Virtio Spec question: Who modifies the used ring?

[Christoffer Dall <christoffer.dall@arm.com>]

Hi,

I was looking at the virtio spec (v1.0-cs04) and I'm confused
about section 2.4.8 "Virtqueue Used Ring".

It says, "idx field indicates where the driver would put the
next descriptor entry in the ring...".

Since this is the used ring, and is only supposed to be written by the
device, shouldn't the text say "...where the device would put..." ?

Or am I missing something fundamental?

Many thanks,
-Christoffer