[PATCH] vfio: replace vfio->class with a const struct class

[PATCH] vfio: replace vfio->class with a const struct class

[Jori Koolstra]

The class_create() call has been deprecated in favor of class_register()
as the driver core now allows for a struct class to be in read-only
memory. Replace vfio->class with a const struct class and drop the
class_create() call.

Compile tested and found no errors/warns in dmesg after enabling
VFIO_GROUP.

Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/

Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
---
 drivers/vfio/group.c | 23 +++++++++++------------
 1 file changed, 11 insertions(+), 12 deletions(-)

diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
index 4f15016d2a5f..d4a53f8c5be0 100644
--- a/drivers/vfio/group.c
+++ b/drivers/vfio/group.c
@@ -15,8 +15,13 @@
 #include <linux/anon_inodes.h>
 #include "vfio.h"
 
+static char *vfio_devnode(const struct device *, umode_t *);
+static const struct class vfio_class = {
+	.name	= "vfio",
+	.devnode = vfio_devnode
+};
+
 static struct vfio {
-	struct class			*class;
 	struct list_head		group_list;
 	struct mutex			group_lock; /* locks group_list */
 	struct ida			group_ida;
@@ -527,7 +532,7 @@ static struct vfio_group *vfio_group_alloc(struct iommu_group *iommu_group,
 
 	device_initialize(&group->dev);
 	group->dev.devt = MKDEV(MAJOR(vfio.group_devt), minor);
-	group->dev.class = vfio.class;
+	group->dev.class = &vfio_class;
 	group->dev.release = vfio_group_release;
 	cdev_init(&group->cdev, &vfio_group_fops);
 	group->cdev.owner = THIS_MODULE;
@@ -901,13 +906,9 @@ int __init vfio_group_init(void)
 		return ret;
 
 	/* /dev/vfio/$GROUP */
-	vfio.class = class_create("vfio");
-	if (IS_ERR(vfio.class)) {
-		ret = PTR_ERR(vfio.class);
+	ret = class_register(&vfio_class);
+	if (ret)
 		goto err_group_class;
-	}
-
-	vfio.class->devnode = vfio_devnode;
 
 	ret = alloc_chrdev_region(&vfio.group_devt, 0, MINORMASK + 1, "vfio");
 	if (ret)
@@ -915,8 +916,7 @@ int __init vfio_group_init(void)
 	return 0;
 
 err_alloc_chrdev:
-	class_destroy(vfio.class);
-	vfio.class = NULL;
+	class_unregister(&vfio_class);
 err_group_class:
 	vfio_container_cleanup();
 	return ret;
@@ -927,7 +927,6 @@ void vfio_group_cleanup(void)
 	WARN_ON(!list_empty(&vfio.group_list));
 	ida_destroy(&vfio.group_ida);
 	unregister_chrdev_region(vfio.group_devt, MINORMASK + 1);
-	class_destroy(vfio.class);
-	vfio.class = NULL;
+	class_unregister(&vfio_class);
 	vfio_container_cleanup();
 }

base-commit: d466c332e106fe666d1e2f5a24d08e308bebbfa1
-- 
2.53.0

Re: [PATCH] vfio: replace vfio->class with a const struct class

[Alex Williamson]

On Fri,  6 Mar 2026 20:06:28 +0100
Jori Koolstra <jkoolstra@xs4all.nl> wrote:

> The class_create() call has been deprecated in favor of class_register()
> as the driver core now allows for a struct class to be in read-only
> memory. Replace vfio->class with a const struct class and drop the
> class_create() call.
> 
> Compile tested and found no errors/warns in dmesg after enabling
> VFIO_GROUP.
> 
> Link: https://lore.kernel.org/all/2023040244-duffel-pushpin-f738@gregkh/
> 
> Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
> ---
>  drivers/vfio/group.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)

Applied to vfio next branch for v7.1.  Thanks,

Alex