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

[Tian, Kevin]

> From: Jason Gunthorpe <jgg at ziepe.ca>
> Sent: Wednesday, August 31, 2022 7:53 AM
> 
> On Tue, Aug 30, 2022 at 04:18:38PM -0600, Alex Williamson wrote:
> > On Sun, 28 Aug 2022 01:10:37 +0800
> > Kevin Tian <kevin.tian at intel.com> wrote:
> >
> > > From: Yi Liu <yi.l.liu at 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.
> >
> > Shall we start Documentation/ABI/testing/vfio-dev now?  Thanks.
> 
> I always thought that was something to use when adding new custom
> sysfs attributes?
> 
> Here we are just creating a standard struct device with its standard
> sysfs?
> 

There is nothing special for vfio-dev/vfioX. But from pci device p.o.v
this does introduce a custom node in the directory, which is probably
what Alex referred to?

Anyway if required following can be introduced:

diff --git a/Documentation/ABI/testing/sysfs-devices-vfio-dev b/Documentation/ABI/testing/sysfs-devices-vfio-dev
new file mode 100644
index 000000000000..dfe8baaf1ccb
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-vfio-dev
@@ -0,0 +1,8 @@
+What:		 /sys/.../<device>/vfio-dev/vfioX/
+Date:		 September 2022
+Contact:	 Yi Liu <yi.l.liu at intel.com>
+Description:
+		 This directory is created when the device is bound to a
+		 vfio driver. The layout under this directory matches what
+		 exists for a standard 'struct device'. 'X' is a random
+		 number marking this device in vfio.

At the start I thought it might make more sense to add it into an
existing vfio ABI file. But looks it doesn't exist.

Curious why nobody asked for ABI doc for /dev/vfio/vfio, /sys/class/vfio, etc...

Thanks
Kevin