[PATCH v2 2/5] drm/nova: use `zerocopy` in booter.rs

[Pedro Yudi Honda <niyudi.honda@usp.br>]

From: Pedro Yudi Honda <niyudi.honda@usp.br>

In firmware/booter.rs, replace the following `transmute` traits with
their `zerocopy` equivalents:

- `transmute::FromBytes` -> `zerocopy::FromBytes`

Update call sites accordingly.

Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
---
 drivers/gpu/nova-core/firmware/booter.rs | 26 +++++++-----------------
 1 file changed, 7 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware/booter.rs b/drivers/gpu/nova-core/firmware/booter.rs
index acb7f4d8a532..fe9389b84b90 100644
--- a/drivers/gpu/nova-core/firmware/booter.rs
+++ b/drivers/gpu/nova-core/firmware/booter.rs
@@ -10,8 +10,7 @@
 use kernel::{
     device,
     dma::Coherent,
-    prelude::*,
-    transmute::FromBytes, //
+    prelude::*, //
 };
 
 use crate::{
@@ -43,7 +42,7 @@ fn frombytes_at<S: FromBytes + Sized>(slice: &[u8], offset: usize) -> Result<S>
     let end = offset.checked_add(size_of::<S>()).ok_or(EINVAL)?;
     slice
         .get(offset..end)
-        .and_then(S::from_bytes_copy)
+        .and_then(|b| S::read_from_bytes(b).ok())
         .ok_or(EINVAL)
 }
 
@@ -52,7 +51,7 @@ fn frombytes_at<S: FromBytes + Sized>(slice: &[u8], offset: usize) -> Result<S>
 /// Such firmwares have an application-specific payload that needs to be patched with a given
 /// signature.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 struct HsHeaderV2 {
     /// Offset to the start of the signatures.
     sig_prod_offset: u32,
@@ -75,9 +74,6 @@ struct HsHeaderV2 {
     header_size: u32,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
-unsafe impl FromBytes for HsHeaderV2 {}
-
 /// Heavy-Secured Firmware image container.
 ///
 /// This provides convenient access to the fields of [`HsHeaderV2`] that are actually indices to
@@ -144,6 +140,7 @@ fn signatures_iter(&'a self) -> Result<impl Iterator<Item = BooterSignature<'a>>
 
 /// Signature parameters, as defined in the firmware.
 #[repr(C)]
+#[derive(FromBytes)]
 struct HsSignatureParams {
     /// Fuse version to use.
     fuse_ver: u32,
@@ -153,9 +150,6 @@ struct HsSignatureParams {
     ucode_id: u32,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
-unsafe impl FromBytes for HsSignatureParams {}
-
 impl HsSignatureParams {
     /// Returns the signature parameters contained in `hs_fw`.
     ///
@@ -170,14 +164,14 @@ fn new(hs_fw: &HsFirmwareV2<'_>) -> Result<Self> {
         hs_fw
             .fw
             .get(start..end)
-            .and_then(Self::from_bytes_copy)
+            .and_then(|b| Self::read_from_bytes(b).ok())
             .ok_or(EINVAL)
     }
 }
 
 /// Header for code and data load offsets.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 struct HsLoadHeaderV2 {
     // Offset at which the code starts.
     os_code_offset: u32,
@@ -191,9 +185,6 @@ struct HsLoadHeaderV2 {
     num_apps: u32,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
-unsafe impl FromBytes for HsLoadHeaderV2 {}
-
 impl HsLoadHeaderV2 {
     /// Returns the load header contained in `hs_fw`.
     ///
@@ -205,7 +196,7 @@ fn new(hs_fw: &HsFirmwareV2<'_>) -> Result<Self> {
 
 /// Header for app code loader.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 struct HsLoadHeaderV2App {
     /// Offset at which to load the app code.
     offset: u32,
@@ -213,9 +204,6 @@ struct HsLoadHeaderV2App {
     len: u32,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
-unsafe impl FromBytes for HsLoadHeaderV2App {}
-
 impl HsLoadHeaderV2App {
     /// Returns the [`HsLoadHeaderV2App`] for app `idx` of `hs_fw`.
     ///
-- 
2.34.1