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Message-Id: <DE8HSL6JS4DU.2V5WDFEN1L4X2@nvidia.com>
Date: Fri, 14 Nov 2025 23:37:26 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "John Hubbard" <jhubbard@...dia.com>, "Danilo Krummrich"
<dakr@...nel.org>
Cc: "Alexandre Courbot" <acourbot@...dia.com>, "Joel Fernandes"
<joelagnelf@...dia.com>, "Timur Tabi" <ttabi@...dia.com>, "Alistair Popple"
<apopple@...dia.com>, "Edwin Peer" <epeer@...dia.com>, "Zhi Wang"
<zhiw@...dia.com>, "David Airlie" <airlied@...il.com>, "Simona Vetter"
<simona@...ll.ch>, "Bjorn Helgaas" <bhelgaas@...gle.com>, "Miguel Ojeda"
<ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>, "Boqun Feng"
<boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Benno Lossin"
<lossin@...nel.org>, "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice
Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>,
<nouveau@...ts.freedesktop.org>, <rust-for-linux@...r.kernel.org>, "LKML"
<linux-kernel@...r.kernel.org>, "Nouveau"
<nouveau-bounces@...ts.freedesktop.org>
Subject: Re: [PATCH v8 2/6] gpu: nova-core: prepare Spec and Revision types
for boot0/boot42
On Fri Nov 14, 2025 at 11:41 AM JST, John Hubbard wrote:
> 1) Decouple Revision from boot0.
>
> 2) Enhance Revision, which in turn simplifies Spec::new().
>
> 3) Also, slightly enhance the comment about Spec, to be more precise.
>
> Cc: Alexandre Courbot <acourbot@...dia.com>
> Cc: Danilo Krummrich <dakr@...nel.org>
> Cc: Timur Tabi <ttabi@...dia.com>
> Reviewed-by: Joel Fernandes <joelagnelf@...dia.com>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> drivers/gpu/nova-core/gpu.rs | 26 ++++++++++++--------------
> drivers/gpu/nova-core/regs.rs | 11 ++++++++++-
> 2 files changed, 22 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/gpu.rs b/drivers/gpu/nova-core/gpu.rs
> index 7fd9e91771a6..8f438188fc03 100644
> --- a/drivers/gpu/nova-core/gpu.rs
> +++ b/drivers/gpu/nova-core/gpu.rs
> @@ -143,17 +143,8 @@ fn try_from(value: u8) -> Result<Self> {
> }
>
> pub(crate) struct Revision {
> - major: u8,
> - minor: u8,
> -}
> -
> -impl Revision {
> - fn from_boot0(boot0: regs::NV_PMC_BOOT_0) -> Self {
> - Self {
> - major: boot0.major_revision(),
> - minor: boot0.minor_revision(),
> - }
> - }
> + pub(crate) major: u8,
> + pub(crate) minor: u8,
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):
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.
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