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Date:   Thu, 27 Jun 2019 10:21:07 +0200
From:   Cornelia Huck <cohuck@redhat.com>
To:     Kirti Wankhede <kwankhede@nvidia.com>
Cc:     Alex Williamson <alex.williamson@redhat.com>,
        <kvm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mdev: Send uevents around parent device registration
Message-ID: <20190627102107.3c7715d9.cohuck@redhat.com>
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On Thu, 27 Jun 2019 00:33:59 +0530
Kirti Wankhede <kwankhede@nvidia.com> wrote:

> On 6/26/2019 11:35 PM, Alex Williamson wrote:
> > On Wed, 26 Jun 2019 23:23:00 +0530
> > Kirti Wankhede <kwankhede@nvidia.com> wrote:
> >   
> >> On 6/26/2019 7:57 PM, Alex Williamson 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";
> >>> +	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);
> >>> +    
> >>
> >> Its good to have udev event, but don't remove debug print from dmesg.
> >> Same for unregister.  
> > 
> > Who consumes these?  They seem noisy.  Thanks,
> >   
> 
> I don't think its noisy, its more of logging purpose. This is seen in
> kernel log only when physical device is registered to mdev.

Yes; but why do you want to log success? If you need to log it
somewhere, wouldn't a trace event be a much better choice?