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Date: Mon, 13 Jul 2026 16:44:24 +0200
Message-Id: <DJXIV7JTU8JG.2U0I0LMHE84NJ@kernel.org>
Cc: "Miguel Ojeda" <ojeda@kernel.org>, "Greg Kroah-Hartman"
 <gregkh@linuxfoundation.org>, "Boqun Feng" <boqun@kernel.org>, "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>, "Alice Ryhl" <aliceryhl@google.com>,
 "Trevor Gross" <tmgross@umich.edu>, "Daniel Almeida"
 <daniel.almeida@collabora.com>, "Tamir Duberstein" <tamird@kernel.org>,
 "Alexandre Courbot" <acourbot@nvidia.com>, =?utf-8?q?Onur_=C3=96zkan?=
 <work@onurozkan.dev>, "Mauro Carvalho Chehab" <mchehab@kernel.org>, "Alan
 Stern" <stern@rowland.harvard.edu>, "Mathias Nyman"
 <mathias.nyman@intel.com>, <linux-kernel@vger.kernel.org>,
 <rust-for-linux@vger.kernel.org>, <linux-usb@vger.kernel.org>,
 <linux-media@vger.kernel.org>, "Colin Braun" <colin.braun.cl@gmail.com>
To: "Colin Braun" <colinbrauncl@gmail.com>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [RFC PATCH 4/4] media: add gv-usb2 audio capture driver
References: <20260712-urb-abstraction-v1-v1-0-9fa011634ead@gmail.com>
 <20260712-urb-abstraction-v1-v1-4-9fa011634ead@gmail.com>
In-Reply-To: <20260712-urb-abstraction-v1-v1-4-9fa011634ead@gmail.com>

On Sun Jul 12, 2026 at 11:08 PM CEST, Colin Braun wrote:
> +/// Write a vendor-specific control register on the GV-USB2 device.
> +///
> +/// Uses a vendor-type control request (`REQ_WRITE_REG`) to write the
> +/// given `value` to the given `reg` address.
> +fn write_reg(intf: &usb::Interface<device::Bound>, reg: u16, value: u8) =
-> Result {

In addition to raw control messages, this can leverage the generic I/O back=
end
infrastructure, so you don't have to roll your own write_reg() function and=
 use
the register!() infrastructure instead. See also [1] and [2].

[1] https://lore.kernel.org/driver-core/20260706-io_projection-v6-0-72cd5d0=
55d54@garyguo.net/
[2] https://lore.kernel.org/lkml/DJVQ852J7SOH.26YBIJTQ9B66G@kernel.org/

> +    let req =3D usb::ch9::CtrlRequest::new(
> +        usb::ch9::RequestType::new(
> +            usb::ch9::Direction::Out,
> +            usb::ch9::Type::Vendor,
> +            usb::ch9::Recipient::Device,
> +        ),
> +        regs::REQ_WRITE_REG,
> +        u16::from(value),
> +        reg,
> +        0,
> +    );
> +    let dev: &usb::Device<device::Bound> =3D intf.as_ref();
> +    dev.control_msg(&req, None, Delta::from_millis(1_000))
> +        .map(|_| ())
> +}