src/libsystemd-terminal/idev-evdev.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU Lesser General Public License as published by
  10   the Free Software Foundation; either version 2.1 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   Lesser General Public License for more details.
  17
  18   You should have received a copy of the GNU Lesser General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <fcntl.h>
  23 #include <libevdev/libevdev.h>
  24 #include <libudev.h>
  25 #include <stdbool.h>
  26 #include <stdlib.h>
  27 #include <systemd/sd-bus.h>
  28 #include <systemd/sd-event.h>
  29 #include "bus-util.h"
  30 #include "idev.h"
  31 #include "idev-internal.h"
  32 #include "macro.h"
  33 #include "util.h"
  34
  35 typedef struct idev_evdev idev_evdev;
  36 typedef struct unmanaged_evdev unmanaged_evdev;
  37 typedef struct managed_evdev managed_evdev;
  38
  39 struct idev_evdev {
  40         idev_element element;
  41         struct libevdev *evdev;
  42         int fd;
  43         sd_event_source *fd_src;
  44         sd_event_source *idle_src;
  45
  46         bool unsync : 1;                /* not in-sync with kernel */
  47         bool resync : 1;                /* re-syncing with kernel */
  48         bool running : 1;
  49 };
  50
  51 struct unmanaged_evdev {
  52         idev_evdev evdev;
  53         char *devnode;
  54 };
  55
  56 struct managed_evdev {
  57         idev_evdev evdev;
  58         dev_t devnum;
  59         sd_bus_slot *slot_take_device;
  60
  61         bool requested : 1;             /* TakeDevice() was sent */
  62         bool acquired : 1;              /* TakeDevice() was successful */
  63 };
  64
  65 #define idev_evdev_from_element(_e) container_of((_e), idev_evdev, element)
  66 #define unmanaged_evdev_from_element(_e) \
  67         container_of(idev_evdev_from_element(_e), unmanaged_evdev, evdev)
  68 #define managed_evdev_from_element(_e) \
  69         container_of(idev_evdev_from_element(_e), managed_evdev, evdev)
  70
  71 #define IDEV_EVDEV_INIT(_vtable, _session) ((idev_evdev){ \
  72                 .element = IDEV_ELEMENT_INIT((_vtable), (_session)), \
  73                 .fd = -1, \
  74         })
  75
  76 #define IDEV_EVDEV_NAME_MAX (8 + DECIMAL_STR_MAX(unsigned) * 2)
  77
  78 static const idev_element_vtable unmanaged_evdev_vtable;
  79 static const idev_element_vtable managed_evdev_vtable;
  80
  81 static int idev_evdev_resume(idev_evdev *evdev, int dev_fd);
  82 static void idev_evdev_pause(idev_evdev *evdev, bool release);
  83
  84 /*
  85  * Virtual Evdev Element
  86  * The virtual evdev element is the base class of all other evdev elements. It
  87  * uses libevdev to access the kernel evdev API. It supports asynchronous
  88  * access revocation, re-syncing if events got dropped and more.
  89  * This element cannot be used by itself. There must be a wrapper around it
  90  * which opens a file-descriptor and passes it to the virtual evdev element.
  91  */
  92
  93 static void idev_evdev_name(char *out, dev_t devnum) {
  94         /* @out must be at least of size IDEV_EVDEV_NAME_MAX */
  95         sprintf(out, "evdev/%u:%u", major(devnum), minor(devnum));
  96 }
  97
  98 static int idev_evdev_feed_resync(idev_evdev *evdev) {
  99         idev_data data = {
 100                 .type = IDEV_DATA_RESYNC,
 101                 .resync = evdev->resync,
 102         };
 103
 104         return idev_element_feed(&evdev->element, &data);
 105 }
 106
 107 static int idev_evdev_feed_evdev(idev_evdev *evdev, struct input_event *event) {
 108         idev_data data = {
 109                 .type = IDEV_DATA_EVDEV,
 110                 .resync = evdev->resync,
 111                 .evdev = {
 112                         .event = *event,
 113                 },
 114         };
 115
 116         return idev_element_feed(&evdev->element, &data);
 117 }
 118
 119 static void idev_evdev_hup(idev_evdev *evdev) {
 120         /*
 121          * On HUP, we close the current fd via idev_evdev_pause(). This drops
 122          * the event-sources from the main-loop and effectively puts the
 123          * element asleep. If the HUP is part of a hotplug-event, a following
 124          * udev-notification will destroy the element. Otherwise, the HUP is
 125          * either result of access-revokation or a serious error.
 126          * For unmanaged devices, we should never receive HUP (except for
 127          * unplug-events). But if we do, something went seriously wrong and we
 128          * shouldn't try to be clever.
 129          * Instead, we simply stay asleep and wait for the device to be
 130          * disabled and then re-enabled (or closed and re-opened). This will
 131          * re-open the device node and restart the device.
 132          * For managed devices, a HUP usually means our device-access was
 133          * revoked. In that case, we simply put the device asleep and wait for
 134          * logind to notify us once the device is alive again. logind also
 135          * passes us a new fd. Hence, we don't have to re-enable the device.
 136          *
 137          * Long story short: The only thing we have to do here, is close() the
 138          * file-descriptor and remove it from the main-loop. Everything else is
 139          * handled via additional events we receive.
 140          */
 141
 142         idev_evdev_pause(evdev, true);
 143 }
 144
 145 static int idev_evdev_io(idev_evdev *evdev) {
 146         idev_element *e = &evdev->element;
 147         struct input_event ev;
 148         unsigned int flags;
 149         int r, error = 0;
 150
 151         /*
 152          * Read input-events via libevdev until the input-queue is drained. In
 153          * case we're disabled, don't do anything. The input-queue might
 154          * overflow, but we don't care as we have to resync after wake-up,
 155          * anyway.
 156          * TODO: libevdev should give us a hint how many events to read. We
 157          * really want to avoid starvation, so we shouldn't read forever in
 158          * case we cannot keep up with the kernel.
 159          * TODO: Make sure libevdev always reports SYN_DROPPED to us, regardless
 160          * whether any event was synced afterwards.
 161          */
 162
 163         flags = LIBEVDEV_READ_FLAG_NORMAL;
 164         while (e->enabled) {
 165                 if (evdev->unsync) {
 166                         /* immediately resync, even if in sync right now */
 167                         evdev->unsync = false;
 168                         evdev->resync = false;
 169                         flags = LIBEVDEV_READ_FLAG_NORMAL;
 170                         r = libevdev_next_event(evdev->evdev, flags | LIBEVDEV_READ_FLAG_FORCE_SYNC, &ev);
 171                         if (r < 0 && r != -EAGAIN) {
 172                                 r = 0;
 173                                 goto error;
 174                         } else if (r != LIBEVDEV_READ_STATUS_SYNC) {
 175                                 log_debug("idev-evdev: %s/%s: cannot force resync: %d",
 176                                           e->session->name, e->name, r);
 177                         }
 178                 } else {
 179                         r = libevdev_next_event(evdev->evdev, flags, &ev);
 180                 }
 181
 182                 if (evdev->resync && r == -EAGAIN) {
 183                         /* end of re-sync */
 184                         evdev->resync = false;
 185                         flags = LIBEVDEV_READ_FLAG_NORMAL;
 186                 } else if (r == -EAGAIN) {
 187                         /* no data available */
 188                         break;
 189                 } else if (r < 0) {
 190                         /* read error */
 191                         goto error;
 192                 } else if (r == LIBEVDEV_READ_STATUS_SYNC) {
 193                         if (evdev->resync) {
 194                                 /* sync-event */
 195                                 r = idev_evdev_feed_evdev(evdev, &ev);
 196                                 if (r != 0) {
 197                                         error = r;
 198                                         break;
 199                                 }
 200                         } else {
 201                                 /* start of sync */
 202                                 evdev->resync = true;
 203                                 flags = LIBEVDEV_READ_FLAG_SYNC;
 204                                 r = idev_evdev_feed_resync(evdev);
 205                                 if (r != 0) {
 206                                         error = r;
 207                                         break;
 208                                 }
 209                         }
 210                 } else {
 211                         /* normal event */
 212                         r = idev_evdev_feed_evdev(evdev, &ev);
 213                         if (r != 0) {
 214                                 error = r;
 215                                 break;
 216                         }
 217                 }
 218         }
 219
 220         if (error < 0)
 221                 log_debug_errno(error, "idev-evdev: %s/%s: error on data event: %m",
 222                                 e->session->name, e->name);
 223         return error;
 224
 225 error:
 226         idev_evdev_hup(evdev);
 227         return 0; /* idev_evdev_hup() handles the error so discard it */
 228 }
 229
 230 static int idev_evdev_event_fn(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 231         idev_evdev *evdev = userdata;
 232
 233         /* fetch data as long as EPOLLIN is signalled */
 234         if (revents & EPOLLIN)
 235                 return idev_evdev_io(evdev);
 236
 237         if (revents & (EPOLLHUP | EPOLLERR))
 238                 idev_evdev_hup(evdev);
 239
 240         return 0;
 241 }
 242
 243 static int idev_evdev_idle_fn(sd_event_source *s, void *userdata) {
 244         idev_evdev *evdev = userdata;
 245
 246         /*
 247          * The idle-event is raised whenever we have to re-sync the libevdev
 248          * state from the kernel. We simply call into idev_evdev_io() which
 249          * flushes the state and re-syncs it if @unsync is set.
 250          * State has to be synced whenever our view of the kernel device is
 251          * out of date. This is the case when we open the device, if the
 252          * kernel's receive buffer overflows, or on other exceptional
 253          * situations. Events during re-syncs must be forwarded to the upper
 254          * layers so they can update their view of the device. However, such
 255          * events must only be handled passively, as they might be out-of-order
 256          * and/or re-ordered. Therefore, we mark them as 'sync' events.
 257          */
 258
 259         if (!evdev->unsync)
 260                 return 0;
 261
 262         return idev_evdev_io(evdev);
 263 }
 264
 265 static void idev_evdev_destroy(idev_evdev *evdev) {
 266         assert(evdev);
 267         assert(evdev->fd < 0);
 268
 269         libevdev_free(evdev->evdev);
 270         evdev->evdev = NULL;
 271 }
 272
 273 static void idev_evdev_enable(idev_evdev *evdev) {
 274         assert(evdev);
 275         assert(evdev->fd_src);
 276         assert(evdev->idle_src);
 277
 278         if (evdev->running)
 279                 return;
 280         if (evdev->fd < 0 || evdev->element.n_open < 1 || !evdev->element.enabled)
 281                 return;
 282
 283         evdev->running = true;
 284         sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_ON);
 285         sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_ONESHOT);
 286 }
 287
 288 static void idev_evdev_disable(idev_evdev *evdev) {
 289         assert(evdev);
 290         assert(evdev->fd_src);
 291         assert(evdev->idle_src);
 292
 293         if (!evdev->running)
 294                 return;
 295
 296         evdev->running = false;
 297         idev_evdev_feed_resync(evdev);
 298         sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_OFF);
 299         sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_OFF);
 300 }
 301
 302 static int idev_evdev_resume(idev_evdev *evdev, int dev_fd) {
 303         idev_element *e = &evdev->element;
 304         _cleanup_close_ int fd = dev_fd;
 305         int r, flags;
 306
 307         if (fd < 0 || evdev->fd == fd) {
 308                 fd = -1;
 309                 idev_evdev_enable(evdev);
 310                 return 0;
 311         }
 312
 313         idev_evdev_pause(evdev, true);
 314         log_debug("idev-evdev: %s/%s: resume", e->session->name, e->name);
 315
 316         r = fd_nonblock(fd, true);
 317         if (r < 0)
 318                 return r;
 319
 320         r = fd_cloexec(fd, true);
 321         if (r < 0)
 322                 return r;
 323
 324         flags = fcntl(fd, F_GETFL, 0);
 325         if (flags < 0)
 326                 return -errno;
 327
 328         flags &= O_ACCMODE;
 329         if (flags == O_WRONLY)
 330                 return -EACCES;
 331
 332         evdev->element.readable = true;
 333         evdev->element.writable = !(flags & O_RDONLY);
 334
 335         /*
 336          * TODO: We *MUST* re-sync the device so we get a delta of the changed
 337          * state while we didn't read events from the device. This works just
 338          * fine with libevdev_change_fd(), however, libevdev_new_from_fd() (or
 339          * libevdev_set_fd()) don't pass us events for the initial device
 340          * state. So even if we force a re-sync, we will not get the delta for
 341          * the initial device state.
 342          * We really need to fix libevdev to support that!
 343          */
 344         if (evdev->evdev)
 345                 r = libevdev_change_fd(evdev->evdev, fd);
 346         else
 347                 r = libevdev_new_from_fd(fd, &evdev->evdev);
 348
 349         if (r < 0)
 350                 return r;
 351
 352         r = sd_event_add_io(e->session->context->event,
 353                             &evdev->fd_src,
 354                             fd,
 355                             EPOLLHUP | EPOLLERR | EPOLLIN,
 356                             idev_evdev_event_fn,
 357                             evdev);
 358         if (r < 0)
 359                 return r;
 360
 361         r = sd_event_add_defer(e->session->context->event,
 362                                &evdev->idle_src,
 363                                idev_evdev_idle_fn,
 364                                evdev);
 365         if (r < 0) {
 366                 evdev->fd_src = sd_event_source_unref(evdev->fd_src);
 367                 return r;
 368         }
 369
 370         sd_event_source_set_enabled(evdev->fd_src, SD_EVENT_OFF);
 371         sd_event_source_set_enabled(evdev->idle_src, SD_EVENT_OFF);
 372
 373         evdev->unsync = true;
 374         evdev->fd = fd;
 375         fd = -1;
 376
 377         idev_evdev_enable(evdev);
 378         return 0;
 379 }
 380
 381 static void idev_evdev_pause(idev_evdev *evdev, bool release) {
 382         idev_element *e = &evdev->element;
 383
 384         if (evdev->fd < 0)
 385                 return;
 386
 387         log_debug("idev-evdev: %s/%s: pause", e->session->name, e->name);
 388
 389         idev_evdev_disable(evdev);
 390         if (release) {
 391                 evdev->idle_src = sd_event_source_unref(evdev->idle_src);
 392                 evdev->fd_src = sd_event_source_unref(evdev->fd_src);
 393                 evdev->fd = safe_close(evdev->fd);
 394         }
 395 }
 396
 397 /*
 398  * Unmanaged Evdev Element
 399  * The unmanaged evdev element opens the evdev node for a given input device
 400  * directly (/dev/input/eventX) and thus needs sufficient privileges. It opens
 401  * the device only if we really require it and releases it as soon as we're
 402  * disabled or closed.
 403  * The unmanaged element can be used in all situations where you have direct
 404  * access to input device nodes. Unlike managed evdev elements, it can be used
 405  * outside of user sessions and in emergency situations where logind is not
 406  * available.
 407  */
 408
 409 static void unmanaged_evdev_resume(idev_element *e) {
 410         unmanaged_evdev *eu = unmanaged_evdev_from_element(e);
 411         int r, fd;
 412
 413         /*
 414          * Unmanaged devices can be acquired on-demand. Therefore, don't
 415          * acquire it unless someone opened the device *and* we're enabled.
 416          */
 417         if (e->n_open < 1 || !e->enabled)
 418                 return;
 419
 420         fd = eu->evdev.fd;
 421         if (fd < 0) {
 422                 fd = open(eu->devnode, O_RDWR | O_CLOEXEC | O_NOCTTY | O_NONBLOCK);
 423                 if (fd < 0) {
 424                         if (errno != EACCES && errno != EPERM) {
 425                                 log_debug_errno(errno, "idev-evdev: %s/%s: cannot open node %s: %m",
 426                                                 e->session->name, e->name, eu->devnode);
 427                                 return;
 428                         }
 429
 430                         fd = open(eu->devnode, O_RDONLY | O_CLOEXEC | O_NOCTTY | O_NONBLOCK);
 431                         if (fd < 0) {
 432                                 log_debug_errno(errno, "idev-evdev: %s/%s: cannot open node %s: %m",
 433                                                 e->session->name, e->name, eu->devnode);
 434                                 return;
 435                         }
 436
 437                         e->readable = true;
 438                         e->writable = false;
 439                 } else {
 440                         e->readable = true;
 441                         e->writable = true;
 442                 }
 443         }
 444
 445         r = idev_evdev_resume(&eu->evdev, fd);
 446         if (r < 0)
 447                 log_debug_errno(r, "idev-evdev: %s/%s: cannot resume: %m",
 448                                 e->session->name, e->name);
 449 }
 450
 451 static void unmanaged_evdev_pause(idev_element *e) {
 452         unmanaged_evdev *eu = unmanaged_evdev_from_element(e);
 453
 454         /*
 455          * Release the device if the device is disabled or there is no-one who
 456          * opened it. This guarantees we stay only available if we're opened
 457          * *and* enabled.
 458          */
 459
 460         idev_evdev_pause(&eu->evdev, true);
 461 }
 462
 463 static int unmanaged_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
 464         _cleanup_(idev_element_freep) idev_element *e = NULL;
 465         char name[IDEV_EVDEV_NAME_MAX];
 466         unmanaged_evdev *eu;
 467         const char *devnode;
 468         dev_t devnum;
 469         int r;
 470
 471         assert_return(s, -EINVAL);
 472         assert_return(ud, -EINVAL);
 473
 474         devnode = udev_device_get_devnode(ud);
 475         devnum = udev_device_get_devnum(ud);
 476         if (!devnode || devnum == 0)
 477                 return -ENODEV;
 478
 479         idev_evdev_name(name, devnum);
 480
 481         eu = new0(unmanaged_evdev, 1);
 482         if (!eu)
 483                 return -ENOMEM;
 484
 485         e = &eu->evdev.element;
 486         eu->evdev = IDEV_EVDEV_INIT(&unmanaged_evdev_vtable, s);
 487
 488         eu->devnode = strdup(devnode);
 489         if (!eu->devnode)
 490                 return -ENOMEM;
 491
 492         r = idev_element_add(e, name);
 493         if (r < 0)
 494                 return r;
 495
 496         if (out)
 497                 *out = e;
 498         e = NULL;
 499         return 0;
 500 }
 501
 502 static void unmanaged_evdev_free(idev_element *e) {
 503         unmanaged_evdev *eu = unmanaged_evdev_from_element(e);
 504
 505         idev_evdev_destroy(&eu->evdev);
 506         free(eu->devnode);
 507         free(eu);
 508 }
 509
 510 static const idev_element_vtable unmanaged_evdev_vtable = {
 511         .free                   = unmanaged_evdev_free,
 512         .enable                 = unmanaged_evdev_resume,
 513         .disable                = unmanaged_evdev_pause,
 514         .open                   = unmanaged_evdev_resume,
 515         .close                  = unmanaged_evdev_pause,
 516 };
 517
 518 /*
 519  * Managed Evdev Element
 520  * The managed evdev element uses systemd-logind to acquire evdev devices. This
 521  * means, we do not open the device node /dev/input/eventX directly. Instead,
 522  * logind passes us a file-descriptor whenever our session is activated. Thus,
 523  * we don't need access to the device node directly.
 524  * Furthermore, whenever the session is put asleep, logind revokes the
 525  * file-descriptor so we loose access to the device.
 526  * Managed evdev elements should be preferred over unmanaged elements whenever
 527  * you run inside a user session with exclusive device access.
 528  */
 529
 530 static int managed_evdev_take_device_fn(sd_bus *bus,
 531                                         sd_bus_message *reply,
 532                                         void *userdata,
 533                                         sd_bus_error *ret_error) {
 534         managed_evdev *em = userdata;
 535         idev_element *e = &em->evdev.element;
 536         idev_session *s = e->session;
 537         int r, paused, fd;
 538
 539         em->slot_take_device = sd_bus_slot_unref(em->slot_take_device);
 540
 541         if (sd_bus_message_is_method_error(reply, NULL)) {
 542                 const sd_bus_error *error = sd_bus_message_get_error(reply);
 543
 544                 log_debug("idev-evdev: %s/%s: TakeDevice failed: %s: %s",
 545                           s->name, e->name, error->name, error->message);
 546                 return 0;
 547         }
 548
 549         em->acquired = true;
 550
 551         r = sd_bus_message_read(reply, "hb", &fd, &paused);
 552         if (r < 0) {
 553                 log_debug("idev-evdev: %s/%s: erroneous TakeDevice reply", s->name, e->name);
 554                 return 0;
 555         }
 556
 557         /* If the device is paused, ignore it; we will get the next fd via
 558          * ResumeDevice signals. */
 559         if (paused)
 560                 return 0;
 561
 562         fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
 563         if (fd < 0) {
 564                 log_debug_errno(errno, "idev-evdev: %s/%s: cannot duplicate evdev fd: %m", s->name, e->name);
 565                 return 0;
 566         }
 567
 568         r = idev_evdev_resume(&em->evdev, fd);
 569         if (r < 0)
 570                 log_debug_errno(r, "idev-evdev: %s/%s: cannot resume: %m",
 571                                 s->name, e->name);
 572
 573         return 0;
 574 }
 575
 576 static void managed_evdev_enable(idev_element *e) {
 577         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
 578         managed_evdev *em = managed_evdev_from_element(e);
 579         idev_session *s = e->session;
 580         idev_context *c = s->context;
 581         int r;
 582
 583         /*
 584          * Acquiring managed devices is heavy, so do it only once we're
 585          * enabled *and* opened by someone.
 586          */
 587         if (e->n_open < 1 || !e->enabled)
 588                 return;
 589
 590         /* bail out if already pending */
 591         if (em->requested)
 592                 return;
 593
 594         r = sd_bus_message_new_method_call(c->sysbus,
 595                                            &m,
 596                                            "org.freedesktop.login1",
 597                                            s->path,
 598                                            "org.freedesktop.login1.Session",
 599                                            "TakeDevice");
 600         if (r < 0)
 601                 goto error;
 602
 603         r = sd_bus_message_append(m, "uu", major(em->devnum), minor(em->devnum));
 604         if (r < 0)
 605                 goto error;
 606
 607         r = sd_bus_call_async(c->sysbus,
 608                               &em->slot_take_device,
 609                               m,
 610                               managed_evdev_take_device_fn,
 611                               em,
 612                               0);
 613         if (r < 0)
 614                 goto error;
 615
 616         em->requested = true;
 617         return;
 618
 619 error:
 620         log_debug_errno(r, "idev-evdev: %s/%s: cannot send TakeDevice request: %m",
 621                         s->name, e->name);
 622 }
 623
 624 static void managed_evdev_disable(idev_element *e) {
 625         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
 626         managed_evdev *em = managed_evdev_from_element(e);
 627         idev_session *s = e->session;
 628         idev_context *c = s->context;
 629         int r;
 630
 631         /*
 632          * Releasing managed devices is heavy. Once acquired, we get
 633          * notifications for sleep/wake-up events, so there's no reason to
 634          * release it if disabled but opened. However, if a device is closed,
 635          * we release it immediately as we don't care for sleep/wake-up events
 636          * then (even if we're actually enabled).
 637          */
 638
 639         idev_evdev_pause(&em->evdev, false);
 640
 641         if (e->n_open > 0 || !em->requested)
 642                 return;
 643
 644         /*
 645          * If TakeDevice() is pending or was successful, make sure to
 646          * release the device again. We don't care for return-values,
 647          * so send it without waiting or callbacks.
 648          * If a failed TakeDevice() is pending, but someone else took
 649          * the device on the same bus-connection, we might incorrectly
 650          * release their device. This is an unlikely race, though.
 651          * Furthermore, you really shouldn't have two users of the
 652          * controller-API on the same session, on the same devices, *AND* on
 653          * the same bus-connection. So we don't care for that race..
 654          */
 655
 656         idev_evdev_pause(&em->evdev, true);
 657         em->requested = false;
 658
 659         if (!em->acquired && !em->slot_take_device)
 660                 return;
 661
 662         em->slot_take_device = sd_bus_slot_unref(em->slot_take_device);
 663         em->acquired = false;
 664
 665         r = sd_bus_message_new_method_call(c->sysbus,
 666                                            &m,
 667                                            "org.freedesktop.login1",
 668                                            s->path,
 669                                            "org.freedesktop.login1.Session",
 670                                            "ReleaseDevice");
 671         if (r >= 0) {
 672                 r = sd_bus_message_append(m, "uu", major(em->devnum), minor(em->devnum));
 673                 if (r >= 0)
 674                         r = sd_bus_send(c->sysbus, m, NULL);
 675         }
 676
 677         if (r < 0 && r != -ENOTCONN)
 678                 log_debug_errno(r, "idev-evdev: %s/%s: cannot send ReleaseDevice: %m",
 679                                 s->name, e->name);
 680 }
 681
 682 static void managed_evdev_resume(idev_element *e, int fd) {
 683         managed_evdev *em = managed_evdev_from_element(e);
 684         idev_session *s = e->session;
 685         int r;
 686
 687         /*
 688          * We get ResumeDevice signals whenever logind resumed a previously
 689          * paused device. The arguments contain the major/minor number of the
 690          * related device and a new file-descriptor for the freshly opened
 691          * device-node. We take the file-descriptor and immediately resume the
 692          * device.
 693          */
 694
 695         fd = fcntl(fd, F_DUPFD_CLOEXEC, 3);
 696         if (fd < 0) {
 697                 log_debug_errno(errno, "idev-evdev: %s/%s: cannot duplicate evdev fd: %m",
 698                                 s->name, e->name);
 699                 return;
 700         }
 701
 702         r = idev_evdev_resume(&em->evdev, fd);
 703         if (r < 0)
 704                 log_debug_errno(r, "idev-evdev: %s/%s: cannot resume: %m",
 705                                 s->name, e->name);
 706
 707         return;
 708 }
 709
 710 static void managed_evdev_pause(idev_element *e, const char *mode) {
 711         managed_evdev *em = managed_evdev_from_element(e);
 712         idev_session *s = e->session;
 713         idev_context *c = s->context;
 714         int r;
 715
 716         /*
 717          * We get PauseDevice() signals from logind whenever a device we
 718          * requested was, or is about to be, paused. Arguments are major/minor
 719          * number of the device and the mode of the operation.
 720          * We treat it as asynchronous access-revocation (as if we got HUP on
 721          * the device fd). Note that we might have already treated the HUP
 722          * event via EPOLLHUP, whichever comes first.
 723          *
 724          * @mode can be one of the following:
 725          *   "pause": The device is about to be paused. We must react
 726          *            immediately and respond with PauseDeviceComplete(). Once
 727          *            we replied, logind will pause the device. Note that
 728          *            logind might apply any kind of timeout and force pause
 729          *            the device if we don't respond in a timely manner. In
 730          *            this case, we will receive a second PauseDevice event
 731          *            with @mode set to "force" (or similar).
 732          *   "force": The device was disabled forecfully by logind. Access is
 733          *            already revoked. This is just an asynchronous
 734          *            notification so we can put the device asleep (in case
 735          *            we didn't already notice the access revocation).
 736          *    "gone": This is like "force" but is sent if the device was
 737          *            paused due to a device-removal event.
 738          *
 739          * We always handle PauseDevice signals as "force" as we properly
 740          * support asynchronous access revocation, anyway. But in case logind
 741          * sent mode "pause", we also call PauseDeviceComplete() to immediately
 742          * acknowledge the request.
 743          */
 744
 745         idev_evdev_pause(&em->evdev, true);
 746
 747         if (streq(mode, "pause")) {
 748                 _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
 749
 750                 /*
 751                  * Sending PauseDeviceComplete() is racy if logind triggers the
 752                  * timeout. That is, if we take too long and logind pauses the
 753                  * device by sending a forced PauseDevice, our
 754                  * PauseDeviceComplete call will be stray. That's fine, though.
 755                  * logind ignores such stray calls. Only if logind also sent a
 756                  * further PauseDevice() signal, it might match our call
 757                  * incorrectly to the newer PauseDevice(). That's fine, too, as
 758                  * we handle that event asynchronously, anyway. Therefore,
 759                  * whatever happens, we're fine. Yay!
 760                  */
 761
 762                 r = sd_bus_message_new_method_call(c->sysbus,
 763                                                    &m,
 764                                                    "org.freedesktop.login1",
 765                                                    s->path,
 766                                                    "org.freedesktop.login1.Session",
 767                                                    "PauseDeviceComplete");
 768                 if (r >= 0) {
 769                         r = sd_bus_message_append(m, "uu", major(em->devnum), minor(em->devnum));
 770                         if (r >= 0)
 771                                 r = sd_bus_send(c->sysbus, m, NULL);
 772                 }
 773
 774                 if (r < 0)
 775                         log_debug_errno(r, "idev-evdev: %s/%s: cannot send PauseDeviceComplete: %m",
 776                                         s->name, e->name);
 777         }
 778 }
 779
 780 static int managed_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
 781         _cleanup_(idev_element_freep) idev_element *e = NULL;
 782         char name[IDEV_EVDEV_NAME_MAX];
 783         managed_evdev *em;
 784         dev_t devnum;
 785         int r;
 786
 787         assert_return(s, -EINVAL);
 788         assert_return(s->managed, -EINVAL);
 789         assert_return(s->context->sysbus, -EINVAL);
 790         assert_return(ud, -EINVAL);
 791
 792         devnum = udev_device_get_devnum(ud);
 793         if (devnum == 0)
 794                 return -ENODEV;
 795
 796         idev_evdev_name(name, devnum);
 797
 798         em = new0(managed_evdev, 1);
 799         if (!em)
 800                 return -ENOMEM;
 801
 802         e = &em->evdev.element;
 803         em->evdev = IDEV_EVDEV_INIT(&managed_evdev_vtable, s);
 804         em->devnum = devnum;
 805
 806         r = idev_element_add(e, name);
 807         if (r < 0)
 808                 return r;
 809
 810         if (out)
 811                 *out = e;
 812         e = NULL;
 813         return 0;
 814 }
 815
 816 static void managed_evdev_free(idev_element *e) {
 817         managed_evdev *em = managed_evdev_from_element(e);
 818
 819         idev_evdev_destroy(&em->evdev);
 820         free(em);
 821 }
 822
 823 static const idev_element_vtable managed_evdev_vtable = {
 824         .free                   = managed_evdev_free,
 825         .enable                 = managed_evdev_enable,
 826         .disable                = managed_evdev_disable,
 827         .open                   = managed_evdev_enable,
 828         .close                  = managed_evdev_disable,
 829         .resume                 = managed_evdev_resume,
 830         .pause                  = managed_evdev_pause,
 831 };
 832
 833 /*
 834  * Generic Constructor
 835  * Instead of relying on the caller to choose between managed and unmanaged
 836  * evdev devices, the idev_evdev_new() constructor does that for you (by
 837  * looking at s->managed).
 838  */
 839
 840 bool idev_is_evdev(idev_element *e) {
 841         return e && (e->vtable == &unmanaged_evdev_vtable ||
 842                      e->vtable == &managed_evdev_vtable);
 843 }
 844
 845 idev_element *idev_find_evdev(idev_session *s, dev_t devnum) {
 846         char name[IDEV_EVDEV_NAME_MAX];
 847
 848         assert_return(s, NULL);
 849         assert_return(devnum != 0, NULL);
 850
 851         idev_evdev_name(name, devnum);
 852         return idev_find_element(s, name);
 853 }
 854
 855 int idev_evdev_new(idev_element **out, idev_session *s, struct udev_device *ud) {
 856         assert_return(s, -EINVAL);
 857         assert_return(ud, -EINVAL);
 858
 859         return s->managed ? managed_evdev_new(out, s, ud) : unmanaged_evdev_new(out, s, ud);
 860 }