Re: [PATCH v4 6/7] drm: nova: Use nova-core to read VRAM_BAR_SIZE parameter

[Danilo Krummrich]

On Tue Aug 11, 2026 at 7:06 AM CEST, Alistair Popple wrote:
> Currently nova-drm reads the VRAM BAR size directly from the PCIe device
> which requires trying to cast the parent device into a PCIe device. This
> obviously requires the parent device to actually be a PCIe bus device.
> Whilst that is true today it may not always be the case, and there
> is no reason to make this assumption now that NovaCoreApi can hold a
> reference to the bound PCIe device.
>
> So convert nova-drm to using nova-core to obtain the VRAM_BAR_SIZE
> parameter.
>
> Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>

Suggested-by: Danilo Krummrich <dakr@xxxxxxxxxx>

> @@ -33,16 +30,13 @@ fn open(_dev: &NovaDevice) -> Result<Pin<KBox<Self>>> {
>  impl File {
>      /// IOCTL: get_param: Query GPU / driver metadata.
>      pub(crate) fn get_param(
> -        dev: &NovaDevice<Registered>,
> -        _reg_data: &DrmRegData<'_>,
> +        _dev: &NovaDevice<Registered>,
> +        reg_data: &DrmRegData<'_>,
>          getparam: &mut uapi::drm_nova_getparam,
>          _file: &drm::File<File>,
>      ) -> Result<u32> {
> -        let adev: &auxiliary::Device<Bound> = dev.as_ref();
> -        let pdev: &pci::Device<Bound> = adev.parent().try_into()?;
> -
>          let value = match getparam.param as u32 {
> -            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => pdev.resource_len(1)?,
> +            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => reg_data.api.bar1_size()?,
>              _ => return Err(EINVAL),
>          };

That's much cleaner, thanks for adding this patch!

Once this landed we can remove the

	impl<Ctx: device::DeviceContext> TryFrom<&device::Device<Ctx>> for &Device<Ctx>

impl in rust/kernel/pci.rs. (I think platform should have the same impl to get
rid of independently.)

If your are interested, feel free to send a follow-up patch (or include it in
this series).