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

["Danilo Krummrich" <dakr@kernel.org>]

On Fri Sep 4, 2026 at 1:13 PM CEST, Gary Guo wrote:
> You mentioned in an earlier email about the typing, but we could still have
> meaningful impl IDs fully typed like this:
>
>     pub enum Arch {
>         Turing(impl_id),
>         Ampere(impl_id),
>         ...
>     }
>
> and some langauges can do better, e.g. TypeScript allow you to write
>
>     enumn ArchId {
>         Turing,
>         Ampere,
>         ...
>     }
>
>     enum TuringImplId { ... }
>     enum AmpereImplId { ... }
>
>     type Id =
>         { arch: ArchId.Turing, impl: TuringImplId } |
>         { arch: ArchId.Ampere, impl: AmpereImplId };
>
> So I think it's a reasonable design to have it.

Of course we could encode this implementation detail, but I think there's no
reason to do so.

For instance currently we refer to GA100 as

	Chipset::GA100

but with the above we'd refer to GA100 as

	Arch::Ampere(AmpereImpl::GA100)

which is not buying us anything, is it?

It also would be confusing because both the architecture and the specific chip
would now be both represented by a type called Arch.

> True, but I think the chip ID is as bad as impl ID. Feature detections should
> use dedicated featuire detection mechanism, not looking up IDs directly. I.e. we
> should have userspace not having to use either chip ID or impl ID as much as we
> can.

This I agree with, which is also why I mentioned we should export SM if GSP
already provides it to us.

> That said, I do think looking up tables are unavoidable, for getting names or
> applying some quirk fixes. And I agree with Alistair that if we include it,
> including impl ID is better than the chip ID, as we should rather not having
> user space relying on an arbitrary encoded chip ID.

No, the only thing userspace ever uses to distinguish between things is either
by architecture or by chip. If we instead provide architecture and some ID
userspace will just go

	if (arch == Ampere && id == 0)
		chip = GA100;
	else if (arch == Ampere && id == 2)
		chip = GA102;
	[...]

and after that never care about the ID again. Whereas with giving userspace the
chip and architecture as separate fields userspace is done.