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Date: Mon, 26 Oct 2026 13:11:47 +0100
Message-Id: <DMERDJZTGIN2.3GG2GSRWTLE2X@kernel.org>
Subject: Re: [PATCH] gpu: nova-core: make bar1 optional
Cc: <airlied@redhat.com>, "Alice Ryhl" <aliceryhl@google.com>, "Alexandre
 Courbot" <acourbot@nvidia.com>, "David Airlie" <airlied@gmail.com>, "Benno
 Lossin" <lossin@kernel.org>, "Gary Guo" <gary@garyguo.net>,
 <nova-gpu@lists.linux.dev>, <dri-devel@lists.freedesktop.org>
To: "Dave Airlie via B4 Relay" <devnull+airlied.redhat.com@kernel.org>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <20261026-nova-bar1-option-v1-1-8b43585881a3@redhat.com>
In-Reply-To: <20261026-nova-bar1-option-v1-1-8b43585881a3@redhat.com>

On Mon Oct 26, 2026 at 4:50 AM CET, Dave Airlie via B4 Relay wrote:
> @@ -135,7 +139,12 @@ fn probe<'bound>(
>                  // SAFETY: `bar` is initialized above, pinned, and outli=
ves `gpu`.
>                  unsafe { &*core::ptr::from_ref(bar) },
>                  // SAFETY: `bar1` is initialized above, pinned, and outl=
ives `gpu`.
> -                unsafe { &*core::ptr::from_ref(bar1) },
> +                unsafe {
> +                    match bar1 {
> +                        None =3D> None,
> +                        Some(bar1) =3D> Some(&*core::ptr::from_ref(bar1)=
),
> +                    }
> +                },

This can just be

	bar1.as_ref().map(|b| unsafe { &*core::ptr::from_ref(b) })

> +    /// BAR1 user interface for CPU access to GPU virtual memory, if the=
 device has BAR1.
> +    bar_user: Option<Pin<KBox<BarUser<'gpu>>>>,

Can we please add a TODO to replace this, once we can get rid of the extra
allocation?

> +            bar_user: match bar1 {
> +                None =3D> None,
> +                Some(bar1) =3D> Some({
> +                    let pdb_addr =3D VramAddress::from_raw(gsp_static_in=
fo.bar1_pde_base);
> +                    let bar1_idx =3D crate::driver::bar1_resource_index(=
pdev)?;
> +                    let bar1_size =3D pdev.resource_len(bar1_idx)?;
> +
> +                    KBox::pin_init(
> +                        BarUser::new(
> +                            pdb_addr,
> +                            gsp_resources.spec.chipset,
> +                            bar1_size,
> +                            bar1,
> +                        ),
> +                        GFP_KERNEL,
> +                    )?
> +                }),

I think this could also use map().