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, 74 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nova/file.rs b/drivers/gpu/drm/nova/file.rs
new file mode 100644
index 000000000000..7e59a34b830d
--- /dev/null
+++ b/drivers/gpu/drm/nova/file.rs
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use crate::driver::{NovaDevice, NovaDriver};
+use crate::gem::NovaObject;
+use crate::uapi::{GemCreate, GemInfo, Getparam};
+use kernel::{
+    alloc::flags::*,
+    drm::{self, gem::BaseObject},
+    pci,
+    prelude::*,
+    types::Opaque,
+    uapi,
+};
+
+pub(crate) struct File;
+
+impl drm::file::DriverFile for File {
+    type Driver = NovaDriver;
+
+    fn open(_dev: &NovaDevice) -> Result<Pin<KBox<Self>>> {
+        Ok(KBox::new(Self, GFP_KERNEL)?.into())
+    }
+}
+
+impl File {
+    /// IOCTL: get_param: Query GPU / driver metadata.
+    pub(crate) fn get_param(
+        dev: &NovaDevice,
+        getparam: &Opaque<uapi::drm_nova_getparam>,
+        _file: &drm::File<File>,
+    ) -> Result<u32> {
+        let adev = &dev.adev;
+        let parent = adev.parent().ok_or(ENOENT)?;
+        let pdev: &pci::Device = parent.try_into()?;
+        let getparam: &Getparam = getparam.into();
+
+        let value = match getparam.param() as u32 {
+            uapi::NOVA_GETPARAM_VRAM_BAR_SIZE => pdev.resource_len(1)?,
+            _ => return Err(EINVAL),
+        };
+
+        getparam.set_value(value);
+
+        Ok(0)
+    }
+
+    /// IOCTL: gem_create: Create a new DRM GEM object.
+    pub(crate) fn gem_create(
+        dev: &NovaDevice,
+        req: &Opaque<uapi::drm_nova_gem_create>,
+        file: &drm::File<File>,
+    ) -> Result<u32> {
+        let req: &GemCreate = req.into();
+        let obj = NovaObject::new(dev, req.size().try_into()?)?;
+
+        req.set_handle(obj.create_handle(file)?);
+
+        Ok(0)
+    }
+
+    /// IOCTL: gem_info: Query GEM metadata.
+    pub(crate) fn gem_info(
+        _dev: &NovaDevice,
+        req: &Opaque<uapi::drm_nova_gem_info>,
+        file: &drm::File<File>,
+    ) -> Result<u32> {
+        let req: &GemInfo = req.into();
+        let bo = NovaObject::lookup_handle(file, req.handle())?;
+
+        req.set_size(bo.size().try_into()?);
+
+        Ok(0)
+    }
+}