aboutsummaryrefslogtreecommitdiffstats
path: root/arch/powerpc/platforms/iseries/viopath.c
blob: 622a30149b48b700131da58ebd52e098acebf573 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
/* -*- linux-c -*-
 *
 *  iSeries Virtual I/O Message Path code
 *
 *  Authors: Dave Boutcher <boutcher@us.ibm.com>
 *           Ryan Arnold <ryanarn@us.ibm.com>
 *           Colin Devilbiss <devilbis@us.ibm.com>
 *
 * (C) Copyright 2000-2005 IBM Corporation
 *
 * This code is used by the iSeries virtual disk, cd,
 * tape, and console to communicate with OS/400 in another
 * partition.
 *
 * This program is free software;  you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) anyu later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 *
 */
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/vmalloc.h>
#include <linux/string.h>
#include <linux/proc_fs.h>
#include <linux/dma-mapping.h>
#include <linux/wait.h>
#include <linux/seq_file.h>
#include <linux/smp_lock.h>
#include <linux/interrupt.h>

#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/iseries/hv_types.h>
#include <asm/iseries/it_exp_vpd_panel.h>
#include <asm/iseries/hv_lp_event.h>
#include <asm/iseries/hv_lp_config.h>
#include <asm/iseries/mf.h>
#include <asm/iseries/vio.h>

/* Status of the path to each other partition in the system.
 * This is overkill, since we will only ever establish connections
 * to our hosting partition and the primary partition on the system.
 * But this allows for other support in the future.
 */
static struct viopathStatus {
	int isOpen;		/* Did we open the path?            */
	int isActive;		/* Do we have a mon msg outstanding */
	int users[VIO_MAX_SUBTYPES];
	HvLpInstanceId mSourceInst;
	HvLpInstanceId mTargetInst;
	int numberAllocated;
} viopathStatus[HVMAXARCHITECTEDLPS];

static DEFINE_SPINLOCK(statuslock);

/*
 * For each kind of event we allocate a buffer that is
 * guaranteed not to cross a page boundary
 */
static unsigned char event_buffer[VIO_MAX_SUBTYPES * 256]
	__attribute__((__aligned__(4096)));
static atomic_t event_buffer_available[VIO_MAX_SUBTYPES];
static int event_buffer_initialised;

static void handleMonitorEvent(struct HvLpEvent *event);

/*
 * We use this structure to handle asynchronous responses.  The caller
 * blocks on the semaphore and the handler posts the semaphore.  However,
 * if system_state is not SYSTEM_RUNNING, then wait_atomic is used ...
 */
struct alloc_parms {
	struct semaphore sem;
	int number;
	atomic_t wait_atomic;
	int used_wait_atomic;
};

/* Put a sequence number in each mon msg.  The value is not
 * important.  Start at something other than 0 just for
 * readability.  wrapping this is ok.
 */
static u8 viomonseq = 22;

/* Our hosting logical partition.  We get this at startup
 * time, and different modules access this variable directly.
 */
HvLpIndex viopath_hostLp = HvLpIndexInvalid;
EXPORT_SYMBOL(viopath_hostLp);
HvLpIndex viopath_ourLp = HvLpIndexInvalid;
EXPORT_SYMBOL(viopath_ourLp);

/* For each kind of incoming event we set a pointer to a
 * routine to call.
 */
static vio_event_handler_t *vio_handler[VIO_MAX_SUBTYPES];

#define VIOPATH_KERN_WARN	KERN_WARNING "viopath: "
#define VIOPATH_KERN_INFO	KERN_INFO "viopath: "

static int proc_viopath_show(struct seq_file *m, void *v)
{
	char *buf;
	u16 vlanMap;
	dma_addr_t handle;
	HvLpEvent_Rc hvrc;
	DECLARE_MUTEX_LOCKED(Semaphore);

	buf = kmalloc(HW_PAGE_SIZE, GFP_KERNEL);
	if (!buf)
		return 0;
	memset(buf, 0, HW_PAGE_SIZE);

	handle = dma_map_single(iSeries_vio_dev, buf, HW_PAGE_SIZE,
				DMA_FROM_DEVICE);

	hvrc = HvCallEvent_signalLpEventFast(viopath_hostLp,
			HvLpEvent_Type_VirtualIo,
			viomajorsubtype_config | vioconfigget,
			HvLpEvent_AckInd_DoAck, HvLpEvent_AckType_ImmediateAck,
			viopath_sourceinst(viopath_hostLp),
			viopath_targetinst(viopath_hostLp),
			(u64)(unsigned long)&Semaphore, VIOVERSION << 16,
			((u64)handle) << 32, HW_PAGE_SIZE, 0, 0);

	if (hvrc != HvLpEvent_Rc_Good)
		printk(VIOPATH_KERN_WARN "hv error on op %d\n", (int)hvrc);

	down(&Semaphore);

	vlanMap = HvLpConfig_getVirtualLanIndexMap();

	buf[HW_PAGE_SIZE-1] = '\0';
	seq_printf(m, "%s", buf);
	seq_printf(m, "AVAILABLE_VETH=%x\n", vlanMap);
	seq_printf(m, "SRLNBR=%c%c%c%c%c%c%c\n",
		   e2a(xItExtVpdPanel.mfgID[2]),
		   e2a(xItExtVpdPanel.mfgID[3]),
		   e2a(xItExtVpdPanel.systemSerial[1]),
		   e2a(xItExtVpdPanel.systemSerial[2]),
		   e2a(xItExtVpdPanel.systemSerial[3]),
		   e2a(xItExtVpdPanel.systemSerial[4]),
		   e2a(xItExtVpdPanel.systemSerial[5]));

	dma_unmap_single(iSeries_vio_dev, handle, HW_PAGE_SIZE,
			 DMA_FROM_DEVICE);
	kfree(buf);

	return 0;
}

static int proc_viopath_open(struct inode *inode, struct file *file)
{
	return single_open(file, proc_viopath_show, NULL);
}

static struct file_operations proc_viopath_operations = {
	.open		= proc_viopath_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= single_release,
};

static int __init vio_proc_init(void)
{
	struct proc_dir_entry *e;

	e = create_proc_entry("iSeries/config", 0, NULL);
	if (e)
		e->proc_fops = &proc_viopath_operations;

        return 0;
}
__initcall(vio_proc_init);

/* See if a given LP is active.  Allow for invalid lps to be passed in
 * and just return invalid
 */
int viopath_isactive(HvLpIndex lp)
{
	if (lp == HvLpIndexInvalid)
		return 0;
	if (lp < HVMAXARCHITECTEDLPS)
		return viopathStatus[lp].isActive;
	else
		return 0;
}
EXPORT_SYMBOL(viopath_isactive);

/*
 * We cache the source and target instance ids for each
 * partition.
 */
HvLpInstanceId viopath_sourceinst(HvLpIndex lp)
{
	return viopathStatus[lp].mSourceInst;
}
EXPORT_SYMBOL(viopath_sourceinst);

HvLpInstanceId viopath_targetinst(HvLpIndex lp)
{
	return viopathStatus[lp].mTargetInst;
}
EXPORT_SYMBOL(viopath_targetinst);

/*
 * Send a monitor message.  This is a message with the acknowledge
 * bit on that the other side will NOT explicitly acknowledge.  When
 * the other side goes down, the hypervisor will acknowledge any
 * outstanding messages....so we will know when the other side dies.
 */
static void sendMonMsg(HvLpIndex remoteLp)
{
	HvLpEvent_Rc hvrc;

	viopathStatus[remoteLp].mSourceInst =
		HvCallEvent_getSourceLpInstanceId(remoteLp,
				HvLpEvent_Type_VirtualIo);
	viopathStatus[remoteLp].mTargetInst =
		HvCallEvent_getTargetLpInstanceId(remoteLp,
				HvLpEvent_Type_VirtualIo);

	/*
	 * Deliberately ignore the return code here.  if we call this
	 * more than once, we don't care.
	 */
	vio_setHandler(viomajorsubtype_monitor, handleMonitorEvent);

	hvrc = HvCallEvent_signalLpEventFast(remoteLp, HvLpEvent_Type_VirtualIo,
			viomajorsubtype_monitor, HvLpEvent_AckInd_DoAck,
			HvLpEvent_AckType_DeferredAck,
			viopathStatus[remoteLp].mSourceInst,
			viopathStatus[remoteLp].mTargetInst,
			viomonseq++, 0, 0, 0, 0, 0);

	if (hvrc == HvLpEvent_Rc_Good)
		viopathStatus[remoteLp].isActive = 1;
	else {
		printk(VIOPATH_KERN_WARN "could not connect to partition %d\n",
				remoteLp);
		viopathStatus[remoteLp].isActive = 0;
	}
}

static void handleMonitorEvent(struct HvLpEvent *event)
{
	HvLpIndex remoteLp;
	int i;

	/*
	 * This handler is _also_ called as part of the loop
	 * at the end of this routine, so it must be able to
	 * ignore NULL events...
	 */
	if (!event)
		return;

	/*
	 * First see if this is just a normal monitor message from the
	 * other partition
	 */
	if (hvlpevent_is_int(event)) {
		remoteLp = event->xSourceLp;
		if (!viopathStatus[remoteLp].isActive)
			sendMonMsg(remoteLp);
		return;
	}

	/*
	 * This path is for an acknowledgement; the other partition
	 * died
	 */
	remoteLp = event->xTargetLp;
	if ((event->xSourceInstanceId != viopathStatus[remoteLp].mSourceInst) ||
	    (event->xTargetInstanceId != viopathStatus[remoteLp].mTargetInst)) {
		printk(VIOPATH_KERN_WARN "ignoring ack....mismatched instances\n");
		return;
	}

	printk(VIOPATH_KERN_WARN "partition %d ended\n", remoteLp);

	viopathStatus[remoteLp].isActive = 0;

	/*
	 * For each active handler, pass them a NULL
	 * message to indicate that the other partition
	 * died
	 */
	for (i = 0; i < VIO_MAX_SUBTYPES; i++) {
		if (vio_handler[i] != NULL)
			(*vio_handler[i])(NULL);
	}
}

int vio_setHandler(int subtype, vio_event_handler_t *beh)
{
	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
		return -EINVAL;
	if (vio_handler[subtype] != NULL)
		return -EBUSY;
	vio_handler[subtype] = beh;
	return 0;
}
EXPORT_SYMBOL(vio_setHandler);

int vio_clearHandler(int subtype)
{
	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
		return -EINVAL;
	if (vio_handler[subtype] == NULL)
		return -EAGAIN;
	vio_handler[subtype] = NULL;
	return 0;
}
EXPORT_SYMBOL(vio_clearHandler);

static void handleConfig(struct HvLpEvent *event)
{
	if (!event)
		return;
	if (hvlpevent_is_int(event)) {
		printk(VIOPATH_KERN_WARN
		       "unexpected config request from partition %d",
		       event->xSourceLp);

		if (hvlpevent_need_ack(event)) {
			event->xRc = HvLpEvent_Rc_InvalidSubtype;
			HvCallEvent_ackLpEvent(event);
		}
		return;
	}

	up((struct semaphore *)event->xCorrelationToken);
}

/*
 * Initialization of the hosting partition
 */
void vio_set_hostlp(void)
{
	/*
	 * If this has already been set then we DON'T want to either change
	 * it or re-register the proc file system
	 */
	if (viopath_hostLp != HvLpIndexInvalid)
		return;

	/*
	 * Figure out our hosting partition.  This isn't allowed to change
	 * while we're active
	 */
	viopath_ourLp = HvLpConfig_getLpIndex();
	viopath_hostLp = HvLpConfig_getHostingLpIndex(viopath_ourLp);

	if (viopath_hostLp != HvLpIndexInvalid)
		vio_setHandler(viomajorsubtype_config, handleConfig);
}
EXPORT_SYMBOL(vio_set_hostlp);

static void vio_handleEvent(struct HvLpEvent *event, struct pt_regs *regs)
{
	HvLpIndex remoteLp;
	int subtype = (event->xSubtype & VIOMAJOR_SUBTYPE_MASK)
		>> VIOMAJOR_SUBTYPE_SHIFT;

	if (hvlpevent_is_int(event)) {
		remoteLp = event->xSourceLp;
		/*
		 * The isActive is checked because if the hosting partition
		 * went down and came back up it would not be active but it
		 * would have different source and target instances, in which
		 * case we'd want to reset them.  This case really protects
		 * against an unauthorized active partition sending interrupts
		 * or acks to this linux partition.
		 */
		if (viopathStatus[remoteLp].isActive
		    && (event->xSourceInstanceId !=
			viopathStatus[remoteLp].mTargetInst)) {
			printk(VIOPATH_KERN_WARN
			       "message from invalid partition. "
			       "int msg rcvd, source inst (%d) doesnt match (%d)\n",
			       viopathStatus[remoteLp].mTargetInst,
			       event->xSourceInstanceId);
			return;
		}

		if (viopathStatus[remoteLp].isActive
		    && (event->xTargetInstanceId !=
			viopathStatus[remoteLp].mSourceInst)) {
			printk(VIOPATH_KERN_WARN
			       "message from invalid partition. "
			       "int msg rcvd, target inst (%d) doesnt match (%d)\n",
			       viopathStatus[remoteLp].mSourceInst,
			       event->xTargetInstanceId);
			return;
		}
	} else {
		remoteLp = event->xTargetLp;
		if (event->xSourceInstanceId !=
		    viopathStatus[remoteLp].mSourceInst) {
			printk(VIOPATH_KERN_WARN
			       "message from invalid partition. "
			       "ack msg rcvd, source inst (%d) doesnt match (%d)\n",
			       viopathStatus[remoteLp].mSourceInst,
			       event->xSourceInstanceId);
			return;
		}

		if (event->xTargetInstanceId !=
		    viopathStatus[remoteLp].mTargetInst) {
			printk(VIOPATH_KERN_WARN
			       "message from invalid partition. "
			       "viopath: ack msg rcvd, target inst (%d) doesnt match (%d)\n",
			       viopathStatus[remoteLp].mTargetInst,
			       event->xTargetInstanceId);
			return;
		}
	}

	if (vio_handler[subtype] == NULL) {
		printk(VIOPATH_KERN_WARN
		       "unexpected virtual io event subtype %d from partition %d\n",
		       event->xSubtype, remoteLp);
		/* No handler.  Ack if necessary */
		if (hvlpevent_is_int(event) && hvlpevent_need_ack(event)) {
			event->xRc = HvLpEvent_Rc_InvalidSubtype;
			HvCallEvent_ackLpEvent(event);
		}
		return;
	}

	/* This innocuous little line is where all the real work happens */
	(*vio_handler[subtype])(event);
}

static void viopath_donealloc(void *parm, int number)
{
	struct alloc_parms *parmsp = parm;

	parmsp->number = number;
	if (parmsp->used_wait_atomic)
		atomic_set(&parmsp->wait_atomic, 0);
	else
		up(&parmsp->sem);
}

static int allocateEvents(HvLpIndex remoteLp, int numEvents)
{
	struct alloc_parms parms;

	if (system_state != SYSTEM_RUNNING) {
		parms.used_wait_atomic = 1;
		atomic_set(&parms.wait_atomic, 1);
	} else {
		parms.used_wait_atomic = 0;
		init_MUTEX_LOCKED(&parms.sem);
	}
	mf_allocate_lp_events(remoteLp, HvLpEvent_Type_VirtualIo, 250,	/* It would be nice to put a real number here! */
			    numEvents, &viopath_donealloc, &parms);
	if (system_state != SYSTEM_RUNNING) {
		while (atomic_read(&parms.wait_atomic))
			mb();
	} else
		down(&parms.sem);
	return parms.number;
}

int viopath_open(HvLpIndex remoteLp, int subtype, int numReq)
{
	int i;
	unsigned long flags;
	int tempNumAllocated;

	if ((remoteLp >= HVMAXARCHITECTEDLPS) || (remoteLp == HvLpIndexInvalid))
		return -EINVAL;

	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
		return -EINVAL;

	spin_lock_irqsave(&statuslock, flags);

	if (!event_buffer_initialised) {
		for (i = 0; i < VIO_MAX_SUBTYPES; i++)
			atomic_set(&event_buffer_available[i], 1);
		event_buffer_initialised = 1;
	}

	viopathStatus[remoteLp].users[subtype]++;

	if (!viopathStatus[remoteLp].isOpen) {
		viopathStatus[remoteLp].isOpen = 1;
		HvCallEvent_openLpEventPath(remoteLp, HvLpEvent_Type_VirtualIo);

		/*
		 * Don't hold the spinlock during an operation that
		 * can sleep.
		 */
		spin_unlock_irqrestore(&statuslock, flags);
		tempNumAllocated = allocateEvents(remoteLp, 1);
		spin_lock_irqsave(&statuslock, flags);

		viopathStatus[remoteLp].numberAllocated += tempNumAllocated;

		if (viopathStatus[remoteLp].numberAllocated == 0) {
			HvCallEvent_closeLpEventPath(remoteLp,
					HvLpEvent_Type_VirtualIo);

			spin_unlock_irqrestore(&statuslock, flags);
			return -ENOMEM;
		}

		viopathStatus[remoteLp].mSourceInst =
			HvCallEvent_getSourceLpInstanceId(remoteLp,
					HvLpEvent_Type_VirtualIo);
		viopathStatus[remoteLp].mTargetInst =
			HvCallEvent_getTargetLpInstanceId(remoteLp,
					HvLpEvent_Type_VirtualIo);
		HvLpEvent_registerHandler(HvLpEvent_Type_VirtualIo,
					  &vio_handleEvent);
		sendMonMsg(remoteLp);
		printk(VIOPATH_KERN_INFO "opening connection to partition %d, "
				"setting sinst %d, tinst %d\n",
				remoteLp, viopathStatus[remoteLp].mSourceInst,
				viopathStatus[remoteLp].mTargetInst);
	}

	spin_unlock_irqrestore(&statuslock, flags);
	tempNumAllocated = allocateEvents(remoteLp, numReq);
	spin_lock_irqsave(&statuslock, flags);
	viopathStatus[remoteLp].numberAllocated += tempNumAllocated;
	spin_unlock_irqrestore(&statuslock, flags);

	return 0;
}
EXPORT_SYMBOL(viopath_open);

int viopath_close(HvLpIndex remoteLp, int subtype, int numReq)
{
	unsigned long flags;
	int i;
	int numOpen;
	struct alloc_parms parms;

	if ((remoteLp >= HVMAXARCHITECTEDLPS) || (remoteLp == HvLpIndexInvalid))
		return -EINVAL;

	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
		return -EINVAL;

	spin_lock_irqsave(&statuslock, flags);
	/*
	 * If the viopath_close somehow gets called before a
	 * viopath_open it could decrement to -1 which is a non
	 * recoverable state so we'll prevent this from
	 * happening.
	 */
	if (viopathStatus[remoteLp].users[subtype] > 0)
		viopathStatus[remoteLp].users[subtype]--;

	spin_unlock_irqrestore(&statuslock, flags);

	parms.used_wait_atomic = 0;
	init_MUTEX_LOCKED(&parms.sem);
	mf_deallocate_lp_events(remoteLp, HvLpEvent_Type_VirtualIo,
			      numReq, &viopath_donealloc, &parms);
	down(&parms.sem);

	spin_lock_irqsave(&statuslock, flags);
	for (i = 0, numOpen = 0; i < VIO_MAX_SUBTYPES; i++)
		numOpen += viopathStatus[remoteLp].users[i];

	if ((viopathStatus[remoteLp].isOpen) && (numOpen == 0)) {
		printk(VIOPATH_KERN_INFO "closing connection to partition %d",
				remoteLp);

		HvCallEvent_closeLpEventPath(remoteLp,
					     HvLpEvent_Type_VirtualIo);
		viopathStatus[remoteLp].isOpen = 0;
		viopathStatus[remoteLp].isActive = 0;

		for (i = 0; i < VIO_MAX_SUBTYPES; i++)
			atomic_set(&event_buffer_available[i], 0);
		event_buffer_initialised = 0;
	}
	spin_unlock_irqrestore(&statuslock, flags);
	return 0;
}
EXPORT_SYMBOL(viopath_close);

void *vio_get_event_buffer(int subtype)
{
	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES))
		return NULL;

	if (atomic_dec_if_positive(&event_buffer_available[subtype]) == 0)
		return &event_buffer[subtype * 256];
	else
		return NULL;
}
EXPORT_SYMBOL(vio_get_event_buffer);

void vio_free_event_buffer(int subtype, void *buffer)
{
	subtype = subtype >> VIOMAJOR_SUBTYPE_SHIFT;
	if ((subtype < 0) || (subtype >= VIO_MAX_SUBTYPES)) {
		printk(VIOPATH_KERN_WARN
		       "unexpected subtype %d freeing event buffer\n", subtype);
		return;
	}

	if (atomic_read(&event_buffer_available[subtype]) != 0) {
		printk(VIOPATH_KERN_WARN
		       "freeing unallocated event buffer, subtype %d\n",
		       subtype);
		return;
	}

	if (buffer != &event_buffer[subtype * 256]) {
		printk(VIOPATH_KERN_WARN
		       "freeing invalid event buffer, subtype %d\n", subtype);
	}

	atomic_set(&event_buffer_available[subtype], 1);
}
EXPORT_SYMBOL(vio_free_event_buffer);

static const struct vio_error_entry vio_no_error =
    { 0, 0, "Non-VIO Error" };
static const struct vio_error_entry vio_unknown_error =
    { 0, EIO, "Unknown Error" };

static const struct vio_error_entry vio_default_errors[] = {
	{0x0001, EIO, "No Connection"},
	{0x0002, EIO, "No Receiver"},
	{0x0003, EIO, "No Buffer Available"},
	{0x0004, EBADRQC, "Invalid Message Type"},
	{0x0000, 0, NULL},
};

const struct vio_error_entry *vio_lookup_rc(
		const struct vio_error_entry *local_table, u16 rc)
{
	const struct vio_error_entry *cur;

	if (!rc)
		return &vio_no_error;
	if (local_table)
		for (cur = local_table; cur->rc; ++cur)
			if (cur->rc == rc)
				return cur;
	for (cur = vio_default_errors; cur->rc; ++cur)
		if (cur->rc == rc)
			return cur;
	return &vio_unknown_error;
}
EXPORT_SYMBOL(vio_lookup_rc);