linux-kernel - Re: [PATCH 1/2] rust: dma: make use of start_ptr() and start_ptr

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Message-ID: <aQyHiezb9Dqsyx1G@google.com>
Date: Thu, 6 Nov 2025 11:33:29 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: abdiel.janulgue@...il.com, daniel.almeida@...labora.com, 
	robin.murphy@....com, a.hindborg@...nel.org, ojeda@...nel.org, 
	alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net, 
	bjorn3_gh@...tonmail.com, lossin@...nel.org, tmgross@...ch.edu, 
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 1/2] rust: dma: make use of start_ptr() and start_ptr_mut()

On Thu, Nov 06, 2025 at 10:44:06AM +0100, Danilo Krummrich wrote:
> On Mon Nov 3, 2025 at 8:06 PM CET, Danilo Krummrich wrote:
> > @@ -576,7 +580,7 @@ pub fn item_from_index(&self, offset: usize) -> Result<*mut T> {
> >          // and we've just checked that the range and index is within bounds.
> >          // - `offset` can't overflow since it is smaller than `self.count` and we've checked
> >          // that `self.count` won't overflow early in the constructor.
> > -        Ok(unsafe { self.cpu_addr.add(offset) })
> > +        Ok(unsafe { self.start_ptr().cast_mut().add(offset) })
> 
> In this specific case start_ptr().cast_mut() is indeed a bit odd, I will use the
> following hunk instead and keep the raw access.
> 
> @@ -576,7 +580,7 @@ pub fn item_from_index(&self, offset: usize) -> Result<*mut T> {
>          // and we've just checked that the range and index is within bounds.
>          // - `offset` can't overflow since it is smaller than `self.count` and we've checked
>          // that `self.count` won't overflow early in the constructor.
> -        Ok(unsafe { self.cpu_addr.add(offset) })
> +        Ok(unsafe { self.cpu_addr.get().add(offset) })

Assuming you got rid of all cast_mut() instances:

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>