[PATCH v2 4/5] drm/nova: use `zerocopy` in bootloader.rs

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

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

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

- `transmute::FromBytes` -> `zerocopy::FromBytes`
- `transmute::AsBytes` -> `zerocopy::IntoBytes`
- add `zerocopy::Immutable` where necessary

Update call sites accordingly.

Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
---
 .../gpu/nova-core/firmware/fwsec/bootloader.rs | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
index 66b9f4d1b41c..03d3090bd9ef 100644
--- a/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
+++ b/drivers/gpu/nova-core/firmware/fwsec/bootloader.rs
@@ -18,15 +18,9 @@
         Alignable,
         Alignment, //
     },
-    sizes,
-    transmute::{
-        AsBytes,
-        FromBytes, //
-    },
+    sizes, //
 };
 
-use zerocopy::FromBytes as _;
-
 use crate::{
     driver::Bar0,
     falcon::{
@@ -57,7 +51,7 @@
 ///
 /// Most of its fields appear to be legacy and carry incorrect values, so they are left unused.
 #[repr(C)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, FromBytes)]
 struct BootloaderDesc {
     /// Starting tag of bootloader.
     start_tag: u32,
@@ -73,15 +67,13 @@ struct BootloaderDesc {
     /// Size of data section in the image. Unused as we build the data section ourselves.
     _data_size: u32,
 }
-// SAFETY: any byte sequence is valid for this struct.
-unsafe impl FromBytes for BootloaderDesc {}
 
 /// Structure used by the boot-loader to load the rest of the code.
 ///
 /// This has to be filled by the GPU driver and copied into DMEM at offset
 /// [`BootloaderDesc.dmem_load_off`].
 #[repr(C, packed)]
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, IntoBytes, zerocopy_derive::Immutable)]
 struct BootloaderDmemDescV2 {
     /// Reserved, should always be first element.
     reserved: [u32; 4],
@@ -120,8 +112,6 @@ struct BootloaderDmemDescV2 {
     /// Arguments to be passed to the target firmware being loaded.
     argv: u32,
 }
-// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
-unsafe impl AsBytes for BootloaderDmemDescV2 {}
 
 /// Wrapper for [`FwsecFirmware`] that includes the bootloader performing the actual load
 /// operation.
@@ -160,7 +150,7 @@ pub(crate) fn new(
 
             fw.data()
                 .get(desc_offset..)
-                .and_then(BootloaderDesc::from_bytes_copy_prefix)
+                .and_then(|b| BootloaderDesc::read_from_prefix(b).ok())
                 .ok_or(EINVAL)?
                 .0
         };
-- 
2.34.1