This patch series implemens an abstraction for io-uring sqe and cmd and
adds uring_cmd callback for miscdevice. Also there is an example that use
uring_cmd in rust-miscdevice sample.

I received a email from kernel bot that `io_tw_state` is not FFI-safe.
It seems that the struct has no field how can I fix this?

Changelog:
v2:
* use pinned &mut for IoUringCmd
* add missing safety comments
* use write_volatile for read uring_cmd in sample

Sidong Yang (4):
  rust: bindings: add io_uring headers in bindings_helper.h
  rust: io_uring: introduce rust abstraction for io-uring cmd
  rust: miscdevice: add uring_cmd() for MiscDevice trait
  samples: rust: rust_misc_device: add uring_cmd example

 rust/bindings/bindings_helper.h  |   2 +
 rust/kernel/io_uring.rs          | 183 +++++++++++++++++++++++++++++++
 rust/kernel/lib.rs               |   1 +
 rust/kernel/miscdevice.rs        |  41 +++++++
 samples/rust/rust_misc_device.rs |  34 ++++++
 5 files changed, 261 insertions(+)
 create mode 100644 rust/kernel/io_uring.rs

-- 
2.43.0

Hi Sidong,

> On 27 Jul 2025, at 12:03, Sidong Yang <sidong.yang@furiosa.ai> wrote:
> 
> This patch series implemens an abstraction for io-uring sqe and cmd and
> adds uring_cmd callback for miscdevice. Also there is an example that use
> uring_cmd in rust-miscdevice sample.
> 
> I received a email from kernel bot that `io_tw_state` is not FFI-safe.
> It seems that the struct has no field how can I fix this?
> 
> Changelog:
> v2:
> * use pinned &mut for IoUringCmd
> * add missing safety comments
> * use write_volatile for read uring_cmd in sample

Why is v2 an RFC when v1 wasn’t? Can you mention it on the changelog?

> 
> Sidong Yang (4):
>  rust: bindings: add io_uring headers in bindings_helper.h
>  rust: io_uring: introduce rust abstraction for io-uring cmd
>  rust: miscdevice: add uring_cmd() for MiscDevice trait
>  samples: rust: rust_misc_device: add uring_cmd example
> 
> rust/bindings/bindings_helper.h  |   2 +
> rust/kernel/io_uring.rs          | 183 +++++++++++++++++++++++++++++++
> rust/kernel/lib.rs               |   1 +
> rust/kernel/miscdevice.rs        |  41 +++++++
> samples/rust/rust_misc_device.rs |  34 ++++++
> 5 files changed, 261 insertions(+)
> create mode 100644 rust/kernel/io_uring.rs
> 
> -- 
> 2.43.0
> 
> 

— Daniel

On Fri, Aug 01, 2025 at 11:13:29AM -0300, Daniel Almeida wrote:
> Hi Sidong,
> 
> > On 27 Jul 2025, at 12:03, Sidong Yang <sidong.yang@furiosa.ai> wrote:
> > 
> > This patch series implemens an abstraction for io-uring sqe and cmd and
> > adds uring_cmd callback for miscdevice. Also there is an example that use
> > uring_cmd in rust-miscdevice sample.
> > 
> > I received a email from kernel bot that `io_tw_state` is not FFI-safe.
> > It seems that the struct has no field how can I fix this?
> > 
> > Changelog:
> > v2:
> > * use pinned &mut for IoUringCmd
> > * add missing safety comments
> > * use write_volatile for read uring_cmd in sample
> 
> Why is v2 an RFC when v1 wasn´t? Can you mention it on the changelog?

It was just miss. v1 should be also RFC. I'll mention it for next v3.

Thanks,
Sidong
> 
> > 
> > Sidong Yang (4):
> >  rust: bindings: add io_uring headers in bindings_helper.h
> >  rust: io_uring: introduce rust abstraction for io-uring cmd
> >  rust: miscdevice: add uring_cmd() for MiscDevice trait
> >  samples: rust: rust_misc_device: add uring_cmd example
> > 
> > rust/bindings/bindings_helper.h  |   2 +
> > rust/kernel/io_uring.rs          | 183 +++++++++++++++++++++++++++++++
> > rust/kernel/lib.rs               |   1 +
> > rust/kernel/miscdevice.rs        |  41 +++++++
> > samples/rust/rust_misc_device.rs |  34 ++++++
> > 5 files changed, 261 insertions(+)
> > create mode 100644 rust/kernel/io_uring.rs
> > 
> > -- 
> > 2.43.0
> > 
> > 
> 
> - Daniel

Hi Sidong,

> On 27 Jul 2025, at 12:03, Sidong Yang <sidong.yang@furiosa.ai> wrote:
> 
> This patch series implemens an abstraction for io-uring sqe and cmd and
> adds uring_cmd callback for miscdevice. Also there is an example that use
> uring_cmd in rust-miscdevice sample.
> 
> I received a email from kernel bot that `io_tw_state` is not FFI-safe.
> It seems that the struct has no field how can I fix this?

It’s not something that you introduced. Empty structs are problematic when
used in FFI, because  ZSTs are not defined in the C standard AFAIK, although
they are supported in some compilers. For example, this is not illegal nor UB
in GCC [0]. The docs say:

> The structure has size zero.

This aligns with Rust's treatment of ZSTs, which are also zero-sized, so I
don't think this will be a problem, but lets wait for others to chime in.

I'll review this tomorrow.

> 
> Changelog:
> v2:
> * use pinned &mut for IoUringCmd
> * add missing safety comments
> * use write_volatile for read uring_cmd in sample
> 
> Sidong Yang (4):
>  rust: bindings: add io_uring headers in bindings_helper.h
>  rust: io_uring: introduce rust abstraction for io-uring cmd
>  rust: miscdevice: add uring_cmd() for MiscDevice trait
>  samples: rust: rust_misc_device: add uring_cmd example
> 
> rust/bindings/bindings_helper.h  |   2 +
> rust/kernel/io_uring.rs          | 183 +++++++++++++++++++++++++++++++
> rust/kernel/lib.rs               |   1 +
> rust/kernel/miscdevice.rs        |  41 +++++++
> samples/rust/rust_misc_device.rs |  34 ++++++
> 5 files changed, 261 insertions(+)
> create mode 100644 rust/kernel/io_uring.rs
> 
> -- 
> 2.43.0
> 
> 


— Daniel

[0]: https://gcc.gnu.org/onlinedocs/gcc/Empty-Structures.html