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, 101 insertions, 0 deletions

diff --git a/include/uapi/drm/nova_drm.h b/include/uapi/drm/nova_drm.h
new file mode 100644
index 000000000000..3ca90ed9d2bb
--- /dev/null
+++ b/include/uapi/drm/nova_drm.h
@@ -0,0 +1,101 @@
+/* SPDX-License-Identifier: MIT */
+
+#ifndef __NOVA_DRM_H__
+#define __NOVA_DRM_H__
+
+#include "drm.h"
+
+/* DISCLAIMER: Do not use, this is not a stable uAPI.
+ *
+ * This uAPI serves only testing purposes as long as this driver is still in
+ * development. It is required to implement and test infrastructure which is
+ * upstreamed in the context of this driver. See also [1].
+ *
+ * [1] https://lore.kernel.org/dri-devel/Zfsj0_tb-0-tNrJy@cassiopeiae/T/#u
+ */
+
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+/*
+ * NOVA_GETPARAM_VRAM_BAR_SIZE
+ *
+ * Query the VRAM BAR size in bytes.
+ */
+#define NOVA_GETPARAM_VRAM_BAR_SIZE	0x1
+
+/**
+ * struct drm_nova_getparam - query GPU and driver metadata
+ */
+struct drm_nova_getparam {
+	/**
+	 * @param: The identifier of the parameter to query.
+	 */
+	__u64 param;
+
+	/**
+	 * @value: The value for the specified parameter.
+	 */
+	__u64 value;
+};
+
+/**
+ * struct drm_nova_gem_create - create a new DRM GEM object
+ */
+struct drm_nova_gem_create {
+	/**
+	 * @handle: The handle of the new DRM GEM object.
+	 */
+	__u32 handle;
+
+	/**
+	 * @pad: 32 bit padding, should be 0.
+	 */
+	__u32 pad;
+
+	/**
+	 * @size: The size of the new DRM GEM object.
+	 */
+	__u64 size;
+};
+
+/**
+ * struct drm_nova_gem_info - query DRM GEM object metadata
+ */
+struct drm_nova_gem_info {
+	/**
+	 * @handle: The handle of the DRM GEM object to query.
+	 */
+	__u32 handle;
+
+	/**
+	 * @pad: 32 bit padding, should be 0.
+	 */
+	__u32 pad;
+
+	/**
+	 * @size: The size of the DRM GEM obejct.
+	 */
+	__u64 size;
+};
+
+#define DRM_NOVA_GETPARAM		0x00
+#define DRM_NOVA_GEM_CREATE		0x01
+#define DRM_NOVA_GEM_INFO		0x02
+
+/* Note: this is an enum so that it can be resolved by Rust bindgen. */
+enum {
+	DRM_IOCTL_NOVA_GETPARAM		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GETPARAM,
+						   struct drm_nova_getparam),
+	DRM_IOCTL_NOVA_GEM_CREATE	= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GEM_CREATE,
+						   struct drm_nova_gem_create),
+	DRM_IOCTL_NOVA_GEM_INFO		= DRM_IOWR(DRM_COMMAND_BASE + DRM_NOVA_GEM_INFO,
+						   struct drm_nova_gem_info),
+};
+
+#if defined(__cplusplus)
+}
+#endif
+
+#endif /* __NOVA_DRM_H__ */