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 <[email protected]>
Acked-by: Dave Airlie <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[ Kconfig: depend on DRM=y rather than just DRM. - Danilo ]
Signed-off-by: Danilo Krummrich <[email protected]>

1 files changed, 61 insertions, 0 deletions

diff --git a/drivers/gpu/drm/nova/uapi.rs b/drivers/gpu/drm/nova/uapi.rs
new file mode 100644
index 000000000000..eb228a58d423
--- /dev/null
+++ b/drivers/gpu/drm/nova/uapi.rs
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0
+
+use kernel::uapi;
+
+// TODO Work out some common infrastructure to avoid boilerplate code for uAPI abstractions.
+
+macro_rules! define_uapi_abstraction {
+    ($name:ident <= $inner:ty) => {
+        #[repr(transparent)]
+        pub struct $name(::kernel::types::Opaque<$inner>);
+
+        impl ::core::convert::From<&::kernel::types::Opaque<$inner>> for &$name {
+            fn from(value: &::kernel::types::Opaque<$inner>) -> Self {
+                // SAFETY: `Self` is a transparent wrapper of `$inner`.
+                unsafe { ::core::mem::transmute(value) }
+            }
+        }
+    };
+}
+
+define_uapi_abstraction!(Getparam <= uapi::drm_nova_getparam);
+
+impl Getparam {
+    pub fn param(&self) -> u64 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_getparam`.
+        unsafe { (*self.0.get()).param }
+    }
+
+    pub fn set_value(&self, v: u64) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_getparam`.
+        unsafe { (*self.0.get()).value = v };
+    }
+}
+
+define_uapi_abstraction!(GemCreate <= uapi::drm_nova_gem_create);
+
+impl GemCreate {
+    pub fn size(&self) -> u64 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_create`.
+        unsafe { (*self.0.get()).size }
+    }
+
+    pub fn set_handle(&self, handle: u32) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_create`.
+        unsafe { (*self.0.get()).handle = handle };
+    }
+}
+
+define_uapi_abstraction!(GemInfo <= uapi::drm_nova_gem_info);
+
+impl GemInfo {
+    pub fn handle(&self) -> u32 {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_info`.
+        unsafe { (*self.0.get()).handle }
+    }
+
+    pub fn set_size(&self, size: u64) {
+        // SAFETY: `self.get()` is a valid pointer to a `struct drm_nova_gem_info`.
+        unsafe { (*self.0.get()).size = size };
+    }
+}