linux-kernel - Re: [RFC PATCH v3 5/5] samples: rust: Add `uring_cmd` example to `rust_misc

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Message-ID: <aK-nUJqy3HSTT71R@fedora>
Date: Thu, 28 Aug 2025 08:48:16 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Sidong Yang <sidong.yang@...iosa.ai>
Cc: Jens Axboe <axboe@...nel.dk>,
	Daniel Almeida <daniel.almeida@...labora.com>,
	Caleb Sander Mateos <csander@...estorage.com>,
	Benno Lossin <lossin@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	io-uring@...r.kernel.org
Subject: Re: [RFC PATCH v3 5/5] samples: rust: Add `uring_cmd` example to
 `rust_misc_device`

On Fri, Aug 22, 2025 at 12:55:55PM +0000, Sidong Yang wrote:
> This patch extends the `rust_misc_device` sample to demonstrate how to
> use the `uring_cmd` interface for asynchronous device operations.
> 
> The new implementation handles two `uring_cmd` operations:
> 
> *   `RUST_MISC_DEV_URING_CMD_SET_VALUE`: Sets a value in the device.
> *   `RUST_MISC_DEV_URING_CMD_GET_VALUE`: Gets a value from the device.
> 
> To use this new functionality, users can submit `IORING_OP_URING_CMD`
> operations to the `rust_misc_device` character device.
> 
> Signed-off-by: Sidong Yang <sidong.yang@...iosa.ai>
> ---
>  samples/rust/rust_misc_device.rs | 27 +++++++++++++++++++++++++++
>  1 file changed, 27 insertions(+)
> 
> diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
> index e7ab77448f75..1f25d2b1f4d8 100644
> --- a/samples/rust/rust_misc_device.rs
> +++ b/samples/rust/rust_misc_device.rs
> @@ -101,6 +101,7 @@
>      c_str,
>      device::Device,
>      fs::File,
> +    io_uring::IoUringCmd,
>      ioctl::{_IO, _IOC_SIZE, _IOR, _IOW},
>      miscdevice::{MiscDevice, MiscDeviceOptions, MiscDeviceRegistration},
>      new_mutex,
> @@ -114,6 +115,9 @@
>  const RUST_MISC_DEV_GET_VALUE: u32 = _IOR::<i32>('|' as u32, 0x81);
>  const RUST_MISC_DEV_SET_VALUE: u32 = _IOW::<i32>('|' as u32, 0x82);
>  
> +const RUST_MISC_DEV_URING_CMD_SET_VALUE: u32 = _IOR::<i32>('|' as u32, 0x83);
> +const RUST_MISC_DEV_URING_CMD_GET_VALUE: u32 = _IOW::<i32>('|' as u32, 0x84);
> +
>  module! {
>      type: RustMiscDeviceModule,
>      name: "rust_misc_device",
> @@ -192,6 +196,29 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
>  
>          Ok(0)
>      }
> +
> +    fn uring_cmd(
> +        me: Pin<&RustMiscDevice>,
> +        io_uring_cmd: Pin<&mut IoUringCmd>,
> +        _issue_flags: u32,
> +    ) -> Result<i32> {
> +        dev_info!(me.dev, "UringCmd Rust Misc Device Sample\n");
> +
> +        let cmd = io_uring_cmd.cmd_op();
> +        let addr: usize = io_uring_cmd.sqe().cmd_data()?;
> +        let user_ptr = UserPtr::from_addr(addr);
> +        let user_slice = UserSlice::new(user_ptr, 8);
> +
> +        match cmd {
> +            RUST_MISC_DEV_URING_CMD_SET_VALUE => me.set_value(user_slice.reader())?,
> +            RUST_MISC_DEV_URING_CMD_GET_VALUE => me.get_value(user_slice.writer())?,
> +            _ => {
> +                dev_err!(me.dev, "-> uring_cmd not recognised: {}\n", cmd);
> +                return Err(ENOTTY);
> +            }
> +        };
> +        Ok(0)
> +    }
>  }

I'd suggest to cover most of methods added in patch 2, so that any kernel
side change can be verified easily.


Thanks,
Ming