xref: /linux/drivers/s390/cio/css.c (revision a0f97e06a43cf524e616f09e6af3398e1e9c1c5b) 
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->lock);
83 		kfree(sch);
84 		return ERR_PTR(ret);
85 	}
86 	return sch;
87 }
88 
89 static void
90 css_free_subchannel(struct subchannel *sch)
91 {
92 	if (sch) {
93 		/* Reset intparm to zeroes. */
94 		sch->schib.pmcw.intparm = 0;
95 		cio_modify(sch);
96 		kfree(sch->lock);
97 		kfree(sch);
98 	}
99 }
100 
101 static void
102 css_subchannel_release(struct device *dev)
103 {
104 	struct subchannel *sch;
105 
106 	sch = to_subchannel(dev);
107 	if (!cio_is_console(sch->schid)) {
108 		kfree(sch->lock);
109 		kfree(sch);
110 	}
111 }
112 
113 static int css_sch_device_register(struct subchannel *sch)
114 {
115 	int ret;
116 
117 	mutex_lock(&sch->reg_mutex);
118 	ret = device_register(&sch->dev);
119 	mutex_unlock(&sch->reg_mutex);
120 	return ret;
121 }
122 
123 void css_sch_device_unregister(struct subchannel *sch)
124 {
125 	mutex_lock(&sch->reg_mutex);
126 	device_unregister(&sch->dev);
127 	mutex_unlock(&sch->reg_mutex);
128 }
129 
130 static void ssd_from_pmcw(struct chsc_ssd_info *ssd, struct pmcw *pmcw)
131 {
132 	int i;
133 	int mask;
134 
135 	memset(ssd, 0, sizeof(struct chsc_ssd_info));
136 	ssd->path_mask = pmcw->pim;
137 	for (i = 0; i < 8; i++) {
138 		mask = 0x80 >> i;
139 		if (pmcw->pim & mask) {
140 			chp_id_init(&ssd->chpid[i]);
141 			ssd->chpid[i].id = pmcw->chpid[i];
142 		}
143 	}
144 }
145 
146 static void ssd_register_chpids(struct chsc_ssd_info *ssd)
147 {
148 	int i;
149 	int mask;
150 
151 	for (i = 0; i < 8; i++) {
152 		mask = 0x80 >> i;
153 		if (ssd->path_mask & mask)
154 			if (!chp_is_registered(ssd->chpid[i]))
155 				chp_new(ssd->chpid[i]);
156 	}
157 }
158 
159 void css_update_ssd_info(struct subchannel *sch)
160 {
161 	int ret;
162 
163 	if (cio_is_console(sch->schid)) {
164 		/* Console is initialized too early for functions requiring
165 		 * memory allocation. */
166 		ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
167 	} else {
168 		ret = chsc_get_ssd_info(sch->schid, &sch->ssd_info);
169 		if (ret)
170 			ssd_from_pmcw(&sch->ssd_info, &sch->schib.pmcw);
171 		ssd_register_chpids(&sch->ssd_info);
172 	}
173 }
174 
175 static int css_register_subchannel(struct subchannel *sch)
176 {
177 	int ret;
178 
179 	/* Initialize the subchannel structure */
180 	sch->dev.parent = &css[0]->device;
181 	sch->dev.bus = &css_bus_type;
182 	sch->dev.release = &css_subchannel_release;
183 	sch->dev.groups = subch_attr_groups;
184 	css_update_ssd_info(sch);
185 	/* make it known to the system */
186 	ret = css_sch_device_register(sch);
187 	if (ret) {
188 		CIO_MSG_EVENT(0, "Could not register sch 0.%x.%04x: %d\n",
189 			      sch->schid.ssid, sch->schid.sch_no, ret);
190 		return ret;
191 	}
192 	return ret;
193 }
194 
195 static int 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 		CIO_MSG_EVENT(0, "could not allocate slow subchannel set\n");
376 		return -ENOMEM;
377 	}
378 	return 0;
379 }
380 
381 static void css_slow_path_func(struct work_struct *unused)
382 {
383 	struct subchannel_id schid;
384 
385 	CIO_TRACE_EVENT(4, "slowpath");
386 	spin_lock_irq(&slow_subchannel_lock);
387 	init_subchannel_id(&schid);
388 	while (idset_sch_get_first(slow_subchannel_set, &schid)) {
389 		idset_sch_del(slow_subchannel_set, schid);
390 		spin_unlock_irq(&slow_subchannel_lock);
391 		css_evaluate_subchannel(schid, 1);
392 		spin_lock_irq(&slow_subchannel_lock);
393 	}
394 	spin_unlock_irq(&slow_subchannel_lock);
395 }
396 
397 static DECLARE_WORK(slow_path_work, css_slow_path_func);
398 struct workqueue_struct *slow_path_wq;
399 
400 void css_schedule_eval(struct subchannel_id schid)
401 {
402 	unsigned long flags;
403 
404 	spin_lock_irqsave(&slow_subchannel_lock, flags);
405 	idset_sch_add(slow_subchannel_set, schid);
406 	queue_work(slow_path_wq, &slow_path_work);
407 	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
408 }
409 
410 void css_schedule_eval_all(void)
411 {
412 	unsigned long flags;
413 
414 	spin_lock_irqsave(&slow_subchannel_lock, flags);
415 	idset_fill(slow_subchannel_set);
416 	queue_work(slow_path_wq, &slow_path_work);
417 	spin_unlock_irqrestore(&slow_subchannel_lock, flags);
418 }
419 
420 /* Reprobe subchannel if unregistered. */
421 static int reprobe_subchannel(struct subchannel_id schid, void *data)
422 {
423 	struct subchannel *sch;
424 	int ret;
425 
426 	CIO_MSG_EVENT(6, "cio: reprobe 0.%x.%04x\n",
427 		      schid.ssid, schid.sch_no);
428 	if (need_reprobe)
429 		return -EAGAIN;
430 
431 	sch = get_subchannel_by_schid(schid);
432 	if (sch) {
433 		/* Already known. */
434 		put_device(&sch->dev);
435 		return 0;
436 	}
437 
438 	ret = css_probe_device(schid);
439 	switch (ret) {
440 	case 0:
441 		break;
442 	case -ENXIO:
443 	case -ENOMEM:
444 		/* These should abort looping */
445 		break;
446 	default:
447 		ret = 0;
448 	}
449 
450 	return ret;
451 }
452 
453 /* Work function used to reprobe all unregistered subchannels. */
454 static void reprobe_all(struct work_struct *unused)
455 {
456 	int ret;
457 
458 	CIO_MSG_EVENT(2, "reprobe start\n");
459 
460 	need_reprobe = 0;
461 	/* Make sure initial subchannel scan is done. */
462 	wait_event(ccw_device_init_wq,
463 		   atomic_read(&ccw_device_init_count) == 0);
464 	ret = for_each_subchannel(reprobe_subchannel, NULL);
465 
466 	CIO_MSG_EVENT(2, "reprobe done (rc=%d, need_reprobe=%d)\n", ret,
467 		      need_reprobe);
468 }
469 
470 static DECLARE_WORK(css_reprobe_work, reprobe_all);
471 
472 /* Schedule reprobing of all unregistered subchannels. */
473 void css_schedule_reprobe(void)
474 {
475 	need_reprobe = 1;
476 	queue_work(ccw_device_work, &css_reprobe_work);
477 }
478 
479 EXPORT_SYMBOL_GPL(css_schedule_reprobe);
480 
481 /*
482  * Called from the machine check handler for subchannel report words.
483  */
484 void css_process_crw(int rsid1, int rsid2)
485 {
486 	struct subchannel_id mchk_schid;
487 
488 	CIO_CRW_EVENT(2, "source is subchannel %04X, subsystem id %x\n",
489 		      rsid1, rsid2);
490 	init_subchannel_id(&mchk_schid);
491 	mchk_schid.sch_no = rsid1;
492 	if (rsid2 != 0)
493 		mchk_schid.ssid = (rsid2 >> 8) & 3;
494 
495 	/*
496 	 * Since we are always presented with IPI in the CRW, we have to
497 	 * use stsch() to find out if the subchannel in question has come
498 	 * or gone.
499 	 */
500 	css_evaluate_subchannel(mchk_schid, 0);
501 }
502 
503 static int __init
504 __init_channel_subsystem(struct subchannel_id schid, void *data)
505 {
506 	struct subchannel *sch;
507 	int ret;
508 
509 	if (cio_is_console(schid))
510 		sch = cio_get_console_subchannel();
511 	else {
512 		sch = css_alloc_subchannel(schid);
513 		if (IS_ERR(sch))
514 			ret = PTR_ERR(sch);
515 		else
516 			ret = 0;
517 		switch (ret) {
518 		case 0:
519 			break;
520 		case -ENOMEM:
521 			panic("Out of memory in init_channel_subsystem\n");
522 		/* -ENXIO: no more subchannels. */
523 		case -ENXIO:
524 			return ret;
525 		/* -EIO: this subchannel set not supported. */
526 		case -EIO:
527 			return ret;
528 		default:
529 			return 0;
530 		}
531 	}
532 	/*
533 	 * We register ALL valid subchannels in ioinfo, even those
534 	 * that have been present before init_channel_subsystem.
535 	 * These subchannels can't have been registered yet (kmalloc
536 	 * not working) so we do it now. This is true e.g. for the
537 	 * console subchannel.
538 	 */
539 	css_register_subchannel(sch);
540 	return 0;
541 }
542 
543 static void __init
544 css_generate_pgid(struct channel_subsystem *css, u32 tod_high)
545 {
546 	if (css_characteristics_avail && css_general_characteristics.mcss) {
547 		css->global_pgid.pgid_high.ext_cssid.version = 0x80;
548 		css->global_pgid.pgid_high.ext_cssid.cssid = css->cssid;
549 	} else {
550 #ifdef CONFIG_SMP
551 		css->global_pgid.pgid_high.cpu_addr = hard_smp_processor_id();
552 #else
553 		css->global_pgid.pgid_high.cpu_addr = 0;
554 #endif
555 	}
556 	css->global_pgid.cpu_id = ((cpuid_t *) __LC_CPUID)->ident;
557 	css->global_pgid.cpu_model = ((cpuid_t *) __LC_CPUID)->machine;
558 	css->global_pgid.tod_high = tod_high;
559 
560 }
561 
562 static void
563 channel_subsystem_release(struct device *dev)
564 {
565 	struct channel_subsystem *css;
566 
567 	css = to_css(dev);
568 	mutex_destroy(&css->mutex);
569 	kfree(css);
570 }
571 
572 static ssize_t
573 css_cm_enable_show(struct device *dev, struct device_attribute *attr,
574 		   char *buf)
575 {
576 	struct channel_subsystem *css = to_css(dev);
577 
578 	if (!css)
579 		return 0;
580 	return sprintf(buf, "%x\n", css->cm_enabled);
581 }
582 
583 static ssize_t
584 css_cm_enable_store(struct device *dev, struct device_attribute *attr,
585 		    const char *buf, size_t count)
586 {
587 	struct channel_subsystem *css = to_css(dev);
588 	int ret;
589 
590 	switch (buf[0]) {
591 	case '0':
592 		ret = css->cm_enabled ? chsc_secm(css, 0) : 0;
593 		break;
594 	case '1':
595 		ret = css->cm_enabled ? 0 : chsc_secm(css, 1);
596 		break;
597 	default:
598 		ret = -EINVAL;
599 	}
600 	return ret < 0 ? ret : count;
601 }
602 
603 static DEVICE_ATTR(cm_enable, 0644, css_cm_enable_show, css_cm_enable_store);
604 
605 static int __init setup_css(int nr)
606 {
607 	u32 tod_high;
608 	int ret;
609 
610 	memset(css[nr], 0, sizeof(struct channel_subsystem));
611 	css[nr]->pseudo_subchannel =
612 		kzalloc(sizeof(*css[nr]->pseudo_subchannel), GFP_KERNEL);
613 	if (!css[nr]->pseudo_subchannel)
614 		return -ENOMEM;
615 	css[nr]->pseudo_subchannel->dev.parent = &css[nr]->device;
616 	css[nr]->pseudo_subchannel->dev.release = css_subchannel_release;
617 	sprintf(css[nr]->pseudo_subchannel->dev.bus_id, "defunct");
618 	ret = cio_create_sch_lock(css[nr]->pseudo_subchannel);
619 	if (ret) {
620 		kfree(css[nr]->pseudo_subchannel);
621 		return ret;
622 	}
623 	mutex_init(&css[nr]->mutex);
624 	css[nr]->valid = 1;
625 	css[nr]->cssid = nr;
626 	sprintf(css[nr]->device.bus_id, "css%x", nr);
627 	css[nr]->device.release = channel_subsystem_release;
628 	tod_high = (u32) (get_clock() >> 32);
629 	css_generate_pgid(css[nr], tod_high);
630 	return 0;
631 }
632 
633 /*
634  * Now that the driver core is running, we can setup our channel subsystem.
635  * The struct subchannel's are created during probing (except for the
636  * static console subchannel).
637  */
638 static int __init
639 init_channel_subsystem (void)
640 {
641 	int ret, i;
642 
643 	ret = chsc_determine_css_characteristics();
644 	if (ret == -ENOMEM)
645 		goto out; /* No need to continue. */
646 	if (ret == 0)
647 		css_characteristics_avail = 1;
648 
649 	ret = chsc_alloc_sei_area();
650 	if (ret)
651 		goto out;
652 
653 	ret = slow_subchannel_init();
654 	if (ret)
655 		goto out;
656 
657 	if ((ret = bus_register(&css_bus_type)))
658 		goto out;
659 
660 	/* Try to enable MSS. */
661 	ret = chsc_enable_facility(CHSC_SDA_OC_MSS);
662 	switch (ret) {
663 	case 0: /* Success. */
664 		max_ssid = __MAX_SSID;
665 		break;
666 	case -ENOMEM:
667 		goto out_bus;
668 	default:
669 		max_ssid = 0;
670 	}
671 	/* Setup css structure. */
672 	for (i = 0; i <= __MAX_CSSID; i++) {
673 		css[i] = kmalloc(sizeof(struct channel_subsystem), GFP_KERNEL);
674 		if (!css[i]) {
675 			ret = -ENOMEM;
676 			goto out_unregister;
677 		}
678 		ret = setup_css(i);
679 		if (ret)
680 			goto out_free;
681 		ret = device_register(&css[i]->device);
682 		if (ret)
683 			goto out_free_all;
684 		if (css_characteristics_avail &&
685 		    css_chsc_characteristics.secm) {
686 			ret = device_create_file(&css[i]->device,
687 						 &dev_attr_cm_enable);
688 			if (ret)
689 				goto out_device;
690 		}
691 		ret = device_register(&css[i]->pseudo_subchannel->dev);
692 		if (ret)
693 			goto out_file;
694 	}
695 	css_init_done = 1;
696 
697 	ctl_set_bit(6, 28);
698 
699 	for_each_subchannel(__init_channel_subsystem, NULL);
700 	return 0;
701 out_file:
702 	device_remove_file(&css[i]->device, &dev_attr_cm_enable);
703 out_device:
704 	device_unregister(&css[i]->device);
705 out_free_all:
706 	kfree(css[i]->pseudo_subchannel->lock);
707 	kfree(css[i]->pseudo_subchannel);
708 out_free:
709 	kfree(css[i]);
710 out_unregister:
711 	while (i > 0) {
712 		i--;
713 		device_unregister(&css[i]->pseudo_subchannel->dev);
714 		if (css_characteristics_avail && css_chsc_characteristics.secm)
715 			device_remove_file(&css[i]->device,
716 					   &dev_attr_cm_enable);
717 		device_unregister(&css[i]->device);
718 	}
719 out_bus:
720 	bus_unregister(&css_bus_type);
721 out:
722 	chsc_free_sei_area();
723 	kfree(slow_subchannel_set);
724 	printk(KERN_WARNING"cio: failed to initialize css driver (%d)!\n",
725 	       ret);
726 	return ret;
727 }
728 
729 int sch_is_pseudo_sch(struct subchannel *sch)
730 {
731 	return sch == to_css(sch->dev.parent)->pseudo_subchannel;
732 }
733 
734 /*
735  * find a driver for a subchannel. They identify by the subchannel
736  * type with the exception that the console subchannel driver has its own
737  * subchannel type although the device is an i/o subchannel
738  */
739 static int
740 css_bus_match (struct device *dev, struct device_driver *drv)
741 {
742 	struct subchannel *sch = container_of (dev, struct subchannel, dev);
743 	struct css_driver *driver = container_of (drv, struct css_driver, drv);
744 
745 	if (sch->st == driver->subchannel_type)
746 		return 1;
747 
748 	return 0;
749 }
750 
751 static int
752 css_probe (struct device *dev)
753 {
754 	struct subchannel *sch;
755 
756 	sch = to_subchannel(dev);
757 	sch->driver = container_of (dev->driver, struct css_driver, drv);
758 	return (sch->driver->probe ? sch->driver->probe(sch) : 0);
759 }
760 
761 static int
762 css_remove (struct device *dev)
763 {
764 	struct subchannel *sch;
765 
766 	sch = to_subchannel(dev);
767 	return (sch->driver->remove ? sch->driver->remove(sch) : 0);
768 }
769 
770 static void
771 css_shutdown (struct device *dev)
772 {
773 	struct subchannel *sch;
774 
775 	sch = to_subchannel(dev);
776 	if (sch->driver->shutdown)
777 		sch->driver->shutdown(sch);
778 }
779 
780 struct bus_type css_bus_type = {
781 	.name     = "css",
782 	.match    = css_bus_match,
783 	.probe    = css_probe,
784 	.remove   = css_remove,
785 	.shutdown = css_shutdown,
786 };
787 
788 subsys_initcall(init_channel_subsystem);
789 
790 MODULE_LICENSE("GPL");
791 EXPORT_SYMBOL(css_bus_type);
792 EXPORT_SYMBOL_GPL(css_characteristics_avail);
793