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Message-ID: <aKVOD-N1lEeHVjQs@archiso>
Date: Wed, 20 Aug 2025 04:24:47 +0000
From: Elle Rhumsaa <elle@...thered-steel.dev>
To: Daniel Almeida <daniel.almeida@...labora.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <lossin@...nel.org>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
Danilo Krummrich <dakr@...nel.org>,
Alexandre Courbot <acourbot@...dia.com>,
linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
kernel@...labora.com, linux-media@...r.kernel.org
Subject: Re: [PATCH 7/7] rust: samples: add the v4l2 sample driver
On Mon, Aug 18, 2025 at 02:49:53AM -0300, Daniel Almeida wrote:
> This driver is the only user of the v4l2 abstractions at the moment. It
> serves as a means to validate the abstractions by proving that the
> device is actually registered as /dev/videoX, and it can be opened and
> queried by v4l2-ctl, while also serving as a display of the current v4l2
> support in Rust, as well as a blueprint for more elaborate Rust v4l2
> drivers in the future.
>
> Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
> ---
> MAINTAINERS | 1 +
> samples/rust/Kconfig | 11 +++
> samples/rust/Makefile | 1 +
> samples/rust/rust_driver_v4l2.rs | 145 +++++++++++++++++++++++++++++++++++++++
> 4 files changed, 158 insertions(+)
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6fc5d57950e474d73d5d65271a0394efc5a8960b..14521bc0585503992da582f2cee361666985e39f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15440,6 +15440,7 @@ L: linux-media@...r.kernel.org
> L: rust-for-linux@...r.kernel.org
> S: Supported
> F: rust/media
> +F: sample/rust/rust_driver_v4l2.rs
>
> MEDIATEK BLUETOOTH DRIVER
> M: Sean Wang <sean.wang@...iatek.com>
> diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
> index 7f7371a004ee0a8f67dca99c836596709a70c4fa..64422acf1e9da9d05f904e14fd423b3b4aef173a 100644
> --- a/samples/rust/Kconfig
> +++ b/samples/rust/Kconfig
> @@ -105,6 +105,17 @@ config SAMPLE_RUST_DRIVER_AUXILIARY
>
> If unsure, say N.
>
> +config SAMPLE_RUST_DRIVER_V4L2
> + tristate "Video4Linux2 driver"
> + depends on MEDIA_SUPPORT && VIDEO_DEV
> + help
> + This option builds the Rust V4L2 driver sample.
> +
> + To compile this as a module, choose M here:
> + the module will be called rust_driver_v4l2.
> +
> + If unsure, say N.
> +
> config SAMPLE_RUST_HOSTPROGS
> bool "Host programs"
> help
> diff --git a/samples/rust/Makefile b/samples/rust/Makefile
> index bd2faad63b4f3befe7d1ed5139fe25c7a8b6d7f6..57e21f0373938bb70b4cb400ea550010895b4c94 100644
> --- a/samples/rust/Makefile
> +++ b/samples/rust/Makefile
> @@ -9,6 +9,7 @@ obj-$(CONFIG_SAMPLE_RUST_DRIVER_PCI) += rust_driver_pci.o
> obj-$(CONFIG_SAMPLE_RUST_DRIVER_PLATFORM) += rust_driver_platform.o
> obj-$(CONFIG_SAMPLE_RUST_DRIVER_FAUX) += rust_driver_faux.o
> obj-$(CONFIG_SAMPLE_RUST_DRIVER_AUXILIARY) += rust_driver_auxiliary.o
> +obj-$(CONFIG_SAMPLE_RUST_DRIVER_V4L2) += rust_driver_v4l2.o
> obj-$(CONFIG_SAMPLE_RUST_CONFIGFS) += rust_configfs.o
>
> rust_print-y := rust_print_main.o rust_print_events.o
> diff --git a/samples/rust/rust_driver_v4l2.rs b/samples/rust/rust_driver_v4l2.rs
> new file mode 100644
> index 0000000000000000000000000000000000000000..a3ef98a613f2fed9e8589f0761ce7e43029c02b6
> --- /dev/null
> +++ b/samples/rust/rust_driver_v4l2.rs
> @@ -0,0 +1,145 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// SPDX-copyrightText: Copyright (C) 2025 Collabora Ltd.
> +
> +//! Rust V4L2 sample driver.
> +//!
> +//! This sample demonstrates how to:
> +//! - Register a V4L2 device (struct v4l2_device),
> +//! - Register a video node (struct video_device) using the Rust V4L2
> +//! abstractions,
> +//! - Implement support for a V4L2 ioctl in a driver.
> +//!
> +//! It implements only `VIDIOC_QUERYCAP` and minimal open/close handling.
> +
> +use kernel::{
> + c_str,
> + device::Core,
> + media::v4l2::{
> + self,
> + caps::{self, DeviceCaps},
> + video,
> + },
> + of, platform,
> + prelude::*,
> + types::ARef,
> + ThisModule,
> +};
> +
> +/// The private data associated with the V4L2 device.
> +#[pin_data]
> +struct Data {}
> +
> +/// The private data associated with a V4L2 device node, i.e. `struct
> +/// video_device`.
> +#[pin_data]
> +struct VideoData {}
> +
> +/// The private data associated with a V4L2 file, i.e. `struct v4l2_fh`.
> +#[pin_data]
> +struct File {}
> +
> +impl v4l2::file::DriverFile for File {
> + type Driver = SampleDriver;
> +
> + const MODULE: &'static ThisModule = &THIS_MODULE;
> +
> + fn open(_vdev: &v4l2::video::Device<Self::Driver>) -> impl PinInit<Self, Error> {
> + try_pin_init!(Self {})
> + }
> +}
> +
> +struct SampleDriver {
> + _pdev: ARef<platform::Device>,
> + _v4l2_reg: v4l2::device::Registration<Self>,
> + video_reg: video::Registration<Self>,
> +}
> +
> +impl v4l2::device::Driver for SampleDriver {
> + type Data = Data;
> +}
> +
> +#[vtable]
> +impl video::Driver for SampleDriver {
> + type Data = VideoData;
> + type File = File;
> +
> + const NODE_TYPE: video::NodeType = video::NodeType::Video;
> + const DIRECTION: video::Direction = video::Direction::Rx;
> + const NAME: &'static CStr = c_str!("rv4l2");
> + const CAPS: DeviceCaps = caps::device_caps::VIDEO_CAPTURE;
> +
> + fn querycap(
> + _file: &v4l2::file::File<Self::File>,
> + _data: &<Self as video::Driver>::Data,
> + cap: &mut caps::Capabilities,
> + ) -> Result {
> + cap.set_driver(c_str!("rv4l2"))?;
> + cap.set_card(c_str!("rv4l2"))?;
> + cap.set_bus_info(c_str!("platform:rv4l2"))?;
> +
> + cap.set_device_caps(Self::CAPS);
> + Ok(())
> + }
> +}
> +
> +kernel::of_device_table!(
> + OF_TABLE,
> + MODULE_OF_TABLE,
> + <SampleDriver as platform::Driver>::IdInfo,
> + [(of::DeviceId::new(c_str!("test, rust-v4l2")), ())]
> +);
> +
> +impl platform::Driver for SampleDriver {
> + type IdInfo = ();
> + const OF_ID_TABLE: Option<of::IdTable<Self::IdInfo>> = Some(&OF_TABLE);
> +
> + fn probe(
> + pdev: &platform::Device<Core>,
> + _info: Option<&Self::IdInfo>,
> + ) -> Result<Pin<KBox<Self>>> {
> + let dev = pdev.as_ref();
> +
> + let v4l2_reg =
> + v4l2::device::Registration::<Self>::new(dev, try_pin_init!(Data {}), GFP_KERNEL)?;
> +
> + let video_reg = video::Registration::<Self>::new(
> + v4l2_reg.device(),
> + try_pin_init!(VideoData {}),
> + GFP_KERNEL,
> + )?;
> +
> + let this = KBox::new(
> + Self {
> + _pdev: pdev.into(),
> + _v4l2_reg: v4l2_reg,
> + video_reg,
> + },
> + GFP_KERNEL,
> + )?;
> +
> + dev_info!(
> + dev,
> + "Registered /dev/video{}\n",
> + this.video_reg.device().num()
> + );
> + Ok(this.into())
> + }
> +
> + fn unbind(pdev: &platform::Device<Core>, _this: Pin<&Self>) {
> + dev_info!(pdev.as_ref(), "Unbinding Rust V4L2 sample driver\n");
> + }
> +}
> +
> +impl Drop for SampleDriver {
> + fn drop(&mut self) {
> + dev_dbg!(self._pdev.as_ref(), "Rust V4L2 sample driver removed\n");
> + }
> +}
> +
> +kernel::module_platform_driver! {
> + type: SampleDriver,
> + name: "rust_driver_v4l2",
> + authors: ["Daniel Almeida"],
> + description: "Rust V4L2 sample video driver",
> + license: "GPL v2",
> +}
>
> --
> 2.50.1
Reviewed-by: Elle Rhumsaa <elle@...thered-steel.dev>
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