Re: [PATCH v4 2/2] docs: driver-api: virtio: virtio on Linux

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Aug 11, 2022 at 03:46:46PM +0200, Cornelia Huck wrote:
> On Wed, Aug 10 2022, Ricardo Cañuelo <ricardo.canuelo@collabora.com> wrote:
> 
> > Basic doc about Virtio on Linux and a short tutorial on Virtio drivers.
> >
> > Signed-off-by: Ricardo Cañuelo <ricardo.canuelo@collabora.com>
> > ---
> >  Documentation/driver-api/index.rst            |   1 +
> >  Documentation/driver-api/virtio/index.rst     |  11 ++
> >  Documentation/driver-api/virtio/virtio.rst    | 144 ++++++++++++++
> >  .../virtio/writing_virtio_drivers.rst         | 186 ++++++++++++++++++
> >  MAINTAINERS                                   |   1 +
> >  5 files changed, 343 insertions(+)
> >  create mode 100644 Documentation/driver-api/virtio/index.rst
> >  create mode 100644 Documentation/driver-api/virtio/virtio.rst
> >  create mode 100644 Documentation/driver-api/virtio/writing_virtio_drivers.rst
> >
> 
> (...)
> 
> > +.. rubric:: Footnotes
> > +
> > +.. [#f1] that's why they may be also referred as virtrings.
> 
> "referred to"
> 
> (...)
> 
> > +The ``probe`` method does the minimum driver setup in this case
> > +(memory allocation for the device data) and initializes the
> > +virtqueue. The virtqueues are automatically enabled after ``probe``
> > +returns, sending the appropriate "DRIVER_OK" status signal to the
> > +device. If the virtqueues need to be enabled before ``probe`` ends, they
> > +can be manually enabled by calling virtio_device_ready():
> > +
> > +.. kernel-doc:: include/linux/virtio_config.h
> > +    :identifiers: virtio_device_ready
> 
> Hm, not quite sure what the actual expectations are here: Should the
> driver set DRIVER_OK in its probe function, and the core only set it as
> a fallback? Michael, Jason?
> 
> (...)
> 
> LGTM in general.

Generally driver should either call device_ready
or defer adding device to linux in a scan callback.

Doing neither is likely a bug since you might
then be asked to add buffers before DRIVER_OK is set,
though e.g. if you are interrupt driven things might work
correctly.

-- 
MST