Re: [PATCH v3 3/5] samples: rust: Provide example using the new Rust MiscDevice abstraction

Arnd Bergmann
2024-12-06T06:53:45Z

On Fri, Dec 6, 2024, at 07:49, Greg KH wrote:
> On Thu, Dec 05, 2024 at 04:25:20PM +0000, Lee Jones wrote:
>> +
>> +#[vtable]
>> +impl MiscDevice for RustMiscDevice {
>> + type Ptr = KBox<Self>;
>> +
>> + fn open() -> Result<KBox<Self>> {
>> + pr_info!("Opening Rust Misc Device Sample\n");
>> +
>> + Ok(KBox::new(RustMiscDevice, GFP_KERNEL)?)
>> + }
>> +
>> + fn ioctl(
>> + _device: <Self::Ptr as kernel::types::ForeignOwnable>::Borrowed<'_>,
>> + cmd: u32,
>> + _arg: usize,
>> + ) -> Result<isize> {
>> + pr_info!("IOCTLing Rust Misc Device Sample\n");
>> +
>> + match cmd {
>> + RUST_MISC_DEV_HELLO => pr_info!("Hello from the Rust Misc Device\n"),
>> + _ => {
>> + pr_err!("IOCTL not recognised: {}\n", cmd);
>> + return Err(ENOIOCTLCMD);
>
> To quote errno.h:
> These should never be seen by user programs
>
> The correct value here is ENOTTY.
>
> Yeah, fun stuff. Not intuitive at all, sorry.

That should get handled by vfs_ioctl() converting the
ENOIOCTLCMD to ENOTTY.

Arnd