[PATCH v2 1/5] drm/nova: use `zerocopy` in firmware.rs

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

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

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

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

Update call sites accordingly.

Note that the module `elf` is untouched, as the bindings generated by
bindgen do not implement `FromBytes` for the structs.

Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
---
 drivers/gpu/nova-core/firmware.rs                  | 10 +++-------
 drivers/gpu/nova-core/firmware/fwsec/bootloader.rs |  4 +++-
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index a94820a3b335..80ce0df244a8 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -11,8 +11,7 @@
     device,
     firmware,
     prelude::*,
-    str::CString,
-    transmute::FromBytes, //
+    str::CString, //
 };
 
 use crate::{
@@ -347,7 +346,7 @@ fn no_patch_signature(self) -> FirmwareObject<F, Signed> {
 
 /// Header common to most firmware files.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 struct BinHdr {
     /// Magic number, must be `0x10de`.
     bin_magic: u32,
@@ -363,9 +362,6 @@ struct BinHdr {
     data_size: u32,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use interior mutability.
-unsafe impl FromBytes for BinHdr {}
-
 // A firmware blob starting with a `BinHdr`.
 struct BinFirmware<'a> {
     hdr: BinHdr,
@@ -381,7 +377,7 @@ fn new(fw: &'a firmware::Firmware) -> Result<Self> {
 
         fw.get(0..size_of::<BinHdr>())
             // Extract header.
-            .and_then(BinHdr::from_bytes_copy)
+            .and_then(|b| BinHdr::read_from_bytes(b).ok())
             // Validate header.
             .filter(|hdr| hdr.bin_magic == BIN_MAGIC)
             .map(|hdr| Self { hdr, fw })
diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
index d9fafd2eea5b..66b9f4d1b41c 100644
--- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
+++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
@@ -25,6 +25,8 @@
     },
 };
 
+use zerocopy::FromBytes as _;
+
 use crate::{
     driver::Bar0,
     falcon::{
@@ -150,7 +152,7 @@ pub(crate) fn new(
         let hdr = fw
             .data()
             .get(0..size_of::<BinHdr>())
-            .and_then(BinHdr::from_bytes_copy)
+            .and_then(|b| BinHdr::read_from_bytes(b).ok())
             .ok_or(EINVAL)?;
 
         let desc = {
-- 
2.34.1