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

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Message-ID: <09e0454c-222b-41e6-a8e5-6d6240b20479@nvidia.com>
Date: Tue, 6 Jan 2026 14:09:51 -0800
From: John Hubbard <jhubbard@...dia.com>
To: 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] gpu: nova-core: use CStr::from_bytes_until_nul() and
 remove util.rs

On 1/6/26 4:02 AM, Danilo Krummrich wrote:
> On Sat Jan 3, 2026 at 2:34 AM CET, John Hubbard wrote:
>> @@ -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())
>>      }
>>  }
> 
> Did you see my reply in [1]? The question is orthogonal to this change, but

I did, but momentarily forgot it during a miserable day in which
Thunderbird and Wayland started violently disagreeing, and every
email turned into a troubleshooting effort. :) Glad to be past that.

> perhaps it can be addressed with a subsequent patch?
> 
> [1] https://lore.kernel.org/lkml/DFEVITW4O9DW.P4ITE1PWIDY6@kernel.org/

Yes, so that would look approximately like this, I can send this as
another patch if it looks reasonable:

diff --git a/drivers/gpu/nova-core/gsp/boot.rs b/drivers/gpu/nova-core/gsp/boot.rs
index a53d80620468..71fca7350b94 100644
--- a/drivers/gpu/nova-core/gsp/boot.rs
+++ b/drivers/gpu/nova-core/gsp/boot.rs
@@ -238,11 +238,11 @@ pub(crate) fn boot(
 
         // Obtain and display basic GPU information.
         let info = commands::get_gsp_info(&mut self.cmdq, bar)?;
-        dev_info!(
-            pdev.as_ref(),
-            "GPU name: {}\n",
-            info.gpu_name().unwrap_or("invalid GPU name")
-        );
+        let gpu_name = info
+            .gpu_name()
+            .inspect_err(|e| dev_warn!(pdev.as_ref(), "GPU name: {}\n", e))
+            .unwrap_or("<unavailable>");
+        dev_info!(pdev.as_ref(), "GPU name: {}\n", gpu_name);
 
         Ok(())
     }
diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
index a11fe6018091..426441978b4b 100644
--- a/drivers/gpu/nova-core/gsp/commands.rs
+++ b/drivers/gpu/nova-core/gsp/commands.rs
@@ -2,7 +2,9 @@
 
 use core::{
     array,
-    convert::Infallible, //
+    convert::Infallible,
+    ffi::FromBytesUntilNulError,
+    str::Utf8Error, //
 };
 
 use kernel::{
@@ -204,13 +206,35 @@ fn read(
     }
 }
 
+/// Error type for [`GetGspStaticInfoReply::gpu_name`].
+#[derive(Debug)]
+pub(crate) enum GpuNameError {
+    /// The GPU name string does not contain a null terminator.
+    NoNullTerminator(FromBytesUntilNulError),
+
+    /// The GPU name string contains invalid UTF-8.
+    InvalidUtf8(Utf8Error),
+}
+
+impl kernel::fmt::Display for GpuNameError {
+    fn fmt(&self, f: &mut kernel::fmt::Formatter<'_>) -> kernel::fmt::Result {
+        match self {
+            Self::NoNullTerminator(_) => write!(f, "no null terminator"),
+            Self::InvalidUtf8(e) => write!(f, "invalid UTF-8 at byte {}", e.valid_up_to()),
+        }
+    }
+}
+
 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> {
+    /// Returns the name of the GPU as a string.
+    ///
+    /// Returns an error if the string given by the GSP does not contain a null terminator or
+    /// contains invalid UTF-8.
+    pub(crate) fn gpu_name(&self) -> core::result::Result<&str, GpuNameError> {
         CStr::from_bytes_until_nul(&self.gpu_name)
-            .ok()
-            .and_then(|cstr| cstr.to_str().ok())
+            .map_err(GpuNameError::NoNullTerminator)?
+            .to_str()
+            .map_err(GpuNameError::InvalidUtf8)
     }
 }



thanks,
-- 
John Hubbard