Re: [PATCH 04/15] vfio/mdev: embedd struct mdev_parent in the parent data structure

Eric Farman
2022-07-07T03:08:46Z

On Wed, 2022-07-06 at 09:42 +0200, Christoph Hellwig wrote:
> Simplify mdev_{un}register_device by requiring the caller to pass in
> a structure allocate as part of the parent device structure. This
> removes the need for a list of parents and the separate mdev_parent
> refcount as we can simplify rely on the reference to the parent
> device.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> ---
> .../driver-api/vfio-mediated-device.rst | 12 +-
> Documentation/s390/vfio-ap.rst | 2 +-
> Documentation/s390/vfio-ccw.rst | 2 +-
> drivers/gpu/drm/i915/gvt/gvt.h | 2 +
> drivers/gpu/drm/i915/gvt/kvmgt.c | 5 +-
> drivers/s390/cio/cio.h | 2 +
> drivers/s390/cio/vfio_ccw_ops.c | 6 +-

(@Vineeth, @Peter FYI regarding struct subchannel)

I haven't had a chance to look at this series with enough focus, but
the change to cio.h (here, and patch 5) caught my eye. I would've
expected the "parent" to be struct vfio_ccw_private, instead of the
subchannel.

Eric

> drivers/s390/crypto/vfio_ap_ops.c | 5 +-
> drivers/s390/crypto/vfio_ap_private.h | 1 +
> drivers/vfio/mdev/mdev_core.c | 120 ++++----------
> ----
> drivers/vfio/mdev/mdev_private.h | 23 ----
> drivers/vfio/mdev/mdev_sysfs.c | 4 +-
> include/linux/mdev.h | 15 ++-
> samples/vfio-mdev/mbochs.c | 5 +-
> samples/vfio-mdev/mdpy.c | 5 +-
> samples/vfio-mdev/mtty.c | 6 +-
> 16 files changed, 69 insertions(+), 146 deletions(-)
>
> diff --git a/Documentation/driver-api/vfio-mediated-device.rst
> b/Documentation/driver-api/vfio-mediated-device.rst
> index 1c57815619fdf..62a82afce161b 100644
> --- a/Documentation/driver-api/vfio-mediated-device.rst
> +++ b/Documentation/driver-api/vfio-mediated-device.rst
> @@ -60,19 +60,19 @@ devices as examples, as these devices are the
> first devices to use this module::
> | MDEV CORE |
> | MODULE |
> | mdev.ko |
> - | +-----------+ | mdev_register_device() +--------------+
> + | +-----------+ | mdev_register_parent() +--------------+
> | | | +<------------------------+ |
> | | | | | nvidia.ko |<->
> physical
> | | | +----------------------
> -->+ | device
> | | | | callbacks +--------------+
> | | Physical | |
> - | | device | | mdev_register_device() +--------------+
> + | | device | | mdev_register_parent() +--------------+
> | | interface | |<------------------------+ |
> | | | | | i915.ko |<->
> physical
> | | | +----------------------
> -->+ | device
> | | | | callbacks +--------------+
> | | | |
> - | | | | mdev_register_device() +--------------+
> + | | | | mdev_register_parent() +--------------+
> | | | +<------------------------+ |
> | | | | | ccw_device.ko|<->
> physical
> | | | +----------------------
> -->+ | device
> @@ -127,8 +127,8 @@ vfio_device_ops.
> When a driver wants to add the GUID creation sysfs to an existing
> device it has
> probe'd to then it should call::
>
> - int mdev_register_device(struct device *dev,
> - struct mdev_driver *mdev_driver);
> + int mdev_register_parent(struct mdev_parent *parent, struct
> device *dev,
> + struct mdev_driver *mdev_driver);
>
> This will provide the 'mdev_supported_types/XX/create' files which
> can then be
> used to trigger the creation of a mdev_device. The created
> mdev_device will be
> @@ -136,7 +136,7 @@ attached to the specified driver.
>
> When the driver needs to remove itself it calls::
>
> - void mdev_unregister_device(struct device *dev);
> + void mdev_unregister_parent(struct mdev_parent *parent);
>
> Which will unbind and destroy all the created mdevs and remove the
> sysfs files.
>
> diff --git a/Documentation/s390/vfio-ap.rst
> b/Documentation/s390/vfio-ap.rst
> index f57ae621f33e8..37e16158c7fbf 100644
> --- a/Documentation/s390/vfio-ap.rst
> +++ b/Documentation/s390/vfio-ap.rst
> @@ -299,7 +299,7 @@ of the VFIO AP mediated matrix device driver::
> | MDEV CORE |
> | MODULE |
> | mdev.ko |
> - | +---------+ | mdev_register_device() +--------------+
> + | +---------+ | mdev_register_parent() +--------------+
> | |Physical | +<-----------------------+ |
> | | device | | | vfio_ap.ko |<-> matrix
> | |interface| +----------------------->+ | device
> diff --git a/Documentation/s390/vfio-ccw.rst
> b/Documentation/s390/vfio-ccw.rst
> index 8aad08a8b8a50..ea928a3806f43 100644
> --- a/Documentation/s390/vfio-ccw.rst
> +++ b/Documentation/s390/vfio-ccw.rst
> @@ -156,7 +156,7 @@ Below is a high Level block diagram::
> | MDEV CORE |
> | MODULE |
> | mdev.ko |
> - | +---------+ | mdev_register_device() +--------------+
> + | +---------+ | mdev_register_parent() +--------------+
> | |Physical | +<-----------------------+ |
> | | device | | | vfio_ccw.ko |<->
> subchannel
> | |interface| +----------------------->+ | device
> diff --git a/drivers/gpu/drm/i915/gvt/gvt.h
> b/drivers/gpu/drm/i915/gvt/gvt.h
> index 392c2ad49d376..bbf0116671ecb 100644
> --- a/drivers/gpu/drm/i915/gvt/gvt.h
> +++ b/drivers/gpu/drm/i915/gvt/gvt.h
> @@ -36,6 +36,7 @@
> #include <uapi/linux/pci_regs.h>
> #include <linux/kvm_host.h>
> #include <linux/vfio.h>
> +#include <linux/mdev.h>
>
> #include "i915_drv.h"
> #include "intel_gvt.h"
> @@ -338,6 +339,7 @@ struct intel_gvt {
> struct intel_gvt_workload_scheduler scheduler;
> struct notifier_block
> shadow_ctx_notifier_block[I915_NUM_ENGINES];
> DECLARE_HASHTABLE(cmd_table, GVT_CMD_HASH_BITS);
> + struct mdev_parent parent;
> struct intel_vgpu_type *types;
> unsigned int num_types;
> struct intel_vgpu *idle_vgpu;
> diff --git a/drivers/gpu/drm/i915/gvt/kvmgt.c
> b/drivers/gpu/drm/i915/gvt/kvmgt.c
> index 85e1393d8e55c..e9dba4c0fe6b5 100644
> --- a/drivers/gpu/drm/i915/gvt/kvmgt.c
> +++ b/drivers/gpu/drm/i915/gvt/kvmgt.c
> @@ -1958,7 +1958,7 @@ static void intel_gvt_clean_device(struct
> drm_i915_private *i915)
> if (drm_WARN_ON(&i915->drm, !gvt))
> return;
>
> - mdev_unregister_device(i915->drm.dev);
> + mdev_unregister_parent(&gvt->parent);
> intel_gvt_cleanup_vgpu_type_groups(gvt);
> intel_gvt_destroy_idle_vgpu(gvt->idle_vgpu);
> intel_gvt_clean_vgpu_types(gvt);
> @@ -2063,7 +2063,8 @@ static int intel_gvt_init_device(struct
> drm_i915_private *i915)
> if (ret)
> goto out_destroy_idle_vgpu;
>
> - ret = mdev_register_device(i915->drm.dev,
> &intel_vgpu_mdev_driver);
> + ret = mdev_register_parent(&gvt->parent, i915->drm.dev,
> + &intel_vgpu_mdev_driver);
> if (ret)
> goto out_cleanup_vgpu_type_groups;
>
> diff --git a/drivers/s390/cio/cio.h b/drivers/s390/cio/cio.h
> index fa8df50bb49e3..22be5ac7d23c1 100644
> --- a/drivers/s390/cio/cio.h
> +++ b/drivers/s390/cio/cio.h
> @@ -5,6 +5,7 @@
> #include <linux/mutex.h>
> #include <linux/device.h>
> #include <linux/mod_devicetable.h>
> +#include <linux/mdev.h>
> #include <asm/chpid.h>
> #include <asm/cio.h>
> #include <asm/fcx.h>
> @@ -108,6 +109,7 @@ struct subchannel {
> * frees it. Use driver_set_override() to set or clear it.
> */
> const char *driver_override;
> + struct mdev_parent parent;
> } __attribute__ ((aligned(8)));
>
> DECLARE_PER_CPU_ALIGNED(struct irb, cio_irb);
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c
> b/drivers/s390/cio/vfio_ccw_ops.c
> index b49e2e9db2dc6..9192a21085ce4 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -11,7 +11,6 @@
> */
>
> #include <linux/vfio.h>
> -#include <linux/mdev.h>
> #include <linux/nospec.h>
> #include <linux/slab.h>
>
> @@ -660,10 +659,11 @@ struct mdev_driver vfio_ccw_mdev_driver = {
>
> int vfio_ccw_mdev_reg(struct subchannel *sch)
> {
> - return mdev_register_device(&sch->dev, &vfio_ccw_mdev_driver);
> + return mdev_register_parent(&sch->parent, &sch->dev,
> + &vfio_ccw_mdev_driver);
> }
>
> void vfio_ccw_mdev_unreg(struct subchannel *sch)
> {
> - mdev_unregister_device(&sch->dev);
> + mdev_unregister_parent(&sch->parent);
> }
> diff --git a/drivers/s390/crypto/vfio_ap_ops.c
> b/drivers/s390/crypto/vfio_ap_ops.c
> index a7d2a95796d36..834945150dc9f 100644
> --- a/drivers/s390/crypto/vfio_ap_ops.c
> +++ b/drivers/s390/crypto/vfio_ap_ops.c
> @@ -1485,7 +1485,8 @@ int vfio_ap_mdev_register(void)
> if (ret)
> return ret;
>
> - ret = mdev_register_device(&matrix_dev->device,
> &vfio_ap_matrix_driver);
> + ret = mdev_register_parent(&matrix_dev->parent, &matrix_dev-
> >device,
> + &vfio_ap_matrix_driver);
> if (ret)
> goto err_driver;
> return 0;
> @@ -1497,6 +1498,6 @@ int vfio_ap_mdev_register(void)
>
> void vfio_ap_mdev_unregister(void)
> {
> - mdev_unregister_device(&matrix_dev->device);
> + mdev_unregister_parent(&matrix_dev->parent);
> mdev_unregister_driver(&vfio_ap_matrix_driver);
> }
> diff --git a/drivers/s390/crypto/vfio_ap_private.h
> b/drivers/s390/crypto/vfio_ap_private.h
> index 6616aa83347ad..0191f6bc973a4 100644
> --- a/drivers/s390/crypto/vfio_ap_private.h
> +++ b/drivers/s390/crypto/vfio_ap_private.h
> @@ -45,6 +45,7 @@ struct ap_matrix_dev {
> struct list_head mdev_list;
> struct mutex lock;
> struct ap_driver *vfio_ap_drv;
> + struct mdev_parent parent;
> };
>
> extern struct ap_matrix_dev *matrix_dev;
> diff --git a/drivers/vfio/mdev/mdev_core.c
> b/drivers/vfio/mdev/mdev_core.c
> index 2c32923fbad27..fa05ac3396950 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -18,8 +18,6 @@
> #define DRIVER_AUTHOR "NVIDIA Corporation"
> #define DRIVER_DESC "Mediated device Core Driver"
>
> -static LIST_HEAD(parent_list);
> -static DEFINE_MUTEX(parent_list_lock);
> static struct class_compat *mdev_bus_compat_class;
>
> static LIST_HEAD(mdev_list);
> @@ -61,28 +59,6 @@ struct device *mtype_get_parent_dev(struct
> mdev_type *mtype)
> }
> EXPORT_SYMBOL(mtype_get_parent_dev);
>
> -/* Should be called holding parent_list_lock */
> -static struct mdev_parent *__find_parent_device(struct device *dev)
> -{
> - struct mdev_parent *parent;
> -
> - list_for_each_entry(parent, &parent_list, next) {
> - if (parent->dev == dev)
> - return parent;
> - }
> - return NULL;
> -}
> -
> -void mdev_release_parent(struct kref *kref)
> -{
> - struct mdev_parent *parent = container_of(kref, struct
> mdev_parent,
> - ref);
> - struct device *dev = parent->dev;
> -
> - kfree(parent);
> - put_device(dev);
> -}
> -
> /* Caller must hold parent unreg_sem read or write lock */
> static void mdev_device_remove_common(struct mdev_device *mdev)
> {
> @@ -105,125 +81,73 @@ static int mdev_device_remove_cb(struct device
> *dev, void *data)
> }
>
> /*
> - * mdev_register_device : Register a device
> + * mdev_register_parent: Register a device as parent for mdevs
> + * @parent: parent structure registered
> * @dev: device structure representing parent device.
> * @mdev_driver: Device driver to bind to the newly created mdev
> *
> - * Add device to list of registered parent devices.
> + * Registers the @parent stucture as a parent for mdev types and
> thus mdev
> + * devices. The caller needs to hold a reference on @dev that must
> not be
> + * released until after the call to mdev_unregister_parent().
> + *
> * Returns a negative value on error, otherwise 0.
> */
> -int mdev_register_device(struct device *dev, struct mdev_driver
> *mdev_driver)
> +int mdev_register_parent(struct mdev_parent *parent, struct device
> *dev,
> + struct mdev_driver *mdev_driver)
> {
> - int ret;
> - struct mdev_parent *parent;
> char *env_string = "MDEV_STATE=registered";
> char *envp[] = { env_string, NULL };
> + int ret;
>
> /* check for mandatory ops */
> if (!mdev_driver->supported_type_groups)
> return -EINVAL;
>
> - dev = get_device(dev);
> - if (!dev)
> - return -EINVAL;
> -
> - mutex_lock(&parent_list_lock);
> -
> - /* Check for duplicate */
> - parent = __find_parent_device(dev);
> - if (parent) {
> - parent = NULL;
> - ret = -EEXIST;
> - goto add_dev_err;
> - }
> -
> - parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> - if (!parent) {
> - ret = -ENOMEM;
> - goto add_dev_err;
> - }
> -
> - kref_init(&parent->ref);
> + memset(parent, 0, sizeof(*parent));
> init_rwsem(&parent->unreg_sem);
> -
> parent->dev = dev;
> parent->mdev_driver = mdev_driver;
>
> if (!mdev_bus_compat_class) {
> mdev_bus_compat_class =
> class_compat_register("mdev_bus");
> - if (!mdev_bus_compat_class) {
> - ret = -ENOMEM;
> - goto add_dev_err;
> - }
> + if (!mdev_bus_compat_class)
> + return -ENOMEM;
> }
>
> ret = parent_create_sysfs_files(parent);
> if (ret)
> - goto add_dev_err;
> + return ret;
>
> ret = class_compat_create_link(mdev_bus_compat_class, dev,
> NULL);
> if (ret)
> dev_warn(dev, "Failed to create compatibility class
> link\n");
>
> - list_add(&parent->next, &parent_list);
> - mutex_unlock(&parent_list_lock);
> -
> dev_info(dev, "MDEV: Registered\n");
> kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
> -
> return 0;
> -
> -add_dev_err:
> - mutex_unlock(&parent_list_lock);
> - if (parent)
> - mdev_put_parent(parent);
> - else
> - put_device(dev);
> - return ret;
> }
> -EXPORT_SYMBOL(mdev_register_device);
> +EXPORT_SYMBOL(mdev_register_parent);
>
> /*
> - * mdev_unregister_device : Unregister a parent device
> - * @dev: device structure representing parent device.
> - *
> - * Remove device from list of registered parent devices. Give a
> chance to free
> - * existing mediated devices for given device.
> + * mdev_unregister_parent : Unregister a parent device
> + * @parent: parent structure to unregister
> */
> -
> -void mdev_unregister_device(struct device *dev)
> +void mdev_unregister_parent(struct mdev_parent *parent)
> {
> - struct mdev_parent *parent;
> char *env_string = "MDEV_STATE=unregistered";
> char *envp[] = { env_string, NULL };
>
> - mutex_lock(&parent_list_lock);
> - parent = __find_parent_device(dev);
> -
> - if (!parent) {
> - mutex_unlock(&parent_list_lock);
> - return;
> - }
> - dev_info(dev, "MDEV: Unregistering\n");
> -
> - list_del(&parent->next);
> - mutex_unlock(&parent_list_lock);
> + dev_info(parent->dev, "MDEV: Unregistering\n");
>
> down_write(&parent->unreg_sem);
> -
> - class_compat_remove_link(mdev_bus_compat_class, dev, NULL);
> -
> - device_for_each_child(dev, NULL, mdev_device_remove_cb);
> -
> + class_compat_remove_link(mdev_bus_compat_class, parent->dev,
> NULL);
> + device_for_each_child(parent->dev, NULL,
> mdev_device_remove_cb);
> parent_remove_sysfs_files(parent);
> up_write(&parent->unreg_sem);
>
> - mdev_put_parent(parent);
> -
> - /* We still have the caller's reference to use for the uevent
> */
> - kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);
> + kobject_uevent_env(&parent->dev->kobj, KOBJ_CHANGE, envp);
> }
> -EXPORT_SYMBOL(mdev_unregister_device);
> +EXPORT_SYMBOL(mdev_unregister_parent);
>
> static void mdev_device_release(struct device *dev)
> {
> diff --git a/drivers/vfio/mdev/mdev_private.h
> b/drivers/vfio/mdev/mdev_private.h
> index 7c9fc79f3d838..297f911fdc890 100644
> --- a/drivers/vfio/mdev/mdev_private.h
> +++ b/drivers/vfio/mdev/mdev_private.h
> @@ -13,17 +13,6 @@
> int mdev_bus_register(void);
> void mdev_bus_unregister(void);
>
> -struct mdev_parent {
> - struct device *dev;
> - struct mdev_driver *mdev_driver;
> - struct kref ref;
> - struct list_head next;
> - struct kset *mdev_types_kset;
> - struct list_head type_list;
> - /* Synchronize device creation/removal with parent
> unregistration */
> - struct rw_semaphore unreg_sem;
> -};
> -
> struct mdev_type {
> struct kobject kobj;
> struct kobject *devices_kobj;
> @@ -48,16 +37,4 @@ void mdev_remove_sysfs_files(struct mdev_device
> *mdev);
> int mdev_device_create(struct mdev_type *kobj, const guid_t *uuid);
> int mdev_device_remove(struct mdev_device *dev);
>
> -void mdev_release_parent(struct kref *kref);
> -
> -static inline void mdev_get_parent(struct mdev_parent *parent)
> -{
> - kref_get(&parent->ref);
> -}
> -
> -static inline void mdev_put_parent(struct mdev_parent *parent)
> -{
> - kref_put(&parent->ref, mdev_release_parent);
> -}
> -
> #endif /* MDEV_PRIVATE_H */
> diff --git a/drivers/vfio/mdev/mdev_sysfs.c
> b/drivers/vfio/mdev/mdev_sysfs.c
> index 4bfbf49aaa66a..b71ffc5594870 100644
> --- a/drivers/vfio/mdev/mdev_sysfs.c
> +++ b/drivers/vfio/mdev/mdev_sysfs.c
> @@ -81,7 +81,7 @@ static void mdev_type_release(struct kobject *kobj)
>
> pr_debug("Releasing group %s\n", kobj->name);
> /* Pairs with the get in add_mdev_supported_type() */
> - mdev_put_parent(type->parent);
> + put_device(type->parent->dev);
> kfree(type);
> }
>
> @@ -110,7 +110,7 @@ static struct mdev_type
> *add_mdev_supported_type(struct mdev_parent *parent,
> type->kobj.kset = parent->mdev_types_kset;
> type->parent = parent;
> /* Pairs with the put in mdev_type_release() */
> - mdev_get_parent(parent);
> + get_device(parent->dev);
> type->type_group_id = type_group_id;
>
> ret = kobject_init_and_add(&type->kobj, &mdev_type_ktype, NULL,
> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 555c1d015b5f0..327ce3e5c6b5f 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -23,6 +23,16 @@ struct mdev_device {
> bool active;
> };
>
> +/* embedded into the struct device that the mdev devices hang off */
> +struct mdev_parent {
> + struct device *dev;
> + struct mdev_driver *mdev_driver;
> + struct kset *mdev_types_kset;
> + struct list_head type_list;
> + /* Synchronize device creation/removal with parent
> unregistration */
> + struct rw_semaphore unreg_sem;
> +};
> +
> static inline struct mdev_device *to_mdev_device(struct device *dev)
> {
> return container_of(dev, struct mdev_device, dev);
> @@ -75,8 +85,9 @@ static inline const guid_t *mdev_uuid(struct
> mdev_device *mdev)
>
> extern struct bus_type mdev_bus_type;
>
> -int mdev_register_device(struct device *dev, struct mdev_driver
> *mdev_driver);
> -void mdev_unregister_device(struct device *dev);
> +int mdev_register_parent(struct mdev_parent *parent, struct device
> *dev,
> + struct mdev_driver *mdev_driver);
> +void mdev_unregister_parent(struct mdev_parent *parent);
>
> int mdev_register_driver(struct mdev_driver *drv);
> void mdev_unregister_driver(struct mdev_driver *drv);
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index d0d1bb7747240..30b3643b3b389 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -128,6 +128,7 @@ static dev_t mbochs_devt;
> static struct class *mbochs_class;
> static struct cdev mbochs_cdev;
> static struct device mbochs_dev;
> +static struct mdev_parent mbochs_parent;
> static atomic_t mbochs_avail_mbytes;
> static const struct vfio_device_ops mbochs_dev_ops;
>
> @@ -1456,7 +1457,7 @@ static int __init mbochs_dev_init(void)
> if (ret)
> goto err_class;
>
> - ret = mdev_register_device(&mbochs_dev, &mbochs_driver);
> + ret = mdev_register_parent(&mbochs_parent, &mbochs_dev,
> &mbochs_driver);
> if (ret)
> goto err_device;
>
> @@ -1477,7 +1478,7 @@ static int __init mbochs_dev_init(void)
> static void __exit mbochs_dev_exit(void)
> {
> mbochs_dev.bus = NULL;
> - mdev_unregister_device(&mbochs_dev);
> + mdev_unregister_parent(&mbochs_parent);
>
> device_unregister(&mbochs_dev);
> mdev_unregister_driver(&mbochs_driver);
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 0c4ca1f4be7ed..132bb055628a6 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -83,6 +83,7 @@ static dev_t mdpy_devt;
> static struct class *mdpy_class;
> static struct cdev mdpy_cdev;
> static struct device mdpy_dev;
> +static struct mdev_parent mdpy_parent;
> static u32 mdpy_count;
> static const struct vfio_device_ops mdpy_dev_ops;
>
> @@ -765,7 +766,7 @@ static int __init mdpy_dev_init(void)
> if (ret)
> goto err_class;
>
> - ret = mdev_register_device(&mdpy_dev, &mdpy_driver);
> + ret = mdev_register_parent(&mdpy_parent, &mdpy_dev,
> &mdpy_driver);
> if (ret)
> goto err_device;
>
> @@ -786,7 +787,7 @@ static int __init mdpy_dev_init(void)
> static void __exit mdpy_dev_exit(void)
> {
> mdpy_dev.bus = NULL;
> - mdev_unregister_device(&mdpy_dev);
> + mdev_unregister_parent(&mdpy_parent);
>
> device_unregister(&mdpy_dev);
> mdev_unregister_driver(&mdpy_driver);
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 4f5a6f2d3629d..8ba5f6084a093 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -72,6 +72,7 @@ static struct mtty_dev {
> struct cdev vd_cdev;
> struct idr vd_idr;
> struct device dev;
> + struct mdev_parent parent;
> } mtty_dev;
>
> struct mdev_region_info {
> @@ -1350,7 +1351,8 @@ static int __init mtty_dev_init(void)
> if (ret)
> goto err_class;
>
> - ret = mdev_register_device(&mtty_dev.dev, &mtty_driver);
> + ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
> + &mtty_driver);
> if (ret)
> goto err_device;
> return 0;
> @@ -1370,7 +1372,7 @@ static int __init mtty_dev_init(void)
> static void __exit mtty_dev_exit(void)
> {
> mtty_dev.dev.bus = NULL;
> - mdev_unregister_device(&mtty_dev.dev);
> + mdev_unregister_parent(&mtty_dev.parent);
>
> device_unregister(&mtty_dev.dev);
> idr_destroy(&mtty_dev.vd_idr);