drivers/char/apm-emulation.c

   1 /*
   2  * bios-less APM driver for ARM Linux
   3  *  Jamey Hicks <jamey@crl.dec.com>
   4  *  adapted from the APM BIOS driver for Linux by Stephen Rothwell (sfr@linuxcare.com)
   5  *
   6  * APM 1.2 Reference:
   7  *   Intel Corporation, Microsoft Corporation. Advanced Power Management
   8  *   (APM) BIOS Interface Specification, Revision 1.2, February 1996.
   9  *
  10  * [This document is available from Microsoft at:
  11  *    http://www.microsoft.com/hwdev/busbios/amp_12.htm]
  12  */
  13 #include <linux/module.h>
  14 #include <linux/poll.h>
  15 #include <linux/slab.h>
  16 #include <linux/proc_fs.h>
  17 #include <linux/miscdevice.h>
  18 #include <linux/apm_bios.h>
  19 #include <linux/capability.h>
  20 #include <linux/sched.h>
  21 #include <linux/suspend.h>
  22 #include <linux/apm-emulation.h>
  23 #include <linux/freezer.h>
  24 #include <linux/device.h>
  25 #include <linux/kernel.h>
  26 #include <linux/list.h>
  27 #include <linux/init.h>
  28 #include <linux/completion.h>
  29 #include <linux/kthread.h>
  30 #include <linux/delay.h>
  31
  32 #include <asm/system.h>
  33
  34 /*
  35  * The apm_bios device is one of the misc char devices.
  36  * This is its minor number.
  37  */
  38 #define APM_MINOR_DEV   134
  39
  40 /*
  41  * See Documentation/Config.help for the configuration options.
  42  *
  43  * Various options can be changed at boot time as follows:
  44  * (We allow underscores for compatibility with the modules code)
  45  *      apm=on/off                      enable/disable APM
  46  */
  47
  48 /*
  49  * Maximum number of events stored
  50  */
  51 #define APM_MAX_EVENTS          16
  52
  53 struct apm_queue {
  54         unsigned int            event_head;
  55         unsigned int            event_tail;
  56         apm_event_t             events[APM_MAX_EVENTS];
  57 };
  58
  59 /*
  60  * The per-file APM data
  61  */
  62 struct apm_user {
  63         struct list_head        list;
  64
  65         unsigned int            suser: 1;
  66         unsigned int            writer: 1;
  67         unsigned int            reader: 1;
  68
  69         int                     suspend_result;
  70         unsigned int            suspend_state;
  71 #define SUSPEND_NONE    0               /* no suspend pending */
  72 #define SUSPEND_PENDING 1               /* suspend pending read */
  73 #define SUSPEND_READ    2               /* suspend read, pending ack */
  74 #define SUSPEND_ACKED   3               /* suspend acked */
  75 #define SUSPEND_WAIT    4               /* waiting for suspend */
  76 #define SUSPEND_DONE    5               /* suspend completed */
  77
  78         struct apm_queue        queue;
  79 };
  80
  81 /*
  82  * Local variables
  83  */
  84 static int suspends_pending;
  85 static int apm_disabled;
  86 static struct task_struct *kapmd_tsk;
  87
  88 static DECLARE_WAIT_QUEUE_HEAD(apm_waitqueue);
  89 static DECLARE_WAIT_QUEUE_HEAD(apm_suspend_waitqueue);
  90
  91 /*
  92  * This is a list of everyone who has opened /dev/apm_bios
  93  */
  94 static DECLARE_RWSEM(user_list_lock);
  95 static LIST_HEAD(apm_user_list);
  96
  97 /*
  98  * kapmd info.  kapmd provides us a process context to handle
  99  * "APM" events within - specifically necessary if we're going
 100  * to be suspending the system.
 101  */
 102 static DECLARE_WAIT_QUEUE_HEAD(kapmd_wait);
 103 static DEFINE_SPINLOCK(kapmd_queue_lock);
 104 static struct apm_queue kapmd_queue;
 105
 106 static DEFINE_MUTEX(state_lock);
 107
 108 static const char driver_version[] = "1.13";    /* no spaces */
 109
 110
 111
 112 /*
 113  * Compatibility cruft until the IPAQ people move over to the new
 114  * interface.
 115  */
 116 static void __apm_get_power_status(struct apm_power_info *info)
 117 {
 118 }
 119
 120 /*
 121  * This allows machines to provide their own "apm get power status" function.
 122  */
 123 void (*apm_get_power_status)(struct apm_power_info *) = __apm_get_power_status;
 124 EXPORT_SYMBOL(apm_get_power_status);
 125
 126
 127 /*
 128  * APM event queue management.
 129  */
 130 static inline int queue_empty(struct apm_queue *q)
 131 {
 132         return q->event_head == q->event_tail;
 133 }
 134
 135 static inline apm_event_t queue_get_event(struct apm_queue *q)
 136 {
 137         q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
 138         return q->events[q->event_tail];
 139 }
 140
 141 static void queue_add_event(struct apm_queue *q, apm_event_t event)
 142 {
 143         q->event_head = (q->event_head + 1) % APM_MAX_EVENTS;
 144         if (q->event_head == q->event_tail) {
 145                 static int notified;
 146
 147                 if (notified++ == 0)
 148                     printk(KERN_ERR "apm: an event queue overflowed\n");
 149                 q->event_tail = (q->event_tail + 1) % APM_MAX_EVENTS;
 150         }
 151         q->events[q->event_head] = event;
 152 }
 153
 154 static void queue_event(apm_event_t event)
 155 {
 156         struct apm_user *as;
 157
 158         down_read(&user_list_lock);
 159         list_for_each_entry(as, &apm_user_list, list) {
 160                 if (as->reader)
 161                         queue_add_event(&as->queue, event);
 162         }
 163         up_read(&user_list_lock);
 164         wake_up_interruptible(&apm_waitqueue);
 165 }
 166
 167 /*
 168  * queue_suspend_event - queue an APM suspend event.
 169  *
 170  * Check that we're in a state where we can suspend.  If not,
 171  * return -EBUSY.  Otherwise, queue an event to all "writer"
 172  * users.  If there are no "writer" users, return '1' to
 173  * indicate that we can immediately suspend.
 174  */
 175 static int queue_suspend_event(apm_event_t event, struct apm_user *sender)
 176 {
 177         struct apm_user *as;
 178         int ret = 1;
 179
 180         mutex_lock(&state_lock);
 181         down_read(&user_list_lock);
 182
 183         /*
 184          * If a thread is still processing, we can't suspend, so reject
 185          * the request.
 186          */
 187         list_for_each_entry(as, &apm_user_list, list) {
 188                 if (as != sender && as->reader && as->writer && as->suser &&
 189                     as->suspend_state != SUSPEND_NONE) {
 190                         ret = -EBUSY;
 191                         goto out;
 192                 }
 193         }
 194
 195         list_for_each_entry(as, &apm_user_list, list) {
 196                 if (as != sender && as->reader && as->writer && as->suser) {
 197                         as->suspend_state = SUSPEND_PENDING;
 198                         suspends_pending++;
 199                         queue_add_event(&as->queue, event);
 200                         ret = 0;
 201                 }
 202         }
 203  out:
 204         up_read(&user_list_lock);
 205         mutex_unlock(&state_lock);
 206         wake_up_interruptible(&apm_waitqueue);
 207         return ret;
 208 }
 209
 210 static void apm_suspend(void)
 211 {
 212         struct apm_user *as;
 213         int err = pm_suspend(PM_SUSPEND_MEM);
 214
 215         /*
 216          * Anyone on the APM queues will think we're still suspended.
 217          * Send a message so everyone knows we're now awake again.
 218          */
 219         queue_event(APM_NORMAL_RESUME);
 220
 221         /*
 222          * Finally, wake up anyone who is sleeping on the suspend.
 223          */
 224         mutex_lock(&state_lock);
 225         down_read(&user_list_lock);
 226         list_for_each_entry(as, &apm_user_list, list) {
 227                 if (as->suspend_state == SUSPEND_WAIT ||
 228                     as->suspend_state == SUSPEND_ACKED) {
 229                         as->suspend_result = err;
 230                         as->suspend_state = SUSPEND_DONE;
 231                 }
 232         }
 233         up_read(&user_list_lock);
 234         mutex_unlock(&state_lock);
 235
 236         wake_up(&apm_suspend_waitqueue);
 237 }
 238
 239 static ssize_t apm_read(struct file *fp, char __user *buf, size_t count, loff_t *ppos)
 240 {
 241         struct apm_user *as = fp->private_data;
 242         apm_event_t event;
 243         int i = count, ret = 0;
 244
 245         if (count < sizeof(apm_event_t))
 246                 return -EINVAL;
 247
 248         if (queue_empty(&as->queue) && fp->f_flags & O_NONBLOCK)
 249                 return -EAGAIN;
 250
 251         wait_event_interruptible(apm_waitqueue, !queue_empty(&as->queue));
 252
 253         while ((i >= sizeof(event)) && !queue_empty(&as->queue)) {
 254                 event = queue_get_event(&as->queue);
 255
 256                 ret = -EFAULT;
 257                 if (copy_to_user(buf, &event, sizeof(event)))
 258                         break;
 259
 260                 mutex_lock(&state_lock);
 261                 if (as->suspend_state == SUSPEND_PENDING &&
 262                     (event == APM_SYS_SUSPEND || event == APM_USER_SUSPEND))
 263                         as->suspend_state = SUSPEND_READ;
 264                 mutex_unlock(&state_lock);
 265
 266                 buf += sizeof(event);
 267                 i -= sizeof(event);
 268         }
 269
 270         if (i < count)
 271                 ret = count - i;
 272
 273         return ret;
 274 }
 275
 276 static unsigned int apm_poll(struct file *fp, poll_table * wait)
 277 {
 278         struct apm_user *as = fp->private_data;
 279
 280         poll_wait(fp, &apm_waitqueue, wait);
 281         return queue_empty(&as->queue) ? 0 : POLLIN | POLLRDNORM;
 282 }
 283
 284 /*
 285  * apm_ioctl - handle APM ioctl
 286  *
 287  * APM_IOC_SUSPEND
 288  *   This IOCTL is overloaded, and performs two functions.  It is used to:
 289  *     - initiate a suspend
 290  *     - acknowledge a suspend read from /dev/apm_bios.
 291  *   Only when everyone who has opened /dev/apm_bios with write permission
 292  *   has acknowledge does the actual suspend happen.
 293  */
 294 static int
 295 apm_ioctl(struct inode * inode, struct file *filp, u_int cmd, u_long arg)
 296 {
 297         struct apm_user *as = filp->private_data;
 298         int err = -EINVAL;
 299
 300         if (!as->suser || !as->writer)
 301                 return -EPERM;
 302
 303         switch (cmd) {
 304         case APM_IOC_SUSPEND:
 305                 mutex_lock(&state_lock);
 306
 307                 as->suspend_result = -EINTR;
 308
 309                 if (as->suspend_state == SUSPEND_READ) {
 310                         int pending;
 311
 312                         /*
 313                          * If we read a suspend command from /dev/apm_bios,
 314                          * then the corresponding APM_IOC_SUSPEND ioctl is
 315                          * interpreted as an acknowledge.
 316                          */
 317                         as->suspend_state = SUSPEND_ACKED;
 318                         suspends_pending--;
 319                         pending = suspends_pending == 0;
 320                         mutex_unlock(&state_lock);
 321
 322                         /*
 323                          * If there are no further acknowledges required,
 324                          * suspend the system.
 325                          */
 326                         if (pending)
 327                                 apm_suspend();
 328
 329                         /*
 330                          * Wait for the suspend/resume to complete.  If there
 331                          * are pending acknowledges, we wait here for them.
 332                          */
 333                         freezer_do_not_count();
 334
 335                         wait_event(apm_suspend_waitqueue,
 336                                    as->suspend_state == SUSPEND_DONE);
 337
 338                         /*
 339                          * Since we are waiting until the suspend is done, the
 340                          * try_to_freeze() in freezer_count() will not trigger
 341                          */
 342                         freezer_count();
 343                 } else {
 344                         as->suspend_state = SUSPEND_WAIT;
 345                         mutex_unlock(&state_lock);
 346
 347                         /*
 348                          * Otherwise it is a request to suspend the system.
 349                          * Queue an event for all readers, and expect an
 350                          * acknowledge from all writers who haven't already
 351                          * acknowledged.
 352                          */
 353                         err = queue_suspend_event(APM_USER_SUSPEND, as);
 354                         if (err < 0) {
 355                                 /*
 356                                  * Avoid taking the lock here - this
 357                                  * should be fine.
 358                                  */
 359                                 as->suspend_state = SUSPEND_NONE;
 360                                 break;
 361                         }
 362
 363                         if (err > 0)
 364                                 apm_suspend();
 365
 366                         /*
 367                          * Wait for the suspend/resume to complete.  If there
 368                          * are pending acknowledges, we wait here for them.
 369                          */
 370                         wait_event_freezable(apm_suspend_waitqueue,
 371                                          as->suspend_state == SUSPEND_DONE);
 372                 }
 373
 374                 mutex_lock(&state_lock);
 375                 err = as->suspend_result;
 376                 as->suspend_state = SUSPEND_NONE;
 377                 mutex_unlock(&state_lock);
 378                 break;
 379         }
 380
 381         return err;
 382 }
 383
 384 static int apm_release(struct inode * inode, struct file * filp)
 385 {
 386         struct apm_user *as = filp->private_data;
 387         int pending = 0;
 388
 389         filp->private_data = NULL;
 390
 391         down_write(&user_list_lock);
 392         list_del(&as->list);
 393         up_write(&user_list_lock);
 394
 395         /*
 396          * We are now unhooked from the chain.  As far as new
 397          * events are concerned, we no longer exist.  However, we
 398          * need to balance suspends_pending, which means the
 399          * possibility of sleeping.
 400          */
 401         mutex_lock(&state_lock);
 402         if (as->suspend_state != SUSPEND_NONE) {
 403                 suspends_pending -= 1;
 404                 pending = suspends_pending == 0;
 405         }
 406         mutex_unlock(&state_lock);
 407         if (pending)
 408                 apm_suspend();
 409
 410         kfree(as);
 411         return 0;
 412 }
 413
 414 static int apm_open(struct inode * inode, struct file * filp)
 415 {
 416         struct apm_user *as;
 417
 418         as = kzalloc(sizeof(*as), GFP_KERNEL);
 419         if (as) {
 420                 /*
 421                  * XXX - this is a tiny bit broken, when we consider BSD
 422                  * process accounting. If the device is opened by root, we
 423                  * instantly flag that we used superuser privs. Who knows,
 424                  * we might close the device immediately without doing a
 425                  * privileged operation -- cevans
 426                  */
 427                 as->suser = capable(CAP_SYS_ADMIN);
 428                 as->writer = (filp->f_mode & FMODE_WRITE) == FMODE_WRITE;
 429                 as->reader = (filp->f_mode & FMODE_READ) == FMODE_READ;
 430
 431                 down_write(&user_list_lock);
 432                 list_add(&as->list, &apm_user_list);
 433                 up_write(&user_list_lock);
 434
 435                 filp->private_data = as;
 436         }
 437
 438         return as ? 0 : -ENOMEM;
 439 }
 440
 441 static struct file_operations apm_bios_fops = {
 442         .owner          = THIS_MODULE,
 443         .read           = apm_read,
 444         .poll           = apm_poll,
 445         .ioctl          = apm_ioctl,
 446         .open           = apm_open,
 447         .release        = apm_release,
 448 };
 449
 450 static struct miscdevice apm_device = {
 451         .minor          = APM_MINOR_DEV,
 452         .name           = "apm_bios",
 453         .fops           = &apm_bios_fops
 454 };
 455
 456
 457 #ifdef CONFIG_PROC_FS
 458 /*
 459  * Arguments, with symbols from linux/apm_bios.h.
 460  *
 461  *   0) Linux driver version (this will change if format changes)
 462  *   1) APM BIOS Version.  Usually 1.0, 1.1 or 1.2.
 463  *   2) APM flags from APM Installation Check (0x00):
 464  *      bit 0: APM_16_BIT_SUPPORT
 465  *      bit 1: APM_32_BIT_SUPPORT
 466  *      bit 2: APM_IDLE_SLOWS_CLOCK
 467  *      bit 3: APM_BIOS_DISABLED
 468  *      bit 4: APM_BIOS_DISENGAGED
 469  *   3) AC line status
 470  *      0x00: Off-line
 471  *      0x01: On-line
 472  *      0x02: On backup power (BIOS >= 1.1 only)
 473  *      0xff: Unknown
 474  *   4) Battery status
 475  *      0x00: High
 476  *      0x01: Low
 477  *      0x02: Critical
 478  *      0x03: Charging
 479  *      0x04: Selected battery not present (BIOS >= 1.2 only)
 480  *      0xff: Unknown
 481  *   5) Battery flag
 482  *      bit 0: High
 483  *      bit 1: Low
 484  *      bit 2: Critical
 485  *      bit 3: Charging
 486  *      bit 7: No system battery
 487  *      0xff: Unknown
 488  *   6) Remaining battery life (percentage of charge):
 489  *      0-100: valid
 490  *      -1: Unknown
 491  *   7) Remaining battery life (time units):
 492  *      Number of remaining minutes or seconds
 493  *      -1: Unknown
 494  *   8) min = minutes; sec = seconds
 495  */
 496 static int apm_get_info(char *buf, char **start, off_t fpos, int length)
 497 {
 498         struct apm_power_info info;
 499         char *units;
 500         int ret;
 501
 502         info.ac_line_status = 0xff;
 503         info.battery_status = 0xff;
 504         info.battery_flag   = 0xff;
 505         info.battery_life   = -1;
 506         info.time           = -1;
 507         info.units          = -1;
 508
 509         if (apm_get_power_status)
 510                 apm_get_power_status(&info);
 511
 512         switch (info.units) {
 513         default:        units = "?";    break;
 514         case 0:         units = "min";  break;
 515         case 1:         units = "sec";  break;
 516         }
 517
 518         ret = sprintf(buf, "%s 1.2 0x%02x 0x%02x 0x%02x 0x%02x %d%% %d %s\n",
 519                      driver_version, APM_32_BIT_SUPPORT,
 520                      info.ac_line_status, info.battery_status,
 521                      info.battery_flag, info.battery_life,
 522                      info.time, units);
 523
 524         return ret;
 525 }
 526 #endif
 527
 528 static int kapmd(void *arg)
 529 {
 530         do {
 531                 apm_event_t event;
 532                 int ret;
 533
 534                 wait_event_interruptible(kapmd_wait,
 535                                 !queue_empty(&kapmd_queue) || kthread_should_stop());
 536
 537                 if (kthread_should_stop())
 538                         break;
 539
 540                 spin_lock_irq(&kapmd_queue_lock);
 541                 event = 0;
 542                 if (!queue_empty(&kapmd_queue))
 543                         event = queue_get_event(&kapmd_queue);
 544                 spin_unlock_irq(&kapmd_queue_lock);
 545
 546                 switch (event) {
 547                 case 0:
 548                         break;
 549
 550                 case APM_LOW_BATTERY:
 551                 case APM_POWER_STATUS_CHANGE:
 552                         queue_event(event);
 553                         break;
 554
 555                 case APM_USER_SUSPEND:
 556                 case APM_SYS_SUSPEND:
 557                         ret = queue_suspend_event(event, NULL);
 558                         if (ret < 0) {
 559                                 /*
 560                                  * We were busy.  Try again in 50ms.
 561                                  */
 562                                 queue_add_event(&kapmd_queue, event);
 563                                 msleep(50);
 564                         }
 565                         if (ret > 0)
 566                                 apm_suspend();
 567                         break;
 568
 569                 case APM_CRITICAL_SUSPEND:
 570                         apm_suspend();
 571                         break;
 572                 }
 573         } while (1);
 574
 575         return 0;
 576 }
 577
 578 static int __init apm_init(void)
 579 {
 580         int ret;
 581
 582         if (apm_disabled) {
 583                 printk(KERN_NOTICE "apm: disabled on user request.\n");
 584                 return -ENODEV;
 585         }
 586
 587         kapmd_tsk = kthread_create(kapmd, NULL, "kapmd");
 588         if (IS_ERR(kapmd_tsk)) {
 589                 ret = PTR_ERR(kapmd_tsk);
 590                 kapmd_tsk = NULL;
 591                 return ret;
 592         }
 593         wake_up_process(kapmd_tsk);
 594
 595 #ifdef CONFIG_PROC_FS
 596         create_proc_info_entry("apm", 0, NULL, apm_get_info);
 597 #endif
 598
 599         ret = misc_register(&apm_device);
 600         if (ret != 0) {
 601                 remove_proc_entry("apm", NULL);
 602                 kthread_stop(kapmd_tsk);
 603         }
 604
 605         return ret;
 606 }
 607
 608 static void __exit apm_exit(void)
 609 {
 610         misc_deregister(&apm_device);
 611         remove_proc_entry("apm", NULL);
 612
 613         kthread_stop(kapmd_tsk);
 614 }
 615
 616 module_init(apm_init);
 617 module_exit(apm_exit);
 618
 619 MODULE_AUTHOR("Stephen Rothwell");
 620 MODULE_DESCRIPTION("Advanced Power Management");
 621 MODULE_LICENSE("GPL");
 622
 623 #ifndef MODULE
 624 static int __init apm_setup(char *str)
 625 {
 626         while ((str != NULL) && (*str != '\0')) {
 627                 if (strncmp(str, "off", 3) == 0)
 628                         apm_disabled = 1;
 629                 if (strncmp(str, "on", 2) == 0)
 630                         apm_disabled = 0;
 631                 str = strchr(str, ',');
 632                 if (str != NULL)
 633                         str += strspn(str, ", \t");
 634         }
 635         return 1;
 636 }
 637
 638 __setup("apm=", apm_setup);
 639 #endif
 640
 641 /**
 642  * apm_queue_event - queue an APM event for kapmd
 643  * @event: APM event
 644  *
 645  * Queue an APM event for kapmd to process and ultimately take the
 646  * appropriate action.  Only a subset of events are handled:
 647  *   %APM_LOW_BATTERY
 648  *   %APM_POWER_STATUS_CHANGE
 649  *   %APM_USER_SUSPEND
 650  *   %APM_SYS_SUSPEND
 651  *   %APM_CRITICAL_SUSPEND
 652  */
 653 void apm_queue_event(apm_event_t event)
 654 {
 655         unsigned long flags;
 656
 657         spin_lock_irqsave(&kapmd_queue_lock, flags);
 658         queue_add_event(&kapmd_queue, event);
 659         spin_unlock_irqrestore(&kapmd_queue_lock, flags);
 660
 661         wake_up_interruptible(&kapmd_wait);
 662 }
 663 EXPORT_SYMBOL(apm_queue_event);