On Mon Jun 23, 2025 at 5:10 PM CEST, Alice Ryhl wrote:
> On Mon, Jun 9, 2025 at 12:47 PM Danilo Krummrich <dakr@xxxxxxxxxx> wrote:
>> On Sun, Jun 08, 2025 at 07:51:08PM -0300, Daniel Almeida wrote:
>> > + dev: &'a Device<Bound>,
>> > + irq: u32,
>> > + flags: Flags,
>> > + name: &'static CStr,
>> > + handler: T,
>> > + ) -> impl PinInit<Self, Error> + 'a {
>> > + let closure = move |slot: *mut Self| {
>> > + // SAFETY: The slot passed to pin initializer is valid for writing.
>> > + unsafe {
>> > + slot.write(Self {
>> > + inner: Devres::new(
>> > + dev,
>> > + RegistrationInner {
>> > + irq,
>> > + cookie: slot.cast(),
>> > + },
>> > + GFP_KERNEL,
>> > + )?,
>> > + handler,
>> > + _pin: PhantomPinned,
>> > + })
>> > + };
>> > +
>> > + // SAFETY:
>> > + // - The callbacks are valid for use with request_irq.
>> > + // - If this succeeds, the slot is guaranteed to be valid until the
>> > + // destructor of Self runs, which will deregister the callbacks
>> > + // before the memory location becomes invalid.
>> > + let res = to_result(unsafe {
>> > + bindings::request_irq(
>> > + irq,
>> > + Some(handle_irq_callback::<T>),
>> > + flags.into_inner() as usize,
>> > + name.as_char_ptr(),
>> > + slot.cast(),
>> > + )
>> > + });
>> > +
>> > + if res.is_err() {
>> > + // SAFETY: We are returning an error, so we can destroy the slot.
>> > + unsafe { core::ptr::drop_in_place(&raw mut (*slot).handler) };
>> > + }
>> > +
>> > + res
>> > + };
>> > +
>> > + // SAFETY:
>> > + // - if this returns Ok, then every field of `slot` is fully
>> > + // initialized.
>> > + // - if this returns an error, then the slot does not need to remain
>> > + // valid.
>> > + unsafe { pin_init_from_closure(closure) }
>>
>> Can't we use try_pin_init!() instead, move request_irq() into the initializer of
>> RegistrationInner and initialize inner last?
>
> We need a pointer to the entire struct when calling
> bindings::request_irq. I'm not sure this allows you to easily get one?
> I don't think using container_of! here is worth it.
There is the `&this in` syntax (`this` is of type `NonNull<Self>`):
try_pin_init!(&this in Self {
inner: Devres::new(
dev,
RegistrationInner {
irq,
cookie: this.as_ptr().cast(),
},
GFP_KERNEL,
)?,
handler,
_pin: {
to_result(unsafe {
bindings::request_irq(
irq,
Some(handle_irq_callback::<T>),
flags.into_inner() as usize,
name.as_char_ptr(),
slot.as_ptr().cast(),
)
})?;
PhantomPinned
},
})
Last time around, I also asked this question and you replied with that
we need to abort the initializer when `request_irq` returns false and
avoid running `Self::drop` (thus we can't do it using `pin_chain`).
I asked what we could do instead and you mentioned the `_: {}`
initializers and those would indeed solve it, but we can abuse the
`_pin` field for that :)
---
Cheers,
Benno
