[PATCH 1/7] drm/nova: use `zerocopy` in firmware.rs

[Pedro Yudi Honda]

From: Pedro Yudi Honda <niyudi.honda em 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 em usp.br>
---
 drivers/gpu/nova-core/firmware.rs                | 16 ++++------------
 .../gpu/nova-core/firmware/fwsec/bootloader.rs   |  4 +++-
 drivers/gpu/nova-core/vbios.rs                   |  4 ++--
 3 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware.rs b/drivers/gpu/nova-core/firmware.rs
index ad37994ac15a..7f35b2e55dce 100644
--- a/drivers/gpu/nova-core/firmware.rs
+++ b/drivers/gpu/nova-core/firmware.rs
@@ -10,8 +10,7 @@
     device,
     firmware,
     prelude::*,
-    str::CString,
-    transmute::FromBytes, //
+    str::CString, //
 };
 
 use crate::{
@@ -86,7 +85,7 @@ pub(crate) struct FalconUCodeDescV2 {
 
 /// Structure used to describe some firmwares, notably FWSEC-FRTS.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 pub(crate) struct FalconUCodeDescV3 {
     /// Header defined by `NV_BIT_FALCON_UCODE_DESC_HEADER_VDESC*` in OpenRM.
     hdr: u32,
@@ -117,10 +116,6 @@ pub(crate) struct FalconUCodeDescV3 {
     _reserved: u16,
 }
 
-// SAFETY: all bit patterns are valid for this type, and it doesn't use
-// interior mutability.
-unsafe impl FromBytes for FalconUCodeDescV3 {}
-
 /// Enum wrapping the different versions of Falcon microcode descriptors.
 ///
 /// This allows handling both V2 and V3 descriptor formats through a
@@ -349,7 +344,7 @@ 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,
@@ -365,9 +360,6 @@ 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,
@@ -383,7 +375,7 @@ 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.
             .and_then(|hdr| {
                 if hdr.bin_magic == BIN_MAGIC {
diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
index bcb713a868e2..5d2ac63b95e8 100644
--- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
+++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
@@ -29,6 +29,8 @@
     },
 };
 
+use zerocopy::FromBytes as _;
+
 use crate::{
     driver::Bar0,
     falcon::{
@@ -154,7 +156,7 @@ 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 = {
diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index 8b7d17a24660..6d700673686f 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -1019,8 +1019,8 @@ pub(crate) fn header(&self) -> Result<FalconUCodeDesc> {
                 Ok(FalconUCodeDesc::V2(v2))
             }
             3 => {
-                let v3 = FalconUCodeDescV3::from_bytes_copy_prefix(data)
-                    .ok_or(EINVAL)?
+                let v3 = FalconUCodeDescV3::read_from_prefix(data)
+                    .map_err(|_| EINVAL)?
                     .0;
                 Ok(FalconUCodeDesc::V3(v3))
             }
-- 
2.34.1