Re: [RFC PATCH] virtio_console: link vq to port with a private pointerin struct virtqueue
From: Paolo Bonzini
Date: Wed Apr 18 2012 - 10:34:22 EST
Il 18/04/2012 16:21, Michael S. Tsirkin ha scritto:
>> @@ -1872,6 +1864,8 @@ static int virtcons_restore(struct virtio_device *vdev)
>> list_for_each_entry(port, &portdev->ports, list) {
>> port->in_vq = portdev->in_vqs[port->id];
>> port->out_vq = portdev->out_vqs[port->id];
>> + port->in_vq->vdev_priv = port;
>> + port->out_vq->vdev_priv = port;
>>
>> fill_queue(port->in_vq, &port->inbuf_lock);
>>
>
> Let's add an API to set this pointer.
> Document that you must not set it after
> probe/restore returned.
Why?
> With an API we can actually have a BUG_ON that checks it's not modified
> after probe.
>
>> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
>> index c193ccf..6b39c1a 100644
>> --- a/include/linux/virtio.h
>> +++ b/include/linux/virtio.h
>> @@ -14,6 +14,7 @@
>> * @callback: the function to call when buffers are consumed (can be NULL).
>> * @name: the name of this virtqueue (mainly for debugging)
>> * @vdev: the virtio device this queue was created for.
>> + * @vdev_priv: a pointer for the virtio device to use.
>
> It's for the driver actually.
Right. However...
>> * @priv: a pointer for the virtqueue implementation to use.
>> */
>> struct virtqueue {
>> @@ -21,6 +22,7 @@ struct virtqueue {
>> void (*callback)(struct virtqueue *vq);
>> const char *name;
>> struct virtio_device *vdev;
>> + void *vdev_priv;
>> void *priv;
>
> The name is confusing: it seems to imply it's a device pointer.
... it's private to the driver that owns vdev, hence the name.
> Maybe we should rename priv to something like __priv and make
> priv useful for devices?
I wanted to go for the smallest possible changes. Right now we have 1
user for each member (virtio-ring vs. virtio-console) so neither member
is really dominating.
Paolo
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