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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(features: vdev->features_array, bit: 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(features: vdev->features_array, bit: 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(features: vdev->features_array, bit: 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: features_out,
276 from: 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, nvqs: 1, vqs: &vq, vqs_info, NULL);
310
311 if (err < 0)
312 return ERR_PTR(error: 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(little_endian: 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(little_endian: 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(little_endian: 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(little_endian: 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(little_endian: 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(little_endian: 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, count: len, bytes: 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, val: 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, val: 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, buf: &ret, count: 1, bytes: sizeof(ret));
664 return virtio64_to_cpu(vdev, val: 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 */
700

source code of linux/include/linux/virtio_config.h