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Date: Wed, 28 Jan 2026 18:40:21 +0100
Message-Id: <DG0ENHNJE4X4.14T1ENBL0SOSE@kernel.org>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v2 1/2] rust: introduce abstractions for fwctlg
Cc: "Jason Gunthorpe" <jgg@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>,
 <gary@garyguo.net>, <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>
To: "Zhi Wang" <zhiw@nvidia.com>
References: <20260122204232.15988-2-zhiw@nvidia.com>
 <20260126181912.GA2131321@nvidia.com>
 <20260127215744.332380fe.zhiw@nvidia.com>
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 <20260128000410.GT1134360@nvidia.com>
 <DFZTU4ZFFCM0.3N8LJ8XBN3DF@kernel.org>
 <20260128132029.GX1134360@nvidia.com>
 <DG09ZUY530SW.K62KDIT4LIXN@kernel.org>
 <20260128145906.GZ1134360@nvidia.com>
 <DG0CABK2DQE8.1TDN35GOJ0DYI@kernel.org>
 <20260128155646.GB1134360@nvidia.com>
 <DG0D9I9P5BO9.6Q9H2BQN5AWU@kernel.org>
 <20260128193011.3294f41e.zhiw@nvidia.com>
In-Reply-To: <20260128193011.3294f41e.zhiw@nvidia.com>

On Wed Jan 28, 2026 at 6:30 PM CET, Zhi Wang wrote:
> On Wed, 28 Jan 2026 17:35:04 +0100
> "Danilo Krummrich" <dakr@kernel.org> wrote:
>
>> On Wed Jan 28, 2026 at 4:56 PM CET, Jason Gunthorpe wrote:
>> > On Wed, Jan 28, 2026 at 04:49:07PM +0100, Danilo Krummrich wrote:
>
> snip
>
>> > Or is it needed to add the typestate?
>>=20
>> This is something we should consider when a fwctl::Device would have
>> different states it can be in, where calling certain methods of a
>> fwctl::Device is only valid for a certain state and would cause
>> undefined behavior if called from the wrong state.
>
> Are you saying we should define typestate like Device<Bound/Core> also fo=
r
> fwctl device? I haven't thought about this and some design consideration
> would be helpful, as the rust PCI subsystem has it, while some of other
> abstractions don't have it. I could start to picture about this if this
> is necessary.

No, I don't see a need for a type state for fwctl::Device.

The DeviceContext type states, such as Core, Bound, etc. are type states fo=
r bus
devices only. If you find other device structures that don't have this, the=
n
those are not bus devices, but class devices (such as {pwm,drm,fwctl}::Devi=
ce).