[PATCH v2 3/5] drm/nova: use `zerocopy` in fwsec.rs

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

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

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

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

Update call sites accordingly.

Signed-off-by: Pedro Yudi Honda <niyudi.honda@usp.br>
---
 drivers/gpu/nova-core/firmware/fwsec.rs | 49 ++++++-------------------
 1 file changed, 12 insertions(+), 37 deletions(-)

diff --git a/drivers/gpu/nova-core/firmware/fwsec.rs b/drivers/gpu/nova-core/firmware/fwsec.rs
index 95e0dd77746b..1b75cdc02256 100644
--- a/drivers/gpu/nova-core/firmware/fwsec.rs
+++ b/drivers/gpu/nova-core/firmware/fwsec.rs
@@ -19,11 +19,7 @@
         self,
         Device, //
     },
-    prelude::*,
-    transmute::{
-        AsBytes,
-        FromBytes, //
-    },
+    prelude::*, //
 };
 
 use crate::{
@@ -49,26 +45,22 @@
 const NVFW_FALCON_APPIF_ID_DMEMMAPPER: u32 = 0x4;
 
 #[repr(C)]
-#[derive(Debug)]
+#[derive(Debug, FromBytes)]
 struct FalconAppifHdrV1 {
     version: u8,
     header_size: u8,
     entry_size: u8,
     entry_count: u8,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for FalconAppifHdrV1 {}
 
 #[repr(C, packed)]
-#[derive(Debug)]
+#[derive(Debug, FromBytes)]
 struct FalconAppifV1 {
     id: u32,
     dmem_base: u32,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for FalconAppifV1 {}
 
-#[derive(Debug)]
+#[derive(Debug, FromBytes, IntoBytes, zerocopy_derive::KnownLayout)]
 #[repr(C, packed)]
 struct FalconAppifDmemmapperV3 {
     signature: u32,
@@ -89,12 +81,8 @@ struct FalconAppifDmemmapperV3 {
     ucode_cmd_mask1: u32,
     multi_tgt_tbl: u32,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for FalconAppifDmemmapperV3 {}
-// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
-unsafe impl AsBytes for FalconAppifDmemmapperV3 {}
 
-#[derive(Debug)]
+#[derive(Debug, FromBytes, IntoBytes, zerocopy_derive::KnownLayout)]
 #[repr(C, packed)]
 struct ReadVbios {
     ver: u32,
@@ -103,12 +91,8 @@ struct ReadVbios {
     size: u32,
     flags: u32,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for ReadVbios {}
-// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
-unsafe impl AsBytes for ReadVbios {}
 
-#[derive(Debug)]
+#[derive(Debug, FromBytes, IntoBytes, zerocopy_derive::KnownLayout)]
 #[repr(C, packed)]
 struct FrtsRegion {
     ver: u32,
@@ -117,22 +101,15 @@ struct FrtsRegion {
     size: u32,
     ftype: u32,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for FrtsRegion {}
-// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
-unsafe impl AsBytes for FrtsRegion {}
 
 const NVFW_FRTS_CMD_REGION_TYPE_FB: u32 = 2;
 
 #[repr(C, packed)]
+#[derive(FromBytes, IntoBytes, zerocopy_derive::KnownLayout)]
 struct FrtsCmd {
     read_vbios: ReadVbios,
     frts_region: FrtsRegion,
 }
-// SAFETY: Any byte sequence is valid for this struct.
-unsafe impl FromBytes for FrtsCmd {}
-// SAFETY: This struct doesn't contain uninitialized bytes and doesn't have interior mutability.
-unsafe impl AsBytes for FrtsCmd {}
 
 const NVFW_FALCON_APPIF_DMEMMAPPER_CMD_FRTS: u32 = 0x15;
 const NVFW_FALCON_APPIF_DMEMMAPPER_CMD_SB: u32 = 0x19;
@@ -151,11 +128,9 @@ pub(crate) enum FwsecCommand {
 
 /// A single signature that can be patched into a FWSEC image.
 #[repr(transparent)]
+#[derive(FromBytes)]
 pub(crate) struct Bcrt30Rsa3kSignature([u8; BCRT30_RSA3K_SIG_SIZE]);
 
-/// SAFETY: A signature is just an array of bytes.
-unsafe impl FromBytes for Bcrt30Rsa3kSignature {}
-
 impl From<[u8; BCRT30_RSA3K_SIG_SIZE]> for Bcrt30Rsa3kSignature {
     fn from(sig: [u8; BCRT30_RSA3K_SIG_SIZE]) -> Self {
         Self(sig)
@@ -228,7 +203,7 @@ fn new_fwsec(bios: &Vbios, cmd: FwsecCommand) -> Result<Self> {
 
         let hdr = ucode
             .get(hdr_offset..)
-            .and_then(FalconAppifHdrV1::from_bytes_prefix)
+            .and_then(|b| FalconAppifHdrV1::read_from_prefix(b).ok())
             .ok_or(EINVAL)?
             .0;
 
@@ -246,7 +221,7 @@ fn new_fwsec(bios: &Vbios, cmd: FwsecCommand) -> Result<Self> {
 
             let app = ucode
                 .get(entry_offset..)
-                .and_then(FalconAppifV1::from_bytes_prefix)
+                .and_then(|b| FalconAppifV1::read_from_prefix(b).ok())
                 .ok_or(EINVAL)?
                 .0;
 
@@ -263,7 +238,7 @@ fn new_fwsec(bios: &Vbios, cmd: FwsecCommand) -> Result<Self> {
 
             let dmem_mapper = ucode
                 .get_mut(dmem_mapper_offset..)
-                .and_then(FalconAppifDmemmapperV3::from_bytes_mut_prefix)
+                .and_then(|b| FalconAppifDmemmapperV3::mut_from_prefix(b).ok())
                 .ok_or(EINVAL)?
                 .0;
 
@@ -281,7 +256,7 @@ fn new_fwsec(bios: &Vbios, cmd: FwsecCommand) -> Result<Self> {
 
             let frts_cmd = ucode
                 .get_mut(frts_cmd_offset..)
-                .and_then(FrtsCmd::from_bytes_mut_prefix)
+                .and_then(|b| FrtsCmd::mut_from_prefix(b).ok())
                 .ok_or(EINVAL)?
                 .0;
 
-- 
2.34.1