Simple framebuffer display, demo-ing the vfio region display interface
(VFIO_GFX_PLANE_TYPE_REGION).

Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
 samples/vfio-mdev/mdpy-defs.h |  19 +
 samples/vfio-mdev/mdpy.c      | 791 ++++++++++++++++++++++++++++++++++++++++++
 samples/Kconfig               |   8 +
 samples/vfio-mdev/Makefile    |   1 +
 4 files changed, 819 insertions(+)
 create mode 100644 samples/vfio-mdev/mdpy-defs.h
 create mode 100644 samples/vfio-mdev/mdpy.c

diff --git a/samples/vfio-mdev/mdpy-defs.h b/samples/vfio-mdev/mdpy-defs.h
new file mode 100644
index 0000000000..79f0795e11
--- /dev/null
+++ b/samples/vfio-mdev/mdpy-defs.h
@@ -0,0 +1,19 @@
+/*
+ * Simple pci display device.
+ *
+ * Framebuffer memory is pci bar 0.
+ * Configuration (read-only) is in pci config space.
+ * Format field uses drm fourcc codes.
+ * ATM only DRM_FORMAT_XRGB8888 is supported.
+ */
+
+/* pci ids */
+#define MDPY_PCI_VENDOR_ID     0x1b36 /* redhat */
+#define MDPY_PCI_DEVICE_ID     0x00f0
+#define MDPY_PCI_SUBVENDOR_ID  PCI_SUBVENDOR_ID_REDHAT_QUMRANET
+#define MDPY_PCI_SUBDEVICE_ID  PCI_SUBDEVICE_ID_QEMU
+
+/* pci cfg space offsets for fb config (dword) */
+#define MDPY_FORMAT_OFFSET     0x40
+#define MDPY_WIDTH_OFFSET      0x44
+#define MDPY_HEIGHT_OFFSET     0x48
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
new file mode 100644
index 0000000000..25882c7b37
--- /dev/null
+++ b/samples/vfio-mdev/mdpy.c
@@ -0,0 +1,791 @@
+/*
+ * Mediated virtual PCI display host device driver
+ *
+ * See mdpy-defs.h for device specs
+ *
+ *   (c) Gerd Hoffmann <kra...@redhat.com>
+ *
+ * based on mtty driver which is:
+ *   Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
+ *      Author: Neo Jia <c...@nvidia.com>
+ *              Kirti Wankhede <kwankh...@nvidia.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <linux/cdev.h>
+#include <linux/vfio.h>
+#include <linux/iommu.h>
+#include <linux/sysfs.h>
+#include <linux/mdev.h>
+#include <linux/pci.h>
+#include <drm/drm_fourcc.h>
+#include "mdpy-defs.h"
+
+#define MDPY_NAME              "mdpy"
+#define MDPY_CLASS_NAME                "mdpy"
+
+#define MDPY_CONFIG_SPACE_SIZE 0xff
+#define MDPY_MEMORY_BAR_OFFSET PAGE_SIZE
+#define MDPY_DISPLAY_REGION    16
+
+#define STORE_LE16(addr, val)  (*(u16 *)addr = val)
+#define STORE_LE32(addr, val)  (*(u32 *)addr = val)
+
+
+MODULE_LICENSE("GPL v2");
+
+static int max_devices = 4;
+module_param_named(count, max_devices, int, 0444);
+MODULE_PARM_DESC(count, "number of " MDPY_NAME " devices");
+
+
+#define MDPY_TYPE_1 "vga"
+#define MDPY_TYPE_2 "xga"
+#define MDPY_TYPE_3 "hd"
+
+static const struct mdpy_type {
+       const char *name;
+       u32 format;
+       u32 bytepp;
+       u32 width;
+       u32 height;
+} mdpy_types[] = {
+       {
+               .name   = MDPY_CLASS_NAME "-" MDPY_TYPE_1,
+               .format = DRM_FORMAT_XRGB8888,
+               .bytepp = 4,
+               .width  = 640,
+               .height = 480,
+       },{
+               .name   = MDPY_CLASS_NAME "-" MDPY_TYPE_2,
+               .format = DRM_FORMAT_XRGB8888,
+               .bytepp = 4,
+               .width  = 1024,
+               .height = 768,
+       },{
+               .name   = MDPY_CLASS_NAME "-" MDPY_TYPE_3,
+               .format = DRM_FORMAT_XRGB8888,
+               .bytepp = 4,
+               .width  = 1920,
+               .height = 1080,
+       },
+};
+
+static dev_t           mdpy_devt;
+static struct class    *mdpy_class;
+static struct cdev     mdpy_cdev;
+static struct device   mdpy_dev;
+static u32             mdpy_count;
+
+/* State of each mdev device */
+struct mdev_state {
+       u8 *vconfig;
+       u32 bar_mask;
+       struct mutex ops_lock;
+       struct mdev_device *mdev;
+       struct vfio_device_info dev_info;
+
+       const struct mdpy_type *type;
+       u32 memsize;
+       void *memblk;
+};
+
+static const struct mdpy_type *mdpy_find_type(struct kobject *kobj)
+{
+       int i;
+
+       for (i = 0; i < ARRAY_SIZE(mdpy_types); i++)
+               if (strcmp(mdpy_types[i].name, kobj->name) == 0)
+                       return mdpy_types + i;
+       return NULL;
+}
+
+static void mdpy_create_config_space(struct mdev_state *mdev_state)
+{
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_VENDOR_ID],
+                  MDPY_PCI_VENDOR_ID);
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_DEVICE_ID],
+                  MDPY_PCI_DEVICE_ID);
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_SUBSYSTEM_VENDOR_ID],
+                  MDPY_PCI_SUBVENDOR_ID);
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_SUBSYSTEM_ID],
+                  MDPY_PCI_SUBDEVICE_ID);
+
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_COMMAND],
+                  PCI_COMMAND_IO | PCI_COMMAND_MEMORY);
+       STORE_LE16((u16 *) &mdev_state->vconfig[PCI_CLASS_DEVICE],
+                  PCI_CLASS_DISPLAY_OTHER);
+       mdev_state->vconfig[PCI_CLASS_REVISION] =  0x01;
+
+       STORE_LE32((u32 *) &mdev_state->vconfig[PCI_BASE_ADDRESS_0],
+                  PCI_BASE_ADDRESS_SPACE_MEMORY |
+                  PCI_BASE_ADDRESS_MEM_TYPE_32  |
+                  PCI_BASE_ADDRESS_MEM_PREFETCH);
+       mdev_state->bar_mask = ~(mdev_state->memsize) + 1;
+
+       /* Vendor specific data */
+       STORE_LE32((u32 *) &mdev_state->vconfig[MDPY_FORMAT_OFFSET],
+                  mdev_state->type->format);
+       STORE_LE32((u32 *) &mdev_state->vconfig[MDPY_WIDTH_OFFSET],
+                  mdev_state->type->width);
+       STORE_LE32((u32 *) &mdev_state->vconfig[MDPY_HEIGHT_OFFSET],
+                  mdev_state->type->height);
+}
+
+static void handle_pci_cfg_write(struct mdev_state *mdev_state, u16 offset,
+                                char *buf, u32 count)
+{
+       struct device *dev = mdev_dev(mdev_state->mdev);
+       u32 cfg_addr;
+
+       switch (offset) {
+       case PCI_BASE_ADDRESS_0:
+               cfg_addr = *(u32 *)buf;
+
+               if (cfg_addr == 0xffffffff) {
+                       cfg_addr = (cfg_addr & mdev_state->bar_mask);
+               } else {
+                       cfg_addr &= PCI_BASE_ADDRESS_MEM_MASK;
+                       if (cfg_addr)
+                               dev_info(dev, "BAR0 @ 0x%x\n", cfg_addr);
+               }
+
+               cfg_addr |= (mdev_state->vconfig[offset] &
+                            ~PCI_BASE_ADDRESS_MEM_MASK);
+               STORE_LE32(&mdev_state->vconfig[offset], cfg_addr);
+               break;
+       }
+}
+
+static ssize_t mdev_access(struct mdev_device *mdev, char *buf, size_t count,
+                          loff_t pos, bool is_write)
+{
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+       struct device *dev = mdev_dev(mdev);
+       int ret = 0;
+
+       mutex_lock(&mdev_state->ops_lock);
+
+       if (pos < MDPY_CONFIG_SPACE_SIZE) {
+               if (is_write) {
+                       handle_pci_cfg_write(mdev_state, pos, buf, count);
+               } else {
+                       memcpy(buf, (mdev_state->vconfig + pos), count);
+               }
+
+       } else {
+               dev_info(dev, "%s: %s @0x%llx (unhandled)\n",
+                        __func__, is_write ? "WR" : "RD", pos);
+               ret = -1;
+               goto accessfailed;
+       }
+
+       ret = count;
+
+
+accessfailed:
+       mutex_unlock(&mdev_state->ops_lock);
+
+       return ret;
+}
+
+int mdpy_reset(struct mdev_device *mdev)
+{
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+       u32 stride, i;
+
+       /* initialize with gray gradient */
+       stride = mdev_state->type->width * mdev_state->type->bytepp;
+       for (i = 0; i < mdev_state->type->height; i++)
+               memset(mdev_state->memblk + i * stride,
+                      i * 255 / mdev_state->type->height,
+                      stride);
+       return 0;
+}
+
+int mdpy_create(struct kobject *kobj, struct mdev_device *mdev)
+{
+       const struct mdpy_type *type = mdpy_find_type(kobj);
+       struct device *dev = mdev_dev(mdev);
+       struct mdev_state *mdev_state;
+       u32 fbsize;
+
+       if (mdpy_count >= max_devices)
+               return -ENOMEM;
+
+       mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
+       if (mdev_state == NULL)
+               return -ENOMEM;
+
+       mdev_state->vconfig = kzalloc(MDPY_CONFIG_SPACE_SIZE, GFP_KERNEL);
+       if (mdev_state->vconfig == NULL) {
+               kfree(mdev_state);
+               return -ENOMEM;
+       }
+
+       if (!type)
+               type = &mdpy_types[0];
+       fbsize = roundup_pow_of_two(type->width * type->height * type->bytepp);
+
+       mdev_state->memblk = vmalloc_user(fbsize);
+       if (!mdev_state->memblk) {
+               kfree(mdev_state->vconfig);
+               kfree(mdev_state);
+               return -ENOMEM;
+       }
+       dev_info(dev, "%s: %s (%dx%d)\n",
+                __func__, kobj->name, type->width, type->height);
+
+       mutex_init(&mdev_state->ops_lock);
+       mdev_state->mdev = mdev;
+       mdev_set_drvdata(mdev, mdev_state);
+
+       mdev_state->type    = type;
+       mdev_state->memsize = fbsize;
+       mdpy_create_config_space(mdev_state);
+       mdpy_reset(mdev);
+
+       mdpy_count++;
+       return 0;
+}
+
+int mdpy_remove(struct mdev_device *mdev)
+{
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+       struct device *dev = mdev_dev(mdev);
+
+       dev_info(dev, "%s\n", __func__);
+
+       mdev_set_drvdata(mdev, NULL);
+       vfree(mdev_state->memblk);
+       kfree(mdev_state->vconfig);
+       kfree(mdev_state);
+
+       mdpy_count--;
+       return 0;
+}
+
+ssize_t mdpy_read(struct mdev_device *mdev, char __user *buf, size_t count,
+                 loff_t *ppos)
+{
+       unsigned int done = 0;
+       int ret;
+
+       while (count) {
+               size_t filled;
+
+               if (count >= 4 && !(*ppos % 4)) {
+                       u32 val;
+
+                       ret =  mdev_access(mdev, (char *)&val, sizeof(val),
+                                          *ppos, false);
+                       if (ret <= 0)
+                               goto read_err;
+
+                       if (copy_to_user(buf, &val, sizeof(val)))
+                               goto read_err;
+
+                       filled = 4;
+               } else if (count >= 2 && !(*ppos % 2)) {
+                       u16 val;
+
+                       ret = mdev_access(mdev, (char *)&val, sizeof(val),
+                                         *ppos, false);
+                       if (ret <= 0)
+                               goto read_err;
+
+                       if (copy_to_user(buf, &val, sizeof(val)))
+                               goto read_err;
+
+                       filled = 2;
+               } else {
+                       u8 val;
+
+                       ret = mdev_access(mdev, (char *)&val, sizeof(val),
+                                         *ppos, false);
+                       if (ret <= 0)
+                               goto read_err;
+
+                       if (copy_to_user(buf, &val, sizeof(val)))
+                               goto read_err;
+
+                       filled = 1;
+               }
+
+               count -= filled;
+               done += filled;
+               *ppos += filled;
+               buf += filled;
+       }
+
+       return done;
+
+read_err:
+       return -EFAULT;
+}
+
+ssize_t mdpy_write(struct mdev_device *mdev, const char __user *buf,
+                  size_t count, loff_t *ppos)
+{
+       unsigned int done = 0;
+       int ret;
+
+       while (count) {
+               size_t filled;
+
+               if (count >= 4 && !(*ppos % 4)) {
+                       u32 val;
+
+                       if (copy_from_user(&val, buf, sizeof(val)))
+                               goto write_err;
+
+                       ret = mdev_access(mdev, (char *)&val, sizeof(val),
+                                         *ppos, true);
+                       if (ret <= 0)
+                               goto write_err;
+
+                       filled = 4;
+               } else if (count >= 2 && !(*ppos % 2)) {
+                       u16 val;
+
+                       if (copy_from_user(&val, buf, sizeof(val)))
+                               goto write_err;
+
+                       ret = mdev_access(mdev, (char *)&val, sizeof(val),
+                                         *ppos, true);
+                       if (ret <= 0)
+                               goto write_err;
+
+                       filled = 2;
+               } else {
+                       u8 val;
+
+                       if (copy_from_user(&val, buf, sizeof(val)))
+                               goto write_err;
+
+                       ret = mdev_access(mdev, (char *)&val, sizeof(val),
+                                         *ppos, true);
+                       if (ret <= 0)
+                               goto write_err;
+
+                       filled = 1;
+               }
+               count -= filled;
+               done += filled;
+               *ppos += filled;
+               buf += filled;
+       }
+
+       return done;
+write_err:
+       return -EFAULT;
+}
+
+int mdpy_mmap(struct mdev_device *mdev, struct vm_area_struct *vma)
+{
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+
+       if (vma->vm_pgoff != MDPY_MEMORY_BAR_OFFSET >> PAGE_SHIFT)
+               return -EINVAL;
+       if (vma->vm_end < vma->vm_start)
+               return -EINVAL;
+       if (vma->vm_end - vma->vm_start > mdev_state->memsize)
+               return -EINVAL;
+       if ((vma->vm_flags & VM_SHARED) == 0)
+               return -EINVAL;
+
+       return remap_vmalloc_range_partial(vma, vma->vm_start,
+                                          mdev_state->memblk,
+                                          vma->vm_end - vma->vm_start);
+}
+
+int mdpy_get_region_info(struct mdev_device *mdev,
+                        struct vfio_region_info *region_info,
+                        u16 *cap_type_id, void **cap_type)
+{
+       struct mdev_state *mdev_state;
+
+       mdev_state = mdev_get_drvdata(mdev);
+       if (!mdev_state)
+               return -EINVAL;
+
+       if (region_info->index >= VFIO_PCI_NUM_REGIONS &&
+           region_info->index != MDPY_DISPLAY_REGION)
+               return -EINVAL;
+
+       switch (region_info->index) {
+       case VFIO_PCI_CONFIG_REGION_INDEX:
+               region_info->offset = 0;
+               region_info->size   = MDPY_CONFIG_SPACE_SIZE;
+               region_info->flags  = (VFIO_REGION_INFO_FLAG_READ |
+                                      VFIO_REGION_INFO_FLAG_WRITE);
+               break;
+       case VFIO_PCI_BAR0_REGION_INDEX:
+       case MDPY_DISPLAY_REGION:
+               region_info->offset = MDPY_MEMORY_BAR_OFFSET;
+               region_info->size   = mdev_state->memsize;
+               region_info->flags  = (VFIO_REGION_INFO_FLAG_READ  |
+                                      VFIO_REGION_INFO_FLAG_WRITE |
+                                      VFIO_REGION_INFO_FLAG_MMAP);
+               break;
+       default:
+               region_info->size   = 0;
+               region_info->offset = 0;
+               region_info->flags  = 0;
+       }
+
+       return 0;
+}
+
+int mdpy_get_irq_info(struct mdev_device *mdev, struct vfio_irq_info *irq_info)
+{
+       irq_info->count = 0;
+       return 0;
+}
+
+int mdpy_get_device_info(struct mdev_device *mdev,
+                        struct vfio_device_info *dev_info)
+{
+       dev_info->flags = VFIO_DEVICE_FLAGS_PCI;
+       dev_info->num_regions = VFIO_PCI_NUM_REGIONS;
+       dev_info->num_irqs = VFIO_PCI_NUM_IRQS;
+       return 0;
+}
+
+int mdpy_query_gfx_plane(struct mdev_device *mdev,
+                        struct vfio_device_gfx_plane_info *plane)
+{
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+
+       if (plane->flags & VFIO_GFX_PLANE_TYPE_PROBE) {
+               if (plane->flags == (VFIO_GFX_PLANE_TYPE_PROBE |
+                                    VFIO_GFX_PLANE_TYPE_REGION))
+                       return 0;
+               return -EINVAL;
+       }
+
+       if (plane->flags != VFIO_GFX_PLANE_TYPE_REGION)
+               return -EINVAL;
+
+       plane->drm_format     = mdev_state->type->format;
+       plane->width          = mdev_state->type->width;
+       plane->height         = mdev_state->type->height;
+       plane->stride         = (mdev_state->type->width *
+                                mdev_state->type->bytepp);
+       plane->size           = mdev_state->memsize;
+       plane->region_index   = MDPY_DISPLAY_REGION;
+
+       /* unused */
+       plane->drm_format_mod = 0;
+       plane->x_pos          = 0;
+       plane->y_pos          = 0;
+       plane->x_hot          = 0;
+       plane->y_hot          = 0;
+
+       return 0;
+}
+
+static long mdpy_ioctl(struct mdev_device *mdev, unsigned int cmd,
+                       unsigned long arg)
+{
+       int ret = 0;
+       unsigned long minsz;
+       struct mdev_state *mdev_state;
+
+       mdev_state = mdev_get_drvdata(mdev);
+
+       switch (cmd) {
+       case VFIO_DEVICE_GET_INFO:
+       {
+               struct vfio_device_info info;
+
+               minsz = offsetofend(struct vfio_device_info, num_irqs);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (info.argsz < minsz)
+                       return -EINVAL;
+
+               ret = mdpy_get_device_info(mdev, &info);
+               if (ret)
+                       return ret;
+
+               memcpy(&mdev_state->dev_info, &info, sizeof(info));
+
+               if (copy_to_user((void __user *)arg, &info, minsz))
+                       return -EFAULT;
+
+               return 0;
+       }
+       case VFIO_DEVICE_GET_REGION_INFO:
+       {
+               struct vfio_region_info info;
+               u16 cap_type_id = 0;
+               void *cap_type = NULL;
+
+               minsz = offsetofend(struct vfio_region_info, offset);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (info.argsz < minsz)
+                       return -EINVAL;
+
+               ret = mdpy_get_region_info(mdev, &info, &cap_type_id,
+                                          &cap_type);
+               if (ret)
+                       return ret;
+
+               if (copy_to_user((void __user *)arg, &info, minsz))
+                       return -EFAULT;
+
+               return 0;
+       }
+
+       case VFIO_DEVICE_GET_IRQ_INFO:
+       {
+               struct vfio_irq_info info;
+
+               minsz = offsetofend(struct vfio_irq_info, count);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if ((info.argsz < minsz) ||
+                   (info.index >= mdev_state->dev_info.num_irqs))
+                       return -EINVAL;
+
+               ret = mdpy_get_irq_info(mdev, &info);
+               if (ret)
+                       return ret;
+
+               if (copy_to_user((void __user *)arg, &info, minsz))
+                       return -EFAULT;
+
+               return 0;
+       }
+
+       case VFIO_DEVICE_QUERY_GFX_PLANE:
+       {
+               struct vfio_device_gfx_plane_info plane;
+
+               minsz = offsetofend(struct vfio_device_gfx_plane_info,
+                                   region_index);
+
+               if (copy_from_user(&plane, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (plane.argsz < minsz)
+                       return -EINVAL;
+
+               ret = mdpy_query_gfx_plane(mdev, &plane);
+               if (ret)
+                       return ret;
+
+               if (copy_to_user((void __user *)arg, &plane, minsz))
+                       return -EFAULT;
+
+               return 0;
+       }
+
+       case VFIO_DEVICE_SET_IRQS:
+               return -EINVAL;
+
+       case VFIO_DEVICE_RESET:
+               return mdpy_reset(mdev);
+       }
+       return -ENOTTY;
+}
+
+int mdpy_open(struct mdev_device *mdev)
+{
+       if (!try_module_get(THIS_MODULE))
+               return -ENODEV;
+
+       return 0;
+}
+
+void mdpy_close(struct mdev_device *mdev)
+{
+       module_put(THIS_MODULE);
+}
+
+static ssize_t
+resolution_show(struct device *dev, struct device_attribute *attr,
+               char *buf)
+{
+       struct mdev_device *mdev = mdev_from_dev(dev);
+       struct mdev_state *mdev_state = mdev_get_drvdata(mdev);
+
+       return sprintf(buf, "%dx%d\n",
+                      mdev_state->type->width,
+                      mdev_state->type->height);
+}
+static DEVICE_ATTR_RO(resolution);
+
+static struct attribute *mdev_dev_attrs[] = {
+       &dev_attr_resolution.attr,
+       NULL,
+};
+
+static const struct attribute_group mdev_dev_group = {
+       .name  = "vendor",
+       .attrs = mdev_dev_attrs,
+};
+
+const struct attribute_group *mdev_dev_groups[] = {
+       &mdev_dev_group,
+       NULL,
+};
+
+static ssize_t
+name_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+       return sprintf(buf, "%s\n", kobj->name);
+}
+MDEV_TYPE_ATTR_RO(name);
+
+static ssize_t
+description_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+       const struct mdpy_type *type = mdpy_find_type(kobj);
+
+       return sprintf(buf, "virtual display, %dx%d framebuffer\n",
+                      type ? type->width  : 0,
+                      type ? type->height : 0);
+}
+MDEV_TYPE_ATTR_RO(description);
+
+static ssize_t
+available_instances_show(struct kobject *kobj, struct device *dev, char *buf)
+{
+       return sprintf(buf, "%d\n", max_devices - mdpy_count);
+}
+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", VFIO_DEVICE_API_PCI_STRING);
+}
+MDEV_TYPE_ATTR_RO(device_api);
+
+static struct attribute *mdev_types_attrs[] = {
+       &mdev_type_attr_name.attr,
+       &mdev_type_attr_description.attr,
+       &mdev_type_attr_device_api.attr,
+       &mdev_type_attr_available_instances.attr,
+       NULL,
+};
+
+static struct attribute_group mdev_type_group1 = {
+       .name  = MDPY_TYPE_1,
+       .attrs = mdev_types_attrs,
+};
+
+static struct attribute_group mdev_type_group2 = {
+       .name  = MDPY_TYPE_2,
+       .attrs = mdev_types_attrs,
+};
+
+static struct attribute_group mdev_type_group3 = {
+       .name  = MDPY_TYPE_3,
+       .attrs = mdev_types_attrs,
+};
+
+static struct attribute_group *mdev_type_groups[] = {
+       &mdev_type_group1,
+       &mdev_type_group2,
+       &mdev_type_group3,
+       NULL,
+};
+
+static const struct mdev_parent_ops mdev_fops = {
+       .owner                  = THIS_MODULE,
+       .mdev_attr_groups       = mdev_dev_groups,
+       .supported_type_groups  = mdev_type_groups,
+       .create                 = mdpy_create,
+       .remove                 = mdpy_remove,
+       .open                   = mdpy_open,
+       .release                = mdpy_close,
+       .read                   = mdpy_read,
+       .write                  = mdpy_write,
+       .ioctl                  = mdpy_ioctl,
+       .mmap                   = mdpy_mmap,
+};
+
+static const struct file_operations vd_fops = {
+       .owner          = THIS_MODULE,
+};
+
+static void mdpy_device_release(struct device *dev)
+{
+       /* nothing */
+}
+
+static int __init mdpy_dev_init(void)
+{
+       int ret = 0;
+
+       ret = alloc_chrdev_region(&mdpy_devt, 0, MINORMASK, MDPY_NAME);
+       if (ret < 0) {
+               pr_err("Error: failed to register mdpy_dev, err: %d\n", ret);
+               return ret;
+       }
+       cdev_init(&mdpy_cdev, &vd_fops);
+       cdev_add(&mdpy_cdev, mdpy_devt, MINORMASK);
+       pr_info("%s: major %d\n", __func__, MAJOR(mdpy_devt));
+
+       mdpy_class = class_create(THIS_MODULE, MDPY_CLASS_NAME);
+       if (IS_ERR(mdpy_class)) {
+               pr_err("Error: failed to register mdpy_dev class\n");
+               ret = PTR_ERR(mdpy_class);
+               goto failed1;
+       }
+       mdpy_dev.class = mdpy_class;
+       mdpy_dev.release = mdpy_device_release;
+       dev_set_name(&mdpy_dev, "%s", MDPY_NAME);
+
+       ret = device_register(&mdpy_dev);
+       if (ret)
+               goto failed2;
+
+       ret = mdev_register_device(&mdpy_dev, &mdev_fops);
+       if (ret)
+               goto failed3;
+
+       return 0;
+
+failed3:
+       device_unregister(&mdpy_dev);
+failed2:
+       class_destroy(mdpy_class);
+failed1:
+       cdev_del(&mdpy_cdev);
+       unregister_chrdev_region(mdpy_devt, MINORMASK);
+       return ret;
+}
+
+static void __exit mdpy_dev_exit(void)
+{
+       mdpy_dev.bus = NULL;
+       mdev_unregister_device(&mdpy_dev);
+
+       device_unregister(&mdpy_dev);
+       cdev_del(&mdpy_cdev);
+       unregister_chrdev_region(mdpy_devt, MINORMASK);
+       class_destroy(mdpy_class);
+       mdpy_class = NULL;
+}
+
+module_init(mdpy_dev_init)
+module_exit(mdpy_dev_exit)
diff --git a/samples/Kconfig b/samples/Kconfig
index c332a3b9de..a0c104adda 100644
--- a/samples/Kconfig
+++ b/samples/Kconfig
@@ -111,6 +111,14 @@ config SAMPLE_VFIO_MDEV_MTTY
          Build a virtual tty sample driver for use as a VFIO
          mediated device
 
+config SAMPLE_VFIO_MDEV_MDPY
+       tristate "Build VFIO mdpy example mediated device sample code -- 
loadable modules only"
+       depends on VFIO_MDEV_DEVICE && m
+       help
+         Build a virtual display sample driver for use as a VFIO
+         mediated device.  It is a simple framebuffer and supports
+         the region display interface (VFIO_GFX_PLANE_TYPE_REGION).
+
 config SAMPLE_STATX
        bool "Build example extended-stat using code"
        depends on BROKEN
diff --git a/samples/vfio-mdev/Makefile b/samples/vfio-mdev/Makefile
index cbbd868a50..031d6b88e9 100644
--- a/samples/vfio-mdev/Makefile
+++ b/samples/vfio-mdev/Makefile
@@ -1 +1,2 @@
 obj-$(CONFIG_SAMPLE_VFIO_MDEV_MTTY) += mtty.o
+obj-$(CONFIG_SAMPLE_VFIO_MDEV_MDPY) += mdpy.o
-- 
2.9.3

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