linux-kernel - Re: [PATCH 3/7] rust: devres: support fallible in-place init for data

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Message-ID: <ec3adfb8-006d-4778-ba4a-e9222461e38d@gmail.com>
Date: Fri, 30 May 2025 18:18:07 +0200
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Danilo Krummrich <dakr@...nel.org>, gregkh@...uxfoundation.org,
 rafael@...nel.org, ojeda@...nel.org, alex.gaynor@...il.com,
 boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com,
 benno.lossin@...ton.me, a.hindborg@...nel.org, aliceryhl@...gle.com,
 tmgross@...ch.edu
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/7] rust: devres: support fallible in-place init for data

On 30.05.25 4:24 PM, Danilo Krummrich wrote:
> Currently, Devres only supports a data argument of type T. However,
> DevresInner already uses pin-init to initialize the Revocable. Hence,
> there is no need for this limitation and we can take a data argument of
> type impl PinInit<T, E> instead.
> 
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---

Reviewed-by: Christian Schrefl <chrisi.schrefl@...il.com>

>  rust/kernel/devres.rs | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index 2dbe17d6ea1f..47aeb5196dd2 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -96,9 +96,16 @@ struct DevresInner<T> {
>  pub struct Devres<T>(Arc<DevresInner<T>>);
>  
>  impl<T> DevresInner<T> {
> -    fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Arc<DevresInner<T>>> {
> -        let inner = Arc::pin_init(
> -            try_pin_init!( DevresInner {
> +    fn new<E>(
> +        dev: &Device<Bound>,
> +        data: impl PinInit<T, E>,
> +        flags: Flags,
> +    ) -> Result<Arc<DevresInner<T>>>
> +    where
> +        Error: From<E>,
> +    {
> +        let inner = Arc::pin_init::<Error>(
> +            try_pin_init!( Self {
>                  dev: dev.into(),
>                  callback: Self::devres_callback,
>                  data <- Revocable::new(data),
> @@ -168,7 +175,10 @@ fn remove_action(this: &Arc<Self>) {
>  impl<T> Devres<T> {
>      /// Creates a new [`Devres`] instance of the given `data`. The `data` encapsulated within the
>      /// returned `Devres` instance' `data` will be revoked once the device is detached.
> -    pub fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Self> {
> +    pub fn new<E>(dev: &Device<Bound>, data: impl PinInit<T, E>, flags: Flags) -> Result<Self>
> +    where
> +        Error: From<E>,
> +    {
>          let inner = DevresInner::new(dev, data, flags)?;
>  
>          Ok(Devres(inner))
> @@ -176,7 +186,14 @@ pub fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Self> {
>  
>      /// Same as [`Devres::new`], but does not return a `Devres` instance. Instead the given `data`
>      /// is owned by devres and will be revoked / dropped, once the device is detached.
> -    pub fn new_foreign_owned(dev: &Device<Bound>, data: T, flags: Flags) -> Result {
> +    pub fn new_foreign_owned<E>(
> +        dev: &Device<Bound>,
> +        data: impl PinInit<T, E>,
> +        flags: Flags,
> +    ) -> Result
> +    where
> +        Error: From<E>,
> +    {
>          let _ = DevresInner::new(dev, data, flags)?;
>  
>          Ok(())