Re: [PATCH] rust: pin-init: add code blocks to `[try_][pin_]init!` macros

["Danilo Krummrich" <dakr@kernel.org>]

On Sun Sep 7, 2025 at 1:33 PM CEST, Alice Ryhl wrote:
> On Sun, Sep 07, 2025 at 01:20:39PM +0200, Danilo Krummrich wrote:
>> On Sun Sep 7, 2025 at 12:57 PM CEST, Alice Ryhl wrote:
>> > On Fri, Sep 05, 2025 at 04:05:31PM +0200, Benno Lossin wrote:
>> >> Allow writing `_: { /* any number of statements */ }` in initializers to
>> >> run arbitrary code during initialization.
>> >> 
>> >>     try_init!(MyStruct {
>> >>         _: {
>> >>             if check_something() {
>> >>                 return Err(MyError);
>> >>             }
>> >>         },
>> >>         foo: Foo::new(val),
>> >>         _: {
>> >>             println!("successfully initialized `MyStruct`");
>> >>         },
>> >>     })
>> >> 
>> >> Link: https://github.com/Rust-for-Linux/pin-init/pull/84/commits/2880a9b898336e2d54f80715f00ce00f21f74d2f
>> >> Signed-off-by: Benno Lossin <lossin@kernel.org>
>> >
>> > Nice! Would it be possible to include a user so I can see it work in
>> > practice? E.g., for the irq feature?
>> 
>> Devres needs this too, but the corresponding devres stuff was a fix and is in
>> the current -rc only, so that's not a candidate.
>> 
>> The IRQ stuff is in driver-core-next going to Linus for v6.18, hence, using it
>> there, this patch would have to go through the driver-core tree as well.
>> 
>> For me it is fine either way.
>
> It doesn't have to land together. I would be happy with:
>
> 	THIS CYCLE: Land just this patch.
> 	NEXT CYCLE: Land the irq and/or devres user.
>
> But I'd like to see it work in practice before I give a Reviewed-by.
> It's hard to evaluate this kind of macro change just from the macro
> itself.

Here's a patch for using it in devres (we backmerged -rc3 into
driver-core-next):

From 23e48f081b7ba6bebd375c6fa929f070f7977fc5 Mon Sep 17 00:00:00 2001
From: Danilo Krummrich <dakr@kernel.org>
Date: Sun, 7 Sep 2025 13:44:43 +0200
Subject: [PATCH] rust: devres: take advantage of initializer code blocks

Use pin-init initializer code blocks to register the devres action.

This resolved the TODO introduced by commit 75a7b151e808 ("rust: devres:
fix leaking call to devm_add_action()").

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 rust/kernel/devres.rs | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
index 132545962218..430fc4880ddb 100644
--- a/rust/kernel/devres.rs
+++ b/rust/kernel/devres.rs
@@ -119,7 +119,6 @@ pub struct Devres<T: Send> {
     // explicit `Send` and `Sync' impls can be removed.
     #[pin]
     inner: Opaque<Inner<T>>,
-    _add_action: (),
 }

 impl<T: Send> Devres<T> {
@@ -146,10 +145,7 @@ pub fn new<'a, E>(
                     revoke <- Completion::new(),
                     data <- Revocable::new(data),
             })),
-            // TODO: Replace with "initializer code blocks" [1] once available.
-            //
-            // [1] https://github.com/Rust-for-Linux/pin-init/pull/69
-            _add_action: {
+            _: {
                 // SAFETY: `this` is a valid pointer to uninitialized memory.
                 let inner = unsafe { &raw mut (*this.as_ptr()).inner };


base-commit: 544c94f0e155614551e0210074597a23d117830c
--
2.51.0