Re: [PATCH 0/6] Initial Rust V4L2 support

Hans Verkuil
2023-07-05T06:41:10Z

Hi Daniel,

On 06/04/2023 23:56, Daniel Almeida wrote:
> Hi all, this is my first attempt at adding Rust support to the
> media subsystem.
>
> It adds just enough support to write a clone of the virtio-camera
> prototype written by my colleague, Dmitry Osipenko, available at [0].
>
> Basically, there's support for video_device_register,
> v4l2_device_register and for some ioctls in v4l2_ioctl_ops. There is
> also some initial vb2 support, alongside some wrappers for some types
> found in videodev2.h.
>
> I wrote a sample Rust driver just to prove that this probes, and
> that you get a message on dmesg whenever an ioctl is called.
>
> As there is no actual implementation for any of the ioctls, this module
> can misbehave with some programs. I can work around this in a future
> submission.
>
> Note that this is based on the rust branch, as opposed to rust-next. The
> reasoning is simple: I expect this series to just kickstart some
> discussion around the subject. Actual upstreaming can come up much
> later, at which point I can rebase on the rust branch.
>
> Lastly, the origins of this series trace back to a v4l2 virtIO driver I
> was writing in Rust. As the project was eventually shelved for other
> reasons, I picked both the virtIO and the v4l2 bindings into their own
> patches which I am now in the process of submitting. This is to say that
> I tested this code with said driver and CrosVM in the past, and it
> worked ok.
>
> Please let me know your thoughts.

Based on our discussions during the Media Summit I am going to mark this
series as RFC in patchwork.

Once we have a new maintenance process up and running and things have
stabilized on that front, then this can be revisited, but by that time
it is better to post a v2, rebased and updated.

Regards,

Hans

>
> [0]: https://gitlab.collabora.com/dmitry.osipenko/linux-kernel-rd/-/commit/055a2c322e931a8b388f864f1db81bbdfd525602
>
> Daniel Almeida (6):
> rust: media: add the media module
> rust: media: add initial videodev2.h abstractions
> rust: sync: introduce FfiMutex
> rust: media: videobuf2: add a videobuf2 abstraction
> rust: media: add {video|v4l2}_device_register support
> rust: media: add v4l2 rust sample
>
> rust/bindings/bindings_helper.h | 8 +
> rust/kernel/lib.rs | 2 +
> rust/kernel/media/mod.rs | 6 +
> rust/kernel/media/v4l2/capabilities.rs | 80 ++++
> rust/kernel/media/v4l2/dev.rs | 369 +++++++++++++++
> rust/kernel/media/v4l2/device.rs | 115 +++++
> rust/kernel/media/v4l2/enums.rs | 135 ++++++
> rust/kernel/media/v4l2/format.rs | 178 ++++++++
> rust/kernel/media/v4l2/framesize.rs | 176 +++++++
> rust/kernel/media/v4l2/inputs.rs | 104 +++++
> rust/kernel/media/v4l2/ioctls.rs | 608 +++++++++++++++++++++++++
> rust/kernel/media/v4l2/mmap.rs | 81 ++++
> rust/kernel/media/v4l2/mod.rs | 13 +
> rust/kernel/media/videobuf2/core.rs | 552 ++++++++++++++++++++++
> rust/kernel/media/videobuf2/mod.rs | 5 +
> rust/kernel/sync.rs | 1 +
> rust/kernel/sync/ffi_mutex.rs | 70 +++
> samples/rust/Kconfig | 11 +
> samples/rust/Makefile | 1 +
> samples/rust/rust_v4l2.rs | 403 ++++++++++++++++
> 20 files changed, 2918 insertions(+)
> create mode 100644 rust/kernel/media/mod.rs
> create mode 100644 rust/kernel/media/v4l2/capabilities.rs
> create mode 100644 rust/kernel/media/v4l2/dev.rs
> create mode 100644 rust/kernel/media/v4l2/device.rs
> create mode 100644 rust/kernel/media/v4l2/enums.rs
> create mode 100644 rust/kernel/media/v4l2/format.rs
> create mode 100644 rust/kernel/media/v4l2/framesize.rs
> create mode 100644 rust/kernel/media/v4l2/inputs.rs
> create mode 100644 rust/kernel/media/v4l2/ioctls.rs
> create mode 100644 rust/kernel/media/v4l2/mmap.rs
> create mode 100644 rust/kernel/media/v4l2/mod.rs
> create mode 100644 rust/kernel/media/videobuf2/core.rs
> create mode 100644 rust/kernel/media/videobuf2/mod.rs
> create mode 100644 rust/kernel/sync/ffi_mutex.rs
> create mode 100644 samples/rust/rust_v4l2.rs
>