linux-kernel - [PATCH v2] gpu: nova-core: vbios: change PmuLookupTableEntry to relax alignment

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Message-ID: <20250714110229.141221-1-krakow20@gmail.com>
Date: Mon, 14 Jul 2025 04:02:23 -0700
From: Rhys Lloyd <krakow20@...il.com>
To: acourbot@...dia.com,
	dakr@...nel.org
Cc: Rhys Lloyd <krakow20@...il.com>,
	rust-for-linux@...r.kernel.org,
	airlied@...il.com,
	simona@...ll.ch,
	nouveau@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] gpu: nova-core: vbios: change PmuLookupTableEntry to relax alignment

Instead of the data field containing a u32 and changing the alignment,
change data to [u8; 4] and convert to u32 with a helper function.
Removes another magic number by making the struct the same size as
the data it needs to read, allowing the use of
`size_of::<PmuLookupTableEntry>()`

Signed-off-by: Rhys Lloyd <krakow20@...il.com>
---
Changes in v2:
- get_data helper function renamed to data

---
 drivers/gpu/nova-core/vbios.rs | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index 5b5d9f38cbb3..339c66e63c7e 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -896,21 +896,26 @@ fn try_from(base: BiosImageBase) -> Result<Self> {
 struct PmuLookupTableEntry {
     application_id: u8,
     target_id: u8,
-    data: u32,
+    data: [u8; 4],
 }
 
 impl PmuLookupTableEntry {
     fn new(data: &[u8]) -> Result<Self> {
-        if data.len() < 6 {
+        if data.len() < core::mem::size_of::<Self>() {
             return Err(EINVAL);
         }
 
         Ok(PmuLookupTableEntry {
             application_id: data[0],
             target_id: data[1],
-            data: u32::from_le_bytes(data[2..6].try_into().map_err(|_| EINVAL)?),
+            data: [data[2], data[3], data[4], data[5]],
         })
     }
+
+    /// Construct a u32 from `self.data`.
+    fn data(&self) -> u32 {
+        u32::from_le_bytes(self.data)
+    }
 }
 
 /// The [`PmuLookupTableEntry`] structure is used to find the [`PmuLookupTableEntry`] for a given
@@ -1037,7 +1042,7 @@ fn setup_falcon_data(
             .find_entry_by_type(FALCON_UCODE_ENTRY_APPID_FWSEC_PROD)
         {
             Ok(entry) => {
-                let mut ucode_offset = entry.data as usize;
+                let mut ucode_offset = entry.data() as usize;
                 ucode_offset -= pci_at_image.base.data.len();
                 if ucode_offset < first_fwsec.base.data.len() {
                     dev_err!(pdev.as_ref(), "Falcon Ucode offset not in second Fwsec.\n");

base-commit: 215a3f91713383a3c0d2da82d223a608a3c17ac1
prerequisite-patch-id: d80f92d314a0693d4c89ffb7810d9ab6990336fa
-- 
2.50.1