On 11/14/25 6:37 AM, Alexandre Courbot wrote:
> On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
...
> Something felt a bit off with this diff, and I only realized why now.
>
> We are moving, for no good reason, the creation of `Revision` into the
> boot0 (and later boot42) register, which forces us to increase the
> visibility of its fields.
>
> And while `Revision` is now created by a method of the register it
> originates from, `Spec` for some reason isn't, and we even add a
> `TryFrom` implementation for it here. This creates an asymmetry that has
> no justification afaict.
>
> Instead, what if we replaced this `from_boot0` method by a `From<BOOT0>`
> implementation? That way, we have consistency in how we derive our chip
> information structures, and this patch can be reduced to this (with the
> other changes below):
Yes, that allows leaving Revision's members private, which shows that
we're laying out the objects in a better way.
I've implemented this for v9.
>
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index dfeba9d5d8f6..57c20d1e7274 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -147,8 +147,8 @@ pub(crate) struct Revision {
> minor: u8,
> }
>
> -impl Revision {
> - fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
> +impl From<regs::NV_PMC_BOOT_0> for Revision {
> + fn from(boot0: regs::NV_PMC_BOOT_0) -> Self {
> Self {
> major: boot0.major_revision(),
> minor: boot0.minor_revision(),
> @@ -162,10 +162,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
> {
> }
> }
>
> -/// Structure holding the metadata of the GPU.
> +/// Structure holding a basic description of the GPU: `Chipset` and
> `Revision`.
> pub(crate) struct Spec {
> chipset: Chipset,
> - /// The revision of the chipset.
> revision: Revision,
> }
>
> @@ -173,9 +172,17 @@ impl Spec {
> fn new(bar: &Bar0) -> Result<Spec> {
> let boot0 = regs::NV_PMC_BOOT_0::read(bar);
>
> + Spec::try_from(boot0)
> + }
> +}
> +
> +impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
> + type Error = Error;
> +
> + fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
> Ok(Self {
> chipset: boot0.chipset()?,
> - revision: Revision::from_boot0(boot0),
> + revision: boot0.into(),
> })
> }
> }
>
> ... and the subsequent patches also get some simplification.
>
>> }
>>
>> impl fmt::Display for Revision {
>> @@ -162,10 +153,9 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) ->
>> fmt::Result {
>> }
>> }
>>
>> -/// Structure holding the metadata of the GPU.
>> +/// Structure holding a basic description of the GPU: `Architecture`,
>> `Chipset` and `Revision`.
>
> There is no `Architecture` in this structure though?
>
>> pub(crate) struct Spec {
>> chipset: Chipset,
>> - /// The revision of the chipset.
>> revision: Revision,
>> }
>>
>> @@ -173,9 +163,17 @@ impl Spec {
>> fn new(bar: &Bar0) -> Result<Spec> {
>> let boot0 = regs::NV_PMC_BOOT_0::read(bar);
>>
>> + Spec::try_from(boot0)
>> + }
>> +}
>> +
>> +impl TryFrom<regs::NV_PMC_BOOT_0> for Spec {
>> + type Error = Error;
>> +
>> + fn try_from(boot0: regs::NV_PMC_BOOT_0) -> Result<Self> {
>> Ok(Self {
>> chipset: boot0.chipset()?,
>> - revision: Revision::from_boot0(boot0),
>> + revision: boot0.revision(),
>> }
>> })
>> }
>> diff --git a/drivers/gpu/nova-core/regs.rs b/drivers/gpu/nova-core/regs.rs
>> index 934003cab8a8..8c9af3c59708 100644
>> --- a/drivers/gpu/nova-core/regs.rs
>> +++ b/drivers/gpu/nova-core/regs.rs
>> @@ -24,7 +24,8 @@
>> },
>> gpu::{
>> Architecture,
>> - Chipset, //
>> + Chipset,
>> + Revision, //
>> },
>> num::FromSafeCast,
>> };
>> @@ -56,6 +57,14 @@ pub(crate) fn chipset(self) -> Result<Chipset> {
>> })
>> .and_then(Chipset::try_from)
>> }
>> +
>> + /// Returns the revision information of the chip.
>> + pub(crate) fn revision(self) -> Revision {
>> + Revision {
>> + major: self.major_revision(),
>> + minor: self.minor_revision(),
>> + }
>> + }
>
> With the `From<BOOT0> for Revision` implementation we can also drop this
> method.
Yes. Done.
thanks,
--
John Hubbard
