vfio: mdev: replace mtty_dev->vd_class with a const struct class

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 mtty_dev->vd_class with a const struct class and drop the
class_create() call.

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

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>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/20260308214939.1215682-1-jkoolstra@xs4all.nl
Signed-off-by: Alex Williamson <alex@shazbot.org>

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index bd92c38379b872f1bb9608e9f4a3caa2f2143353..01a9db84c4ab4989c23f962ee32bdde15f37692a 100644 (file)
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -68,9 +68,12 @@
  * Global Structures
  */
 
+static const struct class mtty_class = {
+       .name   = MTTY_CLASS_NAME
+};
+
 static struct mtty_dev {
        dev_t           vd_devt;
-       struct class    *vd_class;
        struct cdev     vd_cdev;
        struct idr      vd_idr;
        struct device   dev;
@@ -1980,15 +1983,14 @@ static int __init mtty_dev_init(void)
        if (ret)
                goto err_cdev;
 
-       mtty_dev.vd_class = class_create(MTTY_CLASS_NAME);
+       ret = class_register(&mtty_class);
 
-       if (IS_ERR(mtty_dev.vd_class)) {
+       if (ret) {
                pr_err("Error: failed to register mtty_dev class\n");
-               ret = PTR_ERR(mtty_dev.vd_class);
                goto err_driver;
        }
 
-       mtty_dev.dev.class = mtty_dev.vd_class;
+       mtty_dev.dev.class = &mtty_class;
        mtty_dev.dev.release = mtty_device_release;
        dev_set_name(&mtty_dev.dev, "%s", MTTY_NAME);
 
@@ -2007,7 +2009,7 @@ err_device:
        device_del(&mtty_dev.dev);
 err_put:
        put_device(&mtty_dev.dev);
-       class_destroy(mtty_dev.vd_class);
+       class_unregister(&mtty_class);
 err_driver:
        mdev_unregister_driver(&mtty_driver);
 err_cdev:
@@ -2026,8 +2028,7 @@ static void __exit mtty_dev_exit(void)
        mdev_unregister_driver(&mtty_driver);
        cdev_del(&mtty_dev.vd_cdev);
        unregister_chrdev_region(mtty_dev.vd_devt, MINORMASK + 1);
-       class_destroy(mtty_dev.vd_class);
-       mtty_dev.vd_class = NULL;
+       class_unregister(&mtty_class);
        pr_info("mtty_dev: Unloaded!\n");
 }