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From:   Jason Wang <jasowang@redhat.com>
To:     mst@redhat.com, jasowang@redhat.com, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kwankhede@nvidia.com,
        alex.williamson@redhat.com, cohuck@redhat.com, tiwei.bie@intel.com,
        maxime.coquelin@redhat.com, cunming.liang@intel.com,
        zhihong.wang@intel.com, rob.miller@broadcom.com, idos@mellanox.com,
        xiao.w.wang@intel.com, haotian.wang@sifive.com
Subject: [RFC PATCH 4/4] docs: Sample driver to demonstrate how to implement virtio-mdev framework
Date:   Tue, 10 Sep 2019 16:19:35 +0800
Message-Id: <20190910081935.30516-5-jasowang@redhat.com>
In-Reply-To: <20190910081935.30516-1-jasowang@redhat.com>
References: <20190910081935.30516-1-jasowang@redhat.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
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This sample driver creates mdev device that simulate virtio net device
over virtio mdev transport. The device is implemented through vringh
and workqueue.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 samples/Kconfig            |   7 +
 samples/vfio-mdev/Makefile |   1 +
 samples/vfio-mdev/mvnet.c  | 766 +++++++++++++++++++++++++++++++++++++
 3 files changed, 774 insertions(+)
 create mode 100644 samples/vfio-mdev/mvnet.c

diff --git a/samples/Kconfig b/samples/Kconfig
index c8dacb4dda80..a1a1ca2c00b7 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -131,6 +131,13 @@ config SAMPLE_VFIO_MDEV_MDPY
 	  mediated device.  It is a simple framebuffer and supports
 	  the region display interface (VFIO_GFX_PLANE_TYPE_REGION).
 
+config SAMPLE_VIRTIO_MDEV_NET
+        tristate "Build virtio mdev net example mediated device sample code -- loadable modules only"
+	depends on VIRTIO_MDEV_DEVICE && VHOST_RING && m
+	help
+	  Build a networking sample device for use as a virtio
+	  mediated device.
+
 config SAMPLE_VFIO_MDEV_MDPY_FB
 	tristate "Build VFIO mdpy example guest fbdev driver -- loadable module only"
 	depends on FB && m
diff --git a/samples/vfio-mdev/Makefile b/samples/vfio-mdev/Makefile
index 10d179c4fdeb..f34af90ed0a0 100644
--- a/samples/vfio-mdev/Makefile
+++ b/samples/vfio-mdev/Makefile
@@ -3,3 +3,4 @@ obj-$(CONFIG_SAMPLE_VFIO_MDEV_MTTY) += mtty.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MDPY) += mdpy.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MDPY_FB) += mdpy-fb.o
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MBOCHS) += mbochs.o
+obj-$(CONFIG_SAMPLE_VIRTIO_MDEV_NET) += mvnet.o
diff --git a/samples/vfio-mdev/mvnet.c b/samples/vfio-mdev/mvnet.c
new file mode 100644
index 000000000000..da295b41955e
--- /dev/null
+++ b/samples/vfio-mdev/mvnet.c
@@ -0,0 +1,766 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Mediated virtual virtio-net device driver.
+ *
+ * Copyright (c) 2019, Red Hat Inc. All rights reserved.
+ *     Author: Jason Wang <jasowang@redhat.com>
+ *
+ * Sample driver that creates mdev device that simulates ethernet
+ * device virtio mdev transport.
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+#include <linux/uuid.h>
+#include <linux/iommu.h>
+#include <linux/sysfs.h>
+#include <linux/file.h>
+#include <linux/etherdevice.h>
+#include <linux/mdev.h>
+#include <uapi/linux/virtio_mdev.h>
+
+#define VERSION_STRING  "0.1"
+#define DRIVER_AUTHOR   "NVIDIA Corporation"
+
+#define MVNET_CLASS_NAME "mvnet"
+
+#define MVNET_NAME       "mvnet"
+
+/*
+ * Global Structures
+ */
+
+static struct mvnet_dev {
+	struct class	*vd_class;
+	struct idr	vd_idr;
+	struct device	dev;
+} mvnet_dev;
+
+struct mvnet_virtqueue {
+	struct vringh vring;
+	struct vringh_kiov iov;
+	unsigned short head;
+	bool ready;
+	u32 desc_addr_lo;
+	u32 desc_addr_hi;
+	u32 device_addr_lo;
+	u32 device_addr_hi;
+	u32 driver_addr_lo;
+	u32 driver_addr_hi;
+	u64 desc_addr;
+	u64 device_addr;
+	u64 driver_addr;
+	void *private;
+	irqreturn_t (*cb)(void *);
+};
+
+#define MVNET_QUEUE_ALIGN PAGE_SIZE
+#define MVNET_QUEUE_MAX 256
+#define MVNET_MAGIC_VALUE ('v' | 'i' << 8 | 'r' << 16 | 't' << 24)
+#define MVNET_VERSION 0x1 /* Implies virtio 1.0 */
+#define MVNET_DEVICE_ID 0x1 /* network card */
+#define MVNET_VENDOR_ID 0 /* is this correct ? */
+#define MVNET_DEVICE_FEATURES VIRTIO_F_VERSION_1
+
+u64 mvnet_features = (1ULL << VIRTIO_F_ANY_LAYOUT) |
+	             (1ULL << VIRTIO_F_VERSION_1) |
+		     (1ULL << VIRTIO_F_IOMMU_PLATFORM) ;
+
+/* State of each mdev device */
+struct mvnet_state {
+	struct mvnet_virtqueue vqs[2];
+	struct work_struct work;
+	spinlock_t lock;
+	struct mdev_device *mdev;
+	struct virtio_net_config config;
+	struct virtio_mdev_callback *cbs;
+	void *buffer;
+	u32 queue_sel;
+	u32 driver_features_sel;
+	u32 driver_features[2];
+	u32 device_features_sel;
+	u32 status;
+	u32 generation;
+	u32 num;
+	struct list_head next;
+};
+
+static struct mutex mdev_list_lock;
+static struct list_head mdev_devices_list;
+
+static void mvnet_queue_ready(struct mvnet_state *mvnet, unsigned idx)
+{
+	struct mvnet_virtqueue *vq = &mvnet->vqs[idx];
+	int ret;
+
+	vq->desc_addr = (u64)vq->desc_addr_hi << 32 | vq->desc_addr_lo;
+	vq->device_addr = (u64)vq->device_addr_hi << 32 | vq->device_addr_lo;
+	vq->driver_addr = (u64)vq->driver_addr_hi << 32 | vq->driver_addr_lo;
+
+	ret = vringh_init_kern(&vq->vring, mvnet_features, MVNET_QUEUE_MAX,
+			       false, (struct vring_desc *)vq->desc_addr,
+			       (struct vring_avail *)vq->driver_addr,
+			       (struct vring_used *)vq->device_addr);
+}
+
+static ssize_t mvnet_read_config(struct mdev_device *mdev,
+				 u32 *val, loff_t pos)
+{
+	struct mvnet_state *mvnet;
+	struct mvnet_virtqueue *vq;
+	u32 queue_sel;
+
+	if (!mdev || !val)
+		return -EINVAL;
+
+	mvnet = mdev_get_drvdata(mdev);
+	if (!mvnet) {
+		pr_err("%s mvnet not found\n", __func__);
+		return -EINVAL;
+	}
+
+	queue_sel = mvnet->queue_sel;
+	vq = &mvnet->vqs[queue_sel];
+
+	switch (pos) {
+	case VIRTIO_MDEV_MAGIC_VALUE:
+		*val = MVNET_MAGIC_VALUE;
+		break;
+	case VIRTIO_MDEV_VERSION:
+		*val = MVNET_VERSION;
+		break;
+	case VIRTIO_MDEV_DEVICE_ID:
+		*val = MVNET_DEVICE_ID;
+		break;
+	case VIRTIO_MDEV_VENDOR_ID:
+		*val = MVNET_VENDOR_ID;
+		break;
+	case VIRTIO_MDEV_DEVICE_FEATURES:
+		if (mvnet->device_features_sel)
+			*val = mvnet_features >> 32;
+		else
+			*val = mvnet_features;
+		break;
+	case VIRTIO_MDEV_QUEUE_NUM_MAX:
+		*val = MVNET_QUEUE_MAX;
+		break;
+	case VIRTIO_MDEV_QUEUE_READY:
+		*val = vq->ready;
+		break;
+	case VIRTIO_MDEV_QUEUE_ALIGN:
+		*val = MVNET_QUEUE_ALIGN;
+		break;
+	case VIRTIO_MDEV_STATUS:
+		*val = mvnet->status;
+		break;
+	case VIRTIO_MDEV_QUEUE_DESC_LOW:
+		*val = vq->desc_addr_lo;
+		break;
+	case VIRTIO_MDEV_QUEUE_DESC_HIGH:
+		*val = vq->desc_addr_hi;
+		break;
+	case VIRTIO_MDEV_QUEUE_AVAIL_LOW:
+		*val = vq->driver_addr_lo;
+		break;
+	case VIRTIO_MDEV_QUEUE_AVAIL_HIGH:
+		*val = vq->driver_addr_hi;
+		break;
+	case VIRTIO_MDEV_QUEUE_USED_LOW:
+		*val = vq->device_addr_lo;
+		break;
+	case VIRTIO_MDEV_QUEUE_USED_HIGH:
+		*val = vq->device_addr_hi;
+		break;
+	case VIRTIO_MDEV_CONFIG_GENERATION:
+		*val = 1;
+		break;
+	default:
+		pr_err("Unsupported mdev read offset at 0x%x\n", pos);
+		break;
+	}
+
+	return 4;
+}
+
+static ssize_t mvnet_read_net_config(struct mdev_device *mdev,
+				     char *buf, size_t count, loff_t pos)
+{
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+
+	if (!mvnet) {
+		pr_err("%s mvnet not found\n", __func__);
+		return -EINVAL;
+	}
+
+	if (pos + count > sizeof(mvnet->config))
+		return -EINVAL;
+
+	memcpy(buf, &mvnet->config + (unsigned)pos, count);
+
+	return count;
+}
+
+static void mvnet_vq_reset(struct mvnet_virtqueue *vq)
+{
+	vq->ready = 0;
+	vq->desc_addr_lo = vq->desc_addr_hi = 0;
+	vq->device_addr_lo = vq->device_addr_hi = 0;
+	vq->driver_addr_lo = vq->driver_addr_hi = 0;
+	vq->desc_addr = 0;
+	vq->driver_addr = 0;
+	vq->device_addr = 0;
+	vringh_init_kern(&vq->vring, mvnet_features, MVNET_QUEUE_MAX,
+			false, 0, 0, 0);
+}
+
+static void mvnet_reset(struct mvnet_state *mvnet)
+{
+	int i;
+
+	for (i = 0; i < 2; i++)
+		mvnet_vq_reset(&mvnet->vqs[i]);
+
+	mvnet->queue_sel = 0;
+	mvnet->driver_features_sel = 0;
+	mvnet->device_features_sel = 0;
+	mvnet->status = 0;
+	++mvnet->generation;
+}
+
+static ssize_t mvnet_write_config(struct mdev_device *mdev,
+				  u32 *val, loff_t pos)
+{
+	struct mvnet_state *mvnet;
+	struct mvnet_virtqueue *vq;
+	u32 queue_sel;
+
+	if (!mdev || !val)
+		return -EINVAL;
+
+	mvnet = mdev_get_drvdata(mdev);
+	if (!mvnet) {
+		pr_err("%s mvnet not found\n", __func__);
+		return -EINVAL;
+	}
+
+	queue_sel = mvnet->queue_sel;
+	vq = &mvnet->vqs[queue_sel];
+
+	switch (pos) {
+	case VIRTIO_MDEV_DEVICE_FEATURES_SEL:
+		mvnet->device_features_sel = *val;
+		break;
+	case VIRTIO_MDEV_DRIVER_FEATURES:
+		mvnet->driver_features[mvnet->driver_features_sel] = *val;
+		break;
+	case VIRTIO_MDEV_DRIVER_FEATURES_SEL:
+		mvnet->driver_features_sel = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_SEL:
+		mvnet->queue_sel = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_NUM:
+		mvnet->num = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_READY:
+		vq->ready = *val;
+		if (vq->ready) {
+			spin_lock(&mvnet->lock);
+			mvnet_queue_ready(mvnet, queue_sel);
+			spin_unlock(&mvnet->lock);
+		}
+		break;
+	case VIRTIO_MDEV_QUEUE_NOTIFY:
+		if (vq->ready)
+			schedule_work(&mvnet->work);
+		break;
+	case VIRTIO_MDEV_STATUS:
+		mvnet->status = *val;
+		if (*val == 0) {
+			spin_lock(&mvnet->lock);
+			mvnet_reset(mvnet);
+			spin_unlock(&mvnet->lock);
+		}
+		break;
+	case VIRTIO_MDEV_QUEUE_DESC_LOW:
+		vq->desc_addr_lo = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_DESC_HIGH:
+		vq->desc_addr_hi = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_AVAIL_LOW:
+		vq->driver_addr_lo = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_AVAIL_HIGH:
+		vq->driver_addr_hi = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_USED_LOW:
+		vq->device_addr_lo = *val;
+		break;
+	case VIRTIO_MDEV_QUEUE_USED_HIGH:
+		vq->device_addr_hi = *val;
+		break;
+	default:
+		pr_err("Unsupported write offset! 0x%x\n", pos);
+		break;
+	}
+	spin_unlock(&mvnet->lock);
+
+	return 4;
+}
+
+static void mvnet_work(struct work_struct *work)
+{
+	struct mvnet_state *mvnet = container_of(work, struct
+						 mvnet_state, work);
+	struct mvnet_virtqueue *txq = &mvnet->vqs[1];
+	struct mvnet_virtqueue *rxq = &mvnet->vqs[0];
+	size_t read, write, total_write;
+	unsigned long flags;
+	int err;
+	int pkts = 0;
+
+	spin_lock(&mvnet->lock);
+
+	if (!txq->ready || !rxq->ready)
+		goto out;
+
+	while (true) {
+		total_write = 0;
+		err = vringh_getdesc_kern(&txq->vring, &txq->iov, NULL,
+					  &txq->head, GFP_KERNEL);
+		if (err <= 0)
+			break;
+
+		err = vringh_getdesc_kern(&rxq->vring, NULL, &rxq->iov,
+					  &rxq->head, GFP_KERNEL);
+		if (err <= 0) {
+			vringh_complete_kern(&txq->vring, txq->head, 0);
+			break;
+		}
+
+		while (true) {
+			read = vringh_iov_pull_kern(&txq->iov, mvnet->buffer,
+						    PAGE_SIZE);
+			if (read <= 0)
+				break;
+
+			write = vringh_iov_push_kern(&rxq->iov, mvnet->buffer,
+						     read);
+			if (write <= 0)
+				break;
+
+			total_write += write;
+		}
+
+		/* Make sure data is wrote before advancing index */
+		smp_wmb();
+
+		vringh_complete_kern(&txq->vring, txq->head, 0);
+		vringh_complete_kern(&rxq->vring, rxq->head, total_write);
+
+		/* Make sure used is visible before rasing the
+		   interrupt */
+		smp_wmb();
+
+		local_bh_disable();
+		if (txq->cb)
+			txq->cb(txq->private);
+		if (rxq->cb)
+			rxq->cb(rxq->private);
+		local_bh_enable();
+
+		pkts ++;
+		if (pkts > 4) {
+			schedule_work(&mvnet->work);
+			goto out;
+		}
+	}
+
+out:
+	spin_unlock(&mvnet->lock);
+}
+
+static dma_addr_t mvnet_map_page(struct device *dev, struct page *page,
+				 unsigned long offset, size_t size,
+				 enum dma_data_direction dir,
+				 unsigned long attrs)
+{
+	/* Vringh can only use VA */
+	return page_address(page) + offset;
+}
+
+static void mvnet_unmap_page(struct device *dev, dma_addr_t dma_addr,
+			     size_t size, enum dma_data_direction dir,
+			     unsigned long attrs)
+{
+	return ;
+}
+
+static void *mvnet_alloc_coherent(struct device *dev, size_t size,
+				  dma_addr_t *dma_addr, gfp_t flag,
+				  unsigned long attrs)
+{
+	void *ret = kmalloc(size, flag);
+
+	if (ret == NULL)
+		*dma_addr = DMA_MAPPING_ERROR;
+	else
+		*dma_addr = ret;
+
+	return ret;
+}
+
+static void mvnet_free_coherent(struct device *dev, size_t size,
+				void *vaddr, dma_addr_t dma_addr,
+				unsigned long attrs)
+{
+	kfree(dma_addr);
+}
+
+static const struct dma_map_ops mvnet_dma_ops = {
+	.map_page = mvnet_map_page,
+	.unmap_page = mvnet_unmap_page,
+	.alloc = mvnet_alloc_coherent,
+	.free = mvnet_free_coherent,
+};
+
+static int mvnet_create(struct kobject *kobj, struct mdev_device *mdev)
+{
+	struct mvnet_state *mvnet;
+	struct virtio_net_config *config;
+
+	if (!mdev)
+		return -EINVAL;
+
+	mvnet = kzalloc(sizeof(struct mvnet_state), GFP_KERNEL);
+	if (mvnet == NULL)
+		return -ENOMEM;
+
+	mvnet->buffer = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!mvnet->buffer) {
+		kfree(mvnet);
+		return -ENOMEM;
+	}
+
+	config = &mvnet->config;
+	config->mtu = 1500;
+	config->status = VIRTIO_NET_S_LINK_UP;
+	eth_random_addr(config->mac);
+
+	INIT_WORK(&mvnet->work, mvnet_work);
+
+	spin_lock_init(&mvnet->lock);
+	mvnet->mdev = mdev;
+	mdev_set_drvdata(mdev, mvnet);
+
+	mutex_lock(&mdev_list_lock);
+	list_add(&mvnet->next, &mdev_devices_list);
+	mutex_unlock(&mdev_list_lock);
+
+	mdev_set_dma_ops(mdev, &mvnet_dma_ops);
+
+	return 0;
+}
+
+static int mvnet_remove(struct mdev_device *mdev)
+{
+	struct mvnet_state *mds, *tmp_mds;
+	struct mvnet_state *mvnet = mdev_get_drvdata(mdev);
+	int ret = -EINVAL;
+
+	mutex_lock(&mdev_list_lock);
+	list_for_each_entry_safe(mds, tmp_mds, &mdev_devices_list, next) {
+		if (mvnet == mds) {
+			list_del(&mvnet->next);
+			mdev_set_drvdata(mdev, NULL);
+			kfree(mvnet->buffer);
+			kfree(mvnet);
+			ret = 0;
+			break;
+		}
+	}
+	mutex_unlock(&mdev_list_lock);
+
+	return ret;
+}
+
+static ssize_t mvnet_read(struct mdev_device *mdev, char __user *buf,
+			  size_t count, loff_t *ppos)
+{
+	ssize_t ret;
+
+	if (*ppos < VIRTIO_MDEV_CONFIG) {
+		if (count == 4)
+			ret = mvnet_read_config(mdev, (u32 *)buf, *ppos);
+		else
+			ret = -EINVAL;
+		*ppos += 4;
+	} else if (*ppos < VIRTIO_MDEV_CONFIG + sizeof(struct virtio_net_config)) {
+		ret = mvnet_read_net_config(mdev, buf, count,
+					    *ppos - VIRTIO_MDEV_CONFIG);
+		*ppos += count;
+	} else {
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static ssize_t mvnet_write(struct mdev_device *mdev, const char __user *buf,
+			   size_t count, loff_t *ppos)
+{
+	int ret;
+
+	if (*ppos < VIRTIO_MDEV_CONFIG) {
+		if (count == 4)
+			ret = mvnet_write_config(mdev, (u32 *)buf, *ppos);
+		else
+			ret = -EINVAL;
+		*ppos += 4;
+	} else {
+		/* No writable net config */
+		ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+static long mvnet_ioctl(struct mdev_device *mdev, unsigned int cmd,
+			unsigned long arg)
+{
+	int ret = 0;
+	struct mvnet_state *mvnet;
+	struct virtio_mdev_callback *cb;
+
+	if (!mdev)
+		return -EINVAL;
+
+	mvnet = mdev_get_drvdata(mdev);
+	if (!mvnet)
+		return -ENODEV;
+
+	spin_lock(&mvnet->lock);
+
+	switch (cmd) {
+	case VIRTIO_MDEV_SET_VQ_CALLBACK:
+		cb = (struct virtio_mdev_callback *)arg;
+		mvnet->vqs[mvnet->queue_sel].cb = cb->callback;
+		mvnet->vqs[mvnet->queue_sel].private = cb->private;
+		break;
+	case VIRTIO_MDEV_SET_CONFIG_CALLBACK:
+		break;
+	default:
+		pr_err("Not supportted ioctl cmd 0x%x\n", cmd);
+		ret = -ENOTTY;
+		break;
+	}
+
+	spin_unlock(&mvnet->lock);
+
+	return ret;
+}
+
+static int mvnet_open(struct mdev_device *mdev)
+{
+	pr_info("%s\n", __func__);
+	return 0;
+}
+
+static void mvnet_close(struct mdev_device *mdev)
+{
+	pr_info("%s\n", __func__);
+}
+
+static ssize_t
+sample_mvnet_dev_show(struct device *dev, struct device_attribute *attr,
+		     char *buf)
+{
+	return sprintf(buf, "This is phy device\n");
+}
+
+static DEVICE_ATTR_RO(sample_mvnet_dev);
+
+static struct attribute *mvnet_dev_attrs[] = {
+	&dev_attr_sample_mvnet_dev.attr,
+	NULL,
+};
+
+static const struct attribute_group mvnet_dev_group = {
+	.name  = "mvnet_dev",
+	.attrs = mvnet_dev_attrs,
+};
+
+static const struct attribute_group *mvnet_dev_groups[] = {
+	&mvnet_dev_group,
+	NULL,
+};
+
+static ssize_t
+sample_mdev_dev_show(struct device *dev, struct device_attribute *attr,
+		     char *buf)
+{
+	if (mdev_from_dev(dev))
+		return sprintf(buf, "This is MDEV %s\n", dev_name(dev));
+
+	return sprintf(buf, "\n");
+}
+
+static DEVICE_ATTR_RO(sample_mdev_dev);
+
+static struct attribute *mdev_dev_attrs[] = {
+	&dev_attr_sample_mdev_dev.attr,
+	NULL,
+};
+
+static const struct attribute_group mdev_dev_group = {
+	.name  = "vendor",
+	.attrs = mdev_dev_attrs,
+};
+
+static const struct attribute_group *mdev_dev_groups[] = {
+	&mdev_dev_group,
+	NULL,
+};
+
+#define MVNET_STRING_LEN 16
+
+static ssize_t
+name_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+	char name[MVNET_STRING_LEN];
+	const char *name_str = "virtio-net";
+
+	snprintf(name, MVNET_STRING_LEN, "%s", dev_driver_string(dev));
+	if (!strcmp(kobj->name, name))
+		return sprintf(buf, "%s\n", name_str);
+
+	return -EINVAL;
+}
+
+static MDEV_TYPE_ATTR_RO(name);
+
+static ssize_t
+available_instances_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+	return sprintf(buf, "%d\n", INT_MAX);
+}
+
+static MDEV_TYPE_ATTR_RO(available_instances);
+
+static ssize_t device_api_show(struct kobject *kobj, struct device *dev,
+			       char *buf)
+{
+	return sprintf(buf, "%s\n", VIRTIO_MDEV_DEVICE_API_STRING);
+}
+
+static MDEV_TYPE_ATTR_RO(device_api);
+
+static struct attribute *mdev_types_attrs[] = {
+	&mdev_type_attr_name.attr,
+	&mdev_type_attr_device_api.attr,
+	&mdev_type_attr_available_instances.attr,
+	NULL,
+};
+
+static struct attribute_group mdev_type_group = {
+	.name  = "",
+	.attrs = mdev_types_attrs,
+};
+
+static struct attribute_group *mdev_type_groups[] = {
+	&mdev_type_group,
+	NULL,
+};
+
+static const struct mdev_parent_ops mdev_fops = {
+	.owner                  = THIS_MODULE,
+	.dev_attr_groups        = mvnet_dev_groups,
+	.mdev_attr_groups       = mdev_dev_groups,
+	.supported_type_groups  = mdev_type_groups,
+	.create                 = mvnet_create,
+	.remove			= mvnet_remove,
+	.open                   = mvnet_open,
+	.release                = mvnet_close,
+	.read                   = mvnet_read,
+	.write                  = mvnet_write,
+	.ioctl		        = mvnet_ioctl,
+};
+
+static void mvnet_device_release(struct device *dev)
+{
+	dev_dbg(dev, "mvnet: released\n");
+}
+
+static int __init mvnet_dev_init(void)
+{
+	int ret = 0;
+
+	pr_info("mvnet_dev: %s\n", __func__);
+
+	memset(&mvnet_dev, 0, sizeof(mvnet_dev));
+
+	idr_init(&mvnet_dev.vd_idr);
+
+	mvnet_dev.vd_class = class_create(THIS_MODULE, MVNET_CLASS_NAME);
+
+	if (IS_ERR(mvnet_dev.vd_class)) {
+		pr_err("Error: failed to register mvnet_dev class\n");
+		ret = PTR_ERR(mvnet_dev.vd_class);
+		goto failed1;
+	}
+
+	mvnet_dev.dev.class = mvnet_dev.vd_class;
+	mvnet_dev.dev.release = mvnet_device_release;
+	dev_set_name(&mvnet_dev.dev, "%s", MVNET_NAME);
+
+	ret = device_register(&mvnet_dev.dev);
+	if (ret)
+		goto failed2;
+
+	ret = mdev_register_device(&mvnet_dev.dev, &mdev_fops);
+	if (ret)
+		goto failed3;
+
+	mutex_init(&mdev_list_lock);
+	INIT_LIST_HEAD(&mdev_devices_list);
+
+	goto all_done;
+
+failed3:
+
+	device_unregister(&mvnet_dev.dev);
+failed2:
+	class_destroy(mvnet_dev.vd_class);
+
+failed1:
+all_done:
+	return ret;
+}
+
+static void __exit mvnet_dev_exit(void)
+{
+	mvnet_dev.dev.bus = NULL;
+	mdev_unregister_device(&mvnet_dev.dev);
+
+	device_unregister(&mvnet_dev.dev);
+	idr_destroy(&mvnet_dev.vd_idr);
+	class_destroy(mvnet_dev.vd_class);
+	mvnet_dev.vd_class = NULL;
+	pr_info("mvnet_dev: Unloaded!\n");
+}
+
+module_init(mvnet_dev_init)
+module_exit(mvnet_dev_exit)
+
+MODULE_LICENSE("GPL v2");
+MODULE_INFO(supported, "Test driver that simulate serial port over PCI");
+MODULE_VERSION(VERSION_STRING);
+MODULE_AUTHOR(DRIVER_AUTHOR);
-- 
2.19.1