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[PATCH 4/4] samples: rust: rust_misc_device: add uring_cmd example

Sidong Yang posted 4 patches 2 months, 2 weeks ago
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[PATCH 4/4] samples: rust: rust_misc_device: add uring_cmd example
Posted by Sidong Yang 2 months, 2 weeks ago 
This patch makes rust_misc_device handle uring_cmd. Command ops are like
ioctl that set or get values in simple way.

Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
---
 samples/rust/rust_misc_device.rs | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
index c881fd6dbd08..cd0e578231d2 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 = 0x83;
+const RUST_MISC_DEV_URING_CMD_GET_VALUE: u32 = 0x84;
+
 module! {
     type: RustMiscDeviceModule,
     name: "rust_misc_device",
@@ -190,6 +194,32 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
 
         Ok(0)
     }
+
+    fn uring_cmd(
+        me: Pin<&RustMiscDevice>,
+        _file: &File,
+        io_uring_cmd: &IoUringCmd,
+        _issue_flags: u32,
+    ) -> Result<isize> {
+        dev_info!(me.dev, "UringCmd Rust Misc Device Sample\n");
+        let cmd = io_uring_cmd.cmd_op();
+        let cmd_data = io_uring_cmd.sqe().cmd_data().as_ptr() as *const usize;
+        let addr = unsafe { *cmd_data };
+
+        match cmd {
+            RUST_MISC_DEV_URING_CMD_SET_VALUE => {
+                me.set_value(UserSlice::new(addr, 8).reader())?;
+            }
+            RUST_MISC_DEV_URING_CMD_GET_VALUE => {
+                me.get_value(UserSlice::new(addr, 8).writer())?;
+            }
+            _ => {
+                dev_err!(me.dev, "-> uring_cmd not recognised: {}\n", cmd);
+                return Err(ENOTTY);
+            }
+        }
+        Ok(0)
+    }
 }
 
 #[pinned_drop]
-- 
2.43.0
Re: [PATCH 4/4] samples: rust: rust_misc_device: add uring_cmd example
Posted by Caleb Sander Mateos 2 months, 2 weeks ago 
On Sat, Jul 19, 2025 at 10:35 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
>
> This patch makes rust_misc_device handle uring_cmd. Command ops are like
> ioctl that set or get values in simple way.
>
> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
>  samples/rust/rust_misc_device.rs | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
>
> diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
> index c881fd6dbd08..cd0e578231d2 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 = 0x83;
> +const RUST_MISC_DEV_URING_CMD_GET_VALUE: u32 = 0x84;

In real uring_cmd() implementations, the cmd_op values are assigned
using the _IO* macros, same as for ioctls. But I suppose that's not
strictly required for the sample driver.

> +
>  module! {
>      type: RustMiscDeviceModule,
>      name: "rust_misc_device",
> @@ -190,6 +194,32 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
>
>          Ok(0)
>      }
> +
> +    fn uring_cmd(
> +        me: Pin<&RustMiscDevice>,
> +        _file: &File,
> +        io_uring_cmd: &IoUringCmd,
> +        _issue_flags: u32,
> +    ) -> Result<isize> {
> +        dev_info!(me.dev, "UringCmd Rust Misc Device Sample\n");
> +        let cmd = io_uring_cmd.cmd_op();
> +        let cmd_data = io_uring_cmd.sqe().cmd_data().as_ptr() as *const usize;
> +        let addr = unsafe { *cmd_data };

The io_uring_sqe is user-mapped memory, so this load needs to be
atomic. In C, the uring_cmd() implementation would use READ_ONCE().
Sounds like Rust code is currently using read_volatile() (with a FIXME
comment to switch to read_once() once that's available).

Best,
Caleb

> +
> +        match cmd {
> +            RUST_MISC_DEV_URING_CMD_SET_VALUE => {
> +                me.set_value(UserSlice::new(addr, 8).reader())?;
> +            }
> +            RUST_MISC_DEV_URING_CMD_GET_VALUE => {
> +                me.get_value(UserSlice::new(addr, 8).writer())?;
> +            }
> +            _ => {
> +                dev_err!(me.dev, "-> uring_cmd not recognised: {}\n", cmd);
> +                return Err(ENOTTY);
> +            }
> +        }
> +        Ok(0)
> +    }
>  }
>
>  #[pinned_drop]
> --
> 2.43.0
>
>
Re: [PATCH 4/4] samples: rust: rust_misc_device: add uring_cmd example
Posted by Sidong Yang 2 months, 2 weeks ago 
On Sun, Jul 20, 2025 at 04:21:00PM -0400, Caleb Sander Mateos wrote:
> On Sat, Jul 19, 2025 at 10:35 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
> >
> > This patch makes rust_misc_device handle uring_cmd. Command ops are like
> > ioctl that set or get values in simple way.
> >
> > Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> > ---
> >  samples/rust/rust_misc_device.rs | 30 ++++++++++++++++++++++++++++++
> >  1 file changed, 30 insertions(+)
> >
> > diff --git a/samples/rust/rust_misc_device.rs b/samples/rust/rust_misc_device.rs
> > index c881fd6dbd08..cd0e578231d2 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 = 0x83;
> > +const RUST_MISC_DEV_URING_CMD_GET_VALUE: u32 = 0x84;
> 
> In real uring_cmd() implementations, the cmd_op values are assigned
> using the _IO* macros, same as for ioctls. But I suppose that's not
> strictly required for the sample driver.

Okay, I'll use same _IO* pattern with ioctl.
> 
> > +
> >  module! {
> >      type: RustMiscDeviceModule,
> >      name: "rust_misc_device",
> > @@ -190,6 +194,32 @@ fn ioctl(me: Pin<&RustMiscDevice>, _file: &File, cmd: u32, arg: usize) -> Result
> >
> >          Ok(0)
> >      }
> > +
> > +    fn uring_cmd(
> > +        me: Pin<&RustMiscDevice>,
> > +        _file: &File,
> > +        io_uring_cmd: &IoUringCmd,
> > +        _issue_flags: u32,
> > +    ) -> Result<isize> {
> > +        dev_info!(me.dev, "UringCmd Rust Misc Device Sample\n");
> > +        let cmd = io_uring_cmd.cmd_op();
> > +        let cmd_data = io_uring_cmd.sqe().cmd_data().as_ptr() as *const usize;
> > +        let addr = unsafe { *cmd_data };
> 
> The io_uring_sqe is user-mapped memory, so this load needs to be
> atomic. In C, the uring_cmd() implementation would use READ_ONCE().
> Sounds like Rust code is currently using read_volatile() (with a FIXME
> comment to switch to read_once() once that's available).

Yes, I've missed this. read_volatile with comment would be good.

Thanks,
Sidong
> 
> Best,
> Caleb
> 
> > +
> > +        match cmd {
> > +            RUST_MISC_DEV_URING_CMD_SET_VALUE => {
> > +                me.set_value(UserSlice::new(addr, 8).reader())?;
> > +            }
> > +            RUST_MISC_DEV_URING_CMD_GET_VALUE => {
> > +                me.get_value(UserSlice::new(addr, 8).writer())?;
> > +            }
> > +            _ => {
> > +                dev_err!(me.dev, "-> uring_cmd not recognised: {}\n", cmd);
> > +                return Err(ENOTTY);
> > +            }
> > +        }
> > +        Ok(0)
> > +    }
> >  }
> >
> >  #[pinned_drop]
> > --
> > 2.43.0
> >
> >

Patchew 2.1-devel-b67e4c2

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