summaryrefslogtreecommitdiff
path: root/include/virtio.h
blob: 654fdf154b6c9731daa35e303e3dc24a32eeb42a (plain)
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
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
/* SPDX-License-Identifier: GPL-2.0+ */
/*
 * Copyright (C) 2018, Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
 * Copyright (C) 2018, Bin Meng <bmeng.cn@gmail.com>
 *
 * VirtIO is a virtualization standard for network and disk device drivers
 * where just the guest's device driver "knows" it is running in a virtual
 * environment, and cooperates with the hypervisor. This enables guests to
 * get high performance network and disk operations, and gives most of the
 * performance benefits of paravirtualization. In the U-Boot case, the guest
 * is U-Boot itself, while the virtual environment are normally QEMU targets
 * like ARM, RISC-V and x86.
 *
 * See http://docs.oasis-open.org/virtio/virtio/v1.0/virtio-v1.0.pdf for
 * the VirtIO specification v1.0.
 *
 * This file is largely based on Linux kernel virtio_*.h files
 */

#ifndef __VIRTIO_H__
#define __VIRTIO_H__

#define VIRTIO_ID_NET		1 /* virtio net */
#define VIRTIO_ID_BLOCK		2 /* virtio block */
#define VIRTIO_ID_MAX_NUM	3

#define VIRTIO_NET_DRV_NAME	"virtio-net"
#define VIRTIO_BLK_DRV_NAME	"virtio-blk"

/* Status byte for guest to report progress, and synchronize features */

/* We have seen device and processed generic fields (VIRTIO_CONFIG_F_VIRTIO) */
#define VIRTIO_CONFIG_S_ACKNOWLEDGE	1
/* We have found a driver for the device */
#define VIRTIO_CONFIG_S_DRIVER		2
/* Driver has used its parts of the config, and is happy */
#define VIRTIO_CONFIG_S_DRIVER_OK	4
/* Driver has finished configuring features */
#define VIRTIO_CONFIG_S_FEATURES_OK	8
/* Device entered invalid state, driver must reset it */
#define VIRTIO_CONFIG_S_NEEDS_RESET	0x40
/* We've given up on this device */
#define VIRTIO_CONFIG_S_FAILED		0x80

/*
 * Virtio feature bits VIRTIO_TRANSPORT_F_START through VIRTIO_TRANSPORT_F_END
 * are reserved for the transport being used (eg: virtio_ring, virtio_pci etc.),
 * the rest are per-device feature bits.
 */
#define VIRTIO_TRANSPORT_F_START	28
#define VIRTIO_TRANSPORT_F_END		38

#ifndef VIRTIO_CONFIG_NO_LEGACY
/*
 * Do we get callbacks when the ring is completely used,
 * even if we've suppressed them?
 */
#define VIRTIO_F_NOTIFY_ON_EMPTY	24

/* Can the device handle any descriptor layout? */
#define VIRTIO_F_ANY_LAYOUT		27
#endif /* VIRTIO_CONFIG_NO_LEGACY */

/* v1.0 compliant */
#define VIRTIO_F_VERSION_1		32

/*
 * If clear - device has the IOMMU bypass quirk feature.
 * If set - use platform tools to detect the IOMMU.
 *
 * Note the reverse polarity (compared to most other features),
 * this is for compatibility with legacy systems.
 */
#define VIRTIO_F_IOMMU_PLATFORM		33

/* Does the device support Single Root I/O Virtualization? */
#define VIRTIO_F_SR_IOV			37

/**
 * virtio scatter-gather struct
 *
 * @addr:		sg buffer address
 * @lengh:		sg buffer length
 */
struct virtio_sg {
	void *addr;
	size_t length;
};

struct virtqueue;

/* virtio bus operations */
struct dm_virtio_ops {
	/**
	 * get_config() - read the value of a configuration field
	 *
	 * @vdev:	the real virtio device
	 * @offset:	the offset of the configuration field
	 * @buf:	the buffer to write the field value into
	 * @len:	the length of the buffer
	 * @return 0 if OK, -ve on error
	 */
	int (*get_config)(struct udevice *vdev, unsigned int offset,
			  void *buf, unsigned int len);
	/**
	 * set_config() - write the value of a configuration field
	 *
	 * @vdev:	the real virtio device
	 * @offset:	the offset of the configuration field
	 * @buf:	the buffer to read the field value from
	 * @len:	the length of the buffer
	 * @return 0 if OK, -ve on error
	 */
	int (*set_config)(struct udevice *vdev, unsigned int offset,
			  const void *buf, unsigned int len);
	/**
	 * generation() - config generation counter
	 *
	 * @vdev:	the real virtio device
	 * @counter:	the returned config generation counter
	 * @return 0 if OK, -ve on error
	 */
	int (*generation)(struct udevice *vdev, u32 *counter);
	/**
	 * get_status() - read the status byte
	 *
	 * @vdev:	the real virtio device
	 * @status:	the returned status byte
	 * @return 0 if OK, -ve on error
	 */
	int (*get_status)(struct udevice *vdev, u8 *status);
	/**
	 * set_status() - write the status byte
	 *
	 * @vdev:	the real virtio device
	 * @status:	the new status byte
	 * @return 0 if OK, -ve on error
	 */
	int (*set_status)(struct udevice *vdev, u8 status);
	/**
	 * reset() - reset the device
	 *
	 * @vdev:	the real virtio device
	 * @return 0 if OK, -ve on error
	 */
	int (*reset)(struct udevice *vdev);
	/**
	 * get_features() - get the array of feature bits for this device
	 *
	 * @vdev:	the real virtio device
	 * @features:	the first 32 feature bits (all we currently need)
	 * @return 0 if OK, -ve on error
	 */
	int (*get_features)(struct udevice *vdev, u64 *features);
	/**
	 * set_features() - confirm what device features we'll be using
	 *
	 * @vdev:	the real virtio device
	 * @return 0 if OK, -ve on error
	 */
	int (*set_features)(struct udevice *vdev);
	/**
	 * find_vqs() - find virtqueues and instantiate them
	 *
	 * @vdev:	the real virtio device
	 * @nvqs:	the number of virtqueues to find
	 * @vqs:	on success, includes new virtqueues
	 * @return 0 if OK, -ve on error
	 */
	int (*find_vqs)(struct udevice *vdev, unsigned int nvqs,
			struct virtqueue *vqs[]);
	/**
	 * del_vqs() - free virtqueues found by find_vqs()
	 *
	 * @vdev:	the real virtio device
	 * @return 0 if OK, -ve on error
	 */
	int (*del_vqs)(struct udevice *vdev);
	/**
	 * notify() - notify the device to process the queue
	 *
	 * @vdev:	the real virtio device
	 * @vq:		virtqueue to process
	 * @return 0 if OK, -ve on error
	 */
	int (*notify)(struct udevice *vdev, struct virtqueue *vq);
};

/* Get access to a virtio bus' operations */
#define virtio_get_ops(dev)	((struct dm_virtio_ops *)(dev)->driver->ops)

/**
 * virtio uclass per device private data
 *
 * @vqs:			virtualqueue for the virtio device
 * @vdev:			the real virtio device underneath
 * @legacy:			is it a legacy device?
 * @device:			virtio device ID
 * @vendor:			virtio vendor ID
 * @features:			negotiated supported features
 * @feature_table:		an array of feature supported by the driver
 * @feature_table_size:		number of entries in the feature table array
 * @feature_table_legacy:	same as feature_table but working in legacy mode
 * @feature_table_size_legacy:	number of entries in feature table legacy array
 */
struct virtio_dev_priv {
	struct list_head vqs;
	struct udevice *vdev;
	bool legacy;
	u32 device;
	u32 vendor;
	u64 features;
	const u32 *feature_table;
	u32 feature_table_size;
	const u32 *feature_table_legacy;
	u32 feature_table_size_legacy;
};

/**
 * virtio_get_config() - read the value of a configuration field
 *
 * @vdev:	the real virtio device
 * @offset:	the offset of the configuration field
 * @buf:	the buffer to write the field value into
 * @len:	the length of the buffer
 * @return 0 if OK, -ve on error
 */
int virtio_get_config(struct udevice *vdev, unsigned int offset,
		      void *buf, unsigned int len);

/**
 * virtio_set_config() - write the value of a configuration field
 *
 * @vdev:	the real virtio device
 * @offset:	the offset of the configuration field
 * @buf:	the buffer to read the field value from
 * @len:	the length of the buffer
 * @return 0 if OK, -ve on error
 */
int virtio_set_config(struct udevice *vdev, unsigned int offset,
		      void *buf, unsigned int len);

/**
 * virtio_generation() - config generation counter
 *
 * @vdev:	the real virtio device
 * @counter:	the returned config generation counter
 * @return 0 if OK, -ve on error
 */
int virtio_generation(struct udevice *vdev, u32 *counter);

/**
 * virtio_get_status() - read the status byte
 *
 * @vdev:	the real virtio device
 * @status:	the returned status byte
 * @return 0 if OK, -ve on error
 */
int virtio_get_status(struct udevice *vdev, u8 *status);

/**
 * virtio_set_status() - write the status byte
 *
 * @vdev:	the real virtio device
 * @status:	the new status byte
 * @return 0 if OK, -ve on error
 */
int virtio_set_status(struct udevice *vdev, u8 status);

/**
 * virtio_reset() - reset the device
 *
 * @vdev:	the real virtio device
 * @return 0 if OK, -ve on error
 */
int virtio_reset(struct udevice *vdev);

/**
 * virtio_get_features() - get the array of feature bits for this device
 *
 * @vdev:	the real virtio device
 * @features:	the first 32 feature bits (all we currently need)
 * @return 0 if OK, -ve on error
 */
int virtio_get_features(struct udevice *vdev, u64 *features);

/**
 * virtio_set_features() - confirm what device features we'll be using
 *
 * @vdev:	the real virtio device
 * @return 0 if OK, -ve on error
 */
int virtio_set_features(struct udevice *vdev);

/**
 * virtio_find_vqs() - find virtqueues and instantiate them
 *
 * @vdev:	the real virtio device
 * @nvqs:	the number of virtqueues to find
 * @vqs:	on success, includes new virtqueues
 * @return 0 if OK, -ve on error
 */
int virtio_find_vqs(struct udevice *vdev, unsigned int nvqs,
		    struct virtqueue *vqs[]);

/**
 * virtio_del_vqs() - free virtqueues found by find_vqs()
 *
 * @vdev:	the real virtio device
 * @return 0 if OK, -ve on error
 */
int virtio_del_vqs(struct udevice *vdev);

/**
 * virtio_notify() - notify the device to process the queue
 *
 * @vdev:	the real virtio device
 * @vq:		virtqueue to process
 * @return 0 if OK, -ve on error
 */
int virtio_notify(struct udevice *vdev, struct virtqueue *vq);

/**
 * virtio_add_status() - helper to set a new status code to the device
 *
 * @vdev:	the real virtio device
 * @status:	new status code to be added
 */
void virtio_add_status(struct udevice *vdev, u8 status);

/**
 * virtio_finalize_features() - helper to finalize features
 *
 * @vdev:	the real virtio device
 * @return 0 if OK, -ve on error
 */
int virtio_finalize_features(struct udevice *vdev);

/**
 * virtio_driver_features_init() - initialize driver supported features
 *
 * This fills in the virtio device parent per child private data with the given
 * information, which contains driver supported features and legacy features.
 *
 * This API should be called in the virtio device driver's bind method, so that
 * later virtio transport uclass driver can utilize the driver supplied features
 * to negotiate with the device on the final supported features.
 *
 * @priv:		virtio uclass per device private data
 * @feature:		an array of feature supported by the driver
 * @feature_size:	number of entries in the feature table array
 * @feature_legacy:	same as feature_table but working in legacy mode
 * @feature_legacy_size:number of entries in feature table legacy array
 */
void virtio_driver_features_init(struct virtio_dev_priv *priv,
				 const u32 *feature,
				 u32 feature_size,
				 const u32 *feature_legacy,
				 u32 feature_legacy_size);

/**
 * virtio_init() - helper to enumerate all known virtio devices
 *
 * @return 0 if OK, -ve on error
 */
int virtio_init(void);

static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)
{
	if (little_endian)
		return le16_to_cpu((__force __le16)val);
	else
		return be16_to_cpu((__force __be16)val);
}

static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)
{
	if (little_endian)
		return (__force __virtio16)cpu_to_le16(val);
	else
		return (__force __virtio16)cpu_to_be16(val);
}

static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)
{
	if (little_endian)
		return le32_to_cpu((__force __le32)val);
	else
		return be32_to_cpu((__force __be32)val);
}

static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)
{
	if (little_endian)
		return (__force __virtio32)cpu_to_le32(val);
	else
		return (__force __virtio32)cpu_to_be32(val);
}

static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)
{
	if (little_endian)
		return le64_to_cpu((__force __le64)val);
	else
		return be64_to_cpu((__force __be64)val);
}

static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)
{
	if (little_endian)
		return (__force __virtio64)cpu_to_le64(val);
	else
		return (__force __virtio64)cpu_to_be64(val);
}

/**
 * __virtio_test_bit - helper to test feature bits
 *
 * For use by transports. Devices should normally use virtio_has_feature,
 * which includes more checks.
 *
 * @udev: the transport device
 * @fbit: the feature bit
 */
static inline bool __virtio_test_bit(struct udevice *udev, unsigned int fbit)
{
	struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(udev);

	/* Did you forget to fix assumptions on max features? */
	if (__builtin_constant_p(fbit))
		BUILD_BUG_ON(fbit >= 64);
	else
		WARN_ON(fbit >= 64);

	return uc_priv->features & BIT_ULL(fbit);
}

/**
 * __virtio_set_bit - helper to set feature bits
 *
 * For use by transports.
 *
 * @udev: the transport device
 * @fbit: the feature bit
 */
static inline void __virtio_set_bit(struct udevice *udev, unsigned int fbit)
{
	struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(udev);

	/* Did you forget to fix assumptions on max features? */
	if (__builtin_constant_p(fbit))
		BUILD_BUG_ON(fbit >= 64);
	else
		WARN_ON(fbit >= 64);

	uc_priv->features |= BIT_ULL(fbit);
}

/**
 * __virtio_clear_bit - helper to clear feature bits
 *
 * For use by transports.
 *
 * @vdev: the transport device
 * @fbit: the feature bit
 */
static inline void __virtio_clear_bit(struct udevice *udev, unsigned int fbit)
{
	struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(udev);

	/* Did you forget to fix assumptions on max features? */
	if (__builtin_constant_p(fbit))
		BUILD_BUG_ON(fbit >= 64);
	else
		WARN_ON(fbit >= 64);

	uc_priv->features &= ~BIT_ULL(fbit);
}

/**
 * virtio_has_feature - helper to determine if this device has this feature
 *
 * Note this API is only usable after the virtio device driver's bind phase,
 * as the feature has been negotiated between the device and the driver.
 *
 * @vdev: the virtio device
 * @fbit: the feature bit
 */
static inline bool virtio_has_feature(struct udevice *vdev, unsigned int fbit)
{
	if (!(vdev->flags & DM_FLAG_BOUND))
		WARN_ON(true);

	return __virtio_test_bit(vdev->parent, fbit);
}

static inline bool virtio_legacy_is_little_endian(void)
{
#ifdef __LITTLE_ENDIAN
	return true;
#else
	return false;
#endif
}

static inline bool virtio_is_little_endian(struct udevice *vdev)
{
	struct virtio_dev_priv *uc_priv = dev_get_uclass_priv(vdev->parent);

	return !uc_priv->legacy || virtio_legacy_is_little_endian();
}

/* Memory accessors */
static inline u16 virtio16_to_cpu(struct udevice *vdev, __virtio16 val)
{
	return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
}

static inline __virtio16 cpu_to_virtio16(struct udevice *vdev, u16 val)
{
	return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
}

static inline u32 virtio32_to_cpu(struct udevice *vdev, __virtio32 val)
{
	return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
}

static inline __virtio32 cpu_to_virtio32(struct udevice *vdev, u32 val)
{
	return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
}

static inline u64 virtio64_to_cpu(struct udevice *vdev, __virtio64 val)
{
	return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
}

static inline __virtio64 cpu_to_virtio64(struct udevice *vdev, u64 val)
{
	return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
}

/* Read @count fields, @bytes each */
static inline void __virtio_cread_many(struct udevice *vdev,
				       unsigned int offset,
				       void *buf, size_t count, size_t bytes)
{
	u32 old, gen;
	int i;

	/* no need to check return value as generation can be optional */
	virtio_generation(vdev, &gen);
	do {
		old = gen;

		for (i = 0; i < count; i++)
			virtio_get_config(vdev, offset + bytes * i,
					  buf + i * bytes, bytes);

		virtio_generation(vdev, &gen);
	} while (gen != old);
}

static inline void virtio_cread_bytes(struct udevice *vdev,
				      unsigned int offset,
				      void *buf, size_t len)
{
	__virtio_cread_many(vdev, offset, buf, len, 1);
}

static inline u8 virtio_cread8(struct udevice *vdev, unsigned int offset)
{
	u8 ret;

	virtio_get_config(vdev, offset, &ret, sizeof(ret));
	return ret;
}

static inline void virtio_cwrite8(struct udevice *vdev,
				  unsigned int offset, u8 val)
{
	virtio_set_config(vdev, offset, &val, sizeof(val));
}

static inline u16 virtio_cread16(struct udevice *vdev,
				 unsigned int offset)
{
	u16 ret;

	virtio_get_config(vdev, offset, &ret, sizeof(ret));
	return virtio16_to_cpu(vdev, (__force __virtio16)ret);
}

static inline void virtio_cwrite16(struct udevice *vdev,
				   unsigned int offset, u16 val)
{
	val = (__force u16)cpu_to_virtio16(vdev, val);
	virtio_set_config(vdev, offset, &val, sizeof(val));
}

static inline u32 virtio_cread32(struct udevice *vdev,
				 unsigned int offset)
{
	u32 ret;

	virtio_get_config(vdev, offset, &ret, sizeof(ret));
	return virtio32_to_cpu(vdev, (__force __virtio32)ret);
}

static inline void virtio_cwrite32(struct udevice *vdev,
				   unsigned int offset, u32 val)
{
	val = (__force u32)cpu_to_virtio32(vdev, val);
	virtio_set_config(vdev, offset, &val, sizeof(val));
}

static inline u64 virtio_cread64(struct udevice *vdev,
				 unsigned int offset)
{
	u64 ret;

	__virtio_cread_many(vdev, offset, &ret, 1, sizeof(ret));
	return virtio64_to_cpu(vdev, (__force __virtio64)ret);
}

static inline void virtio_cwrite64(struct udevice *vdev,
				   unsigned int offset, u64 val)
{
	val = (__force u64)cpu_to_virtio64(vdev, val);
	virtio_set_config(vdev, offset, &val, sizeof(val));
}

/* Config space read accessor */
#define virtio_cread(vdev, structname, member, ptr)			\
	do {								\
		/* Must match the member's type, and be integer */	\
		if (!typecheck(typeof((((structname *)0)->member)), *(ptr))) \
			(*ptr) = 1;					\
									\
		switch (sizeof(*ptr)) {					\
		case 1:							\
			*(ptr) = virtio_cread8(vdev,			\
					       offsetof(structname, member)); \
			break;						\
		case 2:							\
			*(ptr) = virtio_cread16(vdev,			\
						offsetof(structname, member)); \
			break;						\
		case 4:							\
			*(ptr) = virtio_cread32(vdev,			\
						offsetof(structname, member)); \
			break;						\
		case 8:							\
			*(ptr) = virtio_cread64(vdev,			\
						offsetof(structname, member)); \
			break;						\
		default:						\
			WARN_ON(true);					\
		}							\
	} while (0)

/* Config space write accessor */
#define virtio_cwrite(vdev, structname, member, ptr)			\
	do {								\
		/* Must match the member's type, and be integer */	\
		if (!typecheck(typeof((((structname *)0)->member)), *(ptr))) \
			WARN_ON((*ptr) == 1);				\
									\
		switch (sizeof(*ptr)) {					\
		case 1:							\
			virtio_cwrite8(vdev,				\
				       offsetof(structname, member),	\
				       *(ptr));				\
			break;						\
		case 2:							\
			virtio_cwrite16(vdev,				\
					offsetof(structname, member),	\
					*(ptr));			\
			break;						\
		case 4:							\
			virtio_cwrite32(vdev,				\
					offsetof(structname, member),	\
					*(ptr));			\
			break;						\
		case 8:							\
			virtio_cwrite64(vdev,				\
					offsetof(structname, member),	\
					*(ptr));			\
			break;						\
		default:						\
			WARN_ON(true);					\
		}							\
	} while (0)

/* Conditional config space accessors */
#define virtio_cread_feature(vdev, fbit, structname, member, ptr)	\
	({								\
		int _r = 0;						\
		if (!virtio_has_feature(vdev, fbit))			\
			_r = -ENOENT;					\
		else							\
			virtio_cread(vdev, structname, member, ptr);	\
		_r;							\
	})

#endif /* __VIRTIO_H__ */