Since `BiosImageType` is `repr(u8)`, if can safely be converted into a
`u8` but this is not obvious when doing this in the code.

Instead, implement `From<BiosImageType>` for `u8` so the cast can be
done in a single place, with a justifying comment.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
---
 drivers/gpu/nova-core/vbios.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
index dbe0d6e4a015..a521c0a4df0f 100644
--- a/drivers/gpu/nova-core/vbios.rs
+++ b/drivers/gpu/nova-core/vbios.rs
@@ -50,6 +50,13 @@ fn try_from(code: u8) -> Result<Self> {
     }
 }
 
+impl From<BiosImageType> for u8 {
+    fn from(value: BiosImageType) -> Self {
+        // `BiosImageType` is `repr(u8)` and thus convertible without loss.
+        value as u8
+    }
+}
+
 // PMU lookup table entry types. Used to locate PMU table entries
 // in the Fwsec image, corresponding to falcon ucodes.
 #[expect(dead_code)]
@@ -711,7 +718,7 @@ fn image_type(&self) -> Result<BiosImageType> {
     fn is_last(&self) -> bool {
         // For NBSI images (type == 0x70), return true as they're
         // considered the last image
-        if self.pcir.code_type == BiosImageType::Nbsi as u8 {
+        if self.pcir.code_type == BiosImageType::Nbsi.into() {
             return true;
         }
 

-- 
2.51.0

Hello Alex,

On Mon, Oct 27, 2025 at 09:54:43PM +0900, Alexandre Courbot wrote:
> Since `BiosImageType` is `repr(u8)`, if can safely be converted into a
> `u8` but this is not obvious when doing this in the code.
> 
> Instead, implement `From<BiosImageType>` for `u8` so the cast can be
> done in a single place, with a justifying comment.
> 
> Acked-by: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
>  drivers/gpu/nova-core/vbios.rs | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
> index dbe0d6e4a015..a521c0a4df0f 100644
> --- a/drivers/gpu/nova-core/vbios.rs
> +++ b/drivers/gpu/nova-core/vbios.rs
> @@ -50,6 +50,13 @@ fn try_from(code: u8) -> Result<Self> {
>      }
>  }
>  
> +impl From<BiosImageType> for u8 {
> +    fn from(value: BiosImageType) -> Self {
> +        // `BiosImageType` is `repr(u8)` and thus convertible without loss.
> +        value as u8
> +    }
> +}
> +
>  // PMU lookup table entry types. Used to locate PMU table entries
>  // in the Fwsec image, corresponding to falcon ucodes.
>  #[expect(dead_code)]
> @@ -711,7 +718,7 @@ fn image_type(&self) -> Result<BiosImageType> {
>      fn is_last(&self) -> bool {
>          // For NBSI images (type == 0x70), return true as they're
>          // considered the last image
> -        if self.pcir.code_type == BiosImageType::Nbsi as u8 {
> +        if self.pcir.code_type == BiosImageType::Nbsi.into() {

I strongly prefer u8::from(BiosImageType::Nbsi) here so there is no loss of
readability of the type. Can we please use ::from()?

thanks,

 - Joel


>              return true;
>          }
>  
> 
> -- 
> 2.51.0
>

On Tue Oct 28, 2025 at 2:37 AM JST, Joel Fernandes wrote:
> Hello Alex,
>
> On Mon, Oct 27, 2025 at 09:54:43PM +0900, Alexandre Courbot wrote:
>> Since `BiosImageType` is `repr(u8)`, if can safely be converted into a
>> `u8` but this is not obvious when doing this in the code.
>> 
>> Instead, implement `From<BiosImageType>` for `u8` so the cast can be
>> done in a single place, with a justifying comment.
>> 
>> Acked-by: Danilo Krummrich <dakr@kernel.org>
>> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
>> ---
>>  drivers/gpu/nova-core/vbios.rs | 9 ++++++++-
>>  1 file changed, 8 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/gpu/nova-core/vbios.rs b/drivers/gpu/nova-core/vbios.rs
>> index dbe0d6e4a015..a521c0a4df0f 100644
>> --- a/drivers/gpu/nova-core/vbios.rs
>> +++ b/drivers/gpu/nova-core/vbios.rs
>> @@ -50,6 +50,13 @@ fn try_from(code: u8) -> Result<Self> {
>>      }
>>  }
>>  
>> +impl From<BiosImageType> for u8 {
>> +    fn from(value: BiosImageType) -> Self {
>> +        // `BiosImageType` is `repr(u8)` and thus convertible without loss.
>> +        value as u8
>> +    }
>> +}
>> +
>>  // PMU lookup table entry types. Used to locate PMU table entries
>>  // in the Fwsec image, corresponding to falcon ucodes.
>>  #[expect(dead_code)]
>> @@ -711,7 +718,7 @@ fn image_type(&self) -> Result<BiosImageType> {
>>      fn is_last(&self) -> bool {
>>          // For NBSI images (type == 0x70), return true as they're
>>          // considered the last image
>> -        if self.pcir.code_type == BiosImageType::Nbsi as u8 {
>> +        if self.pcir.code_type == BiosImageType::Nbsi.into() {
>
> I strongly prefer u8::from(BiosImageType::Nbsi) here so there is no loss of
> readability of the type. Can we please use ::from()?

What benefit do we get from knowing the representing type of
BiosImageType? We are only interested in knowing whether the two values
are equal or not.

But you have a point that `::from()` is generally easier to read, only I
would apply it on the left value:

  if BiosImageType::try_from(self.pcir.code_type) == Ok(BiosImageType::Nbsi)

or reusing the already existing code:

  if self.image_type() == Ok(BiosImageType::Nbsi)

That reads even more naturally imho.