Re: [PATCH v5 05/11] drm: nova: Add an info ioctl

[Danilo Krummrich]

On Tue Sep 1, 2026 at 7:09 AM CEST, Alistair Popple wrote:
> On 2026-09-01 at 14:50 +1000, Dave Airlie <airlied@xxxxxxxxx> wrote...
>> > >
>> > > We should make the NovaCoreApi just provide an accessor for &Spec and make every
>> > > subsequent method we need public. Otherwise we end up with endless forwarding
>> > > methods. We can also add as_raw() methods to the specific types as needed.
>> >
>> > Ok. This is where I don't have a good instinct for what we think should be an
>> > accessor/forwarding method vs. where we should just expose the underlying data
>> > structure and required methods to API users.
>> >
>> > In the past it seems there's been some resistance to exposing nova-core or gsp
>> > data structures like this which is why I added the forwarding methods. In future
>> > we're going to have other data-structures that NovaCoreApi will need to access
>> > so it would be good to understand what we should do here so we can keep things
>> > somewhat consistent.
>> 
>> We can expose structure defined in nova-core, we cannot expose
>> structures defined in gsp bindings or firmware.

Yes, those structures are not even exposed to the nova-core layers we are
dealing with here.

There are the structures abstracting firmware interfaces, but despite exposing
trivial cached values, they should not exposed to nova-drm either.

Instead nova-drm should call into nova-core and ask it to do things on its
behalf.

More in general, the same is true for any other device resources. For instance,
we also should not expose the pci::Device or the pci::Bar to nova-drm, but again
provide a higher level API.

> All the fields of self.gpu are structures defined as rust native structures in
> nova-core. Their values may be decoded or derived from GSP responses, but by
> design none of the raw structures from gsp bindings live in self.gpu AFAIK.

We could indeed expose all values from struct Gpu directly and control
everything through visibility, but ...

>> In theory we can internally between core/drm but I'd really really
>> like to keep that boundary as the limits of GSP for auditability
>> purposes.

... exposing struct Gpu and controlling everything through visibility still
means that we could easily miss some device resource being exposed directly to
nova-drm, which also includes GSP abstractions.

So, I think we should provide accessors for the major structures that we
intentionally want to expose (so we have an obvious boundary), but not for every
single fields inside them.

This is also why I said that we can expose an accessor for struct Spec, which I
think serves as a good example.