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

[Greg KH <gregkh@linuxfoundation.org>]

On Sun, Mar 08, 2026 at 02:37:33PM +0100, Jori Koolstra 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 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>
> ---
>  samples/vfio-mdev/mtty.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index bd92c38379b8..792f5c212fd1 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -68,13 +68,16 @@
>   * 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;
> -	struct mdev_parent parent;
> +	dev_t			vd_devt;
> +	struct cdev		vd_cdev;
> +	struct idr		vd_idr;
> +	struct device		dev;
> +	struct mdev_parent	parent;

No need to reformat this structure :(

thanks,

greg k-h