linux-kernel - Re: [PATCH 01/31] gpu: nova-core: print FB sizes, along with ranges

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Message-ID: <19c557e5-5428-42a8-8317-62726b980eff@nvidia.com>
Date: Wed, 3 Dec 2025 23:27:15 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Timur Tabi <ttabi@...dia.com>, "dakr@...nel.org" <dakr@...nel.org>
Cc: Alexandre Courbot <acourbot@...dia.com>,
 "lossin@...nel.org" <lossin@...nel.org>,
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Subject: Re: [PATCH 01/31] gpu: nova-core: print FB sizes, along with ranges

On 12/3/25 11:35 AM, Timur Tabi wrote:
> On Tue, 2025-12-02 at 21:58 -0800, John Hubbard wrote:
>> +impl fmt::Debug for FbRange {
>> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
>> +        let size_mb = (self.0.end - self.0.start) >> 20;
>> +        f.write_fmt(fmt!(
>> +            "{:#x}..{:#x} ({} MB)",
>> +            self.0.start,
>> +            self.0.end,
>> +            size_mb
>> +        ))
>> +    }
>> +}
>> +
> 
> How about printing size_kb if size_mb == 0 or if it's not an even multiple of MB?

Good idea, I'll do that.

> 
> Also, why not just add this function to Range<> instead of creating a new type?

Rust's orphan rules prevent implementing a foreign trait (Debug) on a
foreign type (Range<u64>). Both are defined in core, not in nova-core,
so the compiler won't allow it. The newtype pattern is the standard Rust
workaround for this: by wrapping Range<u64> in a local type FbRange, we
can implement whatever traits we need.

thanks,
-- 
John Hubbard