xref: /openbmc/linux/drivers/virtio/virtio_mmio.c (revision 293d5b43)
1 /*
2  * Virtio memory mapped device driver
3  *
4  * Copyright 2011-2014, ARM Ltd.
5  *
6  * This module allows virtio devices to be used over a virtual, memory mapped
7  * platform device.
8  *
9  * The guest device(s) may be instantiated in one of three equivalent ways:
10  *
11  * 1. Static platform device in board's code, eg.:
12  *
13  *	static struct platform_device v2m_virtio_device = {
14  *		.name = "virtio-mmio",
15  *		.id = -1,
16  *		.num_resources = 2,
17  *		.resource = (struct resource []) {
18  *			{
19  *				.start = 0x1001e000,
20  *				.end = 0x1001e0ff,
21  *				.flags = IORESOURCE_MEM,
22  *			}, {
23  *				.start = 42 + 32,
24  *				.end = 42 + 32,
25  *				.flags = IORESOURCE_IRQ,
26  *			},
27  *		}
28  *	};
29  *
30  * 2. Device Tree node, eg.:
31  *
32  *		virtio_block@1e000 {
33  *			compatible = "virtio,mmio";
34  *			reg = <0x1e000 0x100>;
35  *			interrupts = <42>;
36  *		}
37  *
38  * 3. Kernel module (or command line) parameter. Can be used more than once -
39  *    one device will be created for each one. Syntax:
40  *
41  *		[virtio_mmio.]device=<size>@<baseaddr>:<irq>[:<id>]
42  *    where:
43  *		<size>     := size (can use standard suffixes like K, M or G)
44  *		<baseaddr> := physical base address
45  *		<irq>      := interrupt number (as passed to request_irq())
46  *		<id>       := (optional) platform device id
47  *    eg.:
48  *		virtio_mmio.device=0x100@0x100b0000:48 \
49  *				virtio_mmio.device=1K@0x1001e000:74
50  *
51  *
52  *
53  * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007
54  *
55  * This work is licensed under the terms of the GNU GPL, version 2 or later.
56  * See the COPYING file in the top-level directory.
57  */
58 
59 #define pr_fmt(fmt) "virtio-mmio: " fmt
60 
61 #include <linux/acpi.h>
62 #include <linux/highmem.h>
63 #include <linux/interrupt.h>
64 #include <linux/io.h>
65 #include <linux/list.h>
66 #include <linux/module.h>
67 #include <linux/platform_device.h>
68 #include <linux/slab.h>
69 #include <linux/spinlock.h>
70 #include <linux/virtio.h>
71 #include <linux/virtio_config.h>
72 #include <linux/virtio_mmio.h>
73 #include <linux/virtio_ring.h>
74 
75 
76 
77 /* The alignment to use between consumer and producer parts of vring.
78  * Currently hardcoded to the page size. */
79 #define VIRTIO_MMIO_VRING_ALIGN		PAGE_SIZE
80 
81 
82 
83 #define to_virtio_mmio_device(_plat_dev) \
84 	container_of(_plat_dev, struct virtio_mmio_device, vdev)
85 
86 struct virtio_mmio_device {
87 	struct virtio_device vdev;
88 	struct platform_device *pdev;
89 
90 	void __iomem *base;
91 	unsigned long version;
92 
93 	/* a list of queues so we can dispatch IRQs */
94 	spinlock_t lock;
95 	struct list_head virtqueues;
96 };
97 
98 struct virtio_mmio_vq_info {
99 	/* the actual virtqueue */
100 	struct virtqueue *vq;
101 
102 	/* the list node for the virtqueues list */
103 	struct list_head node;
104 };
105 
106 
107 
108 /* Configuration interface */
109 
110 static u64 vm_get_features(struct virtio_device *vdev)
111 {
112 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
113 	u64 features;
114 
115 	writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
116 	features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
117 	features <<= 32;
118 
119 	writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
120 	features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
121 
122 	return features;
123 }
124 
125 static int vm_finalize_features(struct virtio_device *vdev)
126 {
127 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
128 
129 	/* Give virtio_ring a chance to accept features. */
130 	vring_transport_features(vdev);
131 
132 	/* Make sure there is are no mixed devices */
133 	if (vm_dev->version == 2 &&
134 			!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
135 		dev_err(&vdev->dev, "New virtio-mmio devices (version 2) must provide VIRTIO_F_VERSION_1 feature!\n");
136 		return -EINVAL;
137 	}
138 
139 	writel(1, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
140 	writel((u32)(vdev->features >> 32),
141 			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
142 
143 	writel(0, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
144 	writel((u32)vdev->features,
145 			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);
146 
147 	return 0;
148 }
149 
150 static void vm_get(struct virtio_device *vdev, unsigned offset,
151 		   void *buf, unsigned len)
152 {
153 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
154 	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
155 	u8 b;
156 	__le16 w;
157 	__le32 l;
158 
159 	if (vm_dev->version == 1) {
160 		u8 *ptr = buf;
161 		int i;
162 
163 		for (i = 0; i < len; i++)
164 			ptr[i] = readb(base + offset + i);
165 		return;
166 	}
167 
168 	switch (len) {
169 	case 1:
170 		b = readb(base + offset);
171 		memcpy(buf, &b, sizeof b);
172 		break;
173 	case 2:
174 		w = cpu_to_le16(readw(base + offset));
175 		memcpy(buf, &w, sizeof w);
176 		break;
177 	case 4:
178 		l = cpu_to_le32(readl(base + offset));
179 		memcpy(buf, &l, sizeof l);
180 		break;
181 	case 8:
182 		l = cpu_to_le32(readl(base + offset));
183 		memcpy(buf, &l, sizeof l);
184 		l = cpu_to_le32(ioread32(base + offset + sizeof l));
185 		memcpy(buf + sizeof l, &l, sizeof l);
186 		break;
187 	default:
188 		BUG();
189 	}
190 }
191 
192 static void vm_set(struct virtio_device *vdev, unsigned offset,
193 		   const void *buf, unsigned len)
194 {
195 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
196 	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
197 	u8 b;
198 	__le16 w;
199 	__le32 l;
200 
201 	if (vm_dev->version == 1) {
202 		const u8 *ptr = buf;
203 		int i;
204 
205 		for (i = 0; i < len; i++)
206 			writeb(ptr[i], base + offset + i);
207 
208 		return;
209 	}
210 
211 	switch (len) {
212 	case 1:
213 		memcpy(&b, buf, sizeof b);
214 		writeb(b, base + offset);
215 		break;
216 	case 2:
217 		memcpy(&w, buf, sizeof w);
218 		writew(le16_to_cpu(w), base + offset);
219 		break;
220 	case 4:
221 		memcpy(&l, buf, sizeof l);
222 		writel(le32_to_cpu(l), base + offset);
223 		break;
224 	case 8:
225 		memcpy(&l, buf, sizeof l);
226 		writel(le32_to_cpu(l), base + offset);
227 		memcpy(&l, buf + sizeof l, sizeof l);
228 		writel(le32_to_cpu(l), base + offset + sizeof l);
229 		break;
230 	default:
231 		BUG();
232 	}
233 }
234 
235 static u32 vm_generation(struct virtio_device *vdev)
236 {
237 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
238 
239 	if (vm_dev->version == 1)
240 		return 0;
241 	else
242 		return readl(vm_dev->base + VIRTIO_MMIO_CONFIG_GENERATION);
243 }
244 
245 static u8 vm_get_status(struct virtio_device *vdev)
246 {
247 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
248 
249 	return readl(vm_dev->base + VIRTIO_MMIO_STATUS) & 0xff;
250 }
251 
252 static void vm_set_status(struct virtio_device *vdev, u8 status)
253 {
254 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
255 
256 	/* We should never be setting status to 0. */
257 	BUG_ON(status == 0);
258 
259 	writel(status, vm_dev->base + VIRTIO_MMIO_STATUS);
260 }
261 
262 static void vm_reset(struct virtio_device *vdev)
263 {
264 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
265 
266 	/* 0 status means a reset. */
267 	writel(0, vm_dev->base + VIRTIO_MMIO_STATUS);
268 }
269 
270 
271 
272 /* Transport interface */
273 
274 /* the notify function used when creating a virt queue */
275 static bool vm_notify(struct virtqueue *vq)
276 {
277 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
278 
279 	/* We write the queue's selector into the notification register to
280 	 * signal the other end */
281 	writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);
282 	return true;
283 }
284 
285 /* Notify all virtqueues on an interrupt. */
286 static irqreturn_t vm_interrupt(int irq, void *opaque)
287 {
288 	struct virtio_mmio_device *vm_dev = opaque;
289 	struct virtio_mmio_vq_info *info;
290 	unsigned long status;
291 	unsigned long flags;
292 	irqreturn_t ret = IRQ_NONE;
293 
294 	/* Read and acknowledge interrupts */
295 	status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS);
296 	writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK);
297 
298 	if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)) {
299 		virtio_config_changed(&vm_dev->vdev);
300 		ret = IRQ_HANDLED;
301 	}
302 
303 	if (likely(status & VIRTIO_MMIO_INT_VRING)) {
304 		spin_lock_irqsave(&vm_dev->lock, flags);
305 		list_for_each_entry(info, &vm_dev->virtqueues, node)
306 			ret |= vring_interrupt(irq, info->vq);
307 		spin_unlock_irqrestore(&vm_dev->lock, flags);
308 	}
309 
310 	return ret;
311 }
312 
313 
314 
315 static void vm_del_vq(struct virtqueue *vq)
316 {
317 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
318 	struct virtio_mmio_vq_info *info = vq->priv;
319 	unsigned long flags;
320 	unsigned int index = vq->index;
321 
322 	spin_lock_irqsave(&vm_dev->lock, flags);
323 	list_del(&info->node);
324 	spin_unlock_irqrestore(&vm_dev->lock, flags);
325 
326 	/* Select and deactivate the queue */
327 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
328 	if (vm_dev->version == 1) {
329 		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
330 	} else {
331 		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
332 		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
333 	}
334 
335 	vring_del_virtqueue(vq);
336 
337 	kfree(info);
338 }
339 
340 static void vm_del_vqs(struct virtio_device *vdev)
341 {
342 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
343 	struct virtqueue *vq, *n;
344 
345 	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
346 		vm_del_vq(vq);
347 
348 	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
349 }
350 
351 static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
352 				  void (*callback)(struct virtqueue *vq),
353 				  const char *name)
354 {
355 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
356 	struct virtio_mmio_vq_info *info;
357 	struct virtqueue *vq;
358 	unsigned long flags;
359 	unsigned int num;
360 	int err;
361 
362 	if (!name)
363 		return NULL;
364 
365 	/* Select the queue we're interested in */
366 	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
367 
368 	/* Queue shouldn't already be set up. */
369 	if (readl(vm_dev->base + (vm_dev->version == 1 ?
370 			VIRTIO_MMIO_QUEUE_PFN : VIRTIO_MMIO_QUEUE_READY))) {
371 		err = -ENOENT;
372 		goto error_available;
373 	}
374 
375 	/* Allocate and fill out our active queue description */
376 	info = kmalloc(sizeof(*info), GFP_KERNEL);
377 	if (!info) {
378 		err = -ENOMEM;
379 		goto error_kmalloc;
380 	}
381 
382 	num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
383 	if (num == 0) {
384 		err = -ENOENT;
385 		goto error_new_virtqueue;
386 	}
387 
388 	/* Create the vring */
389 	vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,
390 				 true, true, vm_notify, callback, name);
391 	if (!vq) {
392 		err = -ENOMEM;
393 		goto error_new_virtqueue;
394 	}
395 
396 	/* Activate the queue */
397 	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);
398 	if (vm_dev->version == 1) {
399 		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);
400 		writel(virtqueue_get_desc_addr(vq) >> PAGE_SHIFT,
401 				vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
402 	} else {
403 		u64 addr;
404 
405 		addr = virtqueue_get_desc_addr(vq);
406 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
407 		writel((u32)(addr >> 32),
408 				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);
409 
410 		addr = virtqueue_get_avail_addr(vq);
411 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
412 		writel((u32)(addr >> 32),
413 				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);
414 
415 		addr = virtqueue_get_used_addr(vq);
416 		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
417 		writel((u32)(addr >> 32),
418 				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
419 
420 		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
421 	}
422 
423 	vq->priv = info;
424 	info->vq = vq;
425 
426 	spin_lock_irqsave(&vm_dev->lock, flags);
427 	list_add(&info->node, &vm_dev->virtqueues);
428 	spin_unlock_irqrestore(&vm_dev->lock, flags);
429 
430 	return vq;
431 
432 error_new_virtqueue:
433 	if (vm_dev->version == 1) {
434 		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
435 	} else {
436 		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
437 		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
438 	}
439 	kfree(info);
440 error_kmalloc:
441 error_available:
442 	return ERR_PTR(err);
443 }
444 
445 static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
446 		       struct virtqueue *vqs[],
447 		       vq_callback_t *callbacks[],
448 		       const char * const names[])
449 {
450 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
451 	unsigned int irq = platform_get_irq(vm_dev->pdev, 0);
452 	int i, err;
453 
454 	err = request_irq(irq, vm_interrupt, IRQF_SHARED,
455 			dev_name(&vdev->dev), vm_dev);
456 	if (err)
457 		return err;
458 
459 	for (i = 0; i < nvqs; ++i) {
460 		vqs[i] = vm_setup_vq(vdev, i, callbacks[i], names[i]);
461 		if (IS_ERR(vqs[i])) {
462 			vm_del_vqs(vdev);
463 			return PTR_ERR(vqs[i]);
464 		}
465 	}
466 
467 	return 0;
468 }
469 
470 static const char *vm_bus_name(struct virtio_device *vdev)
471 {
472 	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
473 
474 	return vm_dev->pdev->name;
475 }
476 
477 static const struct virtio_config_ops virtio_mmio_config_ops = {
478 	.get		= vm_get,
479 	.set		= vm_set,
480 	.generation	= vm_generation,
481 	.get_status	= vm_get_status,
482 	.set_status	= vm_set_status,
483 	.reset		= vm_reset,
484 	.find_vqs	= vm_find_vqs,
485 	.del_vqs	= vm_del_vqs,
486 	.get_features	= vm_get_features,
487 	.finalize_features = vm_finalize_features,
488 	.bus_name	= vm_bus_name,
489 };
490 
491 
492 
493 /* Platform device */
494 
495 static int virtio_mmio_probe(struct platform_device *pdev)
496 {
497 	struct virtio_mmio_device *vm_dev;
498 	struct resource *mem;
499 	unsigned long magic;
500 
501 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
502 	if (!mem)
503 		return -EINVAL;
504 
505 	if (!devm_request_mem_region(&pdev->dev, mem->start,
506 			resource_size(mem), pdev->name))
507 		return -EBUSY;
508 
509 	vm_dev = devm_kzalloc(&pdev->dev, sizeof(*vm_dev), GFP_KERNEL);
510 	if (!vm_dev)
511 		return  -ENOMEM;
512 
513 	vm_dev->vdev.dev.parent = &pdev->dev;
514 	vm_dev->vdev.config = &virtio_mmio_config_ops;
515 	vm_dev->pdev = pdev;
516 	INIT_LIST_HEAD(&vm_dev->virtqueues);
517 	spin_lock_init(&vm_dev->lock);
518 
519 	vm_dev->base = devm_ioremap(&pdev->dev, mem->start, resource_size(mem));
520 	if (vm_dev->base == NULL)
521 		return -EFAULT;
522 
523 	/* Check magic value */
524 	magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);
525 	if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {
526 		dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!\n", magic);
527 		return -ENODEV;
528 	}
529 
530 	/* Check device version */
531 	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);
532 	if (vm_dev->version < 1 || vm_dev->version > 2) {
533 		dev_err(&pdev->dev, "Version %ld not supported!\n",
534 				vm_dev->version);
535 		return -ENXIO;
536 	}
537 
538 	vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);
539 	if (vm_dev->vdev.id.device == 0) {
540 		/*
541 		 * virtio-mmio device with an ID 0 is a (dummy) placeholder
542 		 * with no function. End probing now with no error reported.
543 		 */
544 		return -ENODEV;
545 	}
546 	vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);
547 
548 	if (vm_dev->version == 1)
549 		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);
550 
551 	platform_set_drvdata(pdev, vm_dev);
552 
553 	return register_virtio_device(&vm_dev->vdev);
554 }
555 
556 static int virtio_mmio_remove(struct platform_device *pdev)
557 {
558 	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);
559 
560 	unregister_virtio_device(&vm_dev->vdev);
561 
562 	return 0;
563 }
564 
565 
566 
567 /* Devices list parameter */
568 
569 #if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)
570 
571 static struct device vm_cmdline_parent = {
572 	.init_name = "virtio-mmio-cmdline",
573 };
574 
575 static int vm_cmdline_parent_registered;
576 static int vm_cmdline_id;
577 
578 static int vm_cmdline_set(const char *device,
579 		const struct kernel_param *kp)
580 {
581 	int err;
582 	struct resource resources[2] = {};
583 	char *str;
584 	long long int base, size;
585 	unsigned int irq;
586 	int processed, consumed = 0;
587 	struct platform_device *pdev;
588 
589 	/* Consume "size" part of the command line parameter */
590 	size = memparse(device, &str);
591 
592 	/* Get "@<base>:<irq>[:<id>]" chunks */
593 	processed = sscanf(str, "@%lli:%u%n:%d%n",
594 			&base, &irq, &consumed,
595 			&vm_cmdline_id, &consumed);
596 
597 	/*
598 	 * sscanf() must processes at least 2 chunks; also there
599 	 * must be no extra characters after the last chunk, so
600 	 * str[consumed] must be '\0'
601 	 */
602 	if (processed < 2 || str[consumed])
603 		return -EINVAL;
604 
605 	resources[0].flags = IORESOURCE_MEM;
606 	resources[0].start = base;
607 	resources[0].end = base + size - 1;
608 
609 	resources[1].flags = IORESOURCE_IRQ;
610 	resources[1].start = resources[1].end = irq;
611 
612 	if (!vm_cmdline_parent_registered) {
613 		err = device_register(&vm_cmdline_parent);
614 		if (err) {
615 			pr_err("Failed to register parent device!\n");
616 			return err;
617 		}
618 		vm_cmdline_parent_registered = 1;
619 	}
620 
621 	pr_info("Registering device virtio-mmio.%d at 0x%llx-0x%llx, IRQ %d.\n",
622 		       vm_cmdline_id,
623 		       (unsigned long long)resources[0].start,
624 		       (unsigned long long)resources[0].end,
625 		       (int)resources[1].start);
626 
627 	pdev = platform_device_register_resndata(&vm_cmdline_parent,
628 			"virtio-mmio", vm_cmdline_id++,
629 			resources, ARRAY_SIZE(resources), NULL, 0);
630 	if (IS_ERR(pdev))
631 		return PTR_ERR(pdev);
632 
633 	return 0;
634 }
635 
636 static int vm_cmdline_get_device(struct device *dev, void *data)
637 {
638 	char *buffer = data;
639 	unsigned int len = strlen(buffer);
640 	struct platform_device *pdev = to_platform_device(dev);
641 
642 	snprintf(buffer + len, PAGE_SIZE - len, "0x%llx@0x%llx:%llu:%d\n",
643 			pdev->resource[0].end - pdev->resource[0].start + 1ULL,
644 			(unsigned long long)pdev->resource[0].start,
645 			(unsigned long long)pdev->resource[1].start,
646 			pdev->id);
647 	return 0;
648 }
649 
650 static int vm_cmdline_get(char *buffer, const struct kernel_param *kp)
651 {
652 	buffer[0] = '\0';
653 	device_for_each_child(&vm_cmdline_parent, buffer,
654 			vm_cmdline_get_device);
655 	return strlen(buffer) + 1;
656 }
657 
658 static const struct kernel_param_ops vm_cmdline_param_ops = {
659 	.set = vm_cmdline_set,
660 	.get = vm_cmdline_get,
661 };
662 
663 device_param_cb(device, &vm_cmdline_param_ops, NULL, S_IRUSR);
664 
665 static int vm_unregister_cmdline_device(struct device *dev,
666 		void *data)
667 {
668 	platform_device_unregister(to_platform_device(dev));
669 
670 	return 0;
671 }
672 
673 static void vm_unregister_cmdline_devices(void)
674 {
675 	if (vm_cmdline_parent_registered) {
676 		device_for_each_child(&vm_cmdline_parent, NULL,
677 				vm_unregister_cmdline_device);
678 		device_unregister(&vm_cmdline_parent);
679 		vm_cmdline_parent_registered = 0;
680 	}
681 }
682 
683 #else
684 
685 static void vm_unregister_cmdline_devices(void)
686 {
687 }
688 
689 #endif
690 
691 /* Platform driver */
692 
693 static struct of_device_id virtio_mmio_match[] = {
694 	{ .compatible = "virtio,mmio", },
695 	{},
696 };
697 MODULE_DEVICE_TABLE(of, virtio_mmio_match);
698 
699 #ifdef CONFIG_ACPI
700 static const struct acpi_device_id virtio_mmio_acpi_match[] = {
701 	{ "LNRO0005", },
702 	{ }
703 };
704 MODULE_DEVICE_TABLE(acpi, virtio_mmio_acpi_match);
705 #endif
706 
707 static struct platform_driver virtio_mmio_driver = {
708 	.probe		= virtio_mmio_probe,
709 	.remove		= virtio_mmio_remove,
710 	.driver		= {
711 		.name	= "virtio-mmio",
712 		.of_match_table	= virtio_mmio_match,
713 		.acpi_match_table = ACPI_PTR(virtio_mmio_acpi_match),
714 	},
715 };
716 
717 static int __init virtio_mmio_init(void)
718 {
719 	return platform_driver_register(&virtio_mmio_driver);
720 }
721 
722 static void __exit virtio_mmio_exit(void)
723 {
724 	platform_driver_unregister(&virtio_mmio_driver);
725 	vm_unregister_cmdline_devices();
726 }
727 
728 module_init(virtio_mmio_init);
729 module_exit(virtio_mmio_exit);
730 
731 MODULE_AUTHOR("Pawel Moll <pawel.moll@arm.com>");
732 MODULE_DESCRIPTION("Platform bus driver for memory mapped virtio devices");
733 MODULE_LICENSE("GPL");
734