[PATCH v5 2/3] gpu: nova-core: make Architecture behave as a u8 type

[John Hubbard <jhubbard@nvidia.com>]

This allows Architecture to be passed into register!() and bitfield!()
macro calls. That in turn requires a default implementation for
Architecture.

This simplifies transforming BOOT0 (and later, BOOT42) register values
into GPU architectures.

Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Timur Tabi <ttabi@nvidia.com>
Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 drivers/gpu/nova-core/gpu.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index 8173cdcd8378..27b8926977da 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -109,8 +109,10 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 /// Enum representation of the GPU generation.
-#[derive(fmt::Debug)]
+#[derive(fmt::Debug, Default)]
+#[repr(u8)]
 pub(crate) enum Architecture {
+    #[default]
     Turing = 0x16,
     Ampere = 0x17,
     Ada = 0x19,
@@ -129,6 +131,13 @@ fn try_from(value: u8) -> Result<Self> {
     }
 }
 
+impl From<Architecture> for u8 {
+    fn from(value: Architecture) -> Self {
+        // CAST: `Architecture` is `repr(u8)`, so this cast is always lossless.
+        value as u8
+    }
+}
+
 pub(crate) struct Revision {
     pub(crate) major: u8,
     pub(crate) minor: u8,
-- 
2.51.2