// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * Virtio memory mapped device driver
   *

   * Copyright 2011-2014, ARM Ltd.

   *
   * This module allows virtio devices to be used over a virtual, memory mapped
   * platform device.
   *

   * The guest device(s) may be instantiated in one of three equivalent ways:
   *
   * 1. Static platform device in board's code, eg.:
   *
   *	static struct platform_device v2m_virtio_device = {
   *		.name = "virtio-mmio",
   *		.id = -1,
   *		.num_resources = 2,
   *		.resource = (struct resource []) {
   *			{
   *				.start = 0x1001e000,
   *				.end = 0x1001e0ff,
   *				.flags = IORESOURCE_MEM,
   *			}, {
   *				.start = 42 + 32,
   *				.end = 42 + 32,
   *				.flags = IORESOURCE_IRQ,
   *			},
   *		}
   *	};
   *
   * 2. Device Tree node, eg.:
   *
   *		virtio_block@1e000 {
   *			compatible = "virtio,mmio";
   *			reg = <0x1e000 0x100>;
   *			interrupts = <42>;
   *		}
   *
   * 3. Kernel module (or command line) parameter. Can be used more than once -
   *    one device will be created for each one. Syntax:
   *
   *		[virtio_mmio.]device=<size>@<baseaddr>:<irq>[:<id>]
   *    where:
   *		<size>     := size (can use standard suffixes like K, M or G)
   *		<baseaddr> := physical base address
   *		<irq>      := interrupt number (as passed to request_irq())
   *		<id>       := (optional) platform device id
   *    eg.:
   *		virtio_mmio.device=0x100@0x100b0000:48 \
   *				virtio_mmio.device=1K@0x1001e000:74
   *

   * Based on Virtio PCI driver by Anthony Liguori, copyright IBM Corp. 2007

   */

  #define pr_fmt(fmt) "virtio-mmio: " fmt

  #include <linux/acpi.h>

  #include <linux/dma-mapping.h>

  #include <linux/highmem.h>
  #include <linux/interrupt.h>
  #include <linux/io.h>
  #include <linux/list.h>
  #include <linux/module.h>
  #include <linux/platform_device.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/virtio.h>
  #include <linux/virtio_config.h>

  #include <uapi/linux/virtio_mmio.h>

  #include <linux/virtio_ring.h>
  
  
  
  /* The alignment to use between consumer and producer parts of vring.
   * Currently hardcoded to the page size. */
  #define VIRTIO_MMIO_VRING_ALIGN		PAGE_SIZE
  
  
  
  #define to_virtio_mmio_device(_plat_dev) \
  	container_of(_plat_dev, struct virtio_mmio_device, vdev)
  
  struct virtio_mmio_device {
  	struct virtio_device vdev;
  	struct platform_device *pdev;
  
  	void __iomem *base;
  	unsigned long version;
  
  	/* a list of queues so we can dispatch IRQs */
  	spinlock_t lock;
  	struct list_head virtqueues;
  };
  
  struct virtio_mmio_vq_info {
  	/* the actual virtqueue */
  	struct virtqueue *vq;

  	/* the list node for the virtqueues list */
  	struct list_head node;
  };
  
  
  
  /* Configuration interface */

  static u64 vm_get_features(struct virtio_device *vdev)

  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  	u64 features;
  
  	writel(1, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
  	features = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);
  	features <<= 32;

  	writel(0, vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES_SEL);
  	features |= readl(vm_dev->base + VIRTIO_MMIO_DEVICE_FEATURES);

  	return features;

  }

  static int vm_finalize_features(struct virtio_device *vdev)

  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  
  	/* Give virtio_ring a chance to accept features. */
  	vring_transport_features(vdev);

  	/* Make sure there is are no mixed devices */
  	if (vm_dev->version == 2 &&
  			!__virtio_test_bit(vdev, VIRTIO_F_VERSION_1)) {
  		dev_err(&vdev->dev, "New virtio-mmio devices (version 2) must provide VIRTIO_F_VERSION_1 feature!
  ");
  		return -EINVAL;
  	}
  
  	writel(1, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
  	writel((u32)(vdev->features >> 32),
  			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);

  	writel(0, vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES_SEL);
  	writel((u32)vdev->features,
  			vm_dev->base + VIRTIO_MMIO_DRIVER_FEATURES);

  
  	return 0;

  }
  
  static void vm_get(struct virtio_device *vdev, unsigned offset,
  		   void *buf, unsigned len)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
  	u8 b;
  	__le16 w;
  	__le32 l;
  
  	if (vm_dev->version == 1) {
  		u8 *ptr = buf;
  		int i;
  
  		for (i = 0; i < len; i++)
  			ptr[i] = readb(base + offset + i);
  		return;
  	}

  	switch (len) {
  	case 1:
  		b = readb(base + offset);
  		memcpy(buf, &b, sizeof b);
  		break;
  	case 2:
  		w = cpu_to_le16(readw(base + offset));
  		memcpy(buf, &w, sizeof w);
  		break;
  	case 4:
  		l = cpu_to_le32(readl(base + offset));
  		memcpy(buf, &l, sizeof l);
  		break;
  	case 8:
  		l = cpu_to_le32(readl(base + offset));
  		memcpy(buf, &l, sizeof l);
  		l = cpu_to_le32(ioread32(base + offset + sizeof l));
  		memcpy(buf + sizeof l, &l, sizeof l);
  		break;
  	default:
  		BUG();
  	}

  }
  
  static void vm_set(struct virtio_device *vdev, unsigned offset,
  		   const void *buf, unsigned len)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  	void __iomem *base = vm_dev->base + VIRTIO_MMIO_CONFIG;
  	u8 b;
  	__le16 w;
  	__le32 l;
  
  	if (vm_dev->version == 1) {
  		const u8 *ptr = buf;
  		int i;
  
  		for (i = 0; i < len; i++)
  			writeb(ptr[i], base + offset + i);

  		return;
  	}
  
  	switch (len) {
  	case 1:
  		memcpy(&b, buf, sizeof b);
  		writeb(b, base + offset);
  		break;
  	case 2:
  		memcpy(&w, buf, sizeof w);
  		writew(le16_to_cpu(w), base + offset);
  		break;
  	case 4:
  		memcpy(&l, buf, sizeof l);
  		writel(le32_to_cpu(l), base + offset);
  		break;
  	case 8:
  		memcpy(&l, buf, sizeof l);
  		writel(le32_to_cpu(l), base + offset);
  		memcpy(&l, buf + sizeof l, sizeof l);
  		writel(le32_to_cpu(l), base + offset + sizeof l);
  		break;
  	default:
  		BUG();
  	}

  }

  static u32 vm_generation(struct virtio_device *vdev)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  
  	if (vm_dev->version == 1)
  		return 0;
  	else
  		return readl(vm_dev->base + VIRTIO_MMIO_CONFIG_GENERATION);
  }

  static u8 vm_get_status(struct virtio_device *vdev)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  
  	return readl(vm_dev->base + VIRTIO_MMIO_STATUS) & 0xff;
  }
  
  static void vm_set_status(struct virtio_device *vdev, u8 status)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  
  	/* We should never be setting status to 0. */
  	BUG_ON(status == 0);
  
  	writel(status, vm_dev->base + VIRTIO_MMIO_STATUS);
  }
  
  static void vm_reset(struct virtio_device *vdev)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  
  	/* 0 status means a reset. */
  	writel(0, vm_dev->base + VIRTIO_MMIO_STATUS);
  }
  
  
  
  /* Transport interface */
  
  /* the notify function used when creating a virt queue */

  static bool vm_notify(struct virtqueue *vq)

  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);

  
  	/* We write the queue's selector into the notification register to
  	 * signal the other end */

  	writel(vq->index, vm_dev->base + VIRTIO_MMIO_QUEUE_NOTIFY);

  	return true;

  }
  
  /* Notify all virtqueues on an interrupt. */
  static irqreturn_t vm_interrupt(int irq, void *opaque)
  {
  	struct virtio_mmio_device *vm_dev = opaque;
  	struct virtio_mmio_vq_info *info;

  	unsigned long status;
  	unsigned long flags;
  	irqreturn_t ret = IRQ_NONE;
  
  	/* Read and acknowledge interrupts */
  	status = readl(vm_dev->base + VIRTIO_MMIO_INTERRUPT_STATUS);
  	writel(status, vm_dev->base + VIRTIO_MMIO_INTERRUPT_ACK);

  	if (unlikely(status & VIRTIO_MMIO_INT_CONFIG)) {
  		virtio_config_changed(&vm_dev->vdev);

  		ret = IRQ_HANDLED;
  	}
  
  	if (likely(status & VIRTIO_MMIO_INT_VRING)) {
  		spin_lock_irqsave(&vm_dev->lock, flags);
  		list_for_each_entry(info, &vm_dev->virtqueues, node)
  			ret |= vring_interrupt(irq, info->vq);
  		spin_unlock_irqrestore(&vm_dev->lock, flags);
  	}
  
  	return ret;
  }
  
  
  
  static void vm_del_vq(struct virtqueue *vq)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
  	struct virtio_mmio_vq_info *info = vq->priv;

  	unsigned long flags;

  	unsigned int index = vq->index;

  
  	spin_lock_irqsave(&vm_dev->lock, flags);
  	list_del(&info->node);
  	spin_unlock_irqrestore(&vm_dev->lock, flags);

  	/* Select and deactivate the queue */

  	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);

  	if (vm_dev->version == 1) {
  		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
  	} else {
  		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
  		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
  	}

  	vring_del_virtqueue(vq);

  	kfree(info);
  }
  
  static void vm_del_vqs(struct virtio_device *vdev)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  	struct virtqueue *vq, *n;
  
  	list_for_each_entry_safe(vq, n, &vdev->vqs, list)
  		vm_del_vq(vq);
  
  	free_irq(platform_get_irq(vm_dev->pdev, 0), vm_dev);
  }

  static struct virtqueue *vm_setup_vq(struct virtio_device *vdev, unsigned index,
  				  void (*callback)(struct virtqueue *vq),

  				  const char *name, bool ctx)

  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  	struct virtio_mmio_vq_info *info;
  	struct virtqueue *vq;

  	unsigned long flags;
  	unsigned int num;

  	int err;

  	if (!name)
  		return NULL;

  	/* Select the queue we're interested in */
  	writel(index, vm_dev->base + VIRTIO_MMIO_QUEUE_SEL);
  
  	/* Queue shouldn't already be set up. */

  	if (readl(vm_dev->base + (vm_dev->version == 1 ?
  			VIRTIO_MMIO_QUEUE_PFN : VIRTIO_MMIO_QUEUE_READY))) {

  		err = -ENOENT;
  		goto error_available;
  	}
  
  	/* Allocate and fill out our active queue description */
  	info = kmalloc(sizeof(*info), GFP_KERNEL);
  	if (!info) {
  		err = -ENOMEM;
  		goto error_kmalloc;
  	}

  	num = readl(vm_dev->base + VIRTIO_MMIO_QUEUE_NUM_MAX);
  	if (num == 0) {

  		err = -ENOENT;

  		goto error_new_virtqueue;

  	}

  	/* Create the vring */

  	vq = vring_create_virtqueue(index, num, VIRTIO_MMIO_VRING_ALIGN, vdev,

  				 true, true, ctx, vm_notify, callback, name);

  	if (!vq) {
  		err = -ENOMEM;
  		goto error_new_virtqueue;
  	}

  	/* Activate the queue */

  	writel(virtqueue_get_vring_size(vq), vm_dev->base + VIRTIO_MMIO_QUEUE_NUM);

  	if (vm_dev->version == 1) {

  		u64 q_pfn = virtqueue_get_desc_addr(vq) >> PAGE_SHIFT;
  
  		/*
  		 * virtio-mmio v1 uses a 32bit QUEUE PFN. If we have something
  		 * that doesn't fit in 32bit, fail the setup rather than
  		 * pretending to be successful.
  		 */
  		if (q_pfn >> 32) {
  			dev_err(&vdev->dev,
  				"platform bug: legacy virtio-mmio must not be used with RAM above 0x%llxGB
  ",
  				0x1ULL << (32 + PAGE_SHIFT - 30));
  			err = -E2BIG;
  			goto error_bad_pfn;
  		}

  		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_QUEUE_ALIGN);

  		writel(q_pfn, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);

  	} else {
  		u64 addr;

  		addr = virtqueue_get_desc_addr(vq);

  		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_LOW);
  		writel((u32)(addr >> 32),
  				vm_dev->base + VIRTIO_MMIO_QUEUE_DESC_HIGH);

  		addr = virtqueue_get_avail_addr(vq);

  		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_LOW);
  		writel((u32)(addr >> 32),
  				vm_dev->base + VIRTIO_MMIO_QUEUE_AVAIL_HIGH);

  		addr = virtqueue_get_used_addr(vq);

  		writel((u32)addr, vm_dev->base + VIRTIO_MMIO_QUEUE_USED_LOW);
  		writel((u32)(addr >> 32),
  				vm_dev->base + VIRTIO_MMIO_QUEUE_USED_HIGH);
  
  		writel(1, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
  	}

  	vq->priv = info;
  	info->vq = vq;
  
  	spin_lock_irqsave(&vm_dev->lock, flags);
  	list_add(&info->node, &vm_dev->virtqueues);
  	spin_unlock_irqrestore(&vm_dev->lock, flags);
  
  	return vq;

  error_bad_pfn:
  	vring_del_virtqueue(vq);

  error_new_virtqueue:

  	if (vm_dev->version == 1) {
  		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_PFN);
  	} else {
  		writel(0, vm_dev->base + VIRTIO_MMIO_QUEUE_READY);
  		WARN_ON(readl(vm_dev->base + VIRTIO_MMIO_QUEUE_READY));
  	}

  	kfree(info);
  error_kmalloc:
  error_available:
  	return ERR_PTR(err);
  }
  
  static int vm_find_vqs(struct virtio_device *vdev, unsigned nvqs,
  		       struct virtqueue *vqs[],
  		       vq_callback_t *callbacks[],

  		       const char * const names[],

  		       const bool *ctx,

  		       struct irq_affinity *desc)

  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  	int irq = platform_get_irq(vm_dev->pdev, 0);

  	int i, err, queue_idx = 0;

  	if (irq < 0)

  		return irq;

  	err = request_irq(irq, vm_interrupt, IRQF_SHARED,
  			dev_name(&vdev->dev), vm_dev);
  	if (err)
  		return err;
  
  	for (i = 0; i < nvqs; ++i) {

  		if (!names[i]) {
  			vqs[i] = NULL;
  			continue;
  		}
  
  		vqs[i] = vm_setup_vq(vdev, queue_idx++, callbacks[i], names[i],

  				     ctx ? ctx[i] : false);

  		if (IS_ERR(vqs[i])) {
  			vm_del_vqs(vdev);
  			return PTR_ERR(vqs[i]);
  		}
  	}
  
  	return 0;
  }

  static const char *vm_bus_name(struct virtio_device *vdev)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);

  	return vm_dev->pdev->name;
  }

  static bool vm_get_shm_region(struct virtio_device *vdev,
  			      struct virtio_shm_region *region, u8 id)
  {
  	struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vdev);
  	u64 len, addr;
  
  	/* Select the region we're interested in */
  	writel(id, vm_dev->base + VIRTIO_MMIO_SHM_SEL);
  
  	/* Read the region size */
  	len = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_LOW);
  	len |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_LEN_HIGH) << 32;
  
  	region->len = len;
  
  	/* Check if region length is -1. If that's the case, the shared memory
  	 * region does not exist and there is no need to proceed further.
  	 */
  	if (len == ~(u64)0)
  		return false;
  
  	/* Read the region base address */
  	addr = (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_LOW);
  	addr |= (u64) readl(vm_dev->base + VIRTIO_MMIO_SHM_BASE_HIGH) << 32;
  
  	region->addr = addr;
  
  	return true;
  }

  static const struct virtio_config_ops virtio_mmio_config_ops = {

  	.get		= vm_get,
  	.set		= vm_set,

  	.generation	= vm_generation,

  	.get_status	= vm_get_status,
  	.set_status	= vm_set_status,
  	.reset		= vm_reset,
  	.find_vqs	= vm_find_vqs,
  	.del_vqs	= vm_del_vqs,
  	.get_features	= vm_get_features,
  	.finalize_features = vm_finalize_features,

  	.bus_name	= vm_bus_name,

  	.get_shm_region = vm_get_shm_region,

  };

  static void virtio_mmio_release_dev(struct device *_d)
  {
  	struct virtio_device *vdev =
  			container_of(_d, struct virtio_device, dev);
  	struct virtio_mmio_device *vm_dev =
  			container_of(vdev, struct virtio_mmio_device, vdev);
  	struct platform_device *pdev = vm_dev->pdev;
  
  	devm_kfree(&pdev->dev, vm_dev);
  }

  
  /* Platform device */

  static int virtio_mmio_probe(struct platform_device *pdev)

  {
  	struct virtio_mmio_device *vm_dev;

  	unsigned long magic;

  	int rc;

  	vm_dev = devm_kzalloc(&pdev->dev, sizeof(*vm_dev), GFP_KERNEL);

  	if (!vm_dev)
  		return -ENOMEM;

  
  	vm_dev->vdev.dev.parent = &pdev->dev;

  	vm_dev->vdev.dev.release = virtio_mmio_release_dev;

  	vm_dev->vdev.config = &virtio_mmio_config_ops;
  	vm_dev->pdev = pdev;
  	INIT_LIST_HEAD(&vm_dev->virtqueues);
  	spin_lock_init(&vm_dev->lock);

  	vm_dev->base = devm_platform_ioremap_resource(pdev, 0);
  	if (IS_ERR(vm_dev->base))
  		return PTR_ERR(vm_dev->base);

  
  	/* Check magic value */
  	magic = readl(vm_dev->base + VIRTIO_MMIO_MAGIC_VALUE);

  	if (magic != ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)) {

  		dev_warn(&pdev->dev, "Wrong magic value 0x%08lx!
  ", magic);

  		return -ENODEV;

  	}
  
  	/* Check device version */
  	vm_dev->version = readl(vm_dev->base + VIRTIO_MMIO_VERSION);

  	if (vm_dev->version < 1 || vm_dev->version > 2) {

  		dev_err(&pdev->dev, "Version %ld not supported!
  ",
  				vm_dev->version);

  		return -ENXIO;

  	}
  
  	vm_dev->vdev.id.device = readl(vm_dev->base + VIRTIO_MMIO_DEVICE_ID);

  	if (vm_dev->vdev.id.device == 0) {
  		/*
  		 * virtio-mmio device with an ID 0 is a (dummy) placeholder
  		 * with no function. End probing now with no error reported.
  		 */

  		return -ENODEV;

  	}

  	vm_dev->vdev.id.vendor = readl(vm_dev->base + VIRTIO_MMIO_VENDOR_ID);

  	if (vm_dev->version == 1) {

  		writel(PAGE_SIZE, vm_dev->base + VIRTIO_MMIO_GUEST_PAGE_SIZE);

  		rc = dma_set_mask(&pdev->dev, DMA_BIT_MASK(64));
  		/*
  		 * In the legacy case, ensure our coherently-allocated virtio
  		 * ring will be at an address expressable as a 32-bit PFN.
  		 */
  		if (!rc)
  			dma_set_coherent_mask(&pdev->dev,
  					      DMA_BIT_MASK(32 + PAGE_SHIFT));
  	} else {
  		rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(64));
  	}
  	if (rc)
  		rc = dma_set_mask_and_coherent(&pdev->dev, DMA_BIT_MASK(32));
  	if (rc)
  		dev_warn(&pdev->dev, "Failed to enable 64-bit or 32-bit DMA.  Trying to continue, but this might not work.
  ");

  	platform_set_drvdata(pdev, vm_dev);

  	rc = register_virtio_device(&vm_dev->vdev);

  	if (rc)

  		put_device(&vm_dev->vdev.dev);

  	return rc;

  }

  static int virtio_mmio_remove(struct platform_device *pdev)

  {
  	struct virtio_mmio_device *vm_dev = platform_get_drvdata(pdev);

  	unregister_virtio_device(&vm_dev->vdev);
  
  	return 0;
  }

  /* Devices list parameter */
  
  #if defined(CONFIG_VIRTIO_MMIO_CMDLINE_DEVICES)
  
  static struct device vm_cmdline_parent = {
  	.init_name = "virtio-mmio-cmdline",
  };
  
  static int vm_cmdline_parent_registered;
  static int vm_cmdline_id;
  
  static int vm_cmdline_set(const char *device,
  		const struct kernel_param *kp)
  {
  	int err;
  	struct resource resources[2] = {};
  	char *str;

  	long long int base, size;
  	unsigned int irq;

  	int processed, consumed = 0;
  	struct platform_device *pdev;

  	/* Consume "size" part of the command line parameter */
  	size = memparse(device, &str);

  	/* Get "@<base>:<irq>[:<id>]" chunks */

  	processed = sscanf(str, "@%lli:%u%n:%d%n",

  			&base, &irq, &consumed,

  			&vm_cmdline_id, &consumed);

  	/*

  	 * sscanf() must process at least 2 chunks; also there

  	 * must be no extra characters after the last chunk, so
  	 * str[consumed] must be '\0'
  	 */

  	if (processed < 2 || str[consumed] || irq == 0)

  		return -EINVAL;

  	resources[0].flags = IORESOURCE_MEM;

  	resources[0].start = base;

  	resources[0].end = base + size - 1;
  
  	resources[1].flags = IORESOURCE_IRQ;
  	resources[1].start = resources[1].end = irq;

  
  	if (!vm_cmdline_parent_registered) {
  		err = device_register(&vm_cmdline_parent);
  		if (err) {
  			pr_err("Failed to register parent device!
  ");
  			return err;
  		}
  		vm_cmdline_parent_registered = 1;
  	}
  
  	pr_info("Registering device virtio-mmio.%d at 0x%llx-0x%llx, IRQ %d.
  ",
  		       vm_cmdline_id,
  		       (unsigned long long)resources[0].start,
  		       (unsigned long long)resources[0].end,
  		       (int)resources[1].start);
  
  	pdev = platform_device_register_resndata(&vm_cmdline_parent,
  			"virtio-mmio", vm_cmdline_id++,
  			resources, ARRAY_SIZE(resources), NULL, 0);

  	return PTR_ERR_OR_ZERO(pdev);

  }
  
  static int vm_cmdline_get_device(struct device *dev, void *data)
  {
  	char *buffer = data;
  	unsigned int len = strlen(buffer);
  	struct platform_device *pdev = to_platform_device(dev);
  
  	snprintf(buffer + len, PAGE_SIZE - len, "0x%llx@0x%llx:%llu:%d
  ",
  			pdev->resource[0].end - pdev->resource[0].start + 1ULL,
  			(unsigned long long)pdev->resource[0].start,
  			(unsigned long long)pdev->resource[1].start,
  			pdev->id);
  	return 0;
  }
  
  static int vm_cmdline_get(char *buffer, const struct kernel_param *kp)
  {
  	buffer[0] = '\0';
  	device_for_each_child(&vm_cmdline_parent, buffer,
  			vm_cmdline_get_device);
  	return strlen(buffer) + 1;
  }

  static const struct kernel_param_ops vm_cmdline_param_ops = {

  	.set = vm_cmdline_set,
  	.get = vm_cmdline_get,
  };
  
  device_param_cb(device, &vm_cmdline_param_ops, NULL, S_IRUSR);
  
  static int vm_unregister_cmdline_device(struct device *dev,
  		void *data)
  {
  	platform_device_unregister(to_platform_device(dev));
  
  	return 0;
  }
  
  static void vm_unregister_cmdline_devices(void)
  {
  	if (vm_cmdline_parent_registered) {
  		device_for_each_child(&vm_cmdline_parent, NULL,
  				vm_unregister_cmdline_device);
  		device_unregister(&vm_cmdline_parent);
  		vm_cmdline_parent_registered = 0;
  	}
  }
  
  #else
  
  static void vm_unregister_cmdline_devices(void)
  {
  }
  
  #endif

  /* Platform driver */

  static const struct of_device_id virtio_mmio_match[] = {

  	{ .compatible = "virtio,mmio", },
  	{},
  };
  MODULE_DEVICE_TABLE(of, virtio_mmio_match);

  #ifdef CONFIG_ACPI
  static const struct acpi_device_id virtio_mmio_acpi_match[] = {
  	{ "LNRO0005", },
  	{ }
  };
  MODULE_DEVICE_TABLE(acpi, virtio_mmio_acpi_match);
  #endif

  static struct platform_driver virtio_mmio_driver = {
  	.probe		= virtio_mmio_probe,

  	.remove		= virtio_mmio_remove,

  	.driver		= {
  		.name	= "virtio-mmio",

  		.of_match_table	= virtio_mmio_match,

  		.acpi_match_table = ACPI_PTR(virtio_mmio_acpi_match),

  	},
  };
  
  static int __init virtio_mmio_init(void)
  {
  	return platform_driver_register(&virtio_mmio_driver);
  }
  
  static void __exit virtio_mmio_exit(void)
  {
  	platform_driver_unregister(&virtio_mmio_driver);

  	vm_unregister_cmdline_devices();

  }
  
  module_init(virtio_mmio_init);
  module_exit(virtio_mmio_exit);
  
  MODULE_AUTHOR("Pawel Moll <pawel.moll@arm.com>");
  MODULE_DESCRIPTION("Platform bus driver for memory mapped virtio devices");
  MODULE_LICENSE("GPL");