tty was closed */
495 if (!tty)
496 goto recycle;
497
498 /* leave data queued if tty was rx throttled */
499 if (test_bit(TTY_THROTTLED, &tty->flags))
500 break;
501
502 switch (req->status) {
503 case -ESHUTDOWN:
504 disconnect = true;
505 pr_vdebug(PREFIX "%d: shutdown\n", port->port_num);
506 break;
507
508 default:
509 /* presumably a transient fault */
510 pr_warning(PREFIX "%d: unexpected RX status %d\n",
511 port->port_num, req->status);
512 /* FALLTHROUGH */
513 case 0:
514 /* normal completion */
515 break;
516 }
517
518 /* push data to (open) tty */
519 if (req->actual) {
520 char *packet = req->buf;
521 unsigned size = req->actual;
522 unsigned n;
523 int count;
524
525 /* we may have pushed part of this packet already... */
526 n = port->n_read;
527 if (n) {
528 packet += n;
529 size -= n;
530 }
531
532 count = tty_insert_flip_string(tty, packet, size);
533 if (count)
534 do_push = true;
535 if (count != size) {
536 /* stop pushing; TTY layer can't handle more */
537 port->n_read += count;
538 pr_vdebug(PREFIX "%d: rx block %d/%d\n",
539 port->port_num,
540 count, req->actual);
541 break;
542 }
543 port->n_read = 0;
544 }
545recycle:
546 list_move(&req->list, &port->read_pool);
547 port->read_started--;
548 }
549
550 /* Push from tty to ldisc; without low_latency set this is handled by
551 * a workqueue, so we won't get callbacks and can hold port_lock
552 */
553 if (tty && do_push)
554 tty_flip_buffer_push(tty);
555
556
557 /* We want our data queue to become empty ASAP, keeping data
558 * in the tty and ldisc (not here). If we couldn't push any
559 * this time around, there may be trouble unless there's an
560 * implicit tty_unthrottle() call on its way...
561 *
562 * REVISIT we should probably add a timer to keep the tasklet
563 * from starving ... but it's not clear that case ever happens.
564 */
565 if (!list_empty(queue) && tty) {
566 if (!test_bit(TTY_THROTTLED, &tty->flags)) {
567 if (do_push)
568 tasklet_schedule(&port->push);
569 else
570 pr_warning(PREFIX "%d: RX not scheduled?\n",
571 port->port_num);
572 }
573 }
574
575 /* If we're still connected, refill the USB RX queue. */
576 if (!disconnect && port->port_usb)
577 gs_start_rx(port);
578
579 spin_unlock_irq(&port->port_lock);
580}
581
582static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
583{
584 struct gs_port *port = ep->driver_data;
585
586 /* Queue all received data until the tty layer is ready for it. */
587 spin_lock(&port->port_lock);
588 list_add_tail(&req->list, &port->read_queue);
589 tasklet_schedule(&port->push);
590 spin_unlock(&port->port_lock);
591}
592
593static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
594{
595 struct gs_port *port = ep->driver_data;
596
597 spin_lock(&port->port_lock);
598 list_add(&req->list, &port->write_pool);
599 port->write_started--;
600
601 switch (req->status) {
602 default:
603 /* presumably a transient fault */
604 pr_warning("%s: unexpected %s status %d\n",
605 __func__, ep->name, req->status);
606 /* FALL THROUGH */
607 case 0:
608 /* normal completion */
609 gs_start_tx(port);
610 break;
611
612 case -ESHUTDOWN:
613 /* disconnect */
614 pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
615 break;
616 }
617
618 spin_unlock(&port->port_lock);
619}
620
621static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
622 int *allocated)
623{
624 struct usb_request *req;
625
626 while (!list_empty(head)) {
627 req = list_entry(head->next, struct usb_request, list);
628 list_del(&req->list);
629 gs_free_req(ep, req);
630 if (allocated)
631 (*allocated)--;
632 }
633}
634
635static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
636 void (*fn)(struct usb_ep *, struct usb_request *),
637 int *allocated)
638{
639 int i;
640 struct usb_request *req;
641 int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
642
643 /* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
644 * do quite that many this time, don't fail ... we just won't
645 * be as speedy as we might otherwise be.
646 */
647 for (i = 0; i < n; i++) {
648 req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
649 if (!req)
650 return list_empty(head) ? -ENOMEM : 0;
651 req->complete = fn;
652 list_add_tail(&req->list, head);
653 if (allocated)
654 (*allocated)++;
655 }
656 return 0;
657}
658
659/**
660 * gs_start_io - start USB I/O streams
661 * @dev: encapsulates endpoints to use
662 * Context: holding port_lock; port_tty and port_usb are non-null
663 *
664 * We only start I/O when something is connected to both sides of
665 * this port. If nothing is listening on the host side, we may
666 * be pointlessly filling up our TX buffers and FIFO.
667 */
668static int gs_start_io(struct gs_port *port)
669{
670 struct list_head *head = &port->read_pool;
671 struct usb_ep *ep = port->port_usb->out;
672 int status;
673 unsigned started;
674
675 /* Allocate RX and TX I/O buffers. We can't easily do this much
676 * earlier (with GFP_KERNEL) because the requests are coupled to
677 * endpoints, as are the packet sizes we'll be using. Different
678 * configurations may use different endpoints with a given port;
679 * and high speed vs full speed changes packet sizes too.
680 */
681 status = gs_alloc_requests(ep, head, gs_read_complete,
682 &port->read_allocated);
683 if (status)
684 return status;
685
686 status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
687 gs_write_complete, &port->write_allocated);
688 if (status) {
689 gs_free_requests(ep, head, &port->read_allocated);
690 return status;
691 }
692
693 /* queue read requests */
694 port->n_read = 0;
695 started = gs_start_rx(port);
696
697 /* unblock any pending writes into our circular buffer */
698 if (started) {
699 tty_wakeup(port->port.tty);
700 } else {
701 gs_free_requests(ep, head, &port->read_allocated);
702 gs_free_requests(port->port_usb->in, &port->write_pool,
703 &port->write_allocated);
704 status = -EIO;
705 }
706
707 return status;
708}
709
710/*-------------------------------------------------------------------------*/
711
712/* TTY Driver */
713
714/*
715 * gs_open sets up the link between a gs_port and its associated TTY.
716 * That link is broken *only* by TTY close(), and all driver methods
717 * know that.
718 */
719static int gs_open(struct tty_struct *tty, struct file *file)
720{
721 int port_num = tty->index;
722 struct gs_port *port;
723 int status;
724
725 do {
726 mutex_lock(&ports[port_num].lock);
727 port = ports[port_num].port;
728 if (!port)
729 status = -ENODEV;
730 else {
731 spin_lock_irq(&port->port_lock);
732
733 /* already open? Great. */
734 if (port->port.count) {
735 status = 0;
736 port->port.count++;
737
738 /* currently opening/closing? wait ... */
739 } else if (port->openclose) {
740 status = -EBUSY;
741
742 /* ... else we do the work */
743 } else {
744 status = -EAGAIN;
745 port->openclose = true;
746 }
747 spin_unlock_irq(&port->port_lock);
748 }
749 mutex_unlock(&ports[port_num].lock);
750
751 switch (status) {
752 default:
753 /* fully handled */
754 return status;
755 case -EAGAIN:
756 /* must do the work */
757 break;
758 case -EBUSY:
759 /* wait for EAGAIN task to finish */
760 msleep(1);
761 /* REVISIT could have a waitchannel here, if
762 * concurrent open performance is important
763 */
764 break;
765 }
766 } while (status != -EAGAIN);
767
768 /* Do the "real open" */
769 spin_lock_irq(&port->port_lock);
770
771 /* allocate circular buffer on first open */
772 if (port->port_write_buf.buf_buf == NULL) {
773
774 spin_unlock_irq(&port->port_lock);
775 status = gs_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
776 spin_lock_irq(&port->port_lock);
777
778 if (status) {
779 pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
780 port->port_num, tty, file);
781 port->openclose = false;
782 goto exit_unlock_port;
783 }
784 }
785
786 /* REVISIT if REMOVED (ports[].port NULL), abort the open
787 * to let rmmod work faster (but this way isn't wrong).
788 */
789
790 /* REVISIT maybe wait for "carrier detect" */
791
792 tty->driver_data = port;
793 port->port.tty = tty;
794
795 port->port.count = 1;
796 port->openclose = false;
797
798 /* if connected, start the I/O stream */
799 if (port->port_usb) {
800 struct gserial *gser = port->port_usb;
801
802 pr_debug("gs_open: start ttyGS%d\n", port->port_num);
803 gs_start_io(port);
804
805 if (gser->connect)
806 gser->connect(gser);
807 }
808
809 pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
810
811 status = 0;
812
813exit_unlock_port:
814 spin_unlock_irq(&port->port_lock);
815 return status;
816}
817
818static int gs_writes_finished(struct gs_port *p)
819{
820 int cond;
821
822 /* return true on disconnect or empty buffer */
823 spin_lock_irq(&p->port_lock);
824 cond = (p->port_usb == NULL) || !gs_buf_data_avail(&p->port_write_buf);
825 spin_unlock_irq(&p->port_lock);
826
827 return cond;
828}
829
830static void gs_close(struct tty_struct *tty, struct file *file)
831{
832 struct gs_port *port = tty->driver_data;
833 struct gserial *gser;
834
835 spin_lock_irq(&port->port_lock);
836
837 if (port->port.count != 1) {
838 if (port->port.count == 0)
839 WARN_ON(1);
840 else
841 --port->port.count;
842 goto exit;
843 }
844
845 pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
846
847 /* mark port as closing but in use; we can drop port lock
848 * and sleep if necessary
849 */
850 port->openclose = true;
851 port->port.count = 0;
852
853 gser = port->port_usb;
854 if (gser && gser->disconnect)
855 gser->disconnect(gser);
856
857 /* wait for circular write buffer to drain, disconnect, or at
858 * most GS_CLOSE_TIMEOUT seconds; then discard the rest
859 */
860 if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
861 spin_unlock_irq(&port->port_lock);
862 wait_event_interruptible_timeout(port->drain_wait,
863 gs_writes_finished(port),
864 GS_CLOSE_TIMEOUT * HZ);
865 spin_lock_irq(&port->port_lock);
866 gser = port->port_usb;
867 }
868
869 /* Iff we're disconnected, there can be no I/O in flight so it's
870 * ok to free the circular buffer; else just scrub it. And don't
871 * let the push tasklet fire again until we're re-opened.
872 */
873 if (gser == NULL)
874 gs_buf_free(&port->port_write_buf);
875 else
876 gs_buf_clear(&port->port_write_buf);
877
878 tty->driver_data = NULL;
879 port->port.tty = NULL;
880
881 port->openclose = false;
882
883 pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
884 port->port_num, tty, file);
885
886 wake_up_interruptible(&port->port.close_wait);
887exit:
888 spin_unlock_irq(&port->port_lock);
889}
890
891static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
892{
893 struct gs_port *port = tty->driver_data;
894 unsigned long flags;
895 int status;
896
897 pr_vdebug("gs_write: ttyGS%d (%p) writing %d bytes\n",
898 port->port_num, tty, count);
899
900 spin_lock_irqsave(&port->port_lock, flags);
901 if (count)
902 count = gs_buf_put(&port->port_write_buf, buf, count);
903 /* treat count == 0 as flush_chars() */
904 if (port->port_usb)
905 status = gs_start_tx(port);
906 spin_unlock_irqrestore(&port->port_lock, flags);
907
908 return count;
909}
910
911static int gs_put_char(struct tty_struct *tty, unsigned char ch)
912{
913 struct gs_port *port = tty->driver_data;
914 unsigned long flags;
915 int status;
916
917 pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %pf\n",
918 port->port_num, tty, ch, __builtin_return_address(0));
919
920 spin_lock_irqsave(&port->port_lock, flags);
921 status = gs_buf_put(&port->port_write_buf, &ch, 1);
922 spin_unlock_irqrestore(&port->port_lock, flags);
923
924 return status;
925}
926
927static void gs_flush_chars(struct tty_struct *tty)
928{
929 struct gs_port *port = tty->driver_data;
930 unsigned long flags;
931
932 pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
933
934 spin_lock_irqsave(&port->port_lock, flags);
935 if (port->port_usb)
936 gs_start_tx(port);
937 spin_unlock_irqrestore(&port->port_lock, flags);
938}
939
940static int gs_write_room(struct tty_struct *tty)
941{
942 struct gs_port *port = tty->driver_data;
943 unsigned long flags;
944 int room = 0;
945
946 spin_lock_irqsave(&port->port_lock, flags);
947 if (port->port_usb)
948 room = gs_buf_space_avail(&port->port_write_buf);
949 spin_unlock_irqrestore(&port->port_lock, flags);
950
951 pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
952 port->port_num, tty, room);
953
954 return room;
955}
956
957static int gs_chars_in_buffer(struct tty_struct *tty)
958{
959 struct gs_port *port = tty->driver_data;
960 unsigned long flags;
961 int chars = 0;
962
963 spin_lock_irqsave(&port->port_lock, flags);
964 chars = gs_buf_data_avail(&port->port_write_buf);
965 spin_unlock_irqrestore(&port->port_lock, flags);
966
967 pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
968 port->port_num, tty, chars);
969
970 return chars;
971}
972
973/* undo side effects of setting TTY_THROTTLED */
974static void gs_unthrottle(struct tty_struct *tty)
975{
976 struct gs_port *port = tty->driver_data;
977 unsigned long flags;
978
979 spin_lock_irqsave(&port->port_lock, flags);
980 if (port->port_usb) {
981 /* Kickstart read queue processing. We don't do xon/xoff,
982 * rts/cts, or other handshaking with the host, but if the
983 * read queue backs up enough we'll be NAKing OUT packets.
984 */
985 tasklet_schedule(&port->push);
986 pr_vdebug(PREFIX "%d: unthrottle\n", port->port_num);
987 }
988 spin_unlock_irqrestore(&port->port_lock, flags);
989}
990
991static int gs_break_ctl(struct tty_struct *tty, int duration)
992{
993 struct gs_port *port = tty->driver_data;
994 int status = 0;
995 struct gserial *gser;
996
997 pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
998 port->port_num, duration);
999
1000 spin_lock_irq(&port->port_lock);
1001 gser = port->port_usb;
1002 if (gser && gser->send_break)
1003 status = gser->send_break(gser, duration);
1004 spin_unlock_irq(&port->port_lock);
1005
1006 return status;
1007}
1008
1009static const struct tty_operations gs_tty_ops = {
1010 .open = gs_open,
1011 .close = gs_close,
1012 .write = gs_write,
1013 .put_char = gs_put_char,
1014 .flush_chars = gs_flush_chars,
1015 .write_room = gs_write_room,
1016 .chars_in_buffer = gs_chars_in_buffer,
1017 .unthrottle = gs_unthrottle,
1018 .break_ctl = gs_break_ctl,
1019};
1020
1021/*-------------------------------------------------------------------------*/
1022
1023static struct tty_driver *gs_tty_driver;
1024
1025static int
1026gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
1027{
1028 struct gs_port *port;
1029
1030 port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
1031 if (port == NULL)
1032 return -ENOMEM;
1033
1034 tty_port_init(&port->port);
1035 spin_lock_init(&port->port_lock);
1036 init_waitqueue_head(&port->drain_wait);
1037
1038 tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
1039
1040 INIT_LIST_HEAD(&port->read_pool);
1041 INIT_LIST_HEAD(&port->read_queue);
1042 INIT_LIST_HEAD(&port->write_pool);
1043
1044 port->port_num = port_num;
1045 port->port_line_coding = *coding;
1046
1047 ports[port_num].port = port;
1048
1049 return 0;
1050}
1051
1052/**
1053 * gserial_setup - initialize TTY driver for one or more ports
1054 * @g: gadget to associate with these ports
1055 * @count: how many ports to support
1056 * Context: may sleep
1057 *
1058 * The TTY stack needs to know in advance how many devices it should
1059 * plan to manage. Use this call to set up the ports you will be
1060 * exporting through USB. Later, connect them to functions based
1061 * on what configuration is activated by the USB host; and disconnect
1062 * them as appropriate.
1063 *
1064 * An example would be a two-configuration device in which both
1065 * configurations expose port 0, but through different functions.
1066 * One configuration could even expose port 1 while the other
1067 * one doesn't.
1068 *
1069 * Returns negative errno or zero.
1070 */
1071int gserial_setup(struct usb_gadget *g, unsigned count)
1072{
1073 unsigned i;
1074 struct usb_cdc_line_coding coding;
1075 int status;
1076
1077 if (count == 0 || count > N_PORTS)
1078 return -EINVAL;
1079
1080 gs_tty_driver = alloc_tty_driver(count);
1081 if (!gs_tty_driver)
1082 return -ENOMEM;
1083
1084 gs_tty_driver->driver_name = "g_serial";
1085 gs_tty_driver->name = PREFIX;
1086 /* uses dynamically assigned dev_t values */
1087
1088 gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
1089 gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
1090 gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
1091 gs_tty_driver->init_termios = tty_std_termios;
1092
1093 /* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
1094 * MS-Windows. Otherwise, most of these flags shouldn't affect
1095 * anything unless we were to actually hook up to a serial line.
1096 */
1097 gs_tty_driver->init_termios.c_cflag =
1098 B9600 | CS8 | CREAD | HUPCL | CLOCAL;
1099 gs_tty_driver->init_termios.c_ispeed = 9600;
1100 gs_tty_driver->init_termios.c_ospeed = 9600;
1101
1102 coding.dwDTERate = cpu_to_le32(9600);
1103 coding.bCharFormat = 8;
1104 coding.bParityType = USB_CDC_NO_PARITY;
1105 coding.bDataBits = USB_CDC_1_STOP_BITS;
1106
1107 tty_set_operations(gs_tty_driver, &gs_tty_ops);
1108
1109 /* make devices be openable */
1110 for (i = 0; i < count; i++) {
1111 mutex_init(&ports[i].lock);
1112 status = gs_port_alloc(i, &coding);
1113 if (status) {
1114 count = i;
1115 goto fail;
1116 }
1117 }
1118 n_ports = count;
1119
1120 /* export the driver ... */
1121 status = tty_register_driver(gs_tty_driver);
1122 if (status) {
1123 pr_err("%s: cannot register, err %d\n",
1124 __func__, status);
1125 goto fail;
1126 }
1127
1128 /* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
1129 for (i = 0; i < count; i++) {
1130 struct device *tty_dev;
1131
1132 tty_dev = tty_register_device(gs_tty_driver, i, &g->dev);
1133 if (IS_ERR(tty_dev))
1134 pr_warning("%s: no classdev for port %d, err %ld\n",
1135 __func__, i, PTR_ERR(tty_dev));
1136 }
1137
1138 pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
1139 count, (count == 1) ? "" : "s");
1140
1141 return status;
1142fail:
1143 while (count--)
1144 kfree(ports[count].port);
1145 put_tty_driver(gs_tty_driver);
1146 gs_tty_driver = NULL;
1147 return status;
1148}
1149
1150static int gs_closed(struct gs_port *port)
1151{
1152 int cond;
1153
1154 spin_lock_irq(&port->port_lock);
1155 cond = (port->port.count == 0) && !port->openclose;
1156 spin_unlock_irq(&port->port_lock);
1157 return cond;
1158}
1159
1160/**
1161 * gserial_cleanup - remove TTY-over-USB driver and devices
1162 * Context: may sleep
1163 *
1164 * This is called to free all resources allocated by @gserial_setup().
1165 * Accordingly, it may need to wait until some open /dev/ files have
1166 * closed.
1167 *
1168 * The caller must have issued @gserial_disconnect() for any ports
1169 * that had previously been connected, so that there is never any
1170 * I/O pending when it's called.
1171 */
1172void gserial_cleanup(void)
1173{
1174 unsigned i;
1175 struct gs_port *port;
1176
1177 if (!gs_tty_driver)
1178 return;
1179
1180 /* start sysfs and /dev/ttyGS* node removal */
1181 for (i = 0; i < n_ports; i++)
1182 tty_unregister_device(gs_tty_driver, i);
1183
1184 for (i = 0; i < n_ports; i++) {
1185 /* prevent new opens */
1186 mutex_lock(&ports[i].lock);
1187 port = ports[i].port;
1188 ports[i].port = NULL;
1189 mutex_unlock(&ports[i].lock);
1190
1191 tasklet_kill(&port->push);
1192
1193 /* wait for old opens to finish */
1194 wait_event(port->port.close_wait, gs_closed(port));
1195
1196 WARN_ON(port->port_usb != NULL);
1197
1198 kfree(port);
1199 }
1200 n_ports = 0;
1201
1202 tty_unregister_driver(gs_tty_driver);
1203 put_tty_driver(gs_tty_driver);
1204 gs_tty_driver = NULL;
1205
1206 pr_debug("%s: cleaned up ttyGS* support\n", __func__);
1207}
1208
1209/**
1210 * gserial_connect - notify TTY I/O glue that USB link is active
1211 * @gser: the function, set up with endpoints and descriptors
1212 * @port_num: which port is active
1213 * Context: any (usually from irq)
1214 *
1215 * This is called activate endpoints and let the TTY layer know that
1216 * the connection is active ... not unlike "carrier detect". It won't
1217 * necessarily start I/O queues; unless the TTY is held open by any
1218 * task, there would be no point. However, the endpoints will be
1219 * activated so the USB host can perform I/O, subject to basic USB
1220 * hardware flow control.
1221 *
1222 * Caller needs to have set up the endpoints and USB function in @dev
1223 * before calling this, as well as the appropriate (speed-specific)
1224 * endpoint descriptors, and also have set up the TTY driver by calling
1225 * @gserial_setup().
1226 *
1227 * Returns negative errno or zero.
1228 * On success, ep->driver_data will be overwritten.
1229 */
1230int gserial_connect(struct gserial *gser, u8 port_num)
1231{
1232 struct gs_port *port;
1233 unsigned long flags;
1234 int status;
1235
1236 if (!gs_tty_driver || port_num >= n_ports)
1237 return -ENXIO;
1238
1239 /* we "know" gserial_cleanup() hasn't been called */
1240 port = ports[port_num].port;
1241
1242 /* activate the endpoints */
1243 status = usb_ep_enable(gser->in);
1244 if (status < 0)
1245 return status;
1246 gser->in->driver_data = port;
1247
1248 status = usb_ep_enable(gser->out);
1249 if (status < 0)
1250 goto fail_out;
1251 gser->out->driver_data = port;
1252
1253 /* then tell the tty glue that I/O can work */
1254 spin_lock_irqsave(&port->port_lock, flags);
1255 gser->ioport = port;
1256 port->port_usb = gser;
1257
1258 /* REVISIT unclear how best to handle this state...
1259 * we don't really couple it with the Linux TTY.
1260 */
1261 gser->port_line_coding = port->port_line_coding;
1262
1263 /* REVISIT if waiting on "carrier detect", signal. */
1264
1265 /* if it's already open, start I/O ... and notify the serial
1266 * protocol about open/close status (connect/disconnect).
1267 */
1268 if (port->port.count) {
1269 pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
1270 gs_start_io(port);
1271 if (gser->connect)
1272 gser->connect(gser);
1273 } else {
1274 if (gser->disconnect)
1275 gser->disconnect(gser);
1276 }
1277
1278 spin_unlock_irqrestore(&port->port_lock, flags);
1279
1280 return status;
1281
1282fail_out:
1283 usb_ep_disable(gser->in);
1284 gser->in->driver_data = NULL;
1285 return status;
1286}
1287
1288/**
1289 * gserial_disconnect - notify TTY I/O glue that USB link is inactive
1290 * @gser: the function, on which gserial_connect() was called
1291 * Context: any (usually from irq)
1292 *
1293 * This is called to deactivate endpoints and let the TTY layer know
1294 * that the connection went inactive ... not unlike "hangup".
1295 *
1296 * On return, the state is as if gserial_connect() had never been called;
1297 * there is no active USB I/O on these endpoints.
1298 */
1299void gserial_disconnect(struct gserial *gser)
1300{
1301 struct gs_port *port = gser->ioport;
1302 unsigned long flags;
1303
1304 if (!port)
1305 return;
1306
1307 /* tell the TTY glue not to do I/O here any more */
1308 spin_lock_irqsave(&port->port_lock, flags);
1309
1310 /* REVISIT as above: how best to track this? */
1311 port->port_line_coding = gser->port_line_coding;
1312
1313 port->port_usb = NULL;
1314 gser->ioport = NULL;
1315 if (port->port.count > 0 || port->openclose) {
1316 wake_up_interruptible(&port->drain_wait);
1317 if (port->port.tty)
1318 tty_hangup(port->port.tty);
1319 }
1320 spin_unlock_irqrestore(&port->port_lock, flags);
1321
1322 /* disable endpoints, aborting down any active I/O */
1323 usb_ep_disable(gser->out);
1324 gser->out->driver_data = NULL;
1325
1326 usb_ep_disable(gser->in);
1327 gser->in->driver_data = NULL;
1328
1329 /* finally, free any unused/unusable I/O buffers */
1330 spin_lock_irqsave(&port->port_lock, flags);
1331 if (port->port.count == 0 && !port->openclose)
1332 gs_buf_free(&port->port_write_buf);
1333 gs_free_requests(gser->out, &port->read_pool, NULL);
1334 gs_free_requests(gser->out, &port->read_queue, NULL);
1335 gs_free_requests(gser->in, &port->write_pool, NULL);
1336
1337 port->read_allocated = port->read_started =
1338 port->write_allocated = port->write_started = 0;
1339
1340 spin_unlock_irqrestore(&port->port_lock, flags);
1341}