Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc
[linux-2.6] / 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 #include "idset.h"
24 #include "chp.h"
25
26 int css_init_done = 0;
27 static int need_reprobe = 0;
28 static int max_ssid = 0;
29
30 struct channel_subsystem *css[__MAX_CSSID + 1];
31
32 int css_characteristics_avail = 0;
33
34 int
35 for_each_subchannel(int(*fn)(struct subchannel_id, void *), void *data)
36 {
37         struct subchannel_id schid;
38         int ret;
39
40         init_subchannel_id(&schid);
41         ret = -ENODEV;
42         do {
43                 do {
44                         ret = fn(schid, data);
45                         if (ret)
46                                 break;
47                 } while (schid.sch_no++ < __MAX_SUBCHANNEL);
48                 schid.sch_no = 0;
49         } while (schid.ssid++ < max_ssid);
50         return ret;
51 }
52
53 static struct subchannel *
54 css_alloc_subchannel(struct subchannel_id schid)
55 {
56         struct subchannel *sch;
57         int ret;
58
59         sch = kmalloc (sizeof (*sch), GFP_KERNEL | GFP_DMA);
60         if (sch == NULL)
61                 return ERR_PTR(-ENOMEM);
62         ret = cio_validate_subchannel (sch, schid);
63         if (ret < 0) {
64                 kfree(sch);
65                 return ERR_PTR(ret);
66         }
67
68         if (sch->st != SUBCHANNEL_TYPE_IO) {
69                 /* For now we ignore all non-io subchannels. */
70                 kfree(sch);
71                 return ERR_PTR(-EINVAL);
72         }
73
74         /* 
75          * Set intparm to subchannel address.
76          * This is fine even on 64bit since the subchannel is always located
77          * under 2G.
78          */
79         sch->schib.pmcw.intparm = (__u32)(unsigned long)sch;
80         ret = cio_modify(sch);
81         if (ret) {
82                 kfree(sch);
83                 return ERR_PTR(ret);
84         }
85         return sch;
86 }
87
88 static void
89 css_free_subchannel(struct subchannel *sch)
90 {
91         if (sch) {
92                 /* Reset intparm to zeroes. */
93                 sch->schib.pmcw.intparm = 0;
94                 cio_modify(sch);
95                 kfree(sch->lock);
96                 kfree(sch);
97         }
98 }
99
100 static void
101 css_subchannel_release(struct device *dev)
102 {
103         struct subchannel *sch;
104
105         sch = to_subchannel(dev);
106         if (!cio_is_console(sch->schid)) {
107                 kfree(sch->lock);
108                 kfree(sch);
109         }
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 void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
130 {
131         int i;
132         int mask;
133
134         memset(ssd, 0, sizeof(struct chsc_ssd_info));
135         ssd->path_mask = pmcw->pim;
136         for (i = 0; i < 8; i++) {
137                 mask = 0x80 >> i;
138                 if (pmcw->pim & mask) {
139                         chp_id_init(&ssd->chpid[i]);
140                         ssd->chpid[i].id = pmcw->chpid[i];
141                 }
142         }
143 }
144
145 static void ssd_register_chpids(struct chsc_ssd_info *ssd)
146 {
147         int i;
148         int mask;
149
150         for (i = 0; i < 8; i++) {
151                 mask = 0x80 >> i;
152                 if (ssd->path_mask & mask)
153                         if (!chp_is_registered(ssd->chpid[i]))
154                                 chp_new(ssd->chpid[i]);
155         }
156 }
157
158 void css_update_ssd_info(struct subchannel *sch)
159 {
160         int ret;
161
162         if (cio_is_console(sch->schid)) {
163                 /* Console is initialized too early for functions requiring
164                  * memory allocation. */
165                 ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
166         } else {
167                 ret = chsc_get_ssd_info(sch->schid, &sch->ssd_info);
168                 if (ret)
169                         ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
170                 ssd_register_chpids(&sch->ssd_info);
171         }
172 }
173
174 static int css_register_subchannel(struct subchannel *sch)
175 {
176         int ret;
177
178         /* Initialize the subchannel structure */
179         sch->dev.parent = &css[0]->device;
180         sch->dev.bus = &css_bus_type;
181         sch->dev.release = &css_subchannel_release;
182         sch->dev.groups = subch_attr_groups;
183         css_update_ssd_info(sch);
184         /* make it known to the system */
185         ret = css_sch_device_register(sch);
186         if (ret) {
187                 printk (KERN_WARNING "%s: could not register %s\n",
188                         __func__, sch->dev.bus_id);
189                 return ret;
190         }
191         return ret;
192 }
193
194 static int css_probe_device(struct subchannel_id schid)
195 {
196         int ret;
197         struct subchannel *sch;
198
199         sch = css_alloc_subchannel(schid);
200         if (IS_ERR(sch))
201                 return PTR_ERR(sch);
202         ret = css_register_subchannel(sch);
203         if (ret)
204                 css_free_subchannel(sch);
205         return ret;
206 }
207
208 static int
209 check_subchannel(struct device * dev, void * data)
210 {
211         struct subchannel *sch;
212         struct subchannel_id *schid = data;
213
214         sch = to_subchannel(dev);
215         return schid_equal(&sch->schid, schid);
216 }
217
218 struct subchannel *
219 get_subchannel_by_schid(struct subchannel_id schid)
220 {
221         struct device *dev;
222
223         dev = bus_find_device(&css_bus_type, NULL,
224                               &schid, check_subchannel);
225
226         return dev ? to_subchannel(dev) : NULL;
227 }
228
229 static int css_get_subchannel_status(struct subchannel *sch)
230 {
231         struct schib schib;
232
233         if (stsch(sch->schid, &schib) || !schib.pmcw.dnv)
234                 return CIO_GONE;
235         if (sch->schib.pmcw.dnv && (schib.pmcw.dev != sch->schib.pmcw.dev))
236                 return CIO_REVALIDATE;
237         if (!sch->lpm)
238                 return CIO_NO_PATH;
239         return CIO_OPER;
240 }
241
242 static int css_evaluate_known_subchannel(struct subchannel *sch, int slow)
243 {
244         int event, ret, disc;
245         unsigned long flags;
246         enum { NONE, UNREGISTER, UNREGISTER_PROBE, REPROBE } action;
247
248         spin_lock_irqsave(sch->lock, flags);
249         disc = device_is_disconnected(sch);
250         if (disc && slow) {
251                 /* Disconnected devices are evaluated directly only.*/
252                 spin_unlock_irqrestore(sch->lock, flags);
253                 return 0;
254         }
255         /* No interrupt after machine check - kill pending timers. */
256         device_kill_pending_timer(sch);
257         if (!disc && !slow) {
258                 /* Non-disconnected devices are evaluated on the slow path. */
259                 spin_unlock_irqrestore(sch->lock, flags);
260                 return -EAGAIN;
261         }
262         event = css_get_subchannel_status(sch);
263         CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, %s, %s path.\n",
264                       sch->schid.ssid, sch->schid.sch_no, event,
265                       disc ? "disconnected" : "normal",
266                       slow ? "slow" : "fast");
267         /* Analyze subchannel status. */
268         action = NONE;
269         switch (event) {
270         case CIO_NO_PATH:
271                 if (disc) {
272                         /* Check if paths have become available. */
273                         action = REPROBE;
274                         break;
275                 }
276                 /* fall through */
277         case CIO_GONE:
278                 /* Prevent unwanted effects when opening lock. */
279                 cio_disable_subchannel(sch);
280                 device_set_disconnected(sch);
281                 /* Ask driver what to do with device. */
282                 action = UNREGISTER;
283                 if (sch->driver && sch->driver->notify) {
284                         spin_unlock_irqrestore(sch->lock, flags);
285                         ret = sch->driver->notify(&sch->dev, event);
286                         spin_lock_irqsave(sch->lock, flags);
287                         if (ret)
288                                 action = NONE;
289                 }
290                 break;
291         case CIO_REVALIDATE:
292                 /* Device will be removed, so no notify necessary. */
293                 if (disc)
294                         /* Reprobe because immediate unregister might block. */
295                         action = REPROBE;
296                 else
297                         action = UNREGISTER_PROBE;
298                 break;
299         case CIO_OPER:
300                 if (disc)
301                         /* Get device operational again. */
302                         action = REPROBE;
303                 break;
304         }
305         /* Perform action. */
306         ret = 0;
307         switch (action) {
308         case UNREGISTER:
309         case UNREGISTER_PROBE:
310                 /* Unregister device (will use subchannel lock). */
311                 spin_unlock_irqrestore(sch->lock, flags);
312                 css_sch_device_unregister(sch);
313                 spin_lock_irqsave(sch->lock, flags);
314
315                 /* Reset intparm to zeroes. */
316                 sch->schib.pmcw.intparm = 0;
317                 cio_modify(sch);
318                 break;
319         case REPROBE:
320                 device_trigger_reprobe(sch);
321                 break;
322         default:
323                 break;
324         }
325         spin_unlock_irqrestore(sch->lock, flags);
326         /* Probe if necessary. */
327         if (action == UNREGISTER_PROBE)
328                 ret = css_probe_device(sch->schid);
329
330         return ret;
331 }
332
333 static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
334 {
335         struct schib schib;
336
337         if (!slow) {
338                 /* Will be done on the slow path. */
339                 return -EAGAIN;
340         }
341         if (stsch_err(schid, &schib) || !schib.pmcw.dnv) {
342                 /* Unusable - ignore. */
343                 return 0;
344         }
345         CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, unknown, "
346                          "slow path.\n", schid.ssid, schid.sch_no, CIO_OPER);
347
348         return css_probe_device(schid);
349 }
350
351 static void css_evaluate_subchannel(struct subchannel_id schid, int slow)
352 {
353         struct subchannel *sch;
354         int ret;
355
356         sch = get_subchannel_by_schid(schid);
357         if (sch) {
358                 ret = css_evaluate_known_subchannel(sch, slow);
359                 put_device(&sch->dev);
360         } else
361                 ret = css_evaluate_new_subchannel(schid, slow);
362         if (ret == -EAGAIN)
363                 css_schedule_eval(schid);
364 }
365
366 static struct idset *slow_subchannel_set;
367 static spinlock_t slow_subchannel_lock;
368
369 static int __init slow_subchannel_init(void)
370 {
371         spin_lock_init(&slow_subchannel_lock);
372         slow_subchannel_set = idset_sch_new();
373         if (!slow_subchannel_set) {
374                 printk(KERN_WARNING "cio: could not allocate slow subchannel "
375                        "set\n");
376                 return -ENOMEM;
377         }
378         return 0;
379 }
380
381 subsys_initcall(slow_subchannel_init);
382
383 static void css_slow_path_func(struct work_struct *unused)
384 {
385         struct subchannel_id schid;
386
387         CIO_TRACE_EVENT(4, "slowpath");
388         spin_lock_irq(&slow_subchannel_lock);
389         init_subchannel_id(&schid);
390         while (idset_sch_get_first(slow_subchannel_set, &schid)) {
391                 idset_sch_del(slow_subchannel_set, schid);
392                 spin_unlock_irq(&slow_subchannel_lock);
393                 css_evaluate_subchannel(schid, 1);
394                 spin_lock_irq(&slow_subchannel_lock);
395         }
396         spin_unlock_irq(&slow_subchannel_lock);
397 }
398
399 static DECLARE_WORK(slow_path_work, css_slow_path_func);
400 struct workqueue_struct *slow_path_wq;
401
402 void css_schedule_eval(struct subchannel_id schid)
403 {
404         unsigned long flags;
405
406         spin_lock_irqsave(&slow_subchannel_lock, flags);
407         idset_sch_add(slow_subchannel_set, schid);
408         queue_work(slow_path_wq, &slow_path_work);
409         spin_unlock_irqrestore(&slow_subchannel_lock, flags);
410 }
411
412 void css_schedule_eval_all(void)
413 {
414         unsigned long flags;
415
416         spin_lock_irqsave(&slow_subchannel_lock, flags);
417         idset_fill(slow_subchannel_set);
418         queue_work(slow_path_wq, &slow_path_work);
419         spin_unlock_irqrestore(&slow_subchannel_lock, flags);
420 }
421
422 /* Reprobe subchannel if unregistered. */
423 static int reprobe_subchannel(struct subchannel_id schid, void *data)
424 {
425         struct subchannel *sch;
426         int ret;
427
428         CIO_DEBUG(KERN_INFO, 6, "cio: reprobe 0.%x.%04x\n",
429                   schid.ssid, schid.sch_no);
430         if (need_reprobe)
431                 return -EAGAIN;
432
433         sch = get_subchannel_by_schid(schid);
434         if (sch) {
435                 /* Already known. */
436                 put_device(&sch->dev);
437                 return 0;
438         }
439
440         ret = css_probe_device(schid);
441         switch (ret) {
442         case 0:
443                 break;
444         case -ENXIO:
445         case -ENOMEM:
446                 /* These should abort looping */
447                 break;
448         default:
449                 ret = 0;
450         }
451
452         return ret;
453 }
454
455 /* Work function used to reprobe all unregistered subchannels. */
456 static void reprobe_all(struct work_struct *unused)
457 {
458         int ret;
459
460         CIO_MSG_EVENT(2, "reprobe start\n");
461
462         need_reprobe = 0;
463         /* Make sure initial subchannel scan is done. */
464         wait_event(ccw_device_init_wq,
465                    atomic_read(&ccw_device_init_count) == 0);
466         ret = for_each_subchannel(reprobe_subchannel, NULL);
467
468         CIO_MSG_EVENT(2, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
469                       need_reprobe);
470 }
471
472 static DECLARE_WORK(css_reprobe_work, reprobe_all);
473
474 /* Schedule reprobing of all unregistered subchannels. */
475 void css_schedule_reprobe(void)
476 {
477         need_reprobe = 1;
478         queue_work(ccw_device_work, &css_reprobe_work);
479 }
480
481 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
482
483 /*
484  * Called from the machine check handler for subchannel report words.
485  */
486 void css_process_crw(int rsid1, int rsid2)
487 {
488         struct subchannel_id mchk_schid;
489
490         CIO_CRW_EVENT(2, "source is subchannel %04X, subsystem id %x\n",
491                       rsid1, rsid2);
492         init_subchannel_id(&mchk_schid);
493         mchk_schid.sch_no = rsid1;
494         if (rsid2 != 0)
495                 mchk_schid.ssid = (rsid2 >> 8) & 3;
496
497         /* 
498          * Since we are always presented with IPI in the CRW, we have to
499          * use stsch() to find out if the subchannel in question has come
500          * or gone.
501          */
502         css_evaluate_subchannel(mchk_schid, 0);
503 }
504
505 static int __init
506 __init_channel_subsystem(struct subchannel_id schid, void *data)
507 {
508         struct subchannel *sch;
509         int ret;
510
511         if (cio_is_console(schid))
512                 sch = cio_get_console_subchannel();
513         else {
514                 sch = css_alloc_subchannel(schid);
515                 if (IS_ERR(sch))
516                         ret = PTR_ERR(sch);
517                 else
518                         ret = 0;
519                 switch (ret) {
520                 case 0:
521                         break;
522                 case -ENOMEM:
523                         panic("Out of memory in init_channel_subsystem\n");
524                 /* -ENXIO: no more subchannels. */
525                 case -ENXIO:
526                         return ret;
527                 /* -EIO: this subchannel set not supported. */
528                 case -EIO:
529                         return ret;
530                 default:
531                         return 0;
532                 }
533         }
534         /*
535          * We register ALL valid subchannels in ioinfo, even those
536          * that have been present before init_channel_subsystem.
537          * These subchannels can't have been registered yet (kmalloc
538          * not working) so we do it now. This is true e.g. for the
539          * console subchannel.
540          */
541         css_register_subchannel(sch);
542         return 0;
543 }
544
545 static void __init
546 css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
547 {
548         if (css_characteristics_avail && css_general_characteristics.mcss) {
549                 css->global_pgid.pgid_high.ext_cssid.version = 0x80;
550                 css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
551         } else {
552 #ifdef CONFIG_SMP
553                 css->global_pgid.pgid_high.cpu_addr = hard_smp_processor_id();
554 #else
555                 css->global_pgid.pgid_high.cpu_addr = 0;
556 #endif
557         }
558         css->global_pgid.cpu_id = ((cpuid_t *) __LC_CPUID)->ident;
559         css->global_pgid.cpu_model = ((cpuid_t *) __LC_CPUID)->machine;
560         css->global_pgid.tod_high = tod_high;
561
562 }
563
564 static void
565 channel_subsystem_release(struct device *dev)
566 {
567         struct channel_subsystem *css;
568
569         css = to_css(dev);
570         mutex_destroy(&css->mutex);
571         kfree(css);
572 }
573
574 static ssize_t
575 css_cm_enable_show(struct device *dev, struct device_attribute *attr,
576                    char *buf)
577 {
578         struct channel_subsystem *css = to_css(dev);
579
580         if (!css)
581                 return 0;
582         return sprintf(buf, "%x\n", css->cm_enabled);
583 }
584
585 static ssize_t
586 css_cm_enable_store(struct device *dev, struct device_attribute *attr,
587                     const char *buf, size_t count)
588 {
589         struct channel_subsystem *css = to_css(dev);
590         int ret;
591
592         switch (buf[0]) {
593         case '0':
594                 ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
595                 break;
596         case '1':
597                 ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
598                 break;
599         default:
600                 ret = -EINVAL;
601         }
602         return ret < 0 ? ret : count;
603 }
604
605 static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
606
607 static int __init setup_css(int nr)
608 {
609         u32 tod_high;
610         int ret;
611
612         memset(css[nr], 0, sizeof(struct channel_subsystem));
613         css[nr]->pseudo_subchannel =
614                 kzalloc(sizeof(*css[nr]->pseudo_subchannel), GFP_KERNEL);
615         if (!css[nr]->pseudo_subchannel)
616                 return -ENOMEM;
617         css[nr]->pseudo_subchannel->dev.parent = &css[nr]->device;
618         css[nr]->pseudo_subchannel->dev.release = css_subchannel_release;
619         sprintf(css[nr]->pseudo_subchannel->dev.bus_id, "defunct");
620         ret = cio_create_sch_lock(css[nr]->pseudo_subchannel);
621         if (ret) {
622                 kfree(css[nr]->pseudo_subchannel);
623                 return ret;
624         }
625         mutex_init(&css[nr]->mutex);
626         css[nr]->valid = 1;
627         css[nr]->cssid = nr;
628         sprintf(css[nr]->device.bus_id, "css%x", nr);
629         css[nr]->device.release = channel_subsystem_release;
630         tod_high = (u32) (get_clock() >> 32);
631         css_generate_pgid(css[nr], tod_high);
632         return 0;
633 }
634
635 /*
636  * Now that the driver core is running, we can setup our channel subsystem.
637  * The struct subchannel's are created during probing (except for the
638  * static console subchannel).
639  */
640 static int __init
641 init_channel_subsystem (void)
642 {
643         int ret, i;
644
645         if (chsc_determine_css_characteristics() == 0)
646                 css_characteristics_avail = 1;
647
648         if ((ret = bus_register(&css_bus_type)))
649                 goto out;
650
651         /* Try to enable MSS. */
652         ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
653         switch (ret) {
654         case 0: /* Success. */
655                 max_ssid = __MAX_SSID;
656                 break;
657         case -ENOMEM:
658                 goto out_bus;
659         default:
660                 max_ssid = 0;
661         }
662         /* Setup css structure. */
663         for (i = 0; i <= __MAX_CSSID; i++) {
664                 css[i] = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
665                 if (!css[i]) {
666                         ret = -ENOMEM;
667                         goto out_unregister;
668                 }
669                 ret = setup_css(i);
670                 if (ret)
671                         goto out_free;
672                 ret = device_register(&css[i]->device);
673                 if (ret)
674                         goto out_free_all;
675                 if (css_characteristics_avail &&
676                     css_chsc_characteristics.secm) {
677                         ret = device_create_file(&css[i]->device,
678                                                  &dev_attr_cm_enable);
679                         if (ret)
680                                 goto out_device;
681                 }
682                 ret = device_register(&css[i]->pseudo_subchannel->dev);
683                 if (ret)
684                         goto out_file;
685         }
686         css_init_done = 1;
687
688         ctl_set_bit(6, 28);
689
690         for_each_subchannel(__init_channel_subsystem, NULL);
691         return 0;
692 out_file:
693         device_remove_file(&css[i]->device, &dev_attr_cm_enable);
694 out_device:
695         device_unregister(&css[i]->device);
696 out_free_all:
697         kfree(css[i]->pseudo_subchannel->lock);
698         kfree(css[i]->pseudo_subchannel);
699 out_free:
700         kfree(css[i]);
701 out_unregister:
702         while (i > 0) {
703                 i--;
704                 device_unregister(&css[i]->pseudo_subchannel->dev);
705                 if (css_characteristics_avail && css_chsc_characteristics.secm)
706                         device_remove_file(&css[i]->device,
707                                            &dev_attr_cm_enable);
708                 device_unregister(&css[i]->device);
709         }
710 out_bus:
711         bus_unregister(&css_bus_type);
712 out:
713         return ret;
714 }
715
716 int sch_is_pseudo_sch(struct subchannel *sch)
717 {
718         return sch == to_css(sch->dev.parent)->pseudo_subchannel;
719 }
720
721 /*
722  * find a driver for a subchannel. They identify by the subchannel
723  * type with the exception that the console subchannel driver has its own
724  * subchannel type although the device is an i/o subchannel
725  */
726 static int
727 css_bus_match (struct device *dev, struct device_driver *drv)
728 {
729         struct subchannel *sch = container_of (dev, struct subchannel, dev);
730         struct css_driver *driver = container_of (drv, struct css_driver, drv);
731
732         if (sch->st == driver->subchannel_type)
733                 return 1;
734
735         return 0;
736 }
737
738 static int
739 css_probe (struct device *dev)
740 {
741         struct subchannel *sch;
742
743         sch = to_subchannel(dev);
744         sch->driver = container_of (dev->driver, struct css_driver, drv);
745         return (sch->driver->probe ? sch->driver->probe(sch) : 0);
746 }
747
748 static int
749 css_remove (struct device *dev)
750 {
751         struct subchannel *sch;
752
753         sch = to_subchannel(dev);
754         return (sch->driver->remove ? sch->driver->remove(sch) : 0);
755 }
756
757 static void
758 css_shutdown (struct device *dev)
759 {
760         struct subchannel *sch;
761
762         sch = to_subchannel(dev);
763         if (sch->driver->shutdown)
764                 sch->driver->shutdown(sch);
765 }
766
767 struct bus_type css_bus_type = {
768         .name     = "css",
769         .match    = css_bus_match,
770         .probe    = css_probe,
771         .remove   = css_remove,
772         .shutdown = css_shutdown,
773 };
774
775 subsys_initcall(init_channel_subsystem);
776
777 MODULE_LICENSE("GPL");
778 EXPORT_SYMBOL(css_bus_type);
779 EXPORT_SYMBOL_GPL(css_characteristics_avail);