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Date: Wed, 21 Jan 2026 18:12:11 +0100
Message-Id: <DFUFO3WUQL1K.3JH3SS0J1Y0CQ@kernel.org>
To: "Gary Guo" <gary@garyguo.net>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v11 4/5] rust: pci: add config space read/write support
Cc: "Zhi Wang" <zhiw@nvidia.com>, <rust-for-linux@vger.kernel.org>,
 <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <aliceryhl@google.com>, <bhelgaas@google.com>, <kwilczynski@kernel.org>,
 <ojeda@kernel.org>, <alex.gaynor@gmail.com>, <boqun.feng@gmail.com>,
 <bjorn3_gh@protonmail.com>, <lossin@kernel.org>, <a.hindborg@kernel.org>,
 <tmgross@umich.edu>, <markus.probst@posteo.de>, <helgaas@kernel.org>,
 <cjia@nvidia.com>, <smitra@nvidia.com>, <ankita@nvidia.com>,
 <aniketa@nvidia.com>, <kwankhede@nvidia.com>, <targupta@nvidia.com>,
 <acourbot@nvidia.com>, <joelagnelf@nvidia.com>, <jhubbard@nvidia.com>,
 <zhiwang@kernel.org>, <daniel.almeida@collabora.com>
References: <20260121142355.4761-1-zhiw@nvidia.com>
 <20260121142355.4761-5-zhiw@nvidia.com>
 <DFUDN05YDH4W.1VXNXWWZST0C6@garyguo.net>
In-Reply-To: <DFUDN05YDH4W.1VXNXWWZST0C6@garyguo.net>

On Wed Jan 21, 2026 at 4:36 PM CET, Gary Guo wrote:
>> +/// The PCI configuration space of a device.
>> +///
>> +/// Provides typed read and write accessors for configuration registers
>> +/// using the standard `pci_read_config_*` and `pci_write_config_*` hel=
pers.
>> +///
>> +/// The generic const parameter `SIZE` can be used to indicate the
>> +/// maximum size of the configuration space (e.g. `ConfigSpaceSize::Nor=
mal`
>> +/// or `ConfigSpaceSize::Extended`).
>> +pub struct ConfigSpace<'a, const SIZE: usize =3D { ConfigSpaceSize::Ext=
ended as usize }> {
>
> This is quite long to write. Given that it'll either be normal or extende=
d, can
> we just have two marker types instead? So you have
>
>     ConfigSpace<Normal> and ConfigSpace<Extended>

I think in practice users don't have the need to write it anyways. You'd ac=
cess
the config space with either

	let config =3D pdev.config_space()?;

or

	let config =3D pdev.config_space_extended()?;

i.e. there is no need to store an instance of the struct anywhere.

Should it turn out that we do need it for some reason in the future we can =
do
this as follow-up, I think.