summaryrefslogtreecommitdiff
path: root/src/libsystemd-terminal/idev-evdev.c
blob: 241743c3fdc7fafb0c9c5b2eabbd2acd88cabb16 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <fcntl.h>
#include <inttypes.h>
#include <libevdev/libevdev.h>
#include <libudev.h>
#include <stdbool.h>
#include <stdlib.h>
#include <systemd/sd-bus.h>
#include <systemd/sd-event.h>
#include <unistd.h>
#include "bus-util.h"
#include "hashmap.h"
#include "idev.h"
#include "idev-internal.h"
#include "macro.h"
#include "udev-util.h"
#include "util.h"

typedef struct idev_evdev idev_evdev;
typedef struct unmanaged_evdev unmanaged_evdev;
typedef struct managed_evdev managed_evdev;

struct idev_evdev {
        idev_element element;
        struct libevdev *evdev;
        int fd;
        sd_event_source *fd_src;
        sd_event_source *idle_src;

        bool unsync : 1;                /* not in-sync with kernel */
        bool resync : 1;                /* re-syncing with kernel */
};

struct unmanaged_evdev {
        idev_evdev evdev;
        char *devnode;
};

struct managed_evdev {
        idev_evdev evdev;
        dev_t devnum;

        sd_bus_slot *slot_pause_device;
        sd_bus_slot *slot_resume_device;
        sd_bus_slot *slot_take_device;

        bool requested : 1;             /* TakeDevice() was sent */
        bool acquired : 1;              /* TakeDevice() was successful */
};

#define idev_evdev_from_element(_e) container_of((_e), idev_evdev, element)
#define unmanaged_evdev_from_element(_e) \
        container_of(idev_evdev_from_element(_e), unmanaged_evdev, evdev)
#define managed_evdev_from_element(_e) \
        container_of(idev_evdev_from_element(_e), managed_evdev, evdev)

#define IDEV_EVDEV_INIT(_vtable, _session) ((idev_evdev){ \
                .element = IDEV_ELEMENT_INIT((_vtable), (_session)), \
                .fd = -1, \
        })

#define IDEV_EVDEV_NAME_MAX (8 + DECIMAL_STR_MAX(unsigned) * 2)

static const idev_element_vtable unmanaged_evdev_vtable;
static const idev_element_vtable managed_evdev_vtable;

static int idev_evdev_resume(idev_evdev *evdev, int dev_fd);
static void idev_evdev_pause(idev_evdev *evdev, bool release);

/*
 * Virtual Evdev Element
 * The virtual evdev element is the base class of all other evdev elements. It
 * uses libevdev to access the kernel evdev API. It supports asynchronous
 * access revocation, re-syncing if events got dropped and more.
 * This element cannot be used by itself. There must be a wrapper around it
 * which opens a file-descriptor and passes it to the virtual evdev element.
 */

static void idev_evdev_name(char *out, dev_t devnum) {
        /* @out must be at least of size IDEV_EVDEV_NAME_MAX */
        sprintf(out, "evdev/%u:%u", major(devnum), minor(devnum));
}

static int idev_evdev_raise(idev_evdev *evdev, struct input_event *event) {
        idev_data data = {
                .type = IDEV_DATA_EVDEV,
                .resync = evdev->resync,
                .evdev = {
                        .event = *event,
                },
        };

        return idev_element_feed(&evdev->element, &data);
}

static void idev_evdev_hup(idev_evdev *evdev) {
        /*
         * On HUP, we close the current fd via idev_evdev_pause(). This drops
         * the event-sources from the main-loop and effectively puts the
         * element asleep. If the HUP is part of a hotplug-event, a following
         * udev-notification will destroy the element. Otherwise, the HUP is
         * either result of access-revokation or a serious error.
         * For unmanaged devices, we should never receive HUP (except for
         * unplug-events). But if we do, something went seriously wrong and we
         * shouldn't try to be clever.
         * Instead, we simply stay asleep and wait for the device to be
         * disabled and then re-enabled (or closed and re-opened). This will
         * re-open the device node and restart the device.
         * For managed devices, a HUP usually means our device-access was
         * revoked. In that case, we simply put the device asleep and wait for
         * logind to notify us once the device is alive again. logind also
         * passes us a new fd. Hence, we don't have to re-enable the device.
         *
         * Long story short: The only thing we have to do here, is close() the
         * file-descriptor and remove it from the main-loop. Everything else is
         * handled via additional events we receive.
         */

        idev_evdev_pause(evdev, true);
}

static int idev_evdev_io(idev_evdev *evdev) {
        idev_element *e = &evdev->element;
        struct input_event ev;
        unsigned int flags;
        int r, error = 0;

        /*
         * Read input-events via libevdev until the input-queue is drained. In
         * case we're disabled, don't do anything. The input-queue might
         * overflow, but we don't care as we have to resync after wake-up,
         * anyway.
         * TODO: libevdev should give us a hint how many events to read. We
         * really want to avoid starvation, so we shouldn't read forever in
         * case we cannot keep up with the kernel.
         * TODO: Make sure libevdev always reports SYN_DROPPED to us, regardless
         * whether any event was synced afterwards.
         * TODO: Forward SYN_DROPPED to attached devices.
         */

        flags = LIBEVDEV_READ_FLAG_NORMAL;
        while (e->enabled) {
                if (evdev->unsync) {
                        /* immediately resync, even if in sync right now */
                        evdev->unsync = false;
                        evdev->resync = false;
                        flags = LIBEVDEV_READ_FLAG_NORMAL;
                        r = libevdev_next_event(evdev->evdev, flags | LIBEVDEV_READ_FLAG_FORCE_SYNC, &ev);
                        if (r < 0 && r != -EAGAIN) {
                                r = 0;
                                goto error;
                        } else if (r != LIBEVDEV_READ_STATUS_SYNC) {
                                log_debug("idev-evdev: %s/%s: cannot force resync: %d",
                                          e->session->name, e->name, r);
                        }
                } else {
                        r = libevdev_next_event(evdev->evdev, flags, &ev);
                }

                if (evdev->resync && r == -EAGAIN) {
                        /* end of re-sync */
                        evdev->resync = false;
                        flags = LIBEVDEV_READ_FLAG_NORMAL;
                } else if (r == -EAGAIN) {
                        /* no data available */
                        break;
                } else if (r < 0) {
                        /* read error */
                        goto error;
                } else if (r == LIBEVDEV_READ_STATUS_SYNC) {
                        if (evdev->resync) {
                                /* sync-event */
                                r = idev_evdev_raise(evdev, &ev);
                                if (r != 0) {
                                        error = r;
                                        break;
                                }
                        } else {
                                /* start of sync */
                                evdev->resync = true;
                                flags = LIBEVDEV_READ_FLAG_SYNC;
                        }
                } else {
                        /* normal event */
                        r = idev_evdev_raise(evdev, &ev);
                        if (r != 0) {
                                error = r;
                                break;
                        }
                }
        }

        if (error < 0)
                log_debug("idev-evdev: %s/%s: error on data event: %s",
                          e->session->name, e->name, strerror(-error));
        return error;

error:
        idev_evdev_hup(evdev);
        return 0; /* idev_evdev_hup() handles the error so discard it */
}

static int idev_evdev_event_fn(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
        idev_evdev *evdev = userdata;

        /* fetch data as long as EPOLLIN is signalled */
        if (revents & EPOLLIN)
                return idev_evdev_io(evdev);

        if (revents & (EPOLLHUP | EPOLLERR))
                idev_evdev_hup(evdev);

        return 0;
}

static int idev_evdev_idle_fn(sd_event_source *s, void *userdata) {
        idev_evdev *evdev = userdata;

        /*
         * The idle-event is raised whenever we have to re-sync the libevdev
         * state from the kernel. We simply call into idev_evdev_io() which
         * flushes the state and re-syncs it if @unsync is set.
         * State has to be synced whenever our view of the kernel device is
         * out of date. This is the case when we open the device, if the
         * kernel's receive buffer overflows, or on other exceptional
         * situations. Events during re-syncs must be forwarded to the upper
         * layers so they can update their view of the device. However, such
         * events must only be handled passively, as they might be out-of-order
         * and/or re-ordered. Therefore, we mark them as 'sync' events.
         */

        if (!evdev->unsync)
                return 0;

        return idev_evdev_io(evdev);
}

static void idev_evdev_destroy(idev_evdev *evdev) {
        assert(evdev);
        assert(evdev->fd < 0);

        libevdev_free(evdev->evdev);
        evdev->evdev = NULL;
}

static void idev_evdev_enable(idev_evdev *evdev) {
        assert(evdev);
        assert(evdev->fd_src);
        assert(evdev->idle_src);

        sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_ON);
        sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_ONESHOT);
}

static void idev_evdev_disable(idev_evdev *evdev) {
        assert(evdev);
        assert(evdev->fd_src);
        assert(evdev->idle_src);

        sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_OFF);
        sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_OFF);
}

static int idev_evdev_resume(idev_evdev *evdev, int dev_fd) {
        idev_element *e = &evdev->element;
        _cleanup_close_ int fd = dev_fd;
        int r, flags;

        if (fd < 0 || evdev->fd == fd) {
                fd = -1;
                if (evdev->fd >= 0 && e->n_open > 0 && e->enabled)
                        idev_evdev_enable(evdev);

                return 0;
        }

        idev_evdev_pause(evdev, true);
        log_debug("idev-evdev: %s/%s: resume", e->session->name, e->name);

        r = fd_nonblock(fd, true);
        if (r < 0)
                return r;

        r = fd_cloexec(fd, true);
        if (r < 0)
                return r;

        flags = fcntl(fd, F_GETFL, 0);
        if (flags < 0)
                return -errno;

        flags &= O_ACCMODE;
        if (flags == O_WRONLY)
                return -EACCES;

        evdev->element.readable = true;
        evdev->element.writable = true;
        if (flags == O_RDONLY)
                evdev->element.writable = false;
        else if (flags == O_WRONLY)
                evdev->element.readable = false;

        /*
         * TODO: We *MUST* re-sync the device so we get a delta of the changed
         * state while we didn't read events from the device. This works just
         * fine with libevdev_change_fd(), however, libevdev_new_from_fd() (or
         * libevdev_set_fd()) don't pass us events for the initial device
         * state. So even if we force a re-sync, we will not get the delta for
         * the initial device state.
         * We really need to fix libevdev to support that!
         */
        if (evdev->evdev)
                r = libevdev_change_fd(evdev->evdev, fd);
        else
                r = libevdev_new_from_fd(fd, &evdev->evdev);

        if (r < 0)
                return r;

        r = sd_event_add_io(e->session->context->event,
                            &evdev->fd_src,
                            fd,
                            EPOLLHUP | EPOLLERR | EPOLLIN,
                            idev_evdev_event_fn,
                            evdev);
        if (r < 0)
                return r;

        r = sd_event_add_defer(e->session->context->event,
                               &evdev->idle_src,
                               idev_evdev_idle_fn,
                               evdev);
        if (r < 0) {
                evdev->fd_src = sd_event_source_unref(evdev->fd_src);
                return r;
        }

        if (e->n_open < 1 || !e->enabled) {
                sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_OFF);
                sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_OFF);
        }

        evdev->unsync = true;
        evdev->fd = fd;

        fd = -1;
        return 0;
}

static void idev_evdev_pause(idev_evdev *evdev, bool release) {
        idev_element *e = &evdev->element;

        if (evdev->fd < 0)
                return;

        log_debug("idev-evdev: %s/%s: pause", e->session->name, e->name);

        if (release) {
                evdev->idle_src = sd_event_source_unref(evdev->idle_src);
                evdev->fd_src = sd_event_source_unref(evdev->fd_src);
                evdev->fd = safe_close(evdev->fd);
        } else {
                idev_evdev_disable(evdev);
        }
}

/*
 * Unmanaged Evdev Element
 * The unmanaged evdev element opens the evdev node for a given input device
 * directly (/dev/input/eventX) and thus needs sufficient privileges. It opens
 * the device only if we really require it and releases it as soon as we're
 * disabled or closed.
 * The unmanaged element can be used in all situations where you have direct
 * access to input device nodes. Unlike managed evdev elements, it can be used
 * outside of user sessions and in emergency situations where logind is not
 * available.
 */

static void unmanaged_evdev_resume(idev_element *e) {
        unmanaged_evdev *eu = unmanaged_evdev_from_element(e);
        int r, fd;

        /*
         * Unmanaged devices can be acquired on-demand. Therefore, don't
         * acquire it unless someone opened the device *and* we're enabled.
         */
        if (e->n_open < 1 || !e->enabled)
                return;

        fd = eu->evdev.fd;
        if (fd < 0) {
                fd = open(eu->devnode, O_RDWR | O_CLOEXEC | O_NOCTTY | O_NONBLOCK);
                if (fd < 0) {
                        if (errno != EACCES && errno != EPERM) {
                                log_debug("idev-evdev: %s/%s: cannot open node %s: %m",
                                          e->session->name, e->name, eu->devnode);
                                return;
                        }

                        fd = open(eu->devnode, O_RDONLY | O_CLOEXEC | O_NOCTTY | O_NONBLOCK);
                        if (fd < 0) {
                                log_debug("idev-evdev: %s/%s: cannot open node %s: %m",
                                          e->session->name, e->name, eu->devnode);
                                return;
                        }

                        e->readable = true;
                        e->writable = false;
                } else {
                        e->readable = true;
                        e->writable = true;
                }
        }

        r = idev_evdev_resume(&eu->evdev, fd);
        if (r < 0)
                log_debug("idev-evdev: %s/%s: cannot resume: %s",
                          e->session->name, e->name, strerror(-r));
}

static void unmanaged_evdev_pause(idev_element *e) {
        unmanaged_evdev *eu = unmanaged_evdev_from_element(e);

        /*
         * Release the device if the device is disabled or there is no-one who
         * opened it. This guarantees we stay only available if we're opened
         * *and* enabled.
         */

        idev_evdev_pause(&eu->evdev, true);
}

static int unmanaged_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
        _cleanup_(idev_element_freep) idev_element *e = NULL;
        char name[IDEV_EVDEV_NAME_MAX];
        unmanaged_evdev *eu;
        const char *devnode;
        dev_t devnum;
        int r;

        assert_return(s, -EINVAL);
        assert_return(ud, -EINVAL);

        devnode = udev_device_get_devnode(ud);
        devnum = udev_device_get_devnum(ud);
        if (!devnode || devnum == 0)
                return -ENODEV;

        idev_evdev_name(name, devnum);

        eu = new0(unmanaged_evdev, 1);
        if (!eu)
                return -ENOMEM;

        e = &eu->evdev.element;
        eu->evdev = IDEV_EVDEV_INIT(&unmanaged_evdev_vtable, s);

        eu->devnode = strdup(devnode);
        if (!eu->devnode)
                return -ENOMEM;

        r = idev_element_add(e, name);
        if (r < 0)
                return r;

        if (out)
                *out = e;
        e = NULL;
        return 0;
}

static void unmanaged_evdev_free(idev_element *e) {
        unmanaged_evdev *eu = unmanaged_evdev_from_element(e);

        idev_evdev_destroy(&eu->evdev);
        free(eu->devnode);
        free(eu);
}

static const idev_element_vtable unmanaged_evdev_vtable = {
        .free                   = unmanaged_evdev_free,
        .enable                 = unmanaged_evdev_resume,
        .disable                = unmanaged_evdev_pause,
        .open                   = unmanaged_evdev_resume,
        .close                  = unmanaged_evdev_pause,
};

/*
 * Managed Evdev Element
 * The managed evdev element uses systemd-logind to acquire evdev devices. This
 * means, we do not open the device node /dev/input/eventX directly. Instead,
 * logind passes us a file-descriptor whenever our session is activated. Thus,
 * we don't need access to the device node directly.
 * Furthermore, whenever the session is put asleep, logind revokes the
 * file-descriptor so we loose access to the device.
 * Managed evdev elements should be preferred over unmanaged elements whenever
 * you run inside a user session with exclusive device access.
 */

static int managed_evdev_take_device_fn(sd_bus *bus,
                                        sd_bus_message *reply,
                                        void *userdata,
                                        sd_bus_error *ret_error) {
        managed_evdev *em = userdata;
        idev_element *e = &em->evdev.element;
        idev_session *s = e->session;
        int r, paused, fd;

        em->slot_take_device = sd_bus_slot_unref(em->slot_take_device);

        if (sd_bus_message_is_method_error(reply, NULL)) {
                const sd_bus_error *error = sd_bus_message_get_error(reply);

                log_debug("idev-evdev: %s/%s: TakeDevice failed: %s: %s",
                          s->name, e->name, error->name, error->message);
                return 0;
        }

        em->acquired = true;

        r = sd_bus_message_read(reply, "hb", &fd, &paused);
        if (r < 0) {
                log_debug("idev-evdev: %s/%s: erroneous TakeDevice reply", s->name, e->name);
                return 0;
        }

        /* If the device is paused, ignore it; we will get the next fd via
         * ResumeDevice signals. */
        if (paused)
                return 0;

        fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
        if (fd < 0) {
                log_debug("idev-evdev: %s/%s: cannot duplicate evdev fd: %m", s->name, e->name);
                return 0;
        }

        r = idev_evdev_resume(&em->evdev, fd);
        if (r < 0)
                log_debug("idev-evdev: %s/%s: cannot resume: %s",
                          s->name, e->name, strerror(-r));

        return 0;
}

static void managed_evdev_resume(idev_element *e) {
        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
        managed_evdev *em = managed_evdev_from_element(e);
        idev_session *s = e->session;
        idev_context *c = s->context;
        int r;

        /*
         * Acquiring managed devices is heavy, so do it only once we're
         * enabled *and* opened by someone.
         */
        if (e->n_open < 1 || !e->enabled)
                return;

        /* bail out if already pending */
        if (em->requested)
                return;

        r = sd_bus_message_new_method_call(c->sysbus,
                                           &m,
                                           "org.freedesktop.login1",
                                           s->path,
                                           "org.freedesktop.login1.Session",
                                           "TakeDevice");
        if (r < 0)
                goto error;

        r = sd_bus_message_append(m, "uu", major(em->devnum), minor(em->devnum));
        if (r < 0)
                goto error;

        r = sd_bus_call_async(c->sysbus,
                              &em->slot_take_device,
                              m,
                              managed_evdev_take_device_fn,
                              em,
                              0);
        if (r < 0)
                goto error;

        em->requested = true;
        return;

error:
        log_debug("idev-evdev: %s/%s: cannot send TakeDevice request: %s",
                  s->name, e->name, strerror(-r));
}

static void managed_evdev_pause(idev_element *e) {
        _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
        managed_evdev *em = managed_evdev_from_element(e);
        idev_session *s = e->session;
        idev_context *c = s->context;
        int r;

        /*
         * Releasing managed devices is heavy. Once acquired, we get
         * notifications for sleep/wake-up events, so there's no reason to
         * release it if disabled but opened. However, if a device is closed,
         * we release it immediately as we don't care for sleep/wake-up events
         * then (even if we're actually enabled).
         */

        idev_evdev_pause(&em->evdev, false);

        if (e->n_open > 0 || !em->requested)
                return;

        /*
         * If TakeDevice() is pending or was successful, make sure to
         * release the device again. We don't care for return-values,
         * so send it without waiting or callbacks.
         * If a failed TakeDevice() is pending, but someone else took
         * the device on the same bus-connection, we might incorrectly
         * release their device. This is an unlikely race, though.
         * Furthermore, you really shouldn't have two users of the
         * controller-API on the same session, on the same devices, *AND* on
         * the same bus-connection. So we don't care for that race..
         */

        idev_evdev_pause(&em->evdev, true);
        em->requested = false;

        if (!em->acquired && !em->slot_take_device)
                return;

        em->slot_take_device = sd_bus_slot_unref(em->slot_take_device);
        em->acquired = false;

        r = sd_bus_message_new_method_call(c->sysbus,
                                           &m,
                                           "org.freedesktop.login1",
                                           s->path,
                                           "org.freedesktop.login1.Session",
                                           "ReleaseDevice");
        if (r >= 0) {
                r = sd_bus_message_append(m, "uu", major(em->devnum), minor(em->devnum));
                if (r >= 0)
                        r = sd_bus_send(c->sysbus, m, NULL);
        }

        if (r < 0 && r != -ENOTCONN)
                log_debug("idev-evdev: %s/%s: cannot send ReleaseDevice: %s",
                          s->name, e->name, strerror(-r));
}

static int managed_evdev_pause_device_fn(sd_bus *bus,
                                         sd_bus_message *signal,
                                         void *userdata,
                                         sd_bus_error *ret_error) {
        managed_evdev *em = userdata;
        idev_element *e = &em->evdev.element;
        idev_session *s = e->session;
        idev_context *c = s->context;
        uint32_t major, minor;
        const char *mode;
        int r;

        /*
         * We get PauseDevice() signals from logind whenever a device we
         * requested was, or is about to be, paused. Arguments are major/minor
         * number of the device and the mode of the operation.
         * In case the event is not about our device, we ignore it. Otherwise,
         * we treat it as asynchronous access-revocation (as if we got HUP on
         * the device fd). Note that we might have already treated the HUP
         * event via EPOLLHUP, whichever comes first.
         *
         * @mode can be one of the following:
         *   "pause": The device is about to be paused. We must react
         *            immediately and respond with PauseDeviceComplete(). Once
         *            we replied, logind will pause the device. Note that
         *            logind might apply any kind of timeout and force pause
         *            the device if we don't respond in a timely manner. In
         *            this case, we will receive a second PauseDevice event
         *            with @mode set to "force" (or similar).
         *   "force": The device was disabled forecfully by logind. Access is
         *            already revoked. This is just an asynchronous
         *            notification so we can put the device asleep (in case
         *            we didn't already notice the access revocation).
         *    "gone": This is like "force" but is sent if the device was
         *            paused due to a device-removal event.
         *
         * We always handle PauseDevice signals as "force" as we properly
         * support asynchronous access revocation, anyway. But in case logind
         * sent mode "pause", we also call PauseDeviceComplete() to immediately
         * acknowledge the request.
         */

        r = sd_bus_message_read(signal, "uus", &major, &minor, &mode);
        if (r < 0) {
                log_debug("idev-evdev: %s/%s: erroneous PauseDevice signal",
                          s->name, e->name);
                return 0;
        }

        /* not our device? */
        if (makedev(major, minor) != em->devnum)
                return 0;

        idev_evdev_pause(&em->evdev, true);

        if (streq(mode, "pause")) {
                _cleanup_bus_message_unref_ sd_bus_message *m = NULL;

                /*
                 * Sending PauseDeviceComplete() is racy if logind triggers the
                 * timeout. That is, if we take too long and logind pauses the
                 * device by sending a forced PauseDevice, our
                 * PauseDeviceComplete call will be stray. That's fine, though.
                 * logind ignores such stray calls. Only if logind also sent a
                 * further PauseDevice() signal, it might match our call
                 * incorrectly to the newer PauseDevice(). That's fine, too, as
                 * we handle that event asynchronously, anyway. Therefore,
                 * whatever happens, we're fine. Yay!
                 */

                r = sd_bus_message_new_method_call(c->sysbus,
                                                   &m,
                                                   "org.freedesktop.login1",
                                                   s->path,
                                                   "org.freedesktop.login1.Session",
                                                   "PauseDeviceComplete");
                if (r >= 0) {
                        r = sd_bus_message_append(m, "uu", major, minor);
                        if (r >= 0)
                                r = sd_bus_send(c->sysbus, m, NULL);
                }

                if (r < 0)
                        log_debug("idev-evdev: %s/%s: cannot send PauseDeviceComplete: %s",
                                  s->name, e->name, strerror(-r));
        }

        return 0;
}

static int managed_evdev_resume_device_fn(sd_bus *bus,
                                          sd_bus_message *signal,
                                          void *userdata,
                                          sd_bus_error *ret_error) {
        managed_evdev *em = userdata;
        idev_element *e = &em->evdev.element;
        idev_session *s = e->session;
        uint32_t major, minor;
        int r, fd;

        /*
         * We get ResumeDevice signals whenever logind resumed a previously
         * paused device. The arguments contain the major/minor number of the
         * related device and a new file-descriptor for the freshly opened
         * device-node.
         * If the signal is not about our device, we simply ignore it.
         * Otherwise, we take the file-descriptor and immediately resume the
         * device.
         */

        r = sd_bus_message_read(signal, "uuh", &major, &minor, &fd);
        if (r < 0) {
                log_debug("idev-evdev: %s/%s: erroneous ResumeDevice signal",
                          s->name, e->name);
                return 0;
        }

        /* not our device? */
        if (makedev(major, minor) != em->devnum)
                return 0;

        fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
        if (fd < 0) {
                log_debug("idev-evdev: %s/%s: cannot duplicate evdev fd: %m",
                          s->name, e->name);
                return 0;
        }

        r = idev_evdev_resume(&em->evdev, fd);
        if (r < 0)
                log_debug("idev-evdev: %s/%s: cannot resume: %s",
                          s->name, e->name, strerror(-r));

        return 0;
}

static int managed_evdev_setup_bus(managed_evdev *em) {
        idev_element *e = &em->evdev.element;
        idev_session *s = e->session;
        idev_context *c = s->context;
        _cleanup_free_ char *match = NULL;
        int r;

        match = strjoin("type='signal',"
                        "sender='org.freedesktop.login1',"
                        "interface='org.freedesktop.login1.Session',"
                        "member='PauseDevice',"
                        "path='", s->path, "'",
                        NULL);
        if (!match)
                return -ENOMEM;

        r = sd_bus_add_match(c->sysbus,
                             &em->slot_pause_device,
                             match,
                             managed_evdev_pause_device_fn,
                             em);
        if (r < 0)
                return r;

        free(match);
        match = strjoin("type='signal',"
                        "sender='org.freedesktop.login1',"
                        "interface='org.freedesktop.login1.Session',"
                        "member='ResumeDevice',"
                        "path='", s->path, "'",
                        NULL);
        if (!match)
                return -ENOMEM;

        r = sd_bus_add_match(c->sysbus,
                             &em->slot_resume_device,
                             match,
                             managed_evdev_resume_device_fn,
                             em);
        if (r < 0)
                return r;

        return 0;
}

static int managed_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
        _cleanup_(idev_element_freep) idev_element *e = NULL;
        char name[IDEV_EVDEV_NAME_MAX];
        managed_evdev *em;
        dev_t devnum;
        int r;

        assert_return(s, -EINVAL);
        assert_return(s->context->sysbus, -EINVAL);
        assert_return(s->managed, -EINVAL);
        assert_return(s->context->sysbus, -EINVAL);
        assert_return(ud, -EINVAL);

        devnum = udev_device_get_devnum(ud);
        if (devnum == 0)
                return -ENODEV;

        idev_evdev_name(name, devnum);

        em = new0(managed_evdev, 1);
        if (!em)
                return -ENOMEM;

        e = &em->evdev.element;
        em->evdev = IDEV_EVDEV_INIT(&managed_evdev_vtable, s);
        em->devnum = devnum;

        r = managed_evdev_setup_bus(em);
        if (r < 0)
                return r;

        r = idev_element_add(e, name);
        if (r < 0)
                return r;

        if (out)
                *out = e;
        e = NULL;
        return 0;
}

static void managed_evdev_free(idev_element *e) {
        managed_evdev *em = managed_evdev_from_element(e);

        em->slot_resume_device = sd_bus_slot_unref(em->slot_resume_device);
        em->slot_pause_device = sd_bus_slot_unref(em->slot_pause_device);
        idev_evdev_destroy(&em->evdev);
        free(em);
}

static const idev_element_vtable managed_evdev_vtable = {
        .free                   = managed_evdev_free,
        .enable                 = managed_evdev_resume,
        .disable                = managed_evdev_pause,
        .open                   = managed_evdev_resume,
        .close                  = managed_evdev_pause,
};

/*
 * Generic Constructor
 * Instead of relying on the caller to choose between managed and unmanaged
 * evdev devices, the idev_evdev_new() constructor does that for you (by
 * looking at s->managed).
 */

bool idev_is_evdev(idev_element *e) {
        return e && (e->vtable == &unmanaged_evdev_vtable ||
                     e->vtable == &managed_evdev_vtable);
}

idev_element *idev_find_evdev(idev_session *s, dev_t devnum) {
        char name[IDEV_EVDEV_NAME_MAX];

        assert_return(s, NULL);
        assert_return(devnum != 0, NULL);

        idev_evdev_name(name, devnum);
        return idev_find_element(s, name);
}

int idev_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
        assert_return(s, -EINVAL);
        assert_return(ud, -EINVAL);

        return s->managed ? managed_evdev_new(out, s, ud) : unmanaged_evdev_new(out, s, ud);
}