Re: [PATCH v8 1/4] virtio-rtc: Add initial device specification

[Cornelia Huck <cohuck@redhat.com>]

On Tue, Apr 15 2025, Peter Hilber <quic_philber@quicinc.com> wrote:

> On Tue, Apr 15, 2025 at 03:43:30PM +0200, Cornelia Huck wrote:
>> On Thu, Mar 06 2025, Peter Hilber <quic_philber@quicinc.com> wrote:
>> 
>> > The virtio-rtc device provides information about current time through
>> > one or more clocks. As such, it is a Real-Time Clock (RTC) device.
>> >
>> > The normative statements for this device follow in the next patch.
>> >
>> > For this device, there is an RFC Linux kernel driver which is being
>> > upstreamed, and a proprietary device implementation.
>> >
>> > Miscellaneous
>> > -------------
>> >
>> > The spec does not specify how a driver should interpret clock readings,
>> > esp. also not how to perform clock synchronization.
>> >
>> > The device uses the "Timer/Clock" device id which is already part of the
>> > specification. This device id was registered a long time ago and should
>> > be unused according to the author's information. The name "RTC" was
>> > determined to be the best for a device which focuses on current time.
>> >
>> > Signed-off-by: Peter Hilber <quic_philber@quicinc.com>
>> 
>> (...)
>> 
>> [First of all, apologies for the very late feedback...]
>> 
>> > +The \field{status} field indicates whether the device successfully
>> > +executed the request. The device sets the \field{status} field to one of
>> > +the following values:
>> > +
>> > +\begin{lstlisting}
>> > +#define VIRTIO_RTC_S_OK         0
>> > +#define VIRTIO_RTC_S_EOPNOTSUPP 2
>> > +#define VIRTIO_RTC_S_ENODEV     3
>> > +#define VIRTIO_RTC_S_EINVAL     4
>> > +#define VIRTIO_RTC_S_EIO        5
>> > +\end{lstlisting}
>> 
>> Any reason there's no status code 1 here? (I assume there used to be
>> one... not a real problem, I just stumbled over it.)
>> 
>
> Status code 1 would be the same as VIRTIO_NET_ERR.
>
> In the past, there was some discussion about reusing the spec in the net
> device, so I changed the status values to align with the net control
> virtqueue ack values. I am not sure if this will be helpful, should the
> net device reuse ever materialize, since AFAIU the admin queue might
> be used instead of the net control virtqueue.

Thanks for the explanation -- I think it's fine to just leave it as it
is now, the important thing is that the values are specified.