linux-kernel - [PATCH 3/9] gpu: nova-core: gsp: simplify sequencer opcode parsing

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Message-Id: <20251208-nova-misc-v1-3-a3ce01376169@nvidia.com>
Date: Mon, 08 Dec 2025 18:26:55 +0900
From: Alexandre Courbot <acourbot@...dia.com>
To: Danilo Krummrich <dakr@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: John Hubbard <jhubbard@...dia.com>, 
 Alistair Popple <apopple@...dia.com>, 
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>, 
 Edwin Peer <epeer@...dia.com>, nouveau@...ts.freedesktop.org, 
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 rust-for-linux@...r.kernel.org, Alexandre Courbot <acourbot@...dia.com>
Subject: [PATCH 3/9] gpu: nova-core: gsp: simplify sequencer opcode parsing

The opcodes are already the right type in the C union, so we can use
them directly instead of converting them to a byte stream and back again
using `FromBytes`.

Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
---
 drivers/gpu/nova-core/gsp/fw.rs | 40 +++++-----------------------------------
 1 file changed, 5 insertions(+), 35 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 24e4eaaf1265..d06c0fdd6154 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -472,13 +472,7 @@ pub(crate) fn reg_write_payload(&self) -> Result<RegWritePayload> {
             return Err(EINVAL);
         }
         // SAFETY: Opcode is verified to be `RegWrite`, so union contains valid `RegWritePayload`.
-        let payload_bytes = unsafe {
-            core::slice::from_raw_parts(
-                core::ptr::addr_of!(self.0.payload.regWrite).cast::<u8>(),
-                core::mem::size_of::<RegWritePayload>(),
-            )
-        };
-        Ok(*RegWritePayload::from_bytes(payload_bytes).ok_or(EINVAL)?)
+        Ok(RegWritePayload(unsafe { self.0.payload.regWrite }))
     }
 
     /// Returns the register modify payload by value.
@@ -489,13 +483,7 @@ pub(crate) fn reg_modify_payload(&self) -> Result<RegModifyPayload> {
             return Err(EINVAL);
         }
         // SAFETY: Opcode is verified to be `RegModify`, so union contains valid `RegModifyPayload`.
-        let payload_bytes = unsafe {
-            core::slice::from_raw_parts(
-                core::ptr::addr_of!(self.0.payload.regModify).cast::<u8>(),
-                core::mem::size_of::<RegModifyPayload>(),
-            )
-        };
-        Ok(*RegModifyPayload::from_bytes(payload_bytes).ok_or(EINVAL)?)
+        Ok(RegModifyPayload(unsafe { self.0.payload.regModify }))
     }
 
     /// Returns the register poll payload by value.
@@ -506,13 +494,7 @@ pub(crate) fn reg_poll_payload(&self) -> Result<RegPollPayload> {
             return Err(EINVAL);
         }
         // SAFETY: Opcode is verified to be `RegPoll`, so union contains valid `RegPollPayload`.
-        let payload_bytes = unsafe {
-            core::slice::from_raw_parts(
-                core::ptr::addr_of!(self.0.payload.regPoll).cast::<u8>(),
-                core::mem::size_of::<RegPollPayload>(),
-            )
-        };
-        Ok(*RegPollPayload::from_bytes(payload_bytes).ok_or(EINVAL)?)
+        Ok(RegPollPayload(unsafe { self.0.payload.regPoll }))
     }
 
     /// Returns the delay payload by value.
@@ -523,13 +505,7 @@ pub(crate) fn delay_us_payload(&self) -> Result<DelayUsPayload> {
             return Err(EINVAL);
         }
         // SAFETY: Opcode is verified to be `DelayUs`, so union contains valid `DelayUsPayload`.
-        let payload_bytes = unsafe {
-            core::slice::from_raw_parts(
-                core::ptr::addr_of!(self.0.payload.delayUs).cast::<u8>(),
-                core::mem::size_of::<DelayUsPayload>(),
-            )
-        };
-        Ok(*DelayUsPayload::from_bytes(payload_bytes).ok_or(EINVAL)?)
+        Ok(DelayUsPayload(unsafe { self.0.payload.delayUs }))
     }
 
     /// Returns the register store payload by value.
@@ -540,13 +516,7 @@ pub(crate) fn reg_store_payload(&self) -> Result<RegStorePayload> {
             return Err(EINVAL);
         }
         // SAFETY: Opcode is verified to be `RegStore`, so union contains valid `RegStorePayload`.
-        let payload_bytes = unsafe {
-            core::slice::from_raw_parts(
-                core::ptr::addr_of!(self.0.payload.regStore).cast::<u8>(),
-                core::mem::size_of::<RegStorePayload>(),
-            )
-        };
-        Ok(*RegStorePayload::from_bytes(payload_bytes).ok_or(EINVAL)?)
+        Ok(RegStorePayload(unsafe { self.0.payload.regStore }))
     }
 }
 

-- 
2.52.0