xref: /linux/drivers/s390/cio/css.c (revision eb2bce7f5e7ac1ca6da434461217fadf3c688d2c) 
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 int
195 css_probe_device(struct subchannel_id schid)
196 {
197 	int ret;
198 	struct subchannel *sch;
199 
200 	sch = css_alloc_subchannel(schid);
201 	if (IS_ERR(sch))
202 		return PTR_ERR(sch);
203 	ret = css_register_subchannel(sch);
204 	if (ret)
205 		css_free_subchannel(sch);
206 	return ret;
207 }
208 
209 static int
210 check_subchannel(struct device * dev, void * data)
211 {
212 	struct subchannel *sch;
213 	struct subchannel_id *schid = data;
214 
215 	sch = to_subchannel(dev);
216 	return schid_equal(&sch->schid, schid);
217 }
218 
219 struct subchannel *
220 get_subchannel_by_schid(struct subchannel_id schid)
221 {
222 	struct device *dev;
223 
224 	dev = bus_find_device(&css_bus_type, NULL,
225 			      &schid, check_subchannel);
226 
227 	return dev ? to_subchannel(dev) : NULL;
228 }
229 
230 static int css_get_subchannel_status(struct subchannel *sch)
231 {
232 	struct schib schib;
233 
234 	if (stsch(sch->schid, &schib) || !schib.pmcw.dnv)
235 		return CIO_GONE;
236 	if (sch->schib.pmcw.dnv && (schib.pmcw.dev != sch->schib.pmcw.dev))
237 		return CIO_REVALIDATE;
238 	if (!sch->lpm)
239 		return CIO_NO_PATH;
240 	return CIO_OPER;
241 }
242 
243 static int css_evaluate_known_subchannel(struct subchannel *sch, int slow)
244 {
245 	int event, ret, disc;
246 	unsigned long flags;
247 	enum { NONE, UNREGISTER, UNREGISTER_PROBE, REPROBE } action;
248 
249 	spin_lock_irqsave(sch->lock, flags);
250 	disc = device_is_disconnected(sch);
251 	if (disc && slow) {
252 		/* Disconnected devices are evaluated directly only.*/
253 		spin_unlock_irqrestore(sch->lock, flags);
254 		return 0;
255 	}
256 	/* No interrupt after machine check - kill pending timers. */
257 	device_kill_pending_timer(sch);
258 	if (!disc && !slow) {
259 		/* Non-disconnected devices are evaluated on the slow path. */
260 		spin_unlock_irqrestore(sch->lock, flags);
261 		return -EAGAIN;
262 	}
263 	event = css_get_subchannel_status(sch);
264 	CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, %s, %s path.\n",
265 		      sch->schid.ssid, sch->schid.sch_no, event,
266 		      disc ? "disconnected" : "normal",
267 		      slow ? "slow" : "fast");
268 	/* Analyze subchannel status. */
269 	action = NONE;
270 	switch (event) {
271 	case CIO_NO_PATH:
272 		if (disc) {
273 			/* Check if paths have become available. */
274 			action = REPROBE;
275 			break;
276 		}
277 		/* fall through */
278 	case CIO_GONE:
279 		/* Prevent unwanted effects when opening lock. */
280 		cio_disable_subchannel(sch);
281 		device_set_disconnected(sch);
282 		/* Ask driver what to do with device. */
283 		action = UNREGISTER;
284 		if (sch->driver && sch->driver->notify) {
285 			spin_unlock_irqrestore(sch->lock, flags);
286 			ret = sch->driver->notify(&sch->dev, event);
287 			spin_lock_irqsave(sch->lock, flags);
288 			if (ret)
289 				action = NONE;
290 		}
291 		break;
292 	case CIO_REVALIDATE:
293 		/* Device will be removed, so no notify necessary. */
294 		if (disc)
295 			/* Reprobe because immediate unregister might block. */
296 			action = REPROBE;
297 		else
298 			action = UNREGISTER_PROBE;
299 		break;
300 	case CIO_OPER:
301 		if (disc)
302 			/* Get device operational again. */
303 			action = REPROBE;
304 		break;
305 	}
306 	/* Perform action. */
307 	ret = 0;
308 	switch (action) {
309 	case UNREGISTER:
310 	case UNREGISTER_PROBE:
311 		/* Unregister device (will use subchannel lock). */
312 		spin_unlock_irqrestore(sch->lock, flags);
313 		css_sch_device_unregister(sch);
314 		spin_lock_irqsave(sch->lock, flags);
315 
316 		/* Reset intparm to zeroes. */
317 		sch->schib.pmcw.intparm = 0;
318 		cio_modify(sch);
319 		break;
320 	case REPROBE:
321 		device_trigger_reprobe(sch);
322 		break;
323 	default:
324 		break;
325 	}
326 	spin_unlock_irqrestore(sch->lock, flags);
327 	/* Probe if necessary. */
328 	if (action == UNREGISTER_PROBE)
329 		ret = css_probe_device(sch->schid);
330 
331 	return ret;
332 }
333 
334 static int css_evaluate_new_subchannel(struct subchannel_id schid, int slow)
335 {
336 	struct schib schib;
337 
338 	if (!slow) {
339 		/* Will be done on the slow path. */
340 		return -EAGAIN;
341 	}
342 	if (stsch_err(schid, &schib) || !schib.pmcw.dnv) {
343 		/* Unusable - ignore. */
344 		return 0;
345 	}
346 	CIO_MSG_EVENT(4, "Evaluating schid 0.%x.%04x, event %d, unknown, "
347 			 "slow path.\n", schid.ssid, schid.sch_no, CIO_OPER);
348 
349 	return css_probe_device(schid);
350 }
351 
352 static void css_evaluate_subchannel(struct subchannel_id schid, int slow)
353 {
354 	struct subchannel *sch;
355 	int ret;
356 
357 	sch = get_subchannel_by_schid(schid);
358 	if (sch) {
359 		ret = css_evaluate_known_subchannel(sch, slow);
360 		put_device(&sch->dev);
361 	} else
362 		ret = css_evaluate_new_subchannel(schid, slow);
363 	if (ret == -EAGAIN)
364 		css_schedule_eval(schid);
365 }
366 
367 static struct idset *slow_subchannel_set;
368 static spinlock_t slow_subchannel_lock;
369 
370 static int __init slow_subchannel_init(void)
371 {
372 	spin_lock_init(&slow_subchannel_lock);
373 	slow_subchannel_set = idset_sch_new();
374 	if (!slow_subchannel_set) {
375 		printk(KERN_WARNING "cio: could not allocate slow subchannel "
376 		       "set\n");
377 		return -ENOMEM;
378 	}
379 	return 0;
380 }
381 
382 subsys_initcall(slow_subchannel_init);
383 
384 static void css_slow_path_func(struct work_struct *unused)
385 {
386 	struct subchannel_id schid;
387 
388 	CIO_TRACE_EVENT(4, "slowpath");
389 	spin_lock_irq(&slow_subchannel_lock);
390 	init_subchannel_id(&schid);
391 	while (idset_sch_get_first(slow_subchannel_set, &schid)) {
392 		idset_sch_del(slow_subchannel_set, schid);
393 		spin_unlock_irq(&slow_subchannel_lock);
394 		css_evaluate_subchannel(schid, 1);
395 		spin_lock_irq(&slow_subchannel_lock);
396 	}
397 	spin_unlock_irq(&slow_subchannel_lock);
398 }
399 
400 static DECLARE_WORK(slow_path_work, css_slow_path_func);
401 struct workqueue_struct *slow_path_wq;
402 
403 void css_schedule_eval(struct subchannel_id schid)
404 {
405 	unsigned long flags;
406 
407 	spin_lock_irqsave(&slow_subchannel_lock, flags);
408 	idset_sch_add(slow_subchannel_set, schid);
409 	queue_work(slow_path_wq, &slow_path_work);
410 	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
411 }
412 
413 void css_schedule_eval_all(void)
414 {
415 	unsigned long flags;
416 
417 	spin_lock_irqsave(&slow_subchannel_lock, flags);
418 	idset_fill(slow_subchannel_set);
419 	queue_work(slow_path_wq, &slow_path_work);
420 	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
421 }
422 
423 /* Reprobe subchannel if unregistered. */
424 static int reprobe_subchannel(struct subchannel_id schid, void *data)
425 {
426 	struct subchannel *sch;
427 	int ret;
428 
429 	CIO_DEBUG(KERN_INFO, 6, "cio: reprobe 0.%x.%04x\n",
430 		  schid.ssid, schid.sch_no);
431 	if (need_reprobe)
432 		return -EAGAIN;
433 
434 	sch = get_subchannel_by_schid(schid);
435 	if (sch) {
436 		/* Already known. */
437 		put_device(&sch->dev);
438 		return 0;
439 	}
440 
441 	ret = css_probe_device(schid);
442 	switch (ret) {
443 	case 0:
444 		break;
445 	case -ENXIO:
446 	case -ENOMEM:
447 		/* These should abort looping */
448 		break;
449 	default:
450 		ret = 0;
451 	}
452 
453 	return ret;
454 }
455 
456 /* Work function used to reprobe all unregistered subchannels. */
457 static void reprobe_all(struct work_struct *unused)
458 {
459 	int ret;
460 
461 	CIO_MSG_EVENT(2, "reprobe start\n");
462 
463 	need_reprobe = 0;
464 	/* Make sure initial subchannel scan is done. */
465 	wait_event(ccw_device_init_wq,
466 		   atomic_read(&ccw_device_init_count) == 0);
467 	ret = for_each_subchannel(reprobe_subchannel, NULL);
468 
469 	CIO_MSG_EVENT(2, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
470 		      need_reprobe);
471 }
472 
473 static DECLARE_WORK(css_reprobe_work, reprobe_all);
474 
475 /* Schedule reprobing of all unregistered subchannels. */
476 void css_schedule_reprobe(void)
477 {
478 	need_reprobe = 1;
479 	queue_work(ccw_device_work, &css_reprobe_work);
480 }
481 
482 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
483 
484 /*
485  * Called from the machine check handler for subchannel report words.
486  */
487 void css_process_crw(int rsid1, int rsid2)
488 {
489 	struct subchannel_id mchk_schid;
490 
491 	CIO_CRW_EVENT(2, "source is subchannel %04X, subsystem id %x\n",
492 		      rsid1, rsid2);
493 	init_subchannel_id(&mchk_schid);
494 	mchk_schid.sch_no = rsid1;
495 	if (rsid2 != 0)
496 		mchk_schid.ssid = (rsid2 >> 8) & 3;
497 
498 	/*
499 	 * Since we are always presented with IPI in the CRW, we have to
500 	 * use stsch() to find out if the subchannel in question has come
501 	 * or gone.
502 	 */
503 	css_evaluate_subchannel(mchk_schid, 0);
504 }
505 
506 static int __init
507 __init_channel_subsystem(struct subchannel_id schid, void *data)
508 {
509 	struct subchannel *sch;
510 	int ret;
511 
512 	if (cio_is_console(schid))
513 		sch = cio_get_console_subchannel();
514 	else {
515 		sch = css_alloc_subchannel(schid);
516 		if (IS_ERR(sch))
517 			ret = PTR_ERR(sch);
518 		else
519 			ret = 0;
520 		switch (ret) {
521 		case 0:
522 			break;
523 		case -ENOMEM:
524 			panic("Out of memory in init_channel_subsystem\n");
525 		/* -ENXIO: no more subchannels. */
526 		case -ENXIO:
527 			return ret;
528 		/* -EIO: this subchannel set not supported. */
529 		case -EIO:
530 			return ret;
531 		default:
532 			return 0;
533 		}
534 	}
535 	/*
536 	 * We register ALL valid subchannels in ioinfo, even those
537 	 * that have been present before init_channel_subsystem.
538 	 * These subchannels can't have been registered yet (kmalloc
539 	 * not working) so we do it now. This is true e.g. for the
540 	 * console subchannel.
541 	 */
542 	css_register_subchannel(sch);
543 	return 0;
544 }
545 
546 static void __init
547 css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
548 {
549 	if (css_characteristics_avail && css_general_characteristics.mcss) {
550 		css->global_pgid.pgid_high.ext_cssid.version = 0x80;
551 		css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
552 	} else {
553 #ifdef CONFIG_SMP
554 		css->global_pgid.pgid_high.cpu_addr = hard_smp_processor_id();
555 #else
556 		css->global_pgid.pgid_high.cpu_addr = 0;
557 #endif
558 	}
559 	css->global_pgid.cpu_id = ((cpuid_t *) __LC_CPUID)->ident;
560 	css->global_pgid.cpu_model = ((cpuid_t *) __LC_CPUID)->machine;
561 	css->global_pgid.tod_high = tod_high;
562 
563 }
564 
565 static void
566 channel_subsystem_release(struct device *dev)
567 {
568 	struct channel_subsystem *css;
569 
570 	css = to_css(dev);
571 	mutex_destroy(&css->mutex);
572 	kfree(css);
573 }
574 
575 static ssize_t
576 css_cm_enable_show(struct device *dev, struct device_attribute *attr,
577 		   char *buf)
578 {
579 	struct channel_subsystem *css = to_css(dev);
580 
581 	if (!css)
582 		return 0;
583 	return sprintf(buf, "%x\n", css->cm_enabled);
584 }
585 
586 static ssize_t
587 css_cm_enable_store(struct device *dev, struct device_attribute *attr,
588 		    const char *buf, size_t count)
589 {
590 	struct channel_subsystem *css = to_css(dev);
591 	int ret;
592 
593 	switch (buf[0]) {
594 	case '0':
595 		ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
596 		break;
597 	case '1':
598 		ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
599 		break;
600 	default:
601 		ret = -EINVAL;
602 	}
603 	return ret < 0 ? ret : count;
604 }
605 
606 static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
607 
608 static int __init setup_css(int nr)
609 {
610 	u32 tod_high;
611 	int ret;
612 
613 	memset(css[nr], 0, sizeof(struct channel_subsystem));
614 	css[nr]->pseudo_subchannel =
615 		kzalloc(sizeof(*css[nr]->pseudo_subchannel), GFP_KERNEL);
616 	if (!css[nr]->pseudo_subchannel)
617 		return -ENOMEM;
618 	css[nr]->pseudo_subchannel->dev.parent = &css[nr]->device;
619 	css[nr]->pseudo_subchannel->dev.release = css_subchannel_release;
620 	sprintf(css[nr]->pseudo_subchannel->dev.bus_id, "defunct");
621 	ret = cio_create_sch_lock(css[nr]->pseudo_subchannel);
622 	if (ret) {
623 		kfree(css[nr]->pseudo_subchannel);
624 		return ret;
625 	}
626 	mutex_init(&css[nr]->mutex);
627 	css[nr]->valid = 1;
628 	css[nr]->cssid = nr;
629 	sprintf(css[nr]->device.bus_id, "css%x", nr);
630 	css[nr]->device.release = channel_subsystem_release;
631 	tod_high = (u32) (get_clock() >> 32);
632 	css_generate_pgid(css[nr], tod_high);
633 	return 0;
634 }
635 
636 /*
637  * Now that the driver core is running, we can setup our channel subsystem.
638  * The struct subchannel's are created during probing (except for the
639  * static console subchannel).
640  */
641 static int __init
642 init_channel_subsystem (void)
643 {
644 	int ret, i;
645 
646 	if (chsc_determine_css_characteristics() == 0)
647 		css_characteristics_avail = 1;
648 
649 	if ((ret = bus_register(&css_bus_type)))
650 		goto out;
651 
652 	/* Try to enable MSS. */
653 	ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
654 	switch (ret) {
655 	case 0: /* Success. */
656 		max_ssid = __MAX_SSID;
657 		break;
658 	case -ENOMEM:
659 		goto out_bus;
660 	default:
661 		max_ssid = 0;
662 	}
663 	/* Setup css structure. */
664 	for (i = 0; i <= __MAX_CSSID; i++) {
665 		css[i] = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
666 		if (!css[i]) {
667 			ret = -ENOMEM;
668 			goto out_unregister;
669 		}
670 		ret = setup_css(i);
671 		if (ret)
672 			goto out_free;
673 		ret = device_register(&css[i]->device);
674 		if (ret)
675 			goto out_free_all;
676 		if (css_characteristics_avail &&
677 		    css_chsc_characteristics.secm) {
678 			ret = device_create_file(&css[i]->device,
679 						 &dev_attr_cm_enable);
680 			if (ret)
681 				goto out_device;
682 		}
683 		ret = device_register(&css[i]->pseudo_subchannel->dev);
684 		if (ret)
685 			goto out_file;
686 	}
687 	css_init_done = 1;
688 
689 	ctl_set_bit(6, 28);
690 
691 	for_each_subchannel(__init_channel_subsystem, NULL);
692 	return 0;
693 out_file:
694 	device_remove_file(&css[i]->device, &dev_attr_cm_enable);
695 out_device:
696 	device_unregister(&css[i]->device);
697 out_free_all:
698 	kfree(css[i]->pseudo_subchannel->lock);
699 	kfree(css[i]->pseudo_subchannel);
700 out_free:
701 	kfree(css[i]);
702 out_unregister:
703 	while (i > 0) {
704 		i--;
705 		device_unregister(&css[i]->pseudo_subchannel->dev);
706 		if (css_characteristics_avail && css_chsc_characteristics.secm)
707 			device_remove_file(&css[i]->device,
708 					   &dev_attr_cm_enable);
709 		device_unregister(&css[i]->device);
710 	}
711 out_bus:
712 	bus_unregister(&css_bus_type);
713 out:
714 	return ret;
715 }
716 
717 int sch_is_pseudo_sch(struct subchannel *sch)
718 {
719 	return sch == to_css(sch->dev.parent)->pseudo_subchannel;
720 }
721 
722 /*
723  * find a driver for a subchannel. They identify by the subchannel
724  * type with the exception that the console subchannel driver has its own
725  * subchannel type although the device is an i/o subchannel
726  */
727 static int
728 css_bus_match (struct device *dev, struct device_driver *drv)
729 {
730 	struct subchannel *sch = container_of (dev, struct subchannel, dev);
731 	struct css_driver *driver = container_of (drv, struct css_driver, drv);
732 
733 	if (sch->st == driver->subchannel_type)
734 		return 1;
735 
736 	return 0;
737 }
738 
739 static int
740 css_probe (struct device *dev)
741 {
742 	struct subchannel *sch;
743 
744 	sch = to_subchannel(dev);
745 	sch->driver = container_of (dev->driver, struct css_driver, drv);
746 	return (sch->driver->probe ? sch->driver->probe(sch) : 0);
747 }
748 
749 static int
750 css_remove (struct device *dev)
751 {
752 	struct subchannel *sch;
753 
754 	sch = to_subchannel(dev);
755 	return (sch->driver->remove ? sch->driver->remove(sch) : 0);
756 }
757 
758 static void
759 css_shutdown (struct device *dev)
760 {
761 	struct subchannel *sch;
762 
763 	sch = to_subchannel(dev);
764 	if (sch->driver->shutdown)
765 		sch->driver->shutdown(sch);
766 }
767 
768 struct bus_type css_bus_type = {
769 	.name     = "css",
770 	.match    = css_bus_match,
771 	.probe    = css_probe,
772 	.remove   = css_remove,
773 	.shutdown = css_shutdown,
774 };
775 
776 subsys_initcall(init_channel_subsystem);
777 
778 MODULE_LICENSE("GPL");
779 EXPORT_SYMBOL(css_bus_type);
780 EXPORT_SYMBOL_GPL(css_characteristics_avail);
781