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>

1 files changed, 49 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nova/gem.rs b/drivers/gpu/drm/nova/gem.rs
new file mode 100644
index 000000000000..33b62d21400c
--- /dev/null
+++ b/drivers/gpu/drm/nova/gem.rs
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::{
+    drm,
+    drm::{gem, gem::BaseObject},
+    prelude::*,
+    types::ARef,
+};
+
+use crate::{
+    driver::{NovaDevice, NovaDriver},
+    file::File,
+};
+
+/// GEM Object inner driver data
+#[pin_data]
+pub(crate) struct NovaObject {}
+
+impl gem::BaseDriverObject<gem::Object<NovaObject>> for NovaObject {
+    fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> {
+        try_pin_init!(NovaObject {})
+    }
+}
+
+impl gem::DriverObject for NovaObject {
+    type Driver = NovaDriver;
+}
+
+impl NovaObject {
+    /// Create a new DRM GEM object.
+    pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self>>> {
+        let aligned_size = size.next_multiple_of(1 << 12);
+
+        if size == 0 || size > aligned_size {
+            return Err(EINVAL);
+        }
+
+        gem::Object::new(dev, aligned_size)
+    }
+
+    /// Look up a GEM object handle for a `File` and return an `ObjectRef` for it.
+    #[inline]
+    pub(crate) fn lookup_handle(
+        file: &drm::File<File>,
+        handle: u32,
+    ) -> Result<ARef<gem::Object<Self>>> {
+        gem::Object::lookup_handle(file, handle)
+    }
+}