virtio_config.h

  1/* SPDX-License-Identifier: GPL-2.0 */
  2#ifndef _LINUX_VIRTIO_CONFIG_H
  3#define _LINUX_VIRTIO_CONFIG_H
  4
  5#include <linux/err.h>
  6#include <linux/bug.h>
  7#include <linux/virtio.h>
  8#include <linux/virtio_byteorder.h>
  9#include <linux/compiler_types.h>
 10#include <uapi/linux/virtio_config.h>
 11
 12struct irq_affinity;
 13
 14struct virtio_shm_region {
 15	u64 addr;
 16	u64 len;
 17};
 18
 19typedef void vq_callback_t(struct virtqueue *);
 20
 21/**
 22 * struct virtqueue_info - Info for a virtqueue passed to find_vqs().
 23 * @name: virtqueue description. Used mainly for debugging, NULL for
 24 *        a virtqueue unused by the driver.
 25 * @callback: A callback to invoke on a used buffer notification.
 26 *            NULL for a virtqueue that does not need a callback.
 27 * @ctx: whether to maintain an extra context per virtqueue.
 28 */
 29struct virtqueue_info {
 30	const char *name;
 31	vq_callback_t *callback;
 32	bool ctx;
 33};
 34
 35/**
 36 * struct virtio_config_ops - operations for configuring a virtio device
 37 * Note: Do not assume that a transport implements all of the operations
 38 *       getting/setting a value as a simple read/write! Generally speaking,
 39 *       any of @get/@set, @get_status/@set_status, or @get_features/
 40 *       @finalize_features are NOT safe to be called from an atomic
 41 *       context.
 42 * @get: read the value of a configuration field
 43 *	vdev: the virtio_device
 44 *	offset: the offset of the configuration field
 45 *	buf: the buffer to write the field value into.
 46 *	len: the length of the buffer
 47 * @set: write the value of a configuration field
 48 *	vdev: the virtio_device
 49 *	offset: the offset of the configuration field
 50 *	buf: the buffer to read the field value from.
 51 *	len: the length of the buffer
 52 * @generation: config generation counter (optional)
 53 *	vdev: the virtio_device
 54 *	Returns the config generation counter
 55 * @get_status: read the status byte
 56 *	vdev: the virtio_device
 57 *	Returns the status byte
 58 * @set_status: write the status byte
 59 *	vdev: the virtio_device
 60 *	status: the new status byte
 61 * @reset: reset the device
 62 *	vdev: the virtio device
 63 *	After this, status and feature negotiation must be done again
 64 *	Device must not be reset from its vq/config callbacks, or in
 65 *	parallel with being added/removed.
 66 * @find_vqs: find virtqueues and instantiate them.
 67 *	vdev: the virtio_device
 68 *	nvqs: the number of virtqueues to find
 69 *	vqs: on success, includes new virtqueues
 70 *	vqs_info: array of virtqueue info structures
 71 *	Returns 0 on success or error status
 72 * @del_vqs: free virtqueues found by find_vqs().
 73 * @synchronize_cbs: synchronize with the virtqueue callbacks (optional)
 74 *      The function guarantees that all memory operations on the
 75 *      queue before it are visible to the vring_interrupt() that is
 76 *      called after it.
 77 *      vdev: the virtio_device
 78 * @get_features: get the array of feature bits for this device.
 79 *	vdev: the virtio_device
 80 *	Returns the first 64 feature bits.
 81 * @get_extended_features:
 82 *      vdev: the virtio_device
 83 *      Returns the first VIRTIO_FEATURES_BITS feature bits (all we currently
 84 *      need).
 85 * @finalize_features: confirm what device features we'll be using.
 86 *	vdev: the virtio_device
 87 *	This sends the driver feature bits to the device: it can change
 88 *	the dev->feature bits if it wants.
 89 *	Note that despite the name this can be called any number of
 90 *	times.
 91 *	Returns 0 on success or error status
 92 * @bus_name: return the bus name associated with the device (optional)
 93 *	vdev: the virtio_device
 94 *      This returns a pointer to the bus name a la pci_name from which
 95 *      the caller can then copy.
 96 * @set_vq_affinity: set the affinity for a virtqueue (optional).
 97 * @get_vq_affinity: get the affinity for a virtqueue (optional).
 98 * @get_shm_region: get a shared memory region based on the index.
 99 * @disable_vq_and_reset: reset a queue individually (optional).
100 *	vq: the virtqueue
101 *	Returns 0 on success or error status
102 *	disable_vq_and_reset will guarantee that the callbacks are disabled and
103 *	synchronized.
104 *	Except for the callback, the caller should guarantee that the vring is
105 *	not accessed by any functions of virtqueue.
106 * @enable_vq_after_reset: enable a reset queue
107 *	vq: the virtqueue
108 *	Returns 0 on success or error status
109 *	If disable_vq_and_reset is set, then enable_vq_after_reset must also be
110 *	set.
111 */
112struct virtio_config_ops {
113	void (*get)(struct virtio_device *vdev, unsigned offset,
114		    void *buf, unsigned len);
115	void (*set)(struct virtio_device *vdev, unsigned offset,
116		    const void *buf, unsigned len);
117	u32 (*generation)(struct virtio_device *vdev);
118	u8 (*get_status)(struct virtio_device *vdev);
119	void (*set_status)(struct virtio_device *vdev, u8 status);
120	void (*reset)(struct virtio_device *vdev);
121	int (*find_vqs)(struct virtio_device *vdev, unsigned int nvqs,
122			struct virtqueue *vqs[],
123			struct virtqueue_info vqs_info[],
124			struct irq_affinity *desc);
125	void (*del_vqs)(struct virtio_device *);
126	void (*synchronize_cbs)(struct virtio_device *);
127	u64 (*get_features)(struct virtio_device *vdev);
128	void (*get_extended_features)(struct virtio_device *vdev,
129				      u64 *features);
130	int (*finalize_features)(struct virtio_device *vdev);
131	const char *(*bus_name)(struct virtio_device *vdev);
132	int (*set_vq_affinity)(struct virtqueue *vq,
133			       const struct cpumask *cpu_mask);
134	const struct cpumask *(*get_vq_affinity)(struct virtio_device *vdev,
135						 int index);
136	bool (*get_shm_region)(struct virtio_device *vdev,
137			       struct virtio_shm_region *region, u8 id);
138	int (*disable_vq_and_reset)(struct virtqueue *vq);
139	int (*enable_vq_after_reset)(struct virtqueue *vq);
140};
141
142/**
143 * struct virtio_map_ops - operations for mapping buffer for a virtio device
144 * Note: For a transport that has its own mapping logic it must
145 * implement all of the operations
146 * @map_page: map a buffer to the device
147 *      map: metadata for performing mapping
148 *      page: the page that will be mapped by the device
149 *      offset: the offset in the page for a buffer
150 *      size: the buffer size
151 *      dir: mapping direction
152 *      attrs: mapping attributes
153 *      Returns the mapped address
154 * @unmap_page: unmap a buffer from the device
155 *      map: device specific mapping map
156 *      map_handle: the mapped address
157 *      size: the buffer size
158 *      dir: mapping direction
159 *      attrs: unmapping attributes
160 * @sync_single_for_cpu: sync a single buffer from device to cpu
161 *      map: metadata for performing mapping
162 *      map_handle: the mapping address to sync
163 *      size: the size of the buffer
164 *      dir: synchronization direction
165 * @sync_single_for_device: sync a single buffer from cpu to device
166 *      map: metadata for performing mapping
167 *      map_handle: the mapping address to sync
168 *      size: the size of the buffer
169 *      dir: synchronization direction
170 * @alloc: alloc a coherent buffer mapping
171 *      map: metadata for performing mapping
172 *      size: the size of the buffer
173 *      map_handle: the mapping address to sync
174 *      gfp: allocation flag (GFP_XXX)
175 *      Returns virtual address of the allocated buffer
176 * @free: free a coherent buffer mapping
177 *      map: metadata for performing mapping
178 *      size: the size of the buffer
179 *      vaddr: virtual address of the buffer
180 *      map_handle: the mapping address that needs to be freed
181 *      attrs: unmapping attributes
182 * @need_sync: if the buffer needs synchronization
183 *      map: metadata for performing mapping
184 *      map_handle: the mapped address
185 *      Returns whether the buffer needs synchronization
186 * @mapping_error: if the mapping address is error
187 *      map: metadata for performing mapping
188 *      map_handle: the mapped address
189 * @max_mapping_size: get the maximum buffer size that can be mapped
190 *      map: metadata for performing mapping
191 *      Returns the maximum buffer size that can be mapped
192 */
193struct virtio_map_ops {
194	dma_addr_t (*map_page)(union virtio_map map, struct page *page,
195			       unsigned long offset, size_t size,
196			       enum dma_data_direction dir, unsigned long attrs);
197	void (*unmap_page)(union virtio_map map, dma_addr_t map_handle,
198			   size_t size, enum dma_data_direction dir,
199			   unsigned long attrs);
200	void (*sync_single_for_cpu)(union virtio_map map, dma_addr_t map_handle,
201				    size_t size, enum dma_data_direction dir);
202	void (*sync_single_for_device)(union virtio_map map,
203				       dma_addr_t map_handle, size_t size,
204				       enum dma_data_direction dir);
205	void *(*alloc)(union virtio_map map, size_t size,
206		       dma_addr_t *map_handle, gfp_t gfp);
207	void (*free)(union virtio_map map, size_t size, void *vaddr,
208		     dma_addr_t map_handle, unsigned long attrs);
209	bool (*need_sync)(union virtio_map map, dma_addr_t map_handle);
210	int (*mapping_error)(union virtio_map map, dma_addr_t map_handle);
211	size_t (*max_mapping_size)(union virtio_map map);
212};
213
214/* If driver didn't advertise the feature, it will never appear. */
215void virtio_check_driver_offered_feature(const struct virtio_device *vdev,
216					 unsigned int fbit);
217
218/**
219 * __virtio_test_bit - helper to test feature bits. For use by transports.
220 *                     Devices should normally use virtio_has_feature,
221 *                     which includes more checks.
222 * @vdev: the device
223 * @fbit: the feature bit
224 */
225static inline bool __virtio_test_bit(const struct virtio_device *vdev,
226				     unsigned int fbit)
227{
228	return virtio_features_test_bit(vdev->features_array, fbit);
229}
230
231/**
232 * __virtio_set_bit - helper to set feature bits. For use by transports.
233 * @vdev: the device
234 * @fbit: the feature bit
235 */
236static inline void __virtio_set_bit(struct virtio_device *vdev,
237				    unsigned int fbit)
238{
239	virtio_features_set_bit(vdev->features_array, fbit);
240}
241
242/**
243 * __virtio_clear_bit - helper to clear feature bits. For use by transports.
244 * @vdev: the device
245 * @fbit: the feature bit
246 */
247static inline void __virtio_clear_bit(struct virtio_device *vdev,
248				      unsigned int fbit)
249{
250	virtio_features_clear_bit(vdev->features_array, fbit);
251}
252
253/**
254 * virtio_has_feature - helper to determine if this device has this feature.
255 * @vdev: the device
256 * @fbit: the feature bit
257 */
258static inline bool virtio_has_feature(const struct virtio_device *vdev,
259				      unsigned int fbit)
260{
261	if (fbit < VIRTIO_TRANSPORT_F_START)
262		virtio_check_driver_offered_feature(vdev, fbit);
263
264	return __virtio_test_bit(vdev, fbit);
265}
266
267static inline void virtio_get_features(struct virtio_device *vdev,
268				       u64 *features_out)
269{
270	if (vdev->config->get_extended_features) {
271		vdev->config->get_extended_features(vdev, features_out);
272		return;
273	}
274
275	virtio_features_from_u64(features_out,
276		vdev->config->get_features(vdev));
277}
278
279/**
280 * virtio_has_dma_quirk - determine whether this device has the DMA quirk
281 * @vdev: the device
282 */
283static inline bool virtio_has_dma_quirk(const struct virtio_device *vdev)
284{
285	/*
286	 * Note the reverse polarity of the quirk feature (compared to most
287	 * other features), this is for compatibility with legacy systems.
288	 */
289	return !virtio_has_feature(vdev, VIRTIO_F_ACCESS_PLATFORM);
290}
291
292static inline
293int virtio_find_vqs(struct virtio_device *vdev, unsigned int nvqs,
294		    struct virtqueue *vqs[],
295		    struct virtqueue_info vqs_info[],
296		    struct irq_affinity *desc)
297{
298	return vdev->config->find_vqs(vdev, nvqs, vqs, vqs_info, desc);
299}
300
301static inline
302struct virtqueue *virtio_find_single_vq(struct virtio_device *vdev,
303					vq_callback_t *c, const char *n)
304{
305	struct virtqueue_info vqs_info[] = {
306		{ n, c },
307	};
308	struct virtqueue *vq;
309	int err = virtio_find_vqs(vdev, 1, &vq, vqs_info, NULL);
310
311	if (err < 0)
312		return ERR_PTR(err);
313	return vq;
314}
315
316/**
317 * virtio_synchronize_cbs - synchronize with virtqueue callbacks
318 * @dev: the virtio device
319 */
320static inline
321void virtio_synchronize_cbs(struct virtio_device *dev)
322{
323	if (dev->config->synchronize_cbs) {
324		dev->config->synchronize_cbs(dev);
325	} else {
326		/*
327		 * A best effort fallback to synchronize with
328		 * interrupts, preemption and softirq disabled
329		 * regions. See comment above synchronize_rcu().
330		 */
331		synchronize_rcu();
332	}
333}
334
335/**
336 * virtio_device_ready - enable vq use in probe function
337 * @dev: the virtio device
338 *
339 * Driver must call this to use vqs in the probe function.
340 *
341 * Note: vqs are enabled automatically after probe returns.
342 */
343static inline
344void virtio_device_ready(struct virtio_device *dev)
345{
346	unsigned status = dev->config->get_status(dev);
347
348	WARN_ON(status & VIRTIO_CONFIG_S_DRIVER_OK);
349
350#ifdef CONFIG_VIRTIO_HARDEN_NOTIFICATION
351	/*
352	 * The virtio_synchronize_cbs() makes sure vring_interrupt()
353	 * will see the driver specific setup if it sees vq->broken
354	 * as false (even if the notifications come before DRIVER_OK).
355	 */
356	virtio_synchronize_cbs(dev);
357	__virtio_unbreak_device(dev);
358#endif
359	/*
360	 * The transport should ensure the visibility of vq->broken
361	 * before setting DRIVER_OK. See the comments for the transport
362	 * specific set_status() method.
363	 *
364	 * A well behaved device will only notify a virtqueue after
365	 * DRIVER_OK, this means the device should "see" the coherent
366	 * memory write that set vq->broken as false which is done by
367	 * the driver when it sees DRIVER_OK, then the following
368	 * driver's vring_interrupt() will see vq->broken as false so
369	 * we won't lose any notification.
370	 */
371	dev->config->set_status(dev, status | VIRTIO_CONFIG_S_DRIVER_OK);
372}
373
374static inline
375const char *virtio_bus_name(struct virtio_device *vdev)
376{
377	if (!vdev->config->bus_name)
378		return "virtio";
379	return vdev->config->bus_name(vdev);
380}
381
382/**
383 * virtqueue_set_affinity - setting affinity for a virtqueue
384 * @vq: the virtqueue
385 * @cpu_mask: the cpu mask
386 *
387 * Note that this function is best-effort: the affinity hint may not be set
388 * due to config support, irq type and sharing.
389 *
390 */
391static inline
392int virtqueue_set_affinity(struct virtqueue *vq, const struct cpumask *cpu_mask)
393{
394	struct virtio_device *vdev = vq->vdev;
395	if (vdev->config->set_vq_affinity)
396		return vdev->config->set_vq_affinity(vq, cpu_mask);
397	return 0;
398}
399
400static inline
401bool virtio_get_shm_region(struct virtio_device *vdev,
402			   struct virtio_shm_region *region_out, u8 id)
403{
404	if (!vdev->config->get_shm_region)
405		return false;
406	return vdev->config->get_shm_region(vdev, region_out, id);
407}
408
409static inline bool virtio_is_little_endian(struct virtio_device *vdev)
410{
411	return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
412		virtio_legacy_is_little_endian();
413}
414
415/* Memory accessors */
416static inline u16 virtio16_to_cpu(struct virtio_device *vdev, __virtio16 val)
417{
418	return __virtio16_to_cpu(virtio_is_little_endian(vdev), val);
419}
420
421static inline __virtio16 cpu_to_virtio16(struct virtio_device *vdev, u16 val)
422{
423	return __cpu_to_virtio16(virtio_is_little_endian(vdev), val);
424}
425
426static inline u32 virtio32_to_cpu(struct virtio_device *vdev, __virtio32 val)
427{
428	return __virtio32_to_cpu(virtio_is_little_endian(vdev), val);
429}
430
431static inline __virtio32 cpu_to_virtio32(struct virtio_device *vdev, u32 val)
432{
433	return __cpu_to_virtio32(virtio_is_little_endian(vdev), val);
434}
435
436static inline u64 virtio64_to_cpu(struct virtio_device *vdev, __virtio64 val)
437{
438	return __virtio64_to_cpu(virtio_is_little_endian(vdev), val);
439}
440
441static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
442{
443	return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
444}
445
446#define virtio_to_cpu(vdev, x) \
447	_Generic((x), \
448		__u8: (x), \
449		__virtio16: virtio16_to_cpu((vdev), (x)), \
450		__virtio32: virtio32_to_cpu((vdev), (x)), \
451		__virtio64: virtio64_to_cpu((vdev), (x)) \
452		)
453
454#define cpu_to_virtio(vdev, x, m) \
455	_Generic((m), \
456		__u8: (x), \
457		__virtio16: cpu_to_virtio16((vdev), (x)), \
458		__virtio32: cpu_to_virtio32((vdev), (x)), \
459		__virtio64: cpu_to_virtio64((vdev), (x)) \
460		)
461
462#define __virtio_native_type(structname, member) \
463	typeof(virtio_to_cpu(NULL, ((structname*)0)->member))
464
465/* Config space accessors. */
466#define virtio_cread(vdev, structname, member, ptr)			\
467	do {								\
468		typeof(((structname*)0)->member) virtio_cread_v;	\
469									\
470		might_sleep();						\
471		/* Sanity check: must match the member's type */	\
472		typecheck(typeof(virtio_to_cpu((vdev), virtio_cread_v)), *(ptr)); \
473									\
474		switch (sizeof(virtio_cread_v)) {			\
475		case 1:							\
476		case 2:							\
477		case 4:							\
478			vdev->config->get((vdev), 			\
479					  offsetof(structname, member), \
480					  &virtio_cread_v,		\
481					  sizeof(virtio_cread_v));	\
482			break;						\
483		default:						\
484			__virtio_cread_many((vdev), 			\
485					  offsetof(structname, member), \
486					  &virtio_cread_v,		\
487					  1,				\
488					  sizeof(virtio_cread_v));	\
489			break;						\
490		}							\
491		*(ptr) = virtio_to_cpu(vdev, virtio_cread_v);		\
492	} while(0)
493
494/* Config space accessors. */
495#define virtio_cwrite(vdev, structname, member, ptr)			\
496	do {								\
497		typeof(((structname*)0)->member) virtio_cwrite_v =	\
498			cpu_to_virtio(vdev, *(ptr), ((structname*)0)->member); \
499									\
500		might_sleep();						\
501		/* Sanity check: must match the member's type */	\
502		typecheck(typeof(virtio_to_cpu((vdev), virtio_cwrite_v)), *(ptr)); \
503									\
504		vdev->config->set((vdev), offsetof(structname, member),	\
505				  &virtio_cwrite_v,			\
506				  sizeof(virtio_cwrite_v));		\
507	} while(0)
508
509/*
510 * Nothing virtio-specific about these, but let's worry about generalizing
511 * these later.
512 */
513#define virtio_le_to_cpu(x) \
514	_Generic((x), \
515		__u8: (u8)(x), \
516		 __le16: (u16)le16_to_cpu(x), \
517		 __le32: (u32)le32_to_cpu(x), \
518		 __le64: (u64)le64_to_cpu(x) \
519		)
520
521#define virtio_cpu_to_le(x, m) \
522	_Generic((m), \
523		 __u8: (x), \
524		 __le16: cpu_to_le16(x), \
525		 __le32: cpu_to_le32(x), \
526		 __le64: cpu_to_le64(x) \
527		)
528
529/* LE (e.g. modern) Config space accessors. */
530#define virtio_cread_le(vdev, structname, member, ptr)			\
531	do {								\
532		typeof(((structname*)0)->member) virtio_cread_v;	\
533									\
534		might_sleep();						\
535		/* Sanity check: must match the member's type */	\
536		typecheck(typeof(virtio_le_to_cpu(virtio_cread_v)), *(ptr)); \
537									\
538		switch (sizeof(virtio_cread_v)) {			\
539		case 1:							\
540		case 2:							\
541		case 4:							\
542			vdev->config->get((vdev), 			\
543					  offsetof(structname, member), \
544					  &virtio_cread_v,		\
545					  sizeof(virtio_cread_v));	\
546			break;						\
547		default:						\
548			__virtio_cread_many((vdev), 			\
549					  offsetof(structname, member), \
550					  &virtio_cread_v,		\
551					  1,				\
552					  sizeof(virtio_cread_v));	\
553			break;						\
554		}							\
555		*(ptr) = virtio_le_to_cpu(virtio_cread_v);		\
556	} while(0)
557
558#define virtio_cwrite_le(vdev, structname, member, ptr)			\
559	do {								\
560		typeof(((structname*)0)->member) virtio_cwrite_v =	\
561			virtio_cpu_to_le(*(ptr), ((structname*)0)->member); \
562									\
563		might_sleep();						\
564		/* Sanity check: must match the member's type */	\
565		typecheck(typeof(virtio_le_to_cpu(virtio_cwrite_v)), *(ptr)); \
566									\
567		vdev->config->set((vdev), offsetof(structname, member),	\
568				  &virtio_cwrite_v,			\
569				  sizeof(virtio_cwrite_v));		\
570	} while(0)
571
572
573/* Read @count fields, @bytes each. */
574static inline void __virtio_cread_many(struct virtio_device *vdev,
575				       unsigned int offset,
576				       void *buf, size_t count, size_t bytes)
577{
578	u32 old, gen = vdev->config->generation ?
579		vdev->config->generation(vdev) : 0;
580	int i;
581
582	might_sleep();
583	do {
584		old = gen;
585
586		for (i = 0; i < count; i++)
587			vdev->config->get(vdev, offset + bytes * i,
588					  buf + i * bytes, bytes);
589
590		gen = vdev->config->generation ?
591			vdev->config->generation(vdev) : 0;
592	} while (gen != old);
593}
594
595static inline void virtio_cread_bytes(struct virtio_device *vdev,
596				      unsigned int offset,
597				      void *buf, size_t len)
598{
599	__virtio_cread_many(vdev, offset, buf, len, 1);
600}
601
602static inline u8 virtio_cread8(struct virtio_device *vdev, unsigned int offset)
603{
604	u8 ret;
605
606	might_sleep();
607	vdev->config->get(vdev, offset, &ret, sizeof(ret));
608	return ret;
609}
610
611static inline void virtio_cwrite8(struct virtio_device *vdev,
612				  unsigned int offset, u8 val)
613{
614	might_sleep();
615	vdev->config->set(vdev, offset, &val, sizeof(val));
616}
617
618static inline u16 virtio_cread16(struct virtio_device *vdev,
619				 unsigned int offset)
620{
621	__virtio16 ret;
622
623	might_sleep();
624	vdev->config->get(vdev, offset, &ret, sizeof(ret));
625	return virtio16_to_cpu(vdev, ret);
626}
627
628static inline void virtio_cwrite16(struct virtio_device *vdev,
629				   unsigned int offset, u16 val)
630{
631	__virtio16 v;
632
633	might_sleep();
634	v = cpu_to_virtio16(vdev, val);
635	vdev->config->set(vdev, offset, &v, sizeof(v));
636}
637
638static inline u32 virtio_cread32(struct virtio_device *vdev,
639				 unsigned int offset)
640{
641	__virtio32 ret;
642
643	might_sleep();
644	vdev->config->get(vdev, offset, &ret, sizeof(ret));
645	return virtio32_to_cpu(vdev, ret);
646}
647
648static inline void virtio_cwrite32(struct virtio_device *vdev,
649				   unsigned int offset, u32 val)
650{
651	__virtio32 v;
652
653	might_sleep();
654	v = cpu_to_virtio32(vdev, val);
655	vdev->config->set(vdev, offset, &v, sizeof(v));
656}
657
658static inline u64 virtio_cread64(struct virtio_device *vdev,
659				 unsigned int offset)
660{
661	__virtio64 ret;
662
663	__virtio_cread_many(vdev, offset, &ret, 1, sizeof(ret));
664	return virtio64_to_cpu(vdev, ret);
665}
666
667static inline void virtio_cwrite64(struct virtio_device *vdev,
668				   unsigned int offset, u64 val)
669{
670	__virtio64 v;
671
672	might_sleep();
673	v = cpu_to_virtio64(vdev, val);
674	vdev->config->set(vdev, offset, &v, sizeof(v));
675}
676
677/* Conditional config space accessors. */
678#define virtio_cread_feature(vdev, fbit, structname, member, ptr)	\
679	({								\
680		int _r = 0;						\
681		if (!virtio_has_feature(vdev, fbit))			\
682			_r = -ENOENT;					\
683		else							\
684			virtio_cread((vdev), structname, member, ptr);	\
685		_r;							\
686	})
687
688/* Conditional config space accessors. */
689#define virtio_cread_le_feature(vdev, fbit, structname, member, ptr)	\
690	({								\
691		int _r = 0;						\
692		if (!virtio_has_feature(vdev, fbit))			\
693			_r = -ENOENT;					\
694		else							\
695			virtio_cread_le((vdev), structname, member, ptr); \
696		_r;							\
697	})
698
699#endif /* _LINUX_VIRTIO_CONFIG_H */