linux-kernel - Re: [PATCH v2 2/5] gpu: nova-core: add FbRange.len() and use it in boot.rs

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Message-ID: <49997040-a745-44aa-94d5-517845271094@nvidia.com>
Date: Wed, 26 Nov 2025 16:53:38 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Lyude Paul <lyude@...hat.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>
Subject: Re: [PATCH v2 2/5] gpu: nova-core: add FbRange.len() and use it in
 boot.rs

On 11/26/25 3:43 PM, Lyude Paul wrote:
> I'm not sure this is necessary - for one, we could just use the .len() method
> on the Range. As well - if we just implement Deref for FbRange (which I think
> would be fine here) we could just use .len() through that.

Hi Lyude!

Good idea about the deref coercion. It has a minor type mismatch as-is,
though: Range<u64>::len() returns usize, but FbRange::len() returns u64,
which matches the callers that we have so far.

Thoughts?


thanks,
-- 
John Hubbard

> 
> On Tue, 2025-11-25 at 17:39 -0800, John Hubbard wrote:
>> A tiny simplification: now that FbLayout uses its own specific FbRange
>> type, add an FbRange.len() method, and use that to (very slightly)
>> simplify the calculation of Frts::frts_size initialization.
>>
>> Suggested-by: Alexandre Courbot <acourbot@...dia.com>
>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
>> ---
>>  drivers/gpu/nova-core/fb.rs       | 6 ++++++
>>  drivers/gpu/nova-core/gsp/boot.rs | 2 +-
>>  2 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
>> index 333e952400e6..9fcd915e12e1 100644
>> --- a/drivers/gpu/nova-core/fb.rs
>> +++ b/drivers/gpu/nova-core/fb.rs
>> @@ -100,6 +100,12 @@ pub(crate) fn unregister(&self, bar: &Bar0) {
>>  
>>  pub(crate) struct FbRange(Range<u64>);
>>  
>> +impl FbRange {
>> +    pub(crate) fn len(&self) -> u64 {
>> +        self.0.end - self.0.start
>> +    }
>> +}
>> +
>>  impl From<Range<u64>> for FbRange {
>>      fn from(range: Range<u64>) -> Self {
>>          Self(range)
>> diff --git a/drivers/gpu/nova-core/gsp/boot.rs b/drivers/gpu/nova-core/gsp/boot.rs
>> index 54937606b5b0..846064221931 100644
>> --- a/drivers/gpu/nova-core/gsp/boot.rs
>> +++ b/drivers/gpu/nova-core/gsp/boot.rs
>> @@ -70,7 +70,7 @@ fn run_fwsec_frts(
>>              bios,
>>              FwsecCommand::Frts {
>>                  frts_addr: fb_layout.frts.start,
>> -                frts_size: fb_layout.frts.end - fb_layout.frts.start,
>> +                frts_size: fb_layout.frts.len(),
>>              },
>>          )?;
>>  
>