Re: [PATCH v3 1/2] virtio-net: Describe dev cfg fields read only

[Cornelia Huck <cohuck@redhat.com>]

On Wed, Feb 22 2023, "Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Wed, Feb 22, 2023 at 10:01:24AM +0100, Cornelia Huck wrote:
>> On Tue, Feb 21 2023, "Michael S. Tsirkin" <mst@redhat.com> wrote:
>> 
>> > On Tue, Feb 21, 2023 at 05:59:52PM +0000, Parav Pandit wrote:
>> >> 
>> >> > From: Michael S. Tsirkin <mst@redhat.com>
>> >> > Sent: Tuesday, February 21, 2023 12:52 PM
>> >> > 
>> >> > On Tue, Feb 21, 2023 at 05:50:09PM +0000, Parav Pandit wrote:
>> >> > > Hence, it should be mentioned as read-only fields, so when the driver writes
>> >> > something to read-only fields, it can be considered as undefined behavior on
>> >> > such fields.
>> >> > >
>> >> > 
>> >> > In the description not in the normative statements. normative sections just tell
>> >> > driver what it must and must not do, in the standard RFC terms.
>> >> > 
>> >> Got it.
>> >> I will shift them as read-only in the description section.
>> >> And normative in the device and driver section.
>> >> Device section:
>> >> Any writes to config space fields is ignored by the device, because these are read-only fields for the driver.
>> >
>> > writes is plural so "are ignored"
>> >
>> > but more importantly use rfc terms in normative sections.
>> 
>> I don't think you need to talk about "read-only" in the normative
>> sections (that belongs to the descriptive sections.) I'd use
>> 
>> "The device MUST ignore any writes to config space fields by the
>> driver."
>
> Hmm. Is this something we previously required for read only fields?

So, better make it SHOULD?

(The only alternative to ignoring I see is breaking the device, and I
think ignoring is preferable.)

>
>
>> >
>> >> 
>> >> Driver section:
>> >> Driver must not write to read-only fields.
>> 
>> "The driver MUST NOT write to any config space field."