linux-kernel - Re: [PATCH v2 09/10] gpu: nova-core: simplify str_from_null

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Message-Id: <DFEVITW4O9DW.P4ITE1PWIDY6@kernel.org>
Date: Sat, 03 Jan 2026 11:14:55 +0100
From: "Danilo Krummrich" <dakr@...nel.org>
To: "John Hubbard" <jhubbard@...dia.com>
Cc: "Alexandre Courbot" <acourbot@...dia.com>, "Alice Ryhl"
 <aliceryhl@...gle.com>, "David Airlie" <airlied@...il.com>, "Simona Vetter"
 <simona@...ll.ch>, "Alistair Popple" <apopple@...dia.com>, "Joel Fernandes"
 <joelagnelf@...dia.com>, "Timur Tabi" <ttabi@...dia.com>, "Edwin Peer"
 <epeer@...dia.com>, "Eliot Courtney" <ecourtney@...dia.com>,
 <nouveau@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
 <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>, "Lyude
 Paul" <lyude@...hat.com>
Subject: Re: [PATCH v2 09/10] gpu: nova-core: simplify
 str_from_null_terminated

On Sat Jan 3, 2026 at 4:37 AM CET, John Hubbard wrote:
> On 12/15/25 8:27 PM, Alexandre Courbot wrote:
>> The core library's `CStr` has a `from_bytes_until_nul` method that we
>> can leverage to simplify this function.
>> 
>> Reviewed-by: Lyude Paul <lyude@...hat.com>
>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>> ---
>>  drivers/gpu/nova-core/util.rs | 9 ++-------
>>  1 file changed, 2 insertions(+), 7 deletions(-)
>> 
>> diff --git a/drivers/gpu/nova-core/util.rs b/drivers/gpu/nova-core/util.rs
>> index 8b2a4b99c55b..2cccbce78c14 100644
>> --- a/drivers/gpu/nova-core/util.rs
>> +++ b/drivers/gpu/nova-core/util.rs
>> @@ -2,15 +2,10 @@
>>  
>>  /// 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 [`core::ffi::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 core::ffi::CStr;
>>  
>> -    bytes
>> -        .iter()
>> -        .position(|&b| b == 0)
>> -        .and_then(|null_pos| CStr::from_bytes_with_nul(&bytes[..=null_pos]).ok())
>> +    CStr::from_bytes_until_nul(bytes)
>> +        .ok()
>
> I guess I should have reviewed this patch, before creating my version of this.
> I went so far as to delete this file entirely, see if you prefer that, it's
> otherwise the same core idea, but with more cleanup. [1]
>
> [1] https://lore.kernel.org/20260103013438.247759-1-jhubbard@nvidia.com

Yes, let's remove str_from_null_terminated() entirely.

>>          .and_then(|cstr| cstr.to_str().ok())

Additionally, why do we return an Option here? While an error can only ever happen if
the given slice does not contain any NULL byte, I don't see why we discard the
error code.