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Date: Fri, 23 Jan 2026 11:25:15 +0100
Message-Id: <DFVW9MS5YLON.CVJDBYQKJ0P6@kernel.org>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v3 1/3] rust: clk: use the type-state pattern
Cc: "Daniel Almeida" <daniel.almeida@collabora.com>, "Alice Ryhl"
 <aliceryhl@google.com>, "Rafael J. Wysocki" <rafael@kernel.org>, "Viresh
 Kumar" <viresh.kumar@linaro.org>, "Maarten Lankhorst"
 <maarten.lankhorst@linux.intel.com>, "Thomas Zimmermann"
 <tzimmermann@suse.de>, "David Airlie" <airlied@gmail.com>, "Simona Vetter"
 <simona@ffwll.ch>, "Drew Fustini" <fustini@kernel.org>, "Guo Ren"
 <guoren@kernel.org>, "Fu Wei" <wefu@redhat.com>,
 =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= <ukleinek@kernel.org>, "Michael
 Turquette" <mturquette@baylibre.com>, "Stephen Boyd" <sboyd@kernel.org>,
 "Miguel Ojeda" <ojeda@kernel.org>, "Boqun Feng" <boqun.feng@gmail.com>,
 "Gary Guo" <gary@garyguo.net>, =?utf-8?q?Bj=C3=B6rn_Roy_Baron?=
 <bjorn3_gh@protonmail.com>, "Benno Lossin" <lossin@kernel.org>, "Andreas
 Hindborg" <a.hindborg@kernel.org>, "Trevor Gross" <tmgross@umich.edu>,
 <linux-pm@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
 <dri-devel@lists.freedesktop.org>, <linux-riscv@lists.infradead.org>,
 <linux-pwm@vger.kernel.org>, <linux-clk@vger.kernel.org>,
 <rust-for-linux@vger.kernel.org>
To: "Maxime Ripard" <mripard@kernel.org>
References: <20260107-clk-type-state-v3-0-77d3e3ee59c2@collabora.com>
 <20260107-clk-type-state-v3-1-77d3e3ee59c2@collabora.com>
 <20260108-delectable-fennec-of-sunshine-ffca19@houat>
 <98CD0BF6-3350-40B9-B8A9-F569AE3E3220@collabora.com>
 <20260119-thundering-tested-robin-4be817@houat>
 <aW4lCfUyumOKRRJm@google.com>
 <518D8B09-B9A1-4DB4-85CD-37A2DD3D5FB1@collabora.com>
 <DFSLCI9U4NCW.2HI2UPUI7G134@kernel.org>
 <20260119-weightless-pelican-of-anger-190db0@houat>
 <DFSN4FDCYHMW.3J3237PEBV2ZP@kernel.org>
 <20260122-majestic-masterful-jaguarundi-d0abde@houat>
In-Reply-To: <20260122-majestic-masterful-jaguarundi-d0abde@houat>

On Thu Jan 22, 2026 at 2:44 PM CET, Maxime Ripard wrote:
> On Mon, Jan 19, 2026 at 03:37:17PM +0100, Danilo Krummrich wrote:
>> I don't see the issue with devm_regmap_init_mmio_clk()? It takes a refer=
ence
>> count of the clock and prepares it when called and unprepares the clk in=
 drops
>> its reference in regmap_mmio_free_context() called from the devres callb=
ack.
>>=20
>> That something we can easily do with the current API, no?
>
> The current one, yes. Doing that in the API suggested here would involve
> some boilerplate in all those drivers they don't have right now.

No, I did mean the API suggested here.

If you would implement something like devm_regmap_init_mmio_clk() in Rust w=
ith
this API, you'd have some object like

	struct RegmapResource<T: Backend, R: Resource> {
	    map: Regmap<T>,
	    res: R,
	}

and a concrete instance could have the following type

	RegmapResource<MmIo, Clk<Prepared>>

So, eventually you could have:

	fn devm_regmap_init_mmio_clk(dev: &Device<Bound>,  name: &CStr, ...) -> ..=
. {
	    let clk: Clk<Prepared> =3D Clk::get(dev, name)?;
	    let regmap =3D RegmapResource::new(..., clk);

	    Devres::new(dev, regmap)
	}

Of course, we would never design the API in this way, as we have generic I/=
O
backends and register abstractions, and we'd also not have
devm_regmap_init_mmio_clk() as a constructor for a RegmapResource type, but=
 you
get the idea.