linux-kernel - Re: [PATCH] gpu: nova-core: use CStr::from_bytes_until

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Message-ID: <ff80714c-cb9f-417f-8d3b-13c41826134e@nvidia.com>
Date: Mon, 5 Jan 2026 18:29:05 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Joel Fernandes <joelagnelf@...dia.com>, Danilo Krummrich <dakr@...nel.org>
Cc: Alexandre Courbot <acourbot@...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] gpu: nova-core: use CStr::from_bytes_until_nul() and
 remove util.rs

On 1/3/26 1:21 PM, Joel Fernandes wrote:
> 
> 
> On 1/2/2026 8:34 PM, John Hubbard wrote:
>> The util.rs module contained a single helper function,
>> str_from_null_terminated(), which duplicated functionality that is now
>> available in core::ffi::CStr.
>>
>> Specifically, CStr::from_bytes_until_nul() is available in the kernel's
>> minimum supported Rust version (1.78.0), so it time to stop using this
>> custom workaround.
>>
>> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> 
> Reviewed-by: Joel Fernandes <joelagnelf@...dia.com>

Thanks for the review!

> 
> Probably elf64_section() should also use CStr::from_bytes_until_nul() in gsp.rs?
> 
> Right now it does:
>          elf.get(name_idx..)
>              .and_then(|nstr| nstr.get(0..=nstr.iter().position(|b| *b == 0)?))
>              .and_then(|nstr| CStr::from_bytes_with_nul(nstr).ok())
> 

Yes, absolutely! Thanks for spotting that. I'll re-send this out as
a two-patch series that includes that change too.


thanks,
-- 
John Hubbard

> 
>> ---
>>  drivers/gpu/nova-core/gsp/commands.rs |  5 +++--
>>  drivers/gpu/nova-core/nova_core.rs    |  1 -
>>  drivers/gpu/nova-core/util.rs         | 16 ----------------
>>  3 files changed, 3 insertions(+), 19 deletions(-)
>>  delete mode 100644 drivers/gpu/nova-core/util.rs
>>
>> diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
>> index 0425c65b5d6f..a11fe6018091 100644
>> --- a/drivers/gpu/nova-core/gsp/commands.rs
>> +++ b/drivers/gpu/nova-core/gsp/commands.rs
>> @@ -30,7 +30,6 @@
>>          },
>>      },
>>      sbuffer::SBufferIter,
>> -    util,
>>  };
>>  
>>  /// The `GspSetSystemInfo` command.
>> @@ -209,7 +208,9 @@ impl GetGspStaticInfoReply {
>>      /// Returns the name of the GPU as a string, or `None` if the string given by the GSP was
>>      /// invalid.
>>      pub(crate) fn gpu_name(&self) -> Option<&str> {
>> -        util::str_from_null_terminated(&self.gpu_name)
>> +        CStr::from_bytes_until_nul(&self.gpu_name)
>> +            .ok()
>> +            .and_then(|cstr| cstr.to_str().ok())
>>      }
>>  }
>>  
>> diff --git a/drivers/gpu/nova-core/nova_core.rs b/drivers/gpu/nova-core/nova_core.rs
>> index b98a1c03f13d..c1121e7c64c5 100644
>> --- a/drivers/gpu/nova-core/nova_core.rs
>> +++ b/drivers/gpu/nova-core/nova_core.rs
>> @@ -16,7 +16,6 @@
>>  mod num;
>>  mod regs;
>>  mod sbuffer;
>> -mod util;
>>  mod vbios;
>>  
>>  pub(crate) const MODULE_NAME: &kernel::str::CStr = <LocalModule as kernel::ModuleMetadata>::NAME;
>> diff --git a/drivers/gpu/nova-core/util.rs b/drivers/gpu/nova-core/util.rs
>> deleted file mode 100644
>> index 4b503249a3ef..000000000000
>> --- a/drivers/gpu/nova-core/util.rs
>> +++ /dev/null
>> @@ -1,16 +0,0 @@
>> -// SPDX-License-Identifier: GPL-2.0
>> -
>> -/// Converts a null-terminated byte slice to a string, or `None` if the array does not
>> -/// contains any null byte or contains invalid characters.
>> -///
>> -/// Contrary to [`kernel::str::CStr::from_bytes_with_nul`], the null byte can be anywhere in the
>> -/// slice, and not only in the last position.
>> -pub(crate) fn str_from_null_terminated(bytes: &[u8]) -> Option<&str> {
>> -    use kernel::str::CStr;
>> -
>> -    bytes
>> -        .iter()
>> -        .position(|&b| b == 0)
>> -        .and_then(|null_pos| CStr::from_bytes_with_nul(&bytes[..=null_pos]).ok())
>> -        .and_then(|cstr| cstr.to_str().ok())
>> -}
>>
>> base-commit: 7acc70476f14661149774ab88d3fe23d83ba4249
>