drm: nova-drm: add initial driver skeleton

Add the initial nova-drm driver skeleton.

nova-drm is connected to nova-core through the auxiliary bus and
implements the DRM parts of the nova driver stack.

For now, it implements the fundamental DRM abstractions, i.e. creates a
DRM device and registers it, exposing a three sample IOCTLs.

  DRM_IOCTL_NOVA_GETPARAM
    - provides the PCI bar size from the bar that maps the GPUs VRAM
      from nova-core

  DRM_IOCTL_NOVA_GEM_CREATE
    - creates a new dummy DRM GEM object and returns a handle

  DRM_IOCTL_NOVA_GEM_INFO
    - provides metadata for the DRM GEM object behind a given handle

I implemented a small userspace test suite [1] that utilizes this
interface.

Link: https://gitlab.freedesktop.org/dakr/drm-test [1]
Reviewed-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Dave Airlie <airlied@redhat.com>
Link: https://lore.kernel.org/r/20250424160452.8070-3-dakr@kernel.org
[ Kconfig: depend on DRM=y rather than just DRM. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

drivers/gpu/drm/nova/driver.rs

@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::{auxiliary, c_str, device::Core, drm, drm::gem, drm::ioctl, prelude::*, types::ARef};
+
+use crate::file::File;
+use crate::gem::NovaObject;
+
+pub(crate) struct NovaDriver {
+    #[expect(unused)]
+    drm: ARef<drm::Device<Self>>,
+}
+
+/// Convienence type alias for the DRM device type for this driver
+pub(crate) type NovaDevice = drm::Device<NovaDriver>;
+
+#[pin_data]
+pub(crate) struct NovaData {
+    pub(crate) adev: ARef<auxiliary::Device>,
+}
+
+const INFO: drm::DriverInfo = drm::DriverInfo {
+    major: 0,
+    minor: 0,
+    patchlevel: 0,
+    name: c_str!("nova"),
+    desc: c_str!("Nvidia Graphics"),
+};
+
+const NOVA_CORE_MODULE_NAME: &CStr = c_str!("NovaCore");
+const AUXILIARY_NAME: &CStr = c_str!("nova-drm");
+
+kernel::auxiliary_device_table!(
+    AUX_TABLE,
+    MODULE_AUX_TABLE,
+    <NovaDriver as auxiliary::Driver>::IdInfo,
+    [(
+        auxiliary::DeviceId::new(NOVA_CORE_MODULE_NAME, AUXILIARY_NAME),
+        ()
+    )]
+);
+
+impl auxiliary::Driver for NovaDriver {
+    type IdInfo = ();
+    const ID_TABLE: auxiliary::IdTable<Self::IdInfo> = &AUX_TABLE;
+
+    fn probe(adev: &auxiliary::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self>>> {
+        let data = try_pin_init!(NovaData { adev: adev.into() });
+
+        let drm = drm::Device::<Self>::new(adev.as_ref(), data)?;
+        drm::Registration::new_foreign_owned(&drm, adev.as_ref(), 0)?;
+
+        Ok(KBox::new(Self { drm }, GFP_KERNEL)?.into())
+    }
+}
+
+#[vtable]
+impl drm::Driver for NovaDriver {
+    type Data = NovaData;
+    type File = File;
+    type Object = gem::Object<NovaObject>;
+
+    const INFO: drm::DriverInfo = INFO;
+
+    kernel::declare_drm_ioctls! {
+        (NOVA_GETPARAM, drm_nova_getparam, ioctl::RENDER_ALLOW, File::get_param),
+        (NOVA_GEM_CREATE, drm_nova_gem_create, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_create),
+        (NOVA_GEM_INFO, drm_nova_gem_info, ioctl::AUTH | ioctl::RENDER_ALLOW, File::gem_info),
+    }
+}