[PATCH v7 3/4] 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 | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
index acf564fee9c8..cd58040b681b 100644
--- a/drivers/gpu/nova-core/gpu.rs
+++ b/drivers/gpu/nova-core/gpu.rs
@@ -122,8 +122,14 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 }
 
 /// Enum representation of the GPU generation.
-#[derive(fmt::Debug)]
+///
+/// TODO: remove the `Default` trait implementation, and the `#[default]`
+/// attribute, once the register!() macro (which creates Architecture items) no
+/// longer requires it for read-only fields.
+#[derive(fmt::Debug, Default, Copy, Clone)]
+#[repr(u8)]
 pub(crate) enum Architecture {
+    #[default]
     Turing = 0x16,
     Ampere = 0x17,
     Ada = 0x19,
@@ -142,6 +148,13 @@ 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