On Wed, Feb 19, 2020 at 09:11:02AM -0400, Jason Gunthorpe wrote:
> On Wed, Feb 19, 2020 at 10:52:38AM +0800, Tiwei Bie wrote:
> > > > +static int __init vhost_vdpa_init(void)
> > > > +{
> > > > + int r;
> > > > +
> > > > + idr_init(&vhost_vdpa.idr);
> > > > + mutex_init(&vhost_vdpa.mutex);
> > > > + init_waitqueue_head(&vhost_vdpa.release_q);
> > > > +
> > > > + /* /dev/vhost-vdpa/$vdpa_device_index */
> > > > + vhost_vdpa.class = class_create(THIS_MODULE, "vhost-vdpa");
> > > > + if (IS_ERR(vhost_vdpa.class)) {
> > > > + r = PTR_ERR(vhost_vdpa.class);
> > > > + goto err_class;
> > > > + }
> > > > +
> > > > + vhost_vdpa.class->devnode = vhost_vdpa_devnode;
> > > > +
> > > > + r = alloc_chrdev_region(&vhost_vdpa.devt, 0, MINORMASK + 1,
> > > > + "vhost-vdpa");
> > > > + if (r)
> > > > + goto err_alloc_chrdev;
> > > > +
> > > > + cdev_init(&vhost_vdpa.cdev, &vhost_vdpa_fops);
> > > > + r = cdev_add(&vhost_vdpa.cdev, vhost_vdpa.devt, MINORMASK + 1);
> > > > + if (r)
> > > > + goto err_cdev_add;
> > >
> > > It is very strange, is the intention to create a single global char
> > > dev?
> >
> > No. It's to create a per-vdpa char dev named
> > vhost-vdpa/$vdpa_device_index in dev.
> >
> > I followed the code in VFIO which creates char dev
> > vfio/$GROUP dynamically, e.g.:
> >
> > https://github.com/torvalds/linux/blob/b1da3acc781c/drivers/vfio/vfio.c#L2164-L2180
> > https://github.com/torvalds/linux/blob/b1da3acc781c/drivers/vfio/vfio.c#L373-L387
> > https://github.com/torvalds/linux/blob/b1da3acc781c/drivers/vfio/vfio.c#L1553
> >
> > Is it something unwanted?
>
> Yes it is unwanted. This is some special pattern for vfio's unique
> needs.
>
> Since this has a struct device for each char dev instance please use
> the normal cdev_device_add() driven pattern here, or justify why it
> needs to be special like this.
I see. Thanks! I will embed the cdev in each vhost_vdpa
structure directly.
Regards,
Tiwei
>
> Jason
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