gpu: nova-core: add initial driver stub

Add the initial nova-core driver stub.

nova-core is intended to serve as a common base for nova-drm (the
corresponding DRM driver) and the vGPU manager VFIO driver, serving as a
hard- and firmware abstraction layer for GSP-based NVIDIA GPUs.

The Nova project, including nova-core and nova-drm, in the long term,
is intended to serve as the successor of Nouveau for all GSP-based GPUs.

The motivation for both, starting a successor project for Nouveau and
doing so using the Rust programming language, is documented in detail
through a previous post on the mailing list [1], an LWN article [2] and a
talk from LPC '24.

In order to avoid the chicken and egg problem to require a user to
upstream Rust abstractions, but at the same time require the Rust
abstractions to implement the driver, nova-core kicks off as a driver
stub and is subsequently developed upstream.

Link: https://lore.kernel.org/dri-devel/Zfsj0_tb-0-tNrJy@cassiopeiae/T/#u [1]
Link: https://lwn.net/Articles/990736/ [2]
Link: https://youtu.be/3Igmx28B3BQ?si=sBdSEer4tAPKGpOs [3]
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://lore.kernel.org/r/20250306222336.23482-5-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/drivers/gpu/nova-core/util.rs b/drivers/gpu/nova-core/util.rs
new file mode 100644
index 000000000000..332a64cfc6a9
--- /dev/null
+++ b/drivers/gpu/nova-core/util.rs
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0
+
+pub(crate) const fn to_lowercase_bytes<const N: usize>(s: &str) -> [u8; N] {
+    let src = s.as_bytes();
+    let mut dst = [0; N];
+    let mut i = 0;
+
+    while i < src.len() && i < N {
+        dst[i] = (src[i] as char).to_ascii_lowercase() as u8;
+        i += 1;
+    }
+
+    dst
+}
+
+pub(crate) const fn const_bytes_to_str(bytes: &[u8]) -> &str {
+    match core::str::from_utf8(bytes) {
+        Ok(string) => string,
+        Err(_) => kernel::build_error!("Bytes are not valid UTF-8."),
+    }
+}