On Tue, Dec 03, 2024 at 09:11:47PM +0100, Heiner Kallweit wrote:
> vfio/mdev is the last user of class_compat, and it doesn't use it for
> the intended purpose. See kdoc of class_compat_register():
> Compatibility class are meant as a temporary user-space compatibility
> workaround when converting a family of class devices to a bus devices.
True, so waht is mdev doing here?
> In addition it uses only a part of the class_compat functionality.
> So inline the needed functionality, and afterwards all class_compat
> code can be removed.
>
> No functional change intended. Compile-tested only.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> ---
> drivers/vfio/mdev/mdev_core.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index ed4737de4..a22c49804 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -18,7 +18,7 @@
> #define DRIVER_AUTHOR "NVIDIA Corporation"
> #define DRIVER_DESC "Mediated device Core Driver"
>
> -static struct class_compat *mdev_bus_compat_class;
> +static struct kobject *mdev_bus_kobj;
>
> static LIST_HEAD(mdev_list);
> static DEFINE_MUTEX(mdev_list_lock);
> @@ -76,7 +76,7 @@ int mdev_register_parent(struct mdev_parent *parent, struct device *dev,
> if (ret)
> return ret;
>
> - ret = class_compat_create_link(mdev_bus_compat_class, dev, NULL);
> + ret = sysfs_create_link(mdev_bus_kobj, &dev->kobj, dev_name(dev));
This feels really wrong, why create a link to a random kobject? Who is
using this kobject link?
> if (ret)
> dev_warn(dev, "Failed to create compatibility class link\n");
>
> @@ -98,7 +98,7 @@ void mdev_unregister_parent(struct mdev_parent *parent)
> dev_info(parent->dev, "MDEV: Unregistering\n");
>
> down_write(&parent->unreg_sem);
> - class_compat_remove_link(mdev_bus_compat_class, parent->dev, NULL);
> + sysfs_remove_link(mdev_bus_kobj, dev_name(parent->dev));
> device_for_each_child(parent->dev, NULL, mdev_device_remove_cb);
> parent_remove_sysfs_files(parent);
> up_write(&parent->unreg_sem);
> @@ -251,8 +251,8 @@ static int __init mdev_init(void)
> if (ret)
> return ret;
>
> - mdev_bus_compat_class = class_compat_register("mdev_bus");
> - if (!mdev_bus_compat_class) {
> + mdev_bus_kobj = class_pseudo_register("mdev_bus");
But this isn't a class, so let's not fake it please. Let's fix this
properly, odds are all of this code can just be removed entirely, right?
thanks,
greg k-h
