Re: [PATCH] rust: irq: add support for request_irq()

[Daniel Almeida]

Hi Alice,

> On 13 Jan 2025, at 11:42, Alice Ryhl <aliceryhl@xxxxxxxxxx> wrote:
> 
> On Thu, Oct 24, 2024 at 4:20 PM Daniel Almeida
> <daniel.almeida@xxxxxxxxxxxxx> wrote:
>> 
>> +impl<T: Handler> Registration<T> {
>> +    /// Registers the IRQ handler with the system for the given IRQ number. The
>> +    /// handler must be able to be called as soon as this function returns.
>> +    pub fn register(
>> +        irq: u32,
>> +        flags: Flags,
>> +        name: &'static CStr,
>> +        handler: T,
>> +    ) -> impl PinInit<Self, Error> {
>> +        try_pin_init!(Self {
>> +            irq,
>> +            handler: Opaque::new(handler)
>> +        })
>> +        .pin_chain(move |slot| {
>> +            // SAFETY:
>> +            // - `handler` points to a valid function defined below.
>> +            // - only valid flags can be constructed using the `flags` module.
>> +            // - `devname` is a nul-terminated string with a 'static lifetime.
>> +            // - `ptr` is a cookie used to identify the handler. The same cookie is
>> +            // passed back when the system calls the handler.
>> +            to_result(unsafe {
>> +                bindings::request_irq(
>> +                    irq,
>> +                    Some(handle_irq_callback::<T>),
>> +                    flags.0,
>> +                    name.as_char_ptr(),
>> +                    &*slot as *const _ as *mut core::ffi::c_void,
>> +                )
>> +            })?;
>> +
>> +            Ok(())
>> +        })
> 
> I think this does not run the destructor of `handler` when
> `request_irq` returns an error.
> 
> Alice

How? T is passed by value, so if request_irq() fails and thus Registration::register() returns Err,
I assume T is dropped.

Or is the pin_init! stuff somehow special here?

— Daniel