[PATCH v2 1/7] gpu: nova-core: replace `as` with `from` conversions where possible

Alexandre Courbot
2025-10-27T12:54:55Z

The `as` operator is best avoided as it silently drops bits if the
destination type is smaller that the source.

For data types where this is clearly not the case, use `from` to
unambiguously signal that these conversions are lossless.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
drivers/gpu/nova-core/falcon/hal/ga102.rs | 6 ++---
drivers/gpu/nova-core/firmware/fwsec.rs | 4 ++--
drivers/gpu/nova-core/vbios.rs | 38 +++++++++++++++----------------
3 files changed, 23 insertions(+), 25 deletions(-)

diff --git a/drivers/gpu/nova-core/falcon/hal/ga102.rs b/drivers/gpu/nova-core/falcon/hal/ga102.rs
index f2ae9537321d..afed353b24d2 100644
--- a/drivers/gpu/nova-core/falcon/hal/ga102.rs
+++ b/drivers/gpu/nova-core/falcon/hal/ga102.rs
@@ -40,11 +40,9 @@ fn signature_reg_fuse_version_ga102(
engine_id_mask: u16,
ucode_id: u8,
) -> Result<u32> {
- const NV_FUSE_OPT_FPF_SIZE: u8 = regs::NV_FUSE_OPT_FPF_SIZE as u8;
-
// Each engine has 16 ucode version registers numbered from 1 to 16.
- let ucode_idx = match ucode_id {
- 1..=NV_FUSE_OPT_FPF_SIZE => (ucode_id - 1) as usize,
+ let ucode_idx = match usize::from(ucode_id) {
+ ucode_id @ 1..=regs::NV_FUSE_OPT_FPF_SIZE => ucode_id - 1,
_ => {
dev_err!(dev, "invalid ucode id {:#x}", ucode_id);
return Err(EINVAL);
diff --git a/drivers/gpu/nova-core/firmware/fwsec.rs b/drivers/gpu/nova-core/firmware/fwsec.rs
index 8edbb5c0572c..dd3420aaa2bf 100644
--- a/drivers/gpu/nova-core/firmware/fwsec.rs
+++ b/drivers/gpu/nova-core/firmware/fwsec.rs
@@ -259,13 +259,13 @@ fn new_fwsec(dev: &Device<device::Bound>, bios: &Vbios, cmd: FwsecCommand) -> Re
}

// Find the DMEM mapper section in the firmware.
- for i in 0..hdr.entry_count as usize {
+ for i in 0..usize::from(hdr.entry_count) {
let app: &FalconAppifV1 =
// SAFETY: we have exclusive access to `dma_object`.
unsafe {
transmute(
&dma_object,
- hdr_offset + hdr.header_size as usize + i * hdr.entry_size as usize
+ hdr_offset + usize::from(hdr.header_size) + i * usize::from(hdr.entry_size)
)
}?;

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index ad070a0420ca..943b0dac31df 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -361,7 +361,7 @@ fn is_last(&self) -> bool {

/// Calculate image size in bytes from 512-byte blocks.
fn image_size_bytes(&self) -> usize {
- self.image_len as usize * 512
+ usize::from(self.image_len) * 512
}
}

@@ -439,13 +439,13 @@ fn from_id(image: &PciAtBiosImage, token_id: u8) -> Result<Self> {
let header = &image.bit_header;

// Offset to the first token entry
- let tokens_start = image.bit_offset + header.header_size as usize;
+ let tokens_start = image.bit_offset + usize::from(header.header_size);

- for i in 0..header.token_entries as usize {
- let entry_offset = tokens_start + (i * header.token_size as usize);
+ for i in 0..usize::from(header.token_entries) {
+ let entry_offset = tokens_start + (i * usize::from(header.token_size));

// Make sure we don't go out of bounds
- if entry_offset + header.token_size as usize > image.base.data.len() {
+ if entry_offset + usize::from(header.token_size) > image.base.data.len() {
return Err(EINVAL);
}

@@ -601,7 +601,7 @@ fn is_last(&self) -> bool {

/// Calculate image size in bytes from 512-byte blocks.
fn image_size_bytes(&self) -> usize {
- self.subimage_len as usize * 512
+ usize::from(self.subimage_len) * 512
}

/// Try to find NPDE in the data, the NPDE is right after the PCIR.
@@ -613,8 +613,8 @@ fn find_in_data(
) -> Option<Self> {
// Calculate the offset where NPDE might be located
// NPDE should be right after the PCIR structure, aligned to 16 bytes
- let pcir_offset = rom_header.pci_data_struct_offset as usize;
- let npde_start = (pcir_offset + pcir.pci_data_struct_len as usize + 0x0F) & !0x0F;
+ let pcir_offset = usize::from(rom_header.pci_data_struct_offset);
+ let npde_start = (pcir_offset + usize::from(pcir.pci_data_struct_len) + 0x0F) & !0x0F;

// Check if we have enough data
if npde_start + core::mem::size_of::<Self>() > data.len() {
@@ -737,7 +737,7 @@ fn new(dev: &device::Device, data: &[u8]) -> Result<Self> {
.inspect_err(|e| dev_err!(dev, "Failed to create PciRomHeader: {:?}\n", e))?;

// Get the PCI Data Structure using the pointer from the ROM header.
- let pcir_offset = rom_header.pci_data_struct_offset as usize;
+ let pcir_offset = usize::from(rom_header.pci_data_struct_offset);
let pcir_data = data
.get(pcir_offset..pcir_offset + core::mem::size_of::<PcirStruct>())
.ok_or(EINVAL)
@@ -805,12 +805,12 @@ fn falcon_data_ptr(&self) -> Result<u32> {
let token = self.get_bit_token(BIT_TOKEN_ID_FALCON_DATA)?;

// Make sure we don't go out of bounds
- if token.data_offset as usize + 4 > self.base.data.len() {
+ if usize::from(token.data_offset) + 4 > self.base.data.len() {
return Err(EINVAL);
}

// read the 4 bytes at the offset specified in the token
- let offset = token.data_offset as usize;
+ let offset = usize::from(token.data_offset);
let bytes: [u8; 4] = self.base.data[offset..offset + 4].try_into().map_err(|_| {
dev_err!(self.base.dev, "Failed to convert data slice to array");
EINVAL
@@ -818,7 +818,7 @@ fn falcon_data_ptr(&self) -> Result<u32> {

let data_ptr = u32::from_le_bytes(bytes);

- if (data_ptr as usize) < self.base.data.len() {
+ if (usize::from_u32(data_ptr)) < self.base.data.len() {
dev_err!(self.base.dev, "Falcon data pointer out of bounds\n");
return Err(EINVAL);
}
@@ -886,9 +886,9 @@ fn new(dev: &device::Device, data: &[u8]) -> Result<Self> {
return Err(EINVAL);
}

- let header_len = data[1] as usize;
- let entry_len = data[2] as usize;
- let entry_count = data[3] as usize;
+ let header_len = usize::from(data[1]);
+ let entry_len = usize::from(data[2]);
+ let entry_count = usize::from(data[3]);

let required_bytes = header_len + (entry_count * entry_len);

@@ -923,7 +923,7 @@ fn lookup_index(&self, idx: u8) -> Result<PmuLookupTableEntry> {
return Err(EINVAL);
}

- let index = (idx as usize) * self.entry_len as usize;
+ let index = (usize::from(idx)) * usize::from(self.entry_len);
PmuLookupTableEntry::new(&self.table_data[index..])
}

@@ -1092,8 +1092,8 @@ pub(crate) fn ucode(&self, desc: &FalconUCodeDescV3) -> Result<&[u8]> {
pub(crate) fn sigs(&self, desc: &FalconUCodeDescV3) -> Result<&[Bcrt30Rsa3kSignature]> {
// The signatures data follows the descriptor.
let sigs_data_offset = self.falcon_ucode_offset + core::mem::size_of::<FalconUCodeDescV3>();
- let sigs_size =
- desc.signature_count as usize * core::mem::size_of::<Bcrt30Rsa3kSignature>();
+ let sigs_count = usize::from(desc.signature_count);
+ let sigs_size = sigs_count * core::mem::size_of::<Bcrt30Rsa3kSignature>();

// Make sure the data is within bounds.
if sigs_data_offset + sigs_size > self.base.data.len() {
@@ -1113,7 +1113,7 @@ pub(crate) fn sigs(&self, desc: &FalconUCodeDescV3) -> Result<&[Bcrt30Rsa3kSigna
.as_ptr()
.add(sigs_data_offset)
.cast::<Bcrt30Rsa3kSignature>(),
- desc.signature_count as usize,
+ sigs_count,
)
})
}

--
2.51.0