RE: [PATCH v3 15/15] vfio: Add struct device to vfio_device

From: "Tian, Kevin" <kevin.tian@intel.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: Matthew Rosato <mjrosato@linux.ibm.com>,
	David Airlie <airlied@linux.ie>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Kirti Wankhede <kwankhede@nvidia.com>,
	Vineeth Vijayan <vneethv@linux.ibm.com>,
	Diana Craciun <diana.craciun@oss.nxp.com>,
	Alexander Gordeev <agordeev@linux.ibm.com>,
	Longfang Liu <liulongfang@huawei.com>,
	Christoph Hellwig <hch@infradead.org>,
	"Liu, Yi L" <yi.l.liu@intel.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	Leon Romanovsky <leon@kernel.org>,
	Halil Pasic <pasic@linux.ibm.com>, Jason Gunthorpe <jgg@ziepe.ca>,
	Christian Borntraeger <borntraeger@linux.ibm.com>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"Wang, Zhi A" <zhi.a.wang@intel.com>,
	Tony Krowiak <akrowiak@linux.ibm.com>,
	Eric Farman <farman@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	"linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
	Heiko Carstens <hca@linux.ibm.com>,
	Eric Auger <eric.auger@redhat.com>,
	Harald Freudenberger <freude@linux.ibm.com>,
	"Vivi, Rodrigo" <rodrigo.vivi@intel.com>,
	"intel-gvt-dev@lists.freedesktop.org"
	<intel-gvt-dev@lists.freedesktop.org>,
	Jason Herne <jjherne@linux.ibm.com>,
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
	Yishai Hadas <yishaih@nvidia.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Peter Oberparleiter <oberpar@linux.ibm.com>,
	Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	Sven Schnelle <svens@linux.ibm.com>,
	Abhishek Sahu <abhsahu@nvidia.com>
Subject: RE: [PATCH v3 15/15] vfio: Add struct device to vfio_device
Date: Tue, 20 Sep 2022 22:55:40 +0000	[thread overview]
Message-ID: <BN9PR11MB5276484952784F5E336814BD8C4C9@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20220920142639.29b1bdc2.alex.williamson@redhat.com>

> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Wednesday, September 21, 2022 4:27 AM
> 
> On Fri,  9 Sep 2022 18:22:47 +0800
> Kevin Tian <kevin.tian@intel.com> wrote:
> 
> > From: Yi Liu <yi.l.liu@intel.com>
> >
> > and replace kref. With it a 'vfio-dev/vfioX' node is created under the
> > sysfs path of the parent, indicating the device is bound to a vfio
> > driver, e.g.:
> >
> > /sys/devices/pci0000\:6f/0000\:6f\:01.0/vfio-dev/vfio0
> >
> > It is also a preparatory step toward adding cdev for supporting future
> > device-oriented uAPI.
> >
> > Add Documentation/ABI/testing/sysfs-devices-vfio-dev.
> >
> > Also take this chance to rename chardev 'vfio' to 'vfio-group' in
> > /proc/devices.
> 
> What's the risk/reward here, is this just more aesthetically pleasing
> symmetry vs 'vfio-dev'?  The char major number to name association in
> /proc/devices seems pretty obscure, but what due diligence have we done
> to make sure this doesn't break anyone?  Thanks,
> 

I'm not sure whether the content of /proc/devices is considered as ABI.

@Jason?

But to be safe I can remove this change in next version. If it's the right
thing to do such change after discussion then it can be done in a separate
patch after.