drivers/s390/cio/css.c

   1 /*
   2  *  drivers/s390/cio/css.c
   3  *  driver for channel subsystem
   4  *
   5  *    Copyright (C) 2002 IBM Deutschland Entwicklung GmbH,
   6  *                       IBM Corporation
   7  *    Author(s): Arnd Bergmann (arndb@de.ibm.com)
   8  *               Cornelia Huck (cornelia.huck@de.ibm.com)
   9  */
  10 #include <linux/module.h>
  11 #include <linux/init.h>
  12 #include <linux/device.h>
  13 #include <linux/slab.h>
  14 #include <linux/errno.h>
  15 #include <linux/list.h>
  16
  17 #include "css.h"
  18 #include "cio.h"
  19 #include "cio_debug.h"
  20 #include "ioasm.h"
  21 #include "chsc.h"
  22 #include "device.h"
  23
  24 int need_rescan = 0;
  25 int css_init_done = 0;
  26 static int need_reprobe = 0;
  27 static int max_ssid = 0;
  28
  29 struct channel_subsystem *css[__MAX_CSSID + 1];
  30
  31 int css_characteristics_avail = 0;
  32
  33 inline int
  34 for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *data)
  35 {
  36         struct subchannel_id schid;
  37         int ret;
  38
  39         init_subchannel_id(&schid);
  40         ret = -ENODEV;
  41         do {
  42                 do {
  43                         ret = fn(schid, data);
  44                         if (ret)
  45                                 break;
  46                 } while (schid.sch_no++ < __MAX_SUBCHANNEL);
  47                 schid.sch_no = 0;
  48         } while (schid.ssid++ < max_ssid);
  49         return ret;
  50 }
  51
  52 static struct subchannel *
  53 css_alloc_subchannel(struct subchannel_id schid)
  54 {
  55         struct subchannel *sch;
  56         int ret;
  57
  58         sch = kmalloc (sizeof (*sch), GFP_KERNEL | GFP_DMA);
  59         if (sch == NULL)
  60                 return ERR_PTR(-ENOMEM);
  61         ret = cio_validate_subchannel (sch, schid);
  62         if (ret < 0) {
  63                 kfree(sch);
  64                 return ERR_PTR(ret);
  65         }
  66
  67         if (sch->st != SUBCHANNEL_TYPE_IO) {
  68                 /* For now we ignore all non-io subchannels. */
  69                 kfree(sch);
  70                 return ERR_PTR(-EINVAL);
  71         }
  72
  73         /*
  74          * Set intparm to subchannel address.
  75          * This is fine even on 64bit since the subchannel is always located
  76          * under 2G.
  77          */
  78         sch->schib.pmcw.intparm = (__u32)(unsigned long)sch;
  79         ret = cio_modify(sch);
  80         if (ret) {
  81                 kfree(sch);
  82                 return ERR_PTR(ret);
  83         }
  84         return sch;
  85 }
  86
  87 static void
  88 css_free_subchannel(struct subchannel *sch)
  89 {
  90         if (sch) {
  91                 /* Reset intparm to zeroes. */
  92                 sch->schib.pmcw.intparm = 0;
  93                 cio_modify(sch);
  94                 kfree(sch);
  95         }
  96
  97 }
  98
  99 static void
 100 css_subchannel_release(struct device *dev)
 101 {
 102         struct subchannel *sch;
 103
 104         sch = to_subchannel(dev);
 105         if (!cio_is_console(sch->schid))
 106                 kfree(sch);
 107 }
 108
 109 extern int css_get_ssd_info(struct subchannel *sch);
 110
 111
 112 int css_sch_device_register(struct subchannel *sch)
 113 {
 114         int ret;
 115
 116         mutex_lock(&sch->reg_mutex);
 117         ret = device_register(&sch->dev);
 118         mutex_unlock(&sch->reg_mutex);
 119         return ret;
 120 }
 121
 122 void css_sch_device_unregister(struct subchannel *sch)
 123 {
 124         mutex_lock(&sch->reg_mutex);
 125         device_unregister(&sch->dev);
 126         mutex_unlock(&sch->reg_mutex);
 127 }
 128
 129 static int
 130 css_register_subchannel(struct subchannel *sch)
 131 {
 132         int ret;
 133
 134         /* Initialize the subchannel structure */
 135         sch->dev.parent = &css[0]->device;
 136         sch->dev.bus = &css_bus_type;
 137         sch->dev.release = &css_subchannel_release;
 138
 139         /* make it known to the system */
 140         ret = css_sch_device_register(sch);
 141         if (ret)
 142                 printk (KERN_WARNING "%s: could not register %s\n",
 143                         __func__, sch->dev.bus_id);
 144         else
 145                 css_get_ssd_info(sch);
 146         return ret;
 147 }
 148
 149 int
 150 css_probe_device(struct subchannel_id schid)
 151 {
 152         int ret;
 153         struct subchannel *sch;
 154
 155         sch = css_alloc_subchannel(schid);
 156         if (IS_ERR(sch))
 157                 return PTR_ERR(sch);
 158         ret = css_register_subchannel(sch);
 159         if (ret)
 160                 css_free_subchannel(sch);
 161         return ret;
 162 }
 163
 164 static int
 165 check_subchannel(struct device * dev, void * data)
 166 {
 167         struct subchannel *sch;
 168         struct subchannel_id *schid = data;
 169
 170         sch = to_subchannel(dev);
 171         return schid_equal(&sch->schid, schid);
 172 }
 173
 174 struct subchannel *
 175 get_subchannel_by_schid(struct subchannel_id schid)
 176 {
 177         struct device *dev;
 178
 179         dev = bus_find_device(&css_bus_type, NULL,
 180                               &schid, check_subchannel);
 181
 182         return dev ? to_subchannel(dev) : NULL;
 183 }
 184
 185 static inline int css_get_subchannel_status(struct subchannel *sch)
 186 {
 187         struct schib schib;
 188
 189         if (stsch(sch->schid, &schib) || !schib.pmcw.dnv)
 190                 return CIO_GONE;
 191         if (sch->schib.pmcw.dnv && (schib.pmcw.dev != sch->schib.pmcw.dev))
 192                 return CIO_REVALIDATE;
 193         if (!sch->lpm)
 194                 return CIO_NO_PATH;
 195         return CIO_OPER;
 196 }
 197
 198 static int css_evaluate_known_subchannel(struct subchannel *sch, int slow)
 199 {
 200         int event, ret, disc;
 201         unsigned long flags;
 202         enum { NONE, UNREGISTER, UNREGISTER_PROBE, REPROBE } action;
 203
 204         spin_lock_irqsave(&sch->lock, flags);
 205         disc = device_is_disconnected(sch);
 206         if (disc && slow) {
 207                 /* Disconnected devices are evaluated directly only.*/
 208                 spin_unlock_irqrestore(&sch->lock, flags);
 209                 return 0;
 210         }
 211         /* No interrupt after machine check - kill pending timers. */
 212         device_kill_pending_timer(sch);
 213         if (!disc && !slow) {
 214                 /* Non-disconnected devices are evaluated on the slow path. */
 215                 spin_unlock_irqrestore(&sch->lock, flags);
 216                 return -EAGAIN;
 217         }
 218         event = css_get_subchannel_status(sch);
 219         CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, %s, %s path.\n",
 220                       sch->schid.ssid, sch->schid.sch_no, event,
 221                       disc ? "disconnected" : "normal",
 222                       slow ? "slow" : "fast");
 223         /* Analyze subchannel status. */
 224         action = NONE;
 225         switch (event) {
 226         case CIO_NO_PATH:
 227                 if (disc) {
 228                         /* Check if paths have become available. */
 229                         action = REPROBE;
 230                         break;
 231                 }
 232                 /* fall through */
 233         case CIO_GONE:
 234                 /* Prevent unwanted effects when opening lock. */
 235                 cio_disable_subchannel(sch);
 236                 device_set_disconnected(sch);
 237                 /* Ask driver what to do with device. */
 238                 action = UNREGISTER;
 239                 if (sch->driver && sch->driver->notify) {
 240                         spin_unlock_irqrestore(&sch->lock, flags);
 241                         ret = sch->driver->notify(&sch->dev, event);
 242                         spin_lock_irqsave(&sch->lock, flags);
 243                         if (ret)
 244                                 action = NONE;
 245                 }
 246                 break;
 247         case CIO_REVALIDATE:
 248                 /* Device will be removed, so no notify necessary. */
 249                 if (disc)
 250                         /* Reprobe because immediate unregister might block. */
 251                         action = REPROBE;
 252                 else
 253                         action = UNREGISTER_PROBE;
 254                 break;
 255         case CIO_OPER:
 256                 if (disc)
 257                         /* Get device operational again. */
 258                         action = REPROBE;
 259                 break;
 260         }
 261         /* Perform action. */
 262         ret = 0;
 263         switch (action) {
 264         case UNREGISTER:
 265         case UNREGISTER_PROBE:
 266                 /* Unregister device (will use subchannel lock). */
 267                 spin_unlock_irqrestore(&sch->lock, flags);
 268                 css_sch_device_unregister(sch);
 269                 spin_lock_irqsave(&sch->lock, flags);
 270
 271                 /* Reset intparm to zeroes. */
 272                 sch->schib.pmcw.intparm = 0;
 273                 cio_modify(sch);
 274                 break;
 275         case REPROBE:
 276                 device_trigger_reprobe(sch);
 277                 break;
 278         default:
 279                 break;
 280         }
 281         spin_unlock_irqrestore(&sch->lock, flags);
 282         /* Probe if necessary. */
 283         if (action == UNREGISTER_PROBE)
 284                 ret = css_probe_device(sch->schid);
 285
 286         return ret;
 287 }
 288
 289 static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
 290 {
 291         struct schib schib;
 292
 293         if (!slow) {
 294                 /* Will be done on the slow path. */
 295                 return -EAGAIN;
 296         }
 297         if (stsch(schid, &schib) || !schib.pmcw.dnv) {
 298                 /* Unusable - ignore. */
 299                 return 0;
 300         }
 301         CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, unknown, "
 302                          "slow path.\n", schid.ssid, schid.sch_no, CIO_OPER);
 303
 304         return css_probe_device(schid);
 305 }
 306
 307 static int css_evaluate_subchannel(struct subchannel_id schid, int slow)
 308 {
 309         struct subchannel *sch;
 310         int ret;
 311
 312         sch = get_subchannel_by_schid(schid);
 313         if (sch) {
 314                 ret = css_evaluate_known_subchannel(sch, slow);
 315                 put_device(&sch->dev);
 316         } else
 317                 ret = css_evaluate_new_subchannel(schid, slow);
 318
 319         return ret;
 320 }
 321
 322 static int
 323 css_rescan_devices(struct subchannel_id schid, void *data)
 324 {
 325         return css_evaluate_subchannel(schid, 1);
 326 }
 327
 328 struct slow_subchannel {
 329         struct list_head slow_list;
 330         struct subchannel_id schid;
 331 };
 332
 333 static LIST_HEAD(slow_subchannels_head);
 334 static DEFINE_SPINLOCK(slow_subchannel_lock);
 335
 336 static void
 337 css_trigger_slow_path(struct work_struct *unused)
 338 {
 339         CIO_TRACE_EVENT(4, "slowpath");
 340
 341         if (need_rescan) {
 342                 need_rescan = 0;
 343                 for_each_subchannel(css_rescan_devices, NULL);
 344                 return;
 345         }
 346
 347         spin_lock_irq(&slow_subchannel_lock);
 348         while (!list_empty(&slow_subchannels_head)) {
 349                 struct slow_subchannel *slow_sch =
 350                         list_entry(slow_subchannels_head.next,
 351                                    struct slow_subchannel, slow_list);
 352
 353                 list_del_init(slow_subchannels_head.next);
 354                 spin_unlock_irq(&slow_subchannel_lock);
 355                 css_evaluate_subchannel(slow_sch->schid, 1);
 356                 spin_lock_irq(&slow_subchannel_lock);
 357                 kfree(slow_sch);
 358         }
 359         spin_unlock_irq(&slow_subchannel_lock);
 360 }
 361
 362 DECLARE_WORK(slow_path_work, css_trigger_slow_path);
 363 struct workqueue_struct *slow_path_wq;
 364
 365 /* Reprobe subchannel if unregistered. */
 366 static int reprobe_subchannel(struct subchannel_id schid, void *data)
 367 {
 368         struct subchannel *sch;
 369         int ret;
 370
 371         CIO_DEBUG(KERN_INFO, 6, "cio: reprobe 0.%x.%04x\n",
 372                   schid.ssid, schid.sch_no);
 373         if (need_reprobe)
 374                 return -EAGAIN;
 375
 376         sch = get_subchannel_by_schid(schid);
 377         if (sch) {
 378                 /* Already known. */
 379                 put_device(&sch->dev);
 380                 return 0;
 381         }
 382
 383         ret = css_probe_device(schid);
 384         switch (ret) {
 385         case 0:
 386                 break;
 387         case -ENXIO:
 388         case -ENOMEM:
 389                 /* These should abort looping */
 390                 break;
 391         default:
 392                 ret = 0;
 393         }
 394
 395         return ret;
 396 }
 397
 398 /* Work function used to reprobe all unregistered subchannels. */
 399 static void reprobe_all(struct work_struct *unused)
 400 {
 401         int ret;
 402
 403         CIO_MSG_EVENT(2, "reprobe start\n");
 404
 405         need_reprobe = 0;
 406         /* Make sure initial subchannel scan is done. */
 407         wait_event(ccw_device_init_wq,
 408                    atomic_read(&ccw_device_init_count) == 0);
 409         ret = for_each_subchannel(reprobe_subchannel, NULL);
 410
 411         CIO_MSG_EVENT(2, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
 412                       need_reprobe);
 413 }
 414
 415 DECLARE_WORK(css_reprobe_work, reprobe_all);
 416
 417 /* Schedule reprobing of all unregistered subchannels. */
 418 void css_schedule_reprobe(void)
 419 {
 420         need_reprobe = 1;
 421         queue_work(ccw_device_work, &css_reprobe_work);
 422 }
 423
 424 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
 425
 426 /*
 427  * Rescan for new devices. FIXME: This is slow.
 428  * This function is called when we have lost CRWs due to overflows and we have
 429  * to do subchannel housekeeping.
 430  */
 431 void
 432 css_reiterate_subchannels(void)
 433 {
 434         css_clear_subchannel_slow_list();
 435         need_rescan = 1;
 436 }
 437
 438 /*
 439  * Called from the machine check handler for subchannel report words.
 440  */
 441 int
 442 css_process_crw(int rsid1, int rsid2)
 443 {
 444         int ret;
 445         struct subchannel_id mchk_schid;
 446
 447         CIO_CRW_EVENT(2, "source is subchannel %04X, subsystem id %x\n",
 448                       rsid1, rsid2);
 449
 450         if (need_rescan)
 451                 /* We need to iterate all subchannels anyway. */
 452                 return -EAGAIN;
 453
 454         init_subchannel_id(&mchk_schid);
 455         mchk_schid.sch_no = rsid1;
 456         if (rsid2 != 0)
 457                 mchk_schid.ssid = (rsid2 >> 8) & 3;
 458
 459         /*
 460          * Since we are always presented with IPI in the CRW, we have to
 461          * use stsch() to find out if the subchannel in question has come
 462          * or gone.
 463          */
 464         ret = css_evaluate_subchannel(mchk_schid, 0);
 465         if (ret == -EAGAIN) {
 466                 if (css_enqueue_subchannel_slow(mchk_schid)) {
 467                         css_clear_subchannel_slow_list();
 468                         need_rescan = 1;
 469                 }
 470         }
 471         return ret;
 472 }
 473
 474 static int __init
 475 __init_channel_subsystem(struct subchannel_id schid, void *data)
 476 {
 477         struct subchannel *sch;
 478         int ret;
 479
 480         if (cio_is_console(schid))
 481                 sch = cio_get_console_subchannel();
 482         else {
 483                 sch = css_alloc_subchannel(schid);
 484                 if (IS_ERR(sch))
 485                         ret = PTR_ERR(sch);
 486                 else
 487                         ret = 0;
 488                 switch (ret) {
 489                 case 0:
 490                         break;
 491                 case -ENOMEM:
 492                         panic("Out of memory in init_channel_subsystem\n");
 493                 /* -ENXIO: no more subchannels. */
 494                 case -ENXIO:
 495                         return ret;
 496                 /* -EIO: this subchannel set not supported. */
 497                 case -EIO:
 498                         return ret;
 499                 default:
 500                         return 0;
 501                 }
 502         }
 503         /*
 504          * We register ALL valid subchannels in ioinfo, even those
 505          * that have been present before init_channel_subsystem.
 506          * These subchannels can't have been registered yet (kmalloc
 507          * not working) so we do it now. This is true e.g. for the
 508          * console subchannel.
 509          */
 510         css_register_subchannel(sch);
 511         return 0;
 512 }
 513
 514 static void __init
 515 css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
 516 {
 517         if (css_characteristics_avail && css_general_characteristics.mcss) {
 518                 css->global_pgid.pgid_high.ext_cssid.version = 0x80;
 519                 css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
 520         } else {
 521 #ifdef CONFIG_SMP
 522                 css->global_pgid.pgid_high.cpu_addr = hard_smp_processor_id();
 523 #else
 524                 css->global_pgid.pgid_high.cpu_addr = 0;
 525 #endif
 526         }
 527         css->global_pgid.cpu_id = ((cpuid_t *) __LC_CPUID)->ident;
 528         css->global_pgid.cpu_model = ((cpuid_t *) __LC_CPUID)->machine;
 529         css->global_pgid.tod_high = tod_high;
 530
 531 }
 532
 533 static void
 534 channel_subsystem_release(struct device *dev)
 535 {
 536         struct channel_subsystem *css;
 537
 538         css = to_css(dev);
 539         mutex_destroy(&css->mutex);
 540         kfree(css);
 541 }
 542
 543 static ssize_t
 544 css_cm_enable_show(struct device *dev, struct device_attribute *attr,
 545                    char *buf)
 546 {
 547         struct channel_subsystem *css = to_css(dev);
 548
 549         if (!css)
 550                 return 0;
 551         return sprintf(buf, "%x\n", css->cm_enabled);
 552 }
 553
 554 static ssize_t
 555 css_cm_enable_store(struct device *dev, struct device_attribute *attr,
 556                     const char *buf, size_t count)
 557 {
 558         struct channel_subsystem *css = to_css(dev);
 559         int ret;
 560
 561         switch (buf[0]) {
 562         case '0':
 563                 ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
 564                 break;
 565         case '1':
 566                 ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
 567                 break;
 568         default:
 569                 ret = -EINVAL;
 570         }
 571         return ret < 0 ? ret : count;
 572 }
 573
 574 static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
 575
 576 static inline void __init
 577 setup_css(int nr)
 578 {
 579         u32 tod_high;
 580
 581         memset(css[nr], 0, sizeof(struct channel_subsystem));
 582         mutex_init(&css[nr]->mutex);
 583         css[nr]->valid = 1;
 584         css[nr]->cssid = nr;
 585         sprintf(css[nr]->device.bus_id, "css%x", nr);
 586         css[nr]->device.release = channel_subsystem_release;
 587         tod_high = (u32) (get_clock() >> 32);
 588         css_generate_pgid(css[nr], tod_high);
 589 }
 590
 591 /*
 592  * Now that the driver core is running, we can setup our channel subsystem.
 593  * The struct subchannel's are created during probing (except for the
 594  * static console subchannel).
 595  */
 596 static int __init
 597 init_channel_subsystem (void)
 598 {
 599         int ret, i;
 600
 601         if (chsc_determine_css_characteristics() == 0)
 602                 css_characteristics_avail = 1;
 603
 604         if ((ret = bus_register(&css_bus_type)))
 605                 goto out;
 606
 607         /* Try to enable MSS. */
 608         ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
 609         switch (ret) {
 610         case 0: /* Success. */
 611                 max_ssid = __MAX_SSID;
 612                 break;
 613         case -ENOMEM:
 614                 goto out_bus;
 615         default:
 616                 max_ssid = 0;
 617         }
 618         /* Setup css structure. */
 619         for (i = 0; i <= __MAX_CSSID; i++) {
 620                 css[i] = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
 621                 if (!css[i]) {
 622                         ret = -ENOMEM;
 623                         goto out_unregister;
 624                 }
 625                 setup_css(i);
 626                 ret = device_register(&css[i]->device);
 627                 if (ret)
 628                         goto out_free;
 629                 if (css_characteristics_avail &&
 630                     css_chsc_characteristics.secm) {
 631                         ret = device_create_file(&css[i]->device,
 632                                                  &dev_attr_cm_enable);
 633                         if (ret)
 634                                 goto out_device;
 635                 }
 636         }
 637         css_init_done = 1;
 638
 639         ctl_set_bit(6, 28);
 640
 641         for_each_subchannel(__init_channel_subsystem, NULL);
 642         return 0;
 643 out_device:
 644         device_unregister(&css[i]->device);
 645 out_free:
 646         kfree(css[i]);
 647 out_unregister:
 648         while (i > 0) {
 649                 i--;
 650                 if (css_characteristics_avail && css_chsc_characteristics.secm)
 651                         device_remove_file(&css[i]->device,
 652                                            &dev_attr_cm_enable);
 653                 device_unregister(&css[i]->device);
 654         }
 655 out_bus:
 656         bus_unregister(&css_bus_type);
 657 out:
 658         return ret;
 659 }
 660
 661 /*
 662  * find a driver for a subchannel. They identify by the subchannel
 663  * type with the exception that the console subchannel driver has its own
 664  * subchannel type although the device is an i/o subchannel
 665  */
 666 static int
 667 css_bus_match (struct device *dev, struct device_driver *drv)
 668 {
 669         struct subchannel *sch = container_of (dev, struct subchannel, dev);
 670         struct css_driver *driver = container_of (drv, struct css_driver, drv);
 671
 672         if (sch->st == driver->subchannel_type)
 673                 return 1;
 674
 675         return 0;
 676 }
 677
 678 static int
 679 css_probe (struct device *dev)
 680 {
 681         struct subchannel *sch;
 682
 683         sch = to_subchannel(dev);
 684         sch->driver = container_of (dev->driver, struct css_driver, drv);
 685         return (sch->driver->probe ? sch->driver->probe(sch) : 0);
 686 }
 687
 688 static int
 689 css_remove (struct device *dev)
 690 {
 691         struct subchannel *sch;
 692
 693         sch = to_subchannel(dev);
 694         return (sch->driver->remove ? sch->driver->remove(sch) : 0);
 695 }
 696
 697 static void
 698 css_shutdown (struct device *dev)
 699 {
 700         struct subchannel *sch;
 701
 702         sch = to_subchannel(dev);
 703         if (sch->driver->shutdown)
 704                 sch->driver->shutdown(sch);
 705 }
 706
 707 struct bus_type css_bus_type = {
 708         .name     = "css",
 709         .match    = css_bus_match,
 710         .probe    = css_probe,
 711         .remove   = css_remove,
 712         .shutdown = css_shutdown,
 713 };
 714
 715 subsys_initcall(init_channel_subsystem);
 716
 717 int
 718 css_enqueue_subchannel_slow(struct subchannel_id schid)
 719 {
 720         struct slow_subchannel *new_slow_sch;
 721         unsigned long flags;
 722
 723         new_slow_sch = kzalloc(sizeof(struct slow_subchannel), GFP_ATOMIC);
 724         if (!new_slow_sch)
 725                 return -ENOMEM;
 726         new_slow_sch->schid = schid;
 727         spin_lock_irqsave(&slow_subchannel_lock, flags);
 728         list_add_tail(&new_slow_sch->slow_list, &slow_subchannels_head);
 729         spin_unlock_irqrestore(&slow_subchannel_lock, flags);
 730         return 0;
 731 }
 732
 733 void
 734 css_clear_subchannel_slow_list(void)
 735 {
 736         unsigned long flags;
 737
 738         spin_lock_irqsave(&slow_subchannel_lock, flags);
 739         while (!list_empty(&slow_subchannels_head)) {
 740                 struct slow_subchannel *slow_sch =
 741                         list_entry(slow_subchannels_head.next,
 742                                    struct slow_subchannel, slow_list);
 743
 744                 list_del_init(slow_subchannels_head.next);
 745                 kfree(slow_sch);
 746         }
 747         spin_unlock_irqrestore(&slow_subchannel_lock, flags);
 748 }
 749
 750
 751
 752 int
 753 css_slow_subchannels_exist(void)
 754 {
 755         return (!list_empty(&slow_subchannels_head));
 756 }
 757
 758 MODULE_LICENSE("GPL");
 759 EXPORT_SYMBOL(css_bus_type);
 760 EXPORT_SYMBOL_GPL(css_characteristics_avail);