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Date:   Thu, 27 Jun 2019 10:19:14 +0200
From:   Cornelia Huck <cohuck@redhat.com>
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     kwankhede@nvidia.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mdev: Send uevents around parent device registration
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On Wed, 26 Jun 2019 08:27:58 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:

> This allows udev to trigger rules when a parent device is registered
> or unregistered from mdev.
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/vfio/mdev/mdev_core.c |   10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> index ae23151442cb..ecec2a3b13cb 100644
> --- a/drivers/vfio/mdev/mdev_core.c
> +++ b/drivers/vfio/mdev/mdev_core.c
> @@ -146,6 +146,8 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
>  {
>  	int ret;
>  	struct mdev_parent *parent;
> +	char *env_string = "MDEV_STATE=registered";

This string is probably reasonable enough.

> +	char *envp[] = { env_string, NULL };
>  
>  	/* check for mandatory ops */
>  	if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
> @@ -196,7 +198,8 @@ int mdev_register_device(struct device *dev, const struct mdev_parent_ops *ops)
>  	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);

I also agree with the positioning here.

> +
>  	return 0;
>  
>  add_dev_err:
> @@ -220,6 +223,8 @@ EXPORT_SYMBOL(mdev_register_device);
>  void mdev_unregister_device(struct device *dev)
>  {
>  	struct mdev_parent *parent;
> +	char *env_string = "MDEV_STATE=unregistered";

Ok.

> +	char *envp[] = { env_string, NULL };
>  
>  	mutex_lock(&parent_list_lock);
>  	parent = __find_parent_device(dev);
> @@ -228,7 +233,6 @@ void mdev_unregister_device(struct device *dev)
>  		mutex_unlock(&parent_list_lock);
>  		return;
>  	}
> -	dev_info(dev, "MDEV: Unregistering\n");
>  
>  	list_del(&parent->next);
>  	mutex_unlock(&parent_list_lock);
> @@ -243,6 +247,8 @@ void mdev_unregister_device(struct device *dev)
>  	up_write(&parent->unreg_sem);
>  
>  	mdev_put_parent(parent);
> +
> +	kobject_uevent_env(&dev->kobj, KOBJ_CHANGE, envp);

I'm wondering whether we should indicate this uevent earlier: Once we
have detached from the parent list, we're basically done for all
practical purposes. So maybe move this right before we grab the
unreg_sem?

>  }
>  EXPORT_SYMBOL(mdev_unregister_device);
>  
>