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Date: Wed, 25 Mar 2026 14:46:36 +0100
Message-Id: <DHBWR17G0AIE.30MDYBUT7PNZL@kernel.org>
Subject: Re: [PATCH 1/3] rust: uaccess: generalize write_dma() to accept any
 Coherent<T>
Cc: <acourbot@nvidia.com>, <aliceryhl@google.com>,
 <abdiel.janulgue@gmail.com>, <daniel.almeida@collabora.com>,
 <robin.murphy@arm.com>, <a.hindborg@kernel.org>, <ojeda@kernel.org>,
 <boqun@kernel.org>, <bjorn3_gh@protonmail.com>, <lossin@kernel.org>,
 <tmgross@umich.edu>, <ttabi@nvidia.com>, <nouveau@lists.freedesktop.org>,
 <dri-devel@lists.freedesktop.org>, <linux-kernel@vger.kernel.org>,
 <driver-core@lists.linux.dev>, <rust-for-linux@vger.kernel.org>
To: "Gary Guo" <gary@garyguo.net>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <20260325003921.3420-1-dakr@kernel.org>
 <DHBVS7DX89G2.34ELW7TJAH7M8@garyguo.net>
In-Reply-To: <DHBVS7DX89G2.34ELW7TJAH7M8@garyguo.net>

On Wed Mar 25, 2026 at 2:01 PM CET, Gary Guo wrote:
> I think there is a reason, which is that it weakens the strong typing tha=
t we
> have. I think it'll be better to have this be
>
>     fn write_dma<T>(&mut self, view: View<'_, Coherent<T>, [u8]>, offset:=
 usize) -> Result
>
> once we have I/O view and expect people to create cast views into bytes
> explicitly.
>

There is technically no difference between the above and the below, except =
that
for the above the user has to create the View first, i.e. it needs addition=
al
code. What's the advantage?

>> +    pub fn write_dma<T: KnownSize + AsBytes + ?Sized>(
>> +        &mut self,
>> +        alloc: &Coherent<T>,
>> +        offset: usize,
>> +        count: usize,
>> +    ) -> Result {

<snip>

> Although, given that we already have APIs like
>
>     fn write<T: AsBytes>(&mut self, value: &T)
>
> I'm okay with putting this in until we have a replacement solution.

Sounds good.