Version:  2.0.40 2.2.26 2.4.37 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16

Linux/drivers/usb/gadget/u_serial.c

  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 #include <linux/module.h>
 30 
 31 #include "u_serial.h"
 32 
 33 
 34 /*
 35  * This component encapsulates the TTY layer glue needed to provide basic
 36  * "serial port" functionality through the USB gadget stack.  Each such
 37  * port is exposed through a /dev/ttyGS* node.
 38  *
 39  * After this module has been loaded, the individual TTY port can be requested
 40  * (gserial_alloc_line()) and it will stay available until they are removed
 41  * (gserial_free_line()). Each one may be connected to a USB function
 42  * (gserial_connect), or disconnected (with gserial_disconnect) when the USB
 43  * host issues a config change event. Data can only flow when the port is
 44  * connected to the host.
 45  *
 46  * A given TTY port can be made available in multiple configurations.
 47  * For example, each one might expose a ttyGS0 node which provides a
 48  * login application.  In one case that might use CDC ACM interface 0,
 49  * while another configuration might use interface 3 for that.  The
 50  * work to handle that (including descriptor management) is not part
 51  * of this component.
 52  *
 53  * Configurations may expose more than one TTY port.  For example, if
 54  * ttyGS0 provides login service, then ttyGS1 might provide dialer access
 55  * for a telephone or fax link.  And ttyGS2 might be something that just
 56  * needs a simple byte stream interface for some messaging protocol that
 57  * is managed in userspace ... OBEX, PTP, and MTP have been mentioned.
 58  */
 59 
 60 #define PREFIX  "ttyGS"
 61 
 62 /*
 63  * gserial is the lifecycle interface, used by USB functions
 64  * gs_port is the I/O nexus, used by the tty driver
 65  * tty_struct links to the tty/filesystem framework
 66  *
 67  * gserial <---> gs_port ... links will be null when the USB link is
 68  * inactive; managed by gserial_{connect,disconnect}().  each gserial
 69  * instance can wrap its own USB control protocol.
 70  *      gserial->ioport == usb_ep->driver_data ... gs_port
 71  *      gs_port->port_usb ... gserial
 72  *
 73  * gs_port <---> tty_struct ... links will be null when the TTY file
 74  * isn't opened; managed by gs_open()/gs_close()
 75  *      gserial->port_tty ... tty_struct
 76  *      tty_struct->driver_data ... gserial
 77  */
 78 
 79 /* RX and TX queues can buffer QUEUE_SIZE packets before they hit the
 80  * next layer of buffering.  For TX that's a circular buffer; for RX
 81  * consider it a NOP.  A third layer is provided by the TTY code.
 82  */
 83 #define QUEUE_SIZE              16
 84 #define WRITE_BUF_SIZE          8192            /* TX only */
 85 
 86 /* circular buffer */
 87 struct gs_buf {
 88         unsigned                buf_size;
 89         char                    *buf_buf;
 90         char                    *buf_get;
 91         char                    *buf_put;
 92 };
 93 
 94 /*
 95  * The port structure holds info for each port, one for each minor number
 96  * (and thus for each /dev/ node).
 97  */
 98 struct gs_port {
 99         struct tty_port         port;
100         spinlock_t              port_lock;      /* guard port_* access */
101 
102         struct gserial          *port_usb;
103 
104         bool                    openclose;      /* open/close in progress */
105         u8                      port_num;
106 
107         struct list_head        read_pool;
108         int read_started;
109         int read_allocated;
110         struct list_head        read_queue;
111         unsigned                n_read;
112         struct tasklet_struct   push;
113 
114         struct list_head        write_pool;
115         int write_started;
116         int write_allocated;
117         struct gs_buf           port_write_buf;
118         wait_queue_head_t       drain_wait;     /* wait while writes drain */
119 
120         /* REVISIT this state ... */
121         struct usb_cdc_line_coding port_line_coding;    /* 8-N-1 etc */
122 };
123 
124 static struct portmaster {
125         struct mutex    lock;                   /* protect open/close */
126         struct gs_port  *port;
127 } ports[MAX_U_SERIAL_PORTS];
128 
129 #define GS_CLOSE_TIMEOUT                15              /* seconds */
130 
131 
132 
133 #ifdef VERBOSE_DEBUG
134 #ifndef pr_vdebug
135 #define pr_vdebug(fmt, arg...) \
136         pr_debug(fmt, ##arg)
137 #endif /* pr_vdebug */
138 #else
139 #ifndef pr_vdebug
140 #define pr_vdebug(fmt, arg...) \
141         ({ if (0) pr_debug(fmt, ##arg); })
142 #endif /* pr_vdebug */
143 #endif
144 
145 /*-------------------------------------------------------------------------*/
146 
147 /* Circular Buffer */
148 
149 /*
150  * gs_buf_alloc
151  *
152  * Allocate a circular buffer and all associated memory.
153  */
154 static int gs_buf_alloc(struct gs_buf *gb, unsigned size)
155 {
156         gb->buf_buf = kmalloc(size, GFP_KERNEL);
157         if (gb->buf_buf == NULL)
158                 return -ENOMEM;
159 
160         gb->buf_size = size;
161         gb->buf_put = gb->buf_buf;
162         gb->buf_get = gb->buf_buf;
163 
164         return 0;
165 }
166 
167 /*
168  * gs_buf_free
169  *
170  * Free the buffer and all associated memory.
171  */
172 static void gs_buf_free(struct gs_buf *gb)
173 {
174         kfree(gb->buf_buf);
175         gb->buf_buf = NULL;
176 }
177 
178 /*
179  * gs_buf_clear
180  *
181  * Clear out all data in the circular buffer.
182  */
183 static void gs_buf_clear(struct gs_buf *gb)
184 {
185         gb->buf_get = gb->buf_put;
186         /* equivalent to a get of all data available */
187 }
188 
189 /*
190  * gs_buf_data_avail
191  *
192  * Return the number of bytes of data written into the circular
193  * buffer.
194  */
195 static unsigned gs_buf_data_avail(struct gs_buf *gb)
196 {
197         return (gb->buf_size + gb->buf_put - gb->buf_get) % gb->buf_size;
198 }
199 
200 /*
201  * gs_buf_space_avail
202  *
203  * Return the number of bytes of space available in the circular
204  * buffer.
205  */
206 static unsigned gs_buf_space_avail(struct gs_buf *gb)
207 {
208         return (gb->buf_size + gb->buf_get - gb->buf_put - 1) % gb->buf_size;
209 }
210 
211 /*
212  * gs_buf_put
213  *
214  * Copy data data from a user buffer and put it into the circular buffer.
215  * Restrict to the amount of space available.
216  *
217  * Return the number of bytes copied.
218  */
219 static unsigned
220 gs_buf_put(struct gs_buf *gb, const char *buf, unsigned count)
221 {
222         unsigned len;
223 
224         len  = gs_buf_space_avail(gb);
225         if (count > len)
226                 count = len;
227 
228         if (count == 0)
229                 return 0;
230 
231         len = gb->buf_buf + gb->buf_size - gb->buf_put;
232         if (count > len) {
233                 memcpy(gb->buf_put, buf, len);
234                 memcpy(gb->buf_buf, buf+len, count - len);
235                 gb->buf_put = gb->buf_buf + count - len;
236         } else {
237                 memcpy(gb->buf_put, buf, count);
238                 if (count < len)
239                         gb->buf_put += count;
240                 else /* count == len */
241                         gb->buf_put = gb->buf_buf;
242         }
243 
244         return count;
245 }
246 
247 /*
248  * gs_buf_get
249  *
250  * Get data from the circular buffer and copy to the given buffer.
251  * Restrict to the amount of data available.
252  *
253  * Return the number of bytes copied.
254  */
255 static unsigned
256 gs_buf_get(struct gs_buf *gb, char *buf, unsigned count)
257 {
258         unsigned len;
259 
260         len = gs_buf_data_avail(gb);
261         if (count > len)
262                 count = len;
263 
264         if (count == 0)
265                 return 0;
266 
267         len = gb->buf_buf + gb->buf_size - gb->buf_get;
268         if (count > len) {
269                 memcpy(buf, gb->buf_get, len);
270                 memcpy(buf+len, gb->buf_buf, count - len);
271                 gb->buf_get = gb->buf_buf + count - len;
272         } else {
273                 memcpy(buf, gb->buf_get, count);
274                 if (count < len)
275                         gb->buf_get += count;
276                 else /* count == len */
277                         gb->buf_get = gb->buf_buf;
278         }
279 
280         return count;
281 }
282 
283 /*-------------------------------------------------------------------------*/
284 
285 /* I/O glue between TTY (upper) and USB function (lower) driver layers */
286 
287 /*
288  * gs_alloc_req
289  *
290  * Allocate a usb_request and its buffer.  Returns a pointer to the
291  * usb_request or NULL if there is an error.
292  */
293 struct usb_request *
294 gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
295 {
296         struct usb_request *req;
297 
298         req = usb_ep_alloc_request(ep, kmalloc_flags);
299 
300         if (req != NULL) {
301                 req->length = len;
302                 req->buf = kmalloc(len, kmalloc_flags);
303                 if (req->buf == NULL) {
304                         usb_ep_free_request(ep, req);
305                         return NULL;
306                 }
307         }
308 
309         return req;
310 }
311 EXPORT_SYMBOL_GPL(gs_alloc_req);
312 
313 /*
314  * gs_free_req
315  *
316  * Free a usb_request and its buffer.
317  */
318 void gs_free_req(struct usb_ep *ep, struct usb_request *req)
319 {
320         kfree(req->buf);
321         usb_ep_free_request(ep, req);
322 }
323 EXPORT_SYMBOL_GPL(gs_free_req);
324 
325 /*
326  * gs_send_packet
327  *
328  * If there is data to send, a packet is built in the given
329  * buffer and the size is returned.  If there is no data to
330  * send, 0 is returned.
331  *
332  * Called with port_lock held.
333  */
334 static unsigned
335 gs_send_packet(struct gs_port *port, char *packet, unsigned size)
336 {
337         unsigned len;
338 
339         len = gs_buf_data_avail(&port->port_write_buf);
340         if (len < size)
341                 size = len;
342         if (size != 0)
343                 size = gs_buf_get(&port->port_write_buf, packet, size);
344         return size;
345 }
346 
347 /*
348  * gs_start_tx
349  *
350  * This function finds available write requests, calls
351  * gs_send_packet to fill these packets with data, and
352  * continues until either there are no more write requests
353  * available or no more data to send.  This function is
354  * run whenever data arrives or write requests are available.
355  *
356  * Context: caller owns port_lock; port_usb is non-null.
357  */
358 static int gs_start_tx(struct gs_port *port)
359 /*
360 __releases(&port->port_lock)
361 __acquires(&port->port_lock)
362 */
363 {
364         struct list_head        *pool = &port->write_pool;
365         struct usb_ep           *in = port->port_usb->in;
366         int                     status = 0;
367         bool                    do_tty_wake = false;
368 
369         while (!list_empty(pool)) {
370                 struct usb_request      *req;
371                 int                     len;
372 
373                 if (port->write_started >= QUEUE_SIZE)
374                         break;
375 
376                 req = list_entry(pool->next, struct usb_request, list);
377                 len = gs_send_packet(port, req->buf, in->maxpacket);
378                 if (len == 0) {
379                         wake_up_interruptible(&port->drain_wait);
380                         break;
381                 }
382                 do_tty_wake = true;
383 
384                 req->length = len;
385                 list_del(&req->list);
386                 req->zero = (gs_buf_data_avail(&port->port_write_buf) == 0);
387 
388                 pr_vdebug(PREFIX "%d: tx len=%d, 0x%02x 0x%02x 0x%02x ...\n",
389                                 port->port_num, len, *((u8 *)req->buf),
390                                 *((u8 *)req->buf+1), *((u8 *)req->buf+2));
391 
392                 /* Drop lock while we call out of driver; completions
393                  * could be issued while we do so.  Disconnection may
394                  * happen too; maybe immediately before we queue this!
395                  *
396                  * NOTE that we may keep sending data for a while after
397                  * the TTY closed (dev->ioport->port_tty is NULL).
398                  */
399                 spin_unlock(&port->port_lock);
400                 status = usb_ep_queue(in, req, GFP_ATOMIC);
401                 spin_lock(&port->port_lock);
402 
403                 if (status) {
404                         pr_debug("%s: %s %s err %d\n",
405                                         __func__, "queue", in->name, status);
406                         list_add(&req->list, pool);
407                         break;
408                 }
409 
410                 port->write_started++;
411 
412                 /* abort immediately after disconnect */
413                 if (!port->port_usb)
414                         break;
415         }
416 
417         if (do_tty_wake && port->port.tty)
418                 tty_wakeup(port->port.tty);
419         return status;
420 }
421 
422 /*
423  * Context: caller owns port_lock, and port_usb is set
424  */
425 static unsigned gs_start_rx(struct gs_port *port)
426 /*
427 __releases(&port->port_lock)
428 __acquires(&port->port_lock)
429 */
430 {
431         struct list_head        *pool = &port->read_pool;
432         struct usb_ep           *out = port->port_usb->out;
433 
434         while (!list_empty(pool)) {
435                 struct usb_request      *req;
436                 int                     status;
437                 struct tty_struct       *tty;
438 
439                 /* no more rx if closed */
440                 tty = port->port.tty;
441                 if (!tty)
442                         break;
443 
444                 if (port->read_started >= QUEUE_SIZE)
445                         break;
446 
447                 req = list_entry(pool->next, struct usb_request, list);
448                 list_del(&req->list);
449                 req->length = out->maxpacket;
450 
451                 /* drop lock while we call out; the controller driver
452                  * may need to call us back (e.g. for disconnect)
453                  */
454                 spin_unlock(&port->port_lock);
455                 status = usb_ep_queue(out, req, GFP_ATOMIC);
456                 spin_lock(&port->port_lock);
457 
458                 if (status) {
459                         pr_debug("%s: %s %s err %d\n",
460                                         __func__, "queue", out->name, status);
461                         list_add(&req->list, pool);
462                         break;
463                 }
464                 port->read_started++;
465 
466                 /* abort immediately after disconnect */
467                 if (!port->port_usb)
468                         break;
469         }
470         return port->read_started;
471 }
472 
473 /*
474  * RX tasklet takes data out of the RX queue and hands it up to the TTY
475  * layer until it refuses to take any more data (or is throttled back).
476  * Then it issues reads for any further data.
477  *
478  * If the RX queue becomes full enough that no usb_request is queued,
479  * the OUT endpoint may begin NAKing as soon as its FIFO fills up.
480  * So QUEUE_SIZE packets plus however many the FIFO holds (usually two)
481  * can be buffered before the TTY layer's buffers (currently 64 KB).
482  */
483 static void gs_rx_push(unsigned long _port)
484 {
485         struct gs_port          *port = (void *)_port;
486         struct tty_struct       *tty;
487         struct list_head        *queue = &port->read_queue;
488         bool                    disconnect = false;
489         bool                    do_push = false;
490 
491         /* hand any queued data to the tty */
492         spin_lock_irq(&port->port_lock);
493         tty = port->port.tty;
494         while (!list_empty(queue)) {
495                 struct usb_request      *req;
496 
497                 req = list_first_entry(queue, struct usb_request, list);
498 
499                 /* leave data queued if tty was rx throttled */
500                 if (tty && test_bit(TTY_THROTTLED, &tty->flags))
501                         break;
502 
503                 switch (req->status) {
504                 case -ESHUTDOWN:
505                         disconnect = true;
506                         pr_vdebug(PREFIX "%d: shutdown\n", port->port_num);
507                         break;
508 
509                 default:
510                         /* presumably a transient fault */
511                         pr_warning(PREFIX "%d: unexpected RX status %d\n",
512                                         port->port_num, req->status);
513                         /* FALLTHROUGH */
514                 case 0:
515                         /* normal completion */
516                         break;
517                 }
518 
519                 /* push data to (open) tty */
520                 if (req->actual) {
521                         char            *packet = req->buf;
522                         unsigned        size = req->actual;
523                         unsigned        n;
524                         int             count;
525 
526                         /* we may have pushed part of this packet already... */
527                         n = port->n_read;
528                         if (n) {
529                                 packet += n;
530                                 size -= n;
531                         }
532 
533                         count = tty_insert_flip_string(&port->port, packet,
534                                         size);
535                         if (count)
536                                 do_push = true;
537                         if (count != size) {
538                                 /* stop pushing; TTY layer can't handle more */
539                                 port->n_read += count;
540                                 pr_vdebug(PREFIX "%d: rx block %d/%d\n",
541                                                 port->port_num,
542                                                 count, req->actual);
543                                 break;
544                         }
545                         port->n_read = 0;
546                 }
547 
548                 list_move(&req->list, &port->read_pool);
549                 port->read_started--;
550         }
551 
552         /* Push from tty to ldisc; this is handled by a workqueue,
553          * so we won't get callbacks and can hold port_lock
554          */
555         if (do_push)
556                 tty_flip_buffer_push(&port->port);
557 
558 
559         /* We want our data queue to become empty ASAP, keeping data
560          * in the tty and ldisc (not here).  If we couldn't push any
561          * this time around, there may be trouble unless there's an
562          * implicit tty_unthrottle() call on its way...
563          *
564          * REVISIT we should probably add a timer to keep the tasklet
565          * from starving ... but it's not clear that case ever happens.
566          */
567         if (!list_empty(queue) && tty) {
568                 if (!test_bit(TTY_THROTTLED, &tty->flags)) {
569                         if (do_push)
570                                 tasklet_schedule(&port->push);
571                         else
572                                 pr_warning(PREFIX "%d: RX not scheduled?\n",
573                                         port->port_num);
574                 }
575         }
576 
577         /* If we're still connected, refill the USB RX queue. */
578         if (!disconnect && port->port_usb)
579                 gs_start_rx(port);
580 
581         spin_unlock_irq(&port->port_lock);
582 }
583 
584 static void gs_read_complete(struct usb_ep *ep, struct usb_request *req)
585 {
586         struct gs_port  *port = ep->driver_data;
587 
588         /* Queue all received data until the tty layer is ready for it. */
589         spin_lock(&port->port_lock);
590         list_add_tail(&req->list, &port->read_queue);
591         tasklet_schedule(&port->push);
592         spin_unlock(&port->port_lock);
593 }
594 
595 static void gs_write_complete(struct usb_ep *ep, struct usb_request *req)
596 {
597         struct gs_port  *port = ep->driver_data;
598 
599         spin_lock(&port->port_lock);
600         list_add(&req->list, &port->write_pool);
601         port->write_started--;
602 
603         switch (req->status) {
604         default:
605                 /* presumably a transient fault */
606                 pr_warning("%s: unexpected %s status %d\n",
607                                 __func__, ep->name, req->status);
608                 /* FALL THROUGH */
609         case 0:
610                 /* normal completion */
611                 gs_start_tx(port);
612                 break;
613 
614         case -ESHUTDOWN:
615                 /* disconnect */
616                 pr_vdebug("%s: %s shutdown\n", __func__, ep->name);
617                 break;
618         }
619 
620         spin_unlock(&port->port_lock);
621 }
622 
623 static void gs_free_requests(struct usb_ep *ep, struct list_head *head,
624                                                          int *allocated)
625 {
626         struct usb_request      *req;
627 
628         while (!list_empty(head)) {
629                 req = list_entry(head->next, struct usb_request, list);
630                 list_del(&req->list);
631                 gs_free_req(ep, req);
632                 if (allocated)
633                         (*allocated)--;
634         }
635 }
636 
637 static int gs_alloc_requests(struct usb_ep *ep, struct list_head *head,
638                 void (*fn)(struct usb_ep *, struct usb_request *),
639                 int *allocated)
640 {
641         int                     i;
642         struct usb_request      *req;
643         int n = allocated ? QUEUE_SIZE - *allocated : QUEUE_SIZE;
644 
645         /* Pre-allocate up to QUEUE_SIZE transfers, but if we can't
646          * do quite that many this time, don't fail ... we just won't
647          * be as speedy as we might otherwise be.
648          */
649         for (i = 0; i < n; i++) {
650                 req = gs_alloc_req(ep, ep->maxpacket, GFP_ATOMIC);
651                 if (!req)
652                         return list_empty(head) ? -ENOMEM : 0;
653                 req->complete = fn;
654                 list_add_tail(&req->list, head);
655                 if (allocated)
656                         (*allocated)++;
657         }
658         return 0;
659 }
660 
661 /**
662  * gs_start_io - start USB I/O streams
663  * @dev: encapsulates endpoints to use
664  * Context: holding port_lock; port_tty and port_usb are non-null
665  *
666  * We only start I/O when something is connected to both sides of
667  * this port.  If nothing is listening on the host side, we may
668  * be pointlessly filling up our TX buffers and FIFO.
669  */
670 static int gs_start_io(struct gs_port *port)
671 {
672         struct list_head        *head = &port->read_pool;
673         struct usb_ep           *ep = port->port_usb->out;
674         int                     status;
675         unsigned                started;
676 
677         /* Allocate RX and TX I/O buffers.  We can't easily do this much
678          * earlier (with GFP_KERNEL) because the requests are coupled to
679          * endpoints, as are the packet sizes we'll be using.  Different
680          * configurations may use different endpoints with a given port;
681          * and high speed vs full speed changes packet sizes too.
682          */
683         status = gs_alloc_requests(ep, head, gs_read_complete,
684                 &port->read_allocated);
685         if (status)
686                 return status;
687 
688         status = gs_alloc_requests(port->port_usb->in, &port->write_pool,
689                         gs_write_complete, &port->write_allocated);
690         if (status) {
691                 gs_free_requests(ep, head, &port->read_allocated);
692                 return status;
693         }
694 
695         /* queue read requests */
696         port->n_read = 0;
697         started = gs_start_rx(port);
698 
699         /* unblock any pending writes into our circular buffer */
700         if (started) {
701                 tty_wakeup(port->port.tty);
702         } else {
703                 gs_free_requests(ep, head, &port->read_allocated);
704                 gs_free_requests(port->port_usb->in, &port->write_pool,
705                         &port->write_allocated);
706                 status = -EIO;
707         }
708 
709         return status;
710 }
711 
712 /*-------------------------------------------------------------------------*/
713 
714 /* TTY Driver */
715 
716 /*
717  * gs_open sets up the link between a gs_port and its associated TTY.
718  * That link is broken *only* by TTY close(), and all driver methods
719  * know that.
720  */
721 static int gs_open(struct tty_struct *tty, struct file *file)
722 {
723         int             port_num = tty->index;
724         struct gs_port  *port;
725         int             status;
726 
727         do {
728                 mutex_lock(&ports[port_num].lock);
729                 port = ports[port_num].port;
730                 if (!port)
731                         status = -ENODEV;
732                 else {
733                         spin_lock_irq(&port->port_lock);
734 
735                         /* already open?  Great. */
736                         if (port->port.count) {
737                                 status = 0;
738                                 port->port.count++;
739 
740                         /* currently opening/closing? wait ... */
741                         } else if (port->openclose) {
742                                 status = -EBUSY;
743 
744                         /* ... else we do the work */
745                         } else {
746                                 status = -EAGAIN;
747                                 port->openclose = true;
748                         }
749                         spin_unlock_irq(&port->port_lock);
750                 }
751                 mutex_unlock(&ports[port_num].lock);
752 
753                 switch (status) {
754                 default:
755                         /* fully handled */
756                         return status;
757                 case -EAGAIN:
758                         /* must do the work */
759                         break;
760                 case -EBUSY:
761                         /* wait for EAGAIN task to finish */
762                         msleep(1);
763                         /* REVISIT could have a waitchannel here, if
764                          * concurrent open performance is important
765                          */
766                         break;
767                 }
768         } while (status != -EAGAIN);
769 
770         /* Do the "real open" */
771         spin_lock_irq(&port->port_lock);
772 
773         /* allocate circular buffer on first open */
774         if (port->port_write_buf.buf_buf == NULL) {
775 
776                 spin_unlock_irq(&port->port_lock);
777                 status = gs_buf_alloc(&port->port_write_buf, WRITE_BUF_SIZE);
778                 spin_lock_irq(&port->port_lock);
779 
780                 if (status) {
781                         pr_debug("gs_open: ttyGS%d (%p,%p) no buffer\n",
782                                 port->port_num, tty, file);
783                         port->openclose = false;
784                         goto exit_unlock_port;
785                 }
786         }
787 
788         /* REVISIT if REMOVED (ports[].port NULL), abort the open
789          * to let rmmod work faster (but this way isn't wrong).
790          */
791 
792         /* REVISIT maybe wait for "carrier detect" */
793 
794         tty->driver_data = port;
795         port->port.tty = tty;
796 
797         port->port.count = 1;
798         port->openclose = false;
799 
800         /* if connected, start the I/O stream */
801         if (port->port_usb) {
802                 struct gserial  *gser = port->port_usb;
803 
804                 pr_debug("gs_open: start ttyGS%d\n", port->port_num);
805                 gs_start_io(port);
806 
807                 if (gser->connect)
808                         gser->connect(gser);
809         }
810 
811         pr_debug("gs_open: ttyGS%d (%p,%p)\n", port->port_num, tty, file);
812 
813         status = 0;
814 
815 exit_unlock_port:
816         spin_unlock_irq(&port->port_lock);
817         return status;
818 }
819 
820 static int gs_writes_finished(struct gs_port *p)
821 {
822         int cond;
823 
824         /* return true on disconnect or empty buffer */
825         spin_lock_irq(&p->port_lock);
826         cond = (p->port_usb == NULL) || !gs_buf_data_avail(&p->port_write_buf);
827         spin_unlock_irq(&p->port_lock);
828 
829         return cond;
830 }
831 
832 static void gs_close(struct tty_struct *tty, struct file *file)
833 {
834         struct gs_port *port = tty->driver_data;
835         struct gserial  *gser;
836 
837         spin_lock_irq(&port->port_lock);
838 
839         if (port->port.count != 1) {
840                 if (port->port.count == 0)
841                         WARN_ON(1);
842                 else
843                         --port->port.count;
844                 goto exit;
845         }
846 
847         pr_debug("gs_close: ttyGS%d (%p,%p) ...\n", port->port_num, tty, file);
848 
849         /* mark port as closing but in use; we can drop port lock
850          * and sleep if necessary
851          */
852         port->openclose = true;
853         port->port.count = 0;
854 
855         gser = port->port_usb;
856         if (gser && gser->disconnect)
857                 gser->disconnect(gser);
858 
859         /* wait for circular write buffer to drain, disconnect, or at
860          * most GS_CLOSE_TIMEOUT seconds; then discard the rest
861          */
862         if (gs_buf_data_avail(&port->port_write_buf) > 0 && gser) {
863                 spin_unlock_irq(&port->port_lock);
864                 wait_event_interruptible_timeout(port->drain_wait,
865                                         gs_writes_finished(port),
866                                         GS_CLOSE_TIMEOUT * HZ);
867                 spin_lock_irq(&port->port_lock);
868                 gser = port->port_usb;
869         }
870 
871         /* Iff we're disconnected, there can be no I/O in flight so it's
872          * ok to free the circular buffer; else just scrub it.  And don't
873          * let the push tasklet fire again until we're re-opened.
874          */
875         if (gser == NULL)
876                 gs_buf_free(&port->port_write_buf);
877         else
878                 gs_buf_clear(&port->port_write_buf);
879 
880         tty->driver_data = NULL;
881         port->port.tty = NULL;
882 
883         port->openclose = false;
884 
885         pr_debug("gs_close: ttyGS%d (%p,%p) done!\n",
886                         port->port_num, tty, file);
887 
888         wake_up(&port->port.close_wait);
889 exit:
890         spin_unlock_irq(&port->port_lock);
891 }
892 
893 static int gs_write(struct tty_struct *tty, const unsigned char *buf, int count)
894 {
895         struct gs_port  *port = tty->driver_data;
896         unsigned long   flags;
897         int             status;
898 
899         pr_vdebug("gs_write: ttyGS%d (%p) writing %d bytes\n",
900                         port->port_num, tty, count);
901 
902         spin_lock_irqsave(&port->port_lock, flags);
903         if (count)
904                 count = gs_buf_put(&port->port_write_buf, buf, count);
905         /* treat count == 0 as flush_chars() */
906         if (port->port_usb)
907                 status = gs_start_tx(port);
908         spin_unlock_irqrestore(&port->port_lock, flags);
909 
910         return count;
911 }
912 
913 static int gs_put_char(struct tty_struct *tty, unsigned char ch)
914 {
915         struct gs_port  *port = tty->driver_data;
916         unsigned long   flags;
917         int             status;
918 
919         pr_vdebug("gs_put_char: (%d,%p) char=0x%x, called from %pf\n",
920                 port->port_num, tty, ch, __builtin_return_address(0));
921 
922         spin_lock_irqsave(&port->port_lock, flags);
923         status = gs_buf_put(&port->port_write_buf, &ch, 1);
924         spin_unlock_irqrestore(&port->port_lock, flags);
925 
926         return status;
927 }
928 
929 static void gs_flush_chars(struct tty_struct *tty)
930 {
931         struct gs_port  *port = tty->driver_data;
932         unsigned long   flags;
933 
934         pr_vdebug("gs_flush_chars: (%d,%p)\n", port->port_num, tty);
935 
936         spin_lock_irqsave(&port->port_lock, flags);
937         if (port->port_usb)
938                 gs_start_tx(port);
939         spin_unlock_irqrestore(&port->port_lock, flags);
940 }
941 
942 static int gs_write_room(struct tty_struct *tty)
943 {
944         struct gs_port  *port = tty->driver_data;
945         unsigned long   flags;
946         int             room = 0;
947 
948         spin_lock_irqsave(&port->port_lock, flags);
949         if (port->port_usb)
950                 room = gs_buf_space_avail(&port->port_write_buf);
951         spin_unlock_irqrestore(&port->port_lock, flags);
952 
953         pr_vdebug("gs_write_room: (%d,%p) room=%d\n",
954                 port->port_num, tty, room);
955 
956         return room;
957 }
958 
959 static int gs_chars_in_buffer(struct tty_struct *tty)
960 {
961         struct gs_port  *port = tty->driver_data;
962         unsigned long   flags;
963         int             chars = 0;
964 
965         spin_lock_irqsave(&port->port_lock, flags);
966         chars = gs_buf_data_avail(&port->port_write_buf);
967         spin_unlock_irqrestore(&port->port_lock, flags);
968 
969         pr_vdebug("gs_chars_in_buffer: (%d,%p) chars=%d\n",
970                 port->port_num, tty, chars);
971 
972         return chars;
973 }
974 
975 /* undo side effects of setting TTY_THROTTLED */
976 static void gs_unthrottle(struct tty_struct *tty)
977 {
978         struct gs_port          *port = tty->driver_data;
979         unsigned long           flags;
980 
981         spin_lock_irqsave(&port->port_lock, flags);
982         if (port->port_usb) {
983                 /* Kickstart read queue processing.  We don't do xon/xoff,
984                  * rts/cts, or other handshaking with the host, but if the
985                  * read queue backs up enough we'll be NAKing OUT packets.
986                  */
987                 tasklet_schedule(&port->push);
988                 pr_vdebug(PREFIX "%d: unthrottle\n", port->port_num);
989         }
990         spin_unlock_irqrestore(&port->port_lock, flags);
991 }
992 
993 static int gs_break_ctl(struct tty_struct *tty, int duration)
994 {
995         struct gs_port  *port = tty->driver_data;
996         int             status = 0;
997         struct gserial  *gser;
998 
999         pr_vdebug("gs_break_ctl: ttyGS%d, send break (%d) \n",
1000                         port->port_num, duration);
1001 
1002         spin_lock_irq(&port->port_lock);
1003         gser = port->port_usb;
1004         if (gser && gser->send_break)
1005                 status = gser->send_break(gser, duration);
1006         spin_unlock_irq(&port->port_lock);
1007 
1008         return status;
1009 }
1010 
1011 static const struct tty_operations gs_tty_ops = {
1012         .open =                 gs_open,
1013         .close =                gs_close,
1014         .write =                gs_write,
1015         .put_char =             gs_put_char,
1016         .flush_chars =          gs_flush_chars,
1017         .write_room =           gs_write_room,
1018         .chars_in_buffer =      gs_chars_in_buffer,
1019         .unthrottle =           gs_unthrottle,
1020         .break_ctl =            gs_break_ctl,
1021 };
1022 
1023 /*-------------------------------------------------------------------------*/
1024 
1025 static struct tty_driver *gs_tty_driver;
1026 
1027 static int
1028 gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
1029 {
1030         struct gs_port  *port;
1031         int             ret = 0;
1032 
1033         mutex_lock(&ports[port_num].lock);
1034         if (ports[port_num].port) {
1035                 ret = -EBUSY;
1036                 goto out;
1037         }
1038 
1039         port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
1040         if (port == NULL) {
1041                 ret = -ENOMEM;
1042                 goto out;
1043         }
1044 
1045         tty_port_init(&port->port);
1046         spin_lock_init(&port->port_lock);
1047         init_waitqueue_head(&port->drain_wait);
1048 
1049         tasklet_init(&port->push, gs_rx_push, (unsigned long) port);
1050 
1051         INIT_LIST_HEAD(&port->read_pool);
1052         INIT_LIST_HEAD(&port->read_queue);
1053         INIT_LIST_HEAD(&port->write_pool);
1054 
1055         port->port_num = port_num;
1056         port->port_line_coding = *coding;
1057 
1058         ports[port_num].port = port;
1059 out:
1060         mutex_unlock(&ports[port_num].lock);
1061         return ret;
1062 }
1063 
1064 static int gs_closed(struct gs_port *port)
1065 {
1066         int cond;
1067 
1068         spin_lock_irq(&port->port_lock);
1069         cond = (port->port.count == 0) && !port->openclose;
1070         spin_unlock_irq(&port->port_lock);
1071         return cond;
1072 }
1073 
1074 static void gserial_free_port(struct gs_port *port)
1075 {
1076         tasklet_kill(&port->push);
1077         /* wait for old opens to finish */
1078         wait_event(port->port.close_wait, gs_closed(port));
1079         WARN_ON(port->port_usb != NULL);
1080         tty_port_destroy(&port->port);
1081         kfree(port);
1082 }
1083 
1084 void gserial_free_line(unsigned char port_num)
1085 {
1086         struct gs_port  *port;
1087 
1088         mutex_lock(&ports[port_num].lock);
1089         if (WARN_ON(!ports[port_num].port)) {
1090                 mutex_unlock(&ports[port_num].lock);
1091                 return;
1092         }
1093         port = ports[port_num].port;
1094         ports[port_num].port = NULL;
1095         mutex_unlock(&ports[port_num].lock);
1096 
1097         gserial_free_port(port);
1098         tty_unregister_device(gs_tty_driver, port_num);
1099 }
1100 EXPORT_SYMBOL_GPL(gserial_free_line);
1101 
1102 int gserial_alloc_line(unsigned char *line_num)
1103 {
1104         struct usb_cdc_line_coding      coding;
1105         struct device                   *tty_dev;
1106         int                             ret;
1107         int                             port_num;
1108 
1109         coding.dwDTERate = cpu_to_le32(9600);
1110         coding.bCharFormat = 8;
1111         coding.bParityType = USB_CDC_NO_PARITY;
1112         coding.bDataBits = USB_CDC_1_STOP_BITS;
1113 
1114         for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
1115                 ret = gs_port_alloc(port_num, &coding);
1116                 if (ret == -EBUSY)
1117                         continue;
1118                 if (ret)
1119                         return ret;
1120                 break;
1121         }
1122         if (ret)
1123                 return ret;
1124 
1125         /* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
1126 
1127         tty_dev = tty_port_register_device(&ports[port_num].port->port,
1128                         gs_tty_driver, port_num, NULL);
1129         if (IS_ERR(tty_dev)) {
1130                 struct gs_port  *port;
1131                 pr_err("%s: failed to register tty for port %d, err %ld\n",
1132                                 __func__, port_num, PTR_ERR(tty_dev));
1133 
1134                 ret = PTR_ERR(tty_dev);
1135                 port = ports[port_num].port;
1136                 ports[port_num].port = NULL;
1137                 gserial_free_port(port);
1138                 goto err;
1139         }
1140         *line_num = port_num;
1141 err:
1142         return ret;
1143 }
1144 EXPORT_SYMBOL_GPL(gserial_alloc_line);
1145 
1146 /**
1147  * gserial_connect - notify TTY I/O glue that USB link is active
1148  * @gser: the function, set up with endpoints and descriptors
1149  * @port_num: which port is active
1150  * Context: any (usually from irq)
1151  *
1152  * This is called activate endpoints and let the TTY layer know that
1153  * the connection is active ... not unlike "carrier detect".  It won't
1154  * necessarily start I/O queues; unless the TTY is held open by any
1155  * task, there would be no point.  However, the endpoints will be
1156  * activated so the USB host can perform I/O, subject to basic USB
1157  * hardware flow control.
1158  *
1159  * Caller needs to have set up the endpoints and USB function in @dev
1160  * before calling this, as well as the appropriate (speed-specific)
1161  * endpoint descriptors, and also have allocate @port_num by calling
1162  * @gserial_alloc_line().
1163  *
1164  * Returns negative errno or zero.
1165  * On success, ep->driver_data will be overwritten.
1166  */
1167 int gserial_connect(struct gserial *gser, u8 port_num)
1168 {
1169         struct gs_port  *port;
1170         unsigned long   flags;
1171         int             status;
1172 
1173         if (port_num >= MAX_U_SERIAL_PORTS)
1174                 return -ENXIO;
1175 
1176         port = ports[port_num].port;
1177         if (!port) {
1178                 pr_err("serial line %d not allocated.\n", port_num);
1179                 return -EINVAL;
1180         }
1181         if (port->port_usb) {
1182                 pr_err("serial line %d is in use.\n", port_num);
1183                 return -EBUSY;
1184         }
1185 
1186         /* activate the endpoints */
1187         status = usb_ep_enable(gser->in);
1188         if (status < 0)
1189                 return status;
1190         gser->in->driver_data = port;
1191 
1192         status = usb_ep_enable(gser->out);
1193         if (status < 0)
1194                 goto fail_out;
1195         gser->out->driver_data = port;
1196 
1197         /* then tell the tty glue that I/O can work */
1198         spin_lock_irqsave(&port->port_lock, flags);
1199         gser->ioport = port;
1200         port->port_usb = gser;
1201 
1202         /* REVISIT unclear how best to handle this state...
1203          * we don't really couple it with the Linux TTY.
1204          */
1205         gser->port_line_coding = port->port_line_coding;
1206 
1207         /* REVISIT if waiting on "carrier detect", signal. */
1208 
1209         /* if it's already open, start I/O ... and notify the serial
1210          * protocol about open/close status (connect/disconnect).
1211          */
1212         if (port->port.count) {
1213                 pr_debug("gserial_connect: start ttyGS%d\n", port->port_num);
1214                 gs_start_io(port);
1215                 if (gser->connect)
1216                         gser->connect(gser);
1217         } else {
1218                 if (gser->disconnect)
1219                         gser->disconnect(gser);
1220         }
1221 
1222         spin_unlock_irqrestore(&port->port_lock, flags);
1223 
1224         return status;
1225 
1226 fail_out:
1227         usb_ep_disable(gser->in);
1228         gser->in->driver_data = NULL;
1229         return status;
1230 }
1231 EXPORT_SYMBOL_GPL(gserial_connect);
1232 /**
1233  * gserial_disconnect - notify TTY I/O glue that USB link is inactive
1234  * @gser: the function, on which gserial_connect() was called
1235  * Context: any (usually from irq)
1236  *
1237  * This is called to deactivate endpoints and let the TTY layer know
1238  * that the connection went inactive ... not unlike "hangup".
1239  *
1240  * On return, the state is as if gserial_connect() had never been called;
1241  * there is no active USB I/O on these endpoints.
1242  */
1243 void gserial_disconnect(struct gserial *gser)
1244 {
1245         struct gs_port  *port = gser->ioport;
1246         unsigned long   flags;
1247 
1248         if (!port)
1249                 return;
1250 
1251         /* tell the TTY glue not to do I/O here any more */
1252         spin_lock_irqsave(&port->port_lock, flags);
1253 
1254         /* REVISIT as above: how best to track this? */
1255         port->port_line_coding = gser->port_line_coding;
1256 
1257         port->port_usb = NULL;
1258         gser->ioport = NULL;
1259         if (port->port.count > 0 || port->openclose) {
1260                 wake_up_interruptible(&port->drain_wait);
1261                 if (port->port.tty)
1262                         tty_hangup(port->port.tty);
1263         }
1264         spin_unlock_irqrestore(&port->port_lock, flags);
1265 
1266         /* disable endpoints, aborting down any active I/O */
1267         usb_ep_disable(gser->out);
1268         gser->out->driver_data = NULL;
1269 
1270         usb_ep_disable(gser->in);
1271         gser->in->driver_data = NULL;
1272 
1273         /* finally, free any unused/unusable I/O buffers */
1274         spin_lock_irqsave(&port->port_lock, flags);
1275         if (port->port.count == 0 && !port->openclose)
1276                 gs_buf_free(&port->port_write_buf);
1277         gs_free_requests(gser->out, &port->read_pool, NULL);
1278         gs_free_requests(gser->out, &port->read_queue, NULL);
1279         gs_free_requests(gser->in, &port->write_pool, NULL);
1280 
1281         port->read_allocated = port->read_started =
1282                 port->write_allocated = port->write_started = 0;
1283 
1284         spin_unlock_irqrestore(&port->port_lock, flags);
1285 }
1286 EXPORT_SYMBOL_GPL(gserial_disconnect);
1287 
1288 static int userial_init(void)
1289 {
1290         unsigned                        i;
1291         int                             status;
1292 
1293         gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
1294         if (!gs_tty_driver)
1295                 return -ENOMEM;
1296 
1297         gs_tty_driver->driver_name = "g_serial";
1298         gs_tty_driver->name = PREFIX;
1299         /* uses dynamically assigned dev_t values */
1300 
1301         gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
1302         gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
1303         gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
1304         gs_tty_driver->init_termios = tty_std_termios;
1305 
1306         /* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
1307          * MS-Windows.  Otherwise, most of these flags shouldn't affect
1308          * anything unless we were to actually hook up to a serial line.
1309          */
1310         gs_tty_driver->init_termios.c_cflag =
1311                         B9600 | CS8 | CREAD | HUPCL | CLOCAL;
1312         gs_tty_driver->init_termios.c_ispeed = 9600;
1313         gs_tty_driver->init_termios.c_ospeed = 9600;
1314 
1315         tty_set_operations(gs_tty_driver, &gs_tty_ops);
1316         for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
1317                 mutex_init(&ports[i].lock);
1318 
1319         /* export the driver ... */
1320         status = tty_register_driver(gs_tty_driver);
1321         if (status) {
1322                 pr_err("%s: cannot register, err %d\n",
1323                                 __func__, status);
1324                 goto fail;
1325         }
1326 
1327         pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
1328                         MAX_U_SERIAL_PORTS,
1329                         (MAX_U_SERIAL_PORTS == 1) ? "" : "s");
1330 
1331         return status;
1332 fail:
1333         put_tty_driver(gs_tty_driver);
1334         gs_tty_driver = NULL;
1335         return status;
1336 }
1337 module_init(userial_init);
1338 
1339 static void userial_cleanup(void)
1340 {
1341         tty_unregister_driver(gs_tty_driver);
1342         put_tty_driver(gs_tty_driver);
1343         gs_tty_driver = NULL;
1344 }
1345 module_exit(userial_cleanup);
1346 
1347 MODULE_LICENSE("GPL");
1348 

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